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2012 JINST 7 C04012

PUBLISHED BY IOP PUBLISHING FOR SISSA MEDIALAB

RECEIVED November 18 2011ACCEPTED March 8 2012

PUBLISHED April 18 2012

2nd INTERNATIONAL WORKSHOP ON FAST NEUTRON DETECTORS AND APPLICATIONSNOVEMBER 6ndash11 2011EIN GEDI ISRAEL

Fusion neutron diagnostics on ITER tokamak

L Bertalot1 R Barnsley MF Direz JM Drevon A Encheva S JakharY Kashchuk KM Patel AP Arumugam V Udintsev C Walker and M Walsh

ITER OrganisationRoute de Vinon sur Verdon 13115 St Paul Lez Durance France

E-mail LucianoBertalotiterorg

ABSTRACT ITER is an experimental nuclear reactor aiming to demonstrate the feasibility of nu-clear fusion realization in order to use it as a new source of energy ITER is a plasma device(tokamak type) which will be equipped with a set of plasma diagnostic tools to satisfy three keyrequirements machine protection plasma control and physics studies by measuring about 100 dif-ferent parameters ITER diagnostic equipment is integrated in several ports at upper equatorialand divertor levels as well internally in many vacuum vessel locations The Diagnostic Systemswill be procured from ITER Members (Japan Russia India United States Japan Korea and Eu-ropean Union) mainly with the supporting structures in the ports The various diagnostics will bechallenged by high nuclear radiation and electromagnetic fields as well by severe environmentalconditions (ultra high vacuum high thermal loads) Several neutron systems with different sensitiv-ities are foreseen to measure ITER expected neutron emission from 1014 up to almost 1021 ns Themeasurement of total neutron emissivity is performed by means of Neutron Flux Monitors (NFM)installed in diagnostic ports and by Divertor Neutron Flux Monitors (DNFM) plus MicroFissionChambers (MFC) located inside the vacuum vessel The neutron emission profile is measured withradial and vertical neutron cameras Spectroscopy is accomplished with spectrometers lookingparticularly at 25 and 14 MeV neutron energy Neutron Activation System (NAS) with irradiationends inside the vacuum vessel provide neutron yield data A calibration strategy of the neutrondiagnostics has been developed foreseeing in situ and cross calibration campaigns An overviewof ITER neutron diagnostic systems and of the associated challenging engineering and integrationissues will be reported

KEYWORDS Nuclear instruments and methods for hot plasma diagnostics Plasma diagnostics -interferometry spectroscopy and imaging

1Corresponding author

ccopy 2012 IOP Publishing Ltd and Sissa Medialab srl doi1010881748-0221704C04012

2012 JINST 7 C04012

Contents

1 Introduction 1

2 ITER diagnostics 1

3 Neutron diagnostics role 2

4 Neutron diagnostics 541 B1 Radial Neutron Camera 542 B2 Vertical Neutron Camera 643 B3 MicroFission Chambers 744 B4 Neutron Flux Monitor 845 BC Divertor Neutron Flux Monitors 946 B8 Neutron Activation System 1047 BB High Resolution Neutron Spectrometer 12

5 Diagnostic integration 13

1 Introduction

The International Thermonuclear Experiment Reactor ITER is a large-scale scientific experimentintended to prove the viability of fusion as an energy source and to collect the data necessary forthe design and subsequent operation of the first electricity-producing fusion power plant ITER isan experimental nuclear reactor aiming to demonstrate the feasibility of nuclear fusion realizationgenerating DD and DT fusion reactions with characteristic neutrons from keV to 14MeV ITER isa tokamak based plasma device operating with a magnetic toroidal field of 53 T plasma current of15 MA pulse duration of 300 s up to 500s and producing up to 700 MW fusion power

2 ITER diagnostics

Several diagnostics systems are needed for machine protection plasma control and performance aswell physics studies Measurements of about 100 different plasma parameters with specific spatialtemporal resolutions and defined accuracies will be performed [1]

The diagnostics systems shall have the capability to measure all of the plasma parameters thatare necessary to operate and understand the behaviour of the ITER plasma in all phases of thepulse and also during expected deviations from the planned scenario

Access to diagnostic systems in the region of the tokamak area is generally quite limited ITERproject has designed diagnostic access providing viewing apertures of the plasma while maintainingthe nuclear shielding for approximately 40 different diagnostic systems

ndash 1 ndash

2012 JINST 7 C04012

Figure 1 Diagnostics locations on ITER

ITER diagnostic equipment is integrated in a total of 6 equatorial and 12 upper ports of thevacuum vessel 16 divertor cassettes and internally in many vacuum vessel locations figure 1

ITER environment is a quite harsh environment [2] The various diagnostic systems will haveto withstand high neutron flux (up to 1014 ncm2s with 14 MeV neutron energy) high temperaturesdue to plasma radiation and nuclear heating (up to 1000 C degrees) and magnetic field (up to 6 T)as well significant electromagnetic noise due to the auxiliary radiofrequency heating systems Par-ticular efforts are devoted to the maintainability of the various diagnostic systems in particular forthe In vessel ones which face the highest electromagnetic (EM) and nuclear loads [3] Differentlyfrom the diagnostics of the large tokamak devices (JET TFTR and JT 60) ITER diagnostics haveto be designed built and operated within full nuclear regulatory requirements

3 Neutron diagnostics role

Neutron measurement has been considered to be one of the major diagnostic methods to be usedsince the initiation of the ITER design phase The neutron diagnostics will provide key informationon plasma physics [4ndash6] protection and control issues

In the ITER project requirements different classes of parameters have been defined for ma-chine protection (Group 1a1) basic control (Group 1a2) and advanced control (Group 1b) Theneutron diagnostics have to measure the following parameters table 1

ndash 2 ndash

2012 JINST 7 C04012

Table 1 Neutron parameters and roles

Parameter Group

Total Neutron flux 1a1

Fusion power 1a2

Fusion density 1a2

Fluence 1a2

Neutron and alfa source 1b

Fuel ratio 1a2

Ion temperature profile 1b

Among the many plasma and first wall parameters to be measured the neutron diagnostics willallow evaluation of the neutron emissivity ie the fusion power which plays a key role for machineprotection as well for plasma optimization and for achieving ITER goals in particular the fusiongain factor Q related to the reactor performance ITER expected neutron emission strength spansover 7 decades (from 1014 up to almost 1021 ns) ITER needs various neutron diagnostic systemsable to measure the neutron emissivity within 10 accuracy with a temporal resolution of 1 msand spatial resolution of a tenth of the minor plasma radius ie 200 mm

The neutron fluence at the First Wall (FW) delivers information of the damage expected on thematerials facing the plasma

Neutron emission profile measurements deliver data on the alpha birth source Self-heating ofDT plasma by fusion-produced alpha particles is the key to realize self sustainable thermonuclearplasma in a fusion reactor

Another important parameter is the fuel ratio ie the amount of tritium and deuterium (nTnD)in the plasma measured by means of neutron spectroscopy which can provide also information onthe plasma ion temperature ITER neutron diagnostic sub systems are listed in table 2

ndash 3 ndash

2012 JINST 7 C04012

Table 2 ITER neutron diagnostics and related neutron parameters

Subsystem ParameterB1 Radial Neutron Camera Neutronalpha source profile

Total neutron source strengthIon temperature profileFuel ratioNeutron fluence on FW wall

B2 Vertical Neutron Camera Neutronalpha source profileTotal neutron source strengthIon temperature profileFuel ratioNeutron fluence on FW wall

B3 MicroFission Chambers Total neutron source strengthNeutron fluence on FW wall

B4 Neutron Flux Monitors Total neutron source strengthNeutron fluence on FW wall

B8 Neutron Activation System Neutron fluence on FW wallTotal neutron source strength

BB High Resolution Neutron Spec-trometers (Enabled)

Plasma Core Ion temperatureCore Plasma Fuel Ratio

BC Divertor Neutron Flux Monitors Total neutron source strengthNeutron fluence on the Divertor

Diagnostic subsystems responding to each measurement require measurement backup pro-vided by redundancy within the primary diagnostic by multiple primary diagnostics andor byback-up or supplementary diagnostics The role classification is as follows

bull Primary = diagnostic is well suited to the measurement

bull Backup = diagnostic provides similar data to primary but has some

limitations

bull Supplementary = diagnostic validates or calibrates the measurement but is not complete initself

The Neutron Diagnostics matrix flow down is here below shown (figure 2)

ndash 4 ndash

2012 JINST 7 C04012

Figure 2 Neutron Diagnostic matrix flow down

4 Neutron diagnostics

41 B1 Radial Neutron Camera

The Radial Neutron Camera (RNC) [7] consists of a fan-shaped array of 36 flight tubes viewingthe plasma through a vertical slot in the blanket shield module of Equatorial Port Plug 1 The sightlines intersect at a common aperture defined by the port plug and penetrate the vacuum vessel cryo-stat and biological shield through stainless steel windows (figure 3) Each flight tube culminatesin a set of detectors chosen to provide the required range of sensitivity and temporal and spectralresolution Some of the viewing chords will be equipped with compact neutron spectrometersenabling the system to provide emissivity-weighted chord-averaged measurements of ion temper-ature Appropriate spectrometers have not yet been selected but there are several (scintillatorschemical vapoured diamonds etc) that could meet the measurement requirements by further RampDactivity Because of the length of the ports the spatial coverage in the vertical direction of this partof the camera is limited Additionally 8 sight lines with collimators and detectors mounted in theport plug are included to give measurements in the outer regions of the plasma In this locationthere is reduced space for the detectors and this will limit the type and number of detectors andspectrometers that can be accommodated The maintenance of the detectors will also be more dif-ficult but the gain in spatial coverage is significant The in-port detectors have to withstand hightemperature (up to 250 degrees because of Vacuum Vessel baking)) and magnetic fields up sim 4 Tand a transient magnetic field of approx 10Ts Under these load conditions the system requiresa feasible support structure dedicated cooling and magnetic shielding Particular care is given tothe electrical connections of the in port detectors by using triax mineral insulated cables aiming tohigh noise rejection Moreover the in port detectors are enveloped in a Stainless Steel housing fornot affecting the torus vacuum due to a possible leakage of the detector filling gas

ndash 5 ndash

2012 JINST 7 C04012

Figure 3 Radial Neutron Camera with its lines of sight relative to the plasma with an additional obliqueview onto the outside of the port plug

42 B2 Vertical Neutron Camera

Because ITER does not have vertical ports it is difficult to measure the neutron emission in avertical direction (necessary for combination with the radial measurements for tomographic recon-structions of the neutron source profile) A concept for the vertically viewing camera (VNC) isbeen designed [8] This is to mount a camera adjacent to a port at the lower level The plasmawould be viewed through neutron windows in the vacuum vessel and through a slot in the divertorcassette and through the Blanket Shield Module (BSM) 18 Due to limited space only ten linesof sight are viewing the plasma with coverage up to 08 minor radius The cut outs in the Diver-tor Cassette and in BSM 18 require design modification of the interfacing components and morededicated analysis work [9] (figure 4) Mineral insulated cables will connect the detectors to thepreamplifiers unit located in the Lower Port Cell The detectors will be mounted in a box in orderto avoid detector filling gas leakage to the torus vacuum

ndash 6 ndash

2012 JINST 7 C04012

Figure 4 Vertical Neutron Camera mounted adjacent to a port at the lower level

43 B3 MicroFission Chambers

This diagnostic will provide the total neutron strength during the DT operation ie the high fusionpower phase

The neutron flux is typically measured by fission chambers containing 235U or other isotopesand filled typically with Argon gas at few atmospheres Micro-fission chambers (MFC) are de-ployed between the blanket modules and the inner shell of the Vacuum Vessel (VV) Four MFCmodules are located at two toroidal positions with two modules positioned in two different poloidallocations (figure 5) [10] By designing MFC attention has been paid to several issues such as vacuumleak rate of MFC high operational temperature tight clearance between the components and theblanket modules [11] RampD actitivity is required to ensure the proper functioning of the chamberssubjected to vibration and shock caused by various disruption events

Thermal analysis has shown that MFC can be cooled by conduction to the Vacuum Vesselreaching temperatures less than 200 ˚ C degrees if the SS module has a heat transfer coefficient gt

100 Wmminus2 Kminus1 [12]

Guard Vacuum pipes have been connected to the MFC modules to avoid detector gas entryinto the torus vacuum in the event of a fault

ndash 7 ndash

2012 JINST 7 C04012

a) b)

Figure 5 a) Two Microfission Chambers on VV Sector 1 b) detail of the Upper MFC module

44 B4 Neutron Flux Monitor

This diagnostic system will provide the total neutron strength during all phases of ITER operationFour modules containing each three Fission Chambers with different fissile content are at presentlocated in Equatorial Port 1 7 8 and 17 [13] (baseline definition of eq Port 8 and 17 has recentlychanged and as such these ports are under discussion)

The Neutron Flux Monitors (NFM) in ports 1 and 7 are used to measure DD neutron flux orthe insitu calibration flux whereas in ports 8 and 17 are used to detect DT neutron flux in bothmedium-power operation and full power operation respectively Different moderating materials(Be Graphite and B4C) with various thicknesses will be used for obtaining different sensitivities ofthe four NFMs modules with the aim of measure the total neutron strength from 1014 up to around1021 ns

RampD activities are going on to face the many implementation issues as described above (vac-uum leak high operational temperature magnetic stray fields etc)

The NFM in eq Port 7 is shown (figure 6) as example of the integration and interfaces issuesto be faced with Cryostat Thermal shield Bioshield and Neutral Beam Area

ndash 8 ndash

2012 JINST 7 C04012

VV NFM EQ7 Thermal Shield Cryostat

Figure 6 Neutron Flux Monitor integrated into Equatorial port 7

45 BC Divertor Neutron Flux Monitors

The Divertor Neutron Flux Monitors (DNFM) diagnostic [14] measures the time-resolved neutronemission from the ITER for both DD and DT plasmas providing the evaluation of the fusion power

Three DNFM modules will be installed in ITER Divertor Cassettes under the dome Thelocations of these modules are at three different toroidal positions Divertor Cassette 3 in lowerport 2 Divertor Cassette 21 in lower port 8 and Divertor Cassette 39 at lower port 14

Each module is composed of six fission chambers (FC) identical in dimension and coatedwith varying amount of 235U amp 238U fissile material

The six fission chambers are enclosed in two cylinders three U235 FC in one cylinder and threeU238 FC in the other one forming the DNFM module see figure 7

By developing a good and structuraly sound design some major challenges have been facedhigh nuclear and radiation power loads transient magnetic field causing large forces and momentsacting on the sturcture and non-negligible halo currents The Divertor water cooling system will beused also for the DNFM

ndash 9 ndash

2012 JINST 7 C04012

Figure 7 Integration of DNFM in Lower Port

Risk analysis has been carried out on the failure probability of the several DNFM weldingjoints causing water leakage in the torus vacuum Such failure event can cause the stop of theplasma operations for several weeks As mitigation action a DNFM prototype will be manufacturedfor test at high temperatures (up to 350 degrees C) and high water pressure (20 divide 40 MPa)

The use of the various time resolved flux detection systems (B3 B4 and BC) and use ofmultiple locations allow compensation of effects due to changes in plasma position or shape andprovides redundancy in case of detectors failure Together these systems give the global neutronsource strength from which the total fusion power is obtained and the measurement should beinsensitive to plasma position

46 B8 Neutron Activation System

This diagnostic system (NAS) provides time integrated measurements of the neutron fluence at theFirst Wall and total fusion power through neutronic calculations [15]

Foil samples are irradiated at positions near the FW Several irradiation ends have been po-sitioned between various Blanket Modules and on the VV inner wall as well in the Upper andEquatorial Ports (figure 8) The foils samples are transferred using a pneumatic capsule system tocounting stations through port feedthroughs

ndash 10 ndash

2012 JINST 7 C04012

a) b) c) Support IE

Figure 8 a) NAS transfer lines inside the Vacuum Vessel b) Poloidal position of the various IrradiationEnds c) Support and Irradiation End of Position F

High thermal loads are expected at the irradiation ends because of the plasma radiation andnuclear heating This fact precludes a number of materials for the capsule or sample such aspolyethylene In and Al Moreover EM forces induced by plasma disruptions require the design ofdedicated strong supports

RampD activity is on-going on the selection of material and mass of the samples in order to limitactivation and avoid counting saturation effect for the various ITER operation scenarios (from 300s up to 3000 s)

The NAS diagnostic plays a fundamental role in the ITER Neutron Calibration Strategy be-cause is the only neutron diagnostic having a dynamic range of 10 orders of magnitude due toappropriate selection of mass and foils materials

In ITER the extended nature of the plasma neutron source means that the spatial dependence ofthe sensitivity of the different neutron systems is needed and this is obtained by in-situ calibrationsin these a source of known intensity is moved inside the tokamak vacuum chamber and the responseof the neutron detectors is recorded For ITER a powerful source with an intensity sim 1011ns isneeded Account needs to be taken of the potential screening and scattering effects of the structurethat is supporting the neutron source and this is done by use of the neutron transport codes code

NAS will be absolutely calibrated during the ITER in situ neutron calibration and during theITER DD and DT phases with well-characterized plasma reference shots allowing the cross cali-bration of all other ITER neutron diagnostic systems [16 17]

ndash 11 ndash

2012 JINST 7 C04012

47 BB High Resolution Neutron Spectrometer

Provision is made for a later installation of high-resolution neutron spectrometers (HRNS) for DDand DT neutron spectroscopy by adding a collimator into the neutron camera on equatorial port 1(figure 9a b) so that instruments can be installed later

In order to measure the neutron energy distribution of DD and DT emission two or threeneutron spectroscopy instruments are required Different type of spectrometer will be considered(Time of Flight Thin Proton Recoil etc)

Because of the high neutron flux (around 109 ncm2 s) needed to meet ITER measurementrequirements (100 ms time resolution and 10divide 20 accuracy) a neutron beam dump and housingsurrounding HRNS for local shield (figure 9c) have to be installed in the Port Cell 1 in order tomeet radiation safety parameters

a) b)

ndash 12 ndash

2012 JINST 7 C04012

c)

Figure 9 a b c High Resolution Neutron Spectrometers

5 Diagnostic integration

ITER neutronic diagnostics are installed within the vacuum vessel in the port plugs in the divertorand in-cryostat The installation integrations issues and loading conditions in each of these fourlocations are different and this could preclude the use of the same design for one particular systempositioned in different locations

The integration of several diagnostics in the port plugs as well in the interspaces and portcells is a key issue Several ITER systems are interfacing with the diagnostics Remote Handlingfor maintenance provision of water cooling cabling and power supply Bioshield for radiationdose reduction etc Here after some examples of integration and interface matters are reportedconcerning the neutron diagnostics at different locations The same issues are faced also by forother diagnostics systems

Diagnostics in Equatorial Ports diagnostic equipment is mounted in a port plug assembly [18]The port plug geometry consists of two basic parts -the Diagnostic Shield Module (DSM) andthe generic port plug structure figure 10a The Diagnostic Shield Module (DSM) consists ofseveral parts the Diagnostic First Wall (DFW) which is designed to handle the radiant heat fluxfrom the plasma the Diagnostic Shielding Block (DSB) which is designed to handle most of theneutronic heat load and the supporting moduledrawer which fastens the components to the portplug structure and provides a platform or housing for the diagnostic components Figure 10b showsthe drawer in eq Port 1 containing the inport detectors and collimators of B1 RNC

ndash 13 ndash

2012 JINST 7 C04012

a) Typical Equatorial port plug geometry b) In port RNC drawer in EqPort1

Figure 10 Equatorial port plug geometry

Figure 11 Recess of Diagnostic First Wall

The port plug assembly provides also the primary vacuum boundary at that port as well as thefeed-out for diagnostic signals (windows and feedthroughs) and feed-in for control signals

In the DSM there are a number of apertures for diagnostic viewing In designing the RNCsight lines of the inport detectors and related focal points attention has been paid to minimize theaperture (figure 10b) in the DFW which is recessed with respect to the nearby blanket modules(figure 11) This recess is needed to reduce the plasma interaction with the DFW

As an example eq Port Plug 1 is shown (figure 12) which is the most congested with diag-nostics The rational behind this is the need for being as close as possible to the plasma Followingsystems will be installed Radial Neutron Camera Divertor Impurity Monitor Bolometers Mo-tional Stark Effect Many factors have to be taken into account in optimizing the distribution ofdiagnostics within the available ports Because of neutron streaming considerations typically nomore than two systems with large labyrinths can be installed in one port with large aperture sys-tems placed near the port centres distributed systems are located evenly toroidally sometimescoordinated with the location of corresponding systems in the upper ports

ndash 14 ndash

2012 JINST 7 C04012

a) b)

Figure 12 Equatorial port plug 1 a) back view of feedthroughs and connections b) front view

Diagnostics in Vacuum Vessel for the systems installed in the vacuum vessel like B3 MFC andB8 Neutron Activation System a support structure ensuring a very good thermal and mechanicalanchoring to the vacuum vessel wall is required This together with the routing and clamping of thecables and pipes adjusting the irradiation ends to the gaps between the blanket modules leads to acontinuous integration work assuring enough clearance to the neighbouring components and properdefinition of the large variety of in-vacuum vessel interfaces Even though partially shielded by theblanket modules the design of some of the components are challenged by the varying magneticfields high nuclear heat and the loop voltage created around the vessel Last but not least are theinterfacing loads like ECRH stray power and additional acceleration due to disruption events Thelatter one is more important to systems like MFC which should be tested in order to prove that theymaintain performance under shock and vibration

Diagnostics in Cryostat for the B4 Neutron flux monitor located in the in-cryostat area the loadconditions are less severe Because the system is mounted on an extended support structure attachedto the cryostat wall the major loads which should be taken into account are the acceleration due togravity acceleration due to seismic events and those during plasma disruptions and displacements

Diagnostics in Divertor the most demanding among all the mentioned locations is the divertorwhere the load conditions are very severe and it requires an active cooling of all diagnostic compo-nents This on the other hand creates an additional interface with the divertor cooling water branchof which is used for the cooling of the diagnostic components and a development of a good strategyfor a leak localization and detection

The BC Divertor Neutron Flux Monitor is mounted on a cassette body which is remote handleable through the divertor port The divertor dome provides an opportunity to place diagnosticsinside the vacuum vessel since it provides some degree of shelter from the neutron flux and plasmaradiation In the same cassette bolometers which are used for measuring the power of incidentelectromagnetic radiation are required to sit in the gap between two adjacent cassette bodies Thiscreates some integration issues as the one presented in figure 13

ndash 15 ndash

2012 JINST 7 C04012

Figure 13 Integration issue bolometers and DNFM ldquosharingrdquo the same support structure

The B2 Lower Vertical Neutron Camera (LVNC) is integrated into the lower port A genericdiagnostic rack to house diagnostics or optical relays in the port is being developed which willbe customized for each diagnostic while keeping the same interfaces with the vacuum vessel Thediagnostic rack is attached to the side walls of the port and includes features for alignment to thedivertor central cassette On the basis of the recently performed neutronic analysis it became clearthat the vertical camera could not co-exist with any optical system in the same port as this is thecase now Activity is going on the possible relocation either of LVNC or of the optical systems

One of the most difficult interfaces between the blanket system and the diagnostics is pre-sented by the integration of the B2 LVNC The line of sights of the detectors need to protrude theblanket shielding module 18 and the first wall exactly in the middle where the remote handlingattachment the hydraulic connector and the cooling channels are designed as shown in figure 14This fact can bring to the reduction of number of sight lines Design work is being carried out tosort out this problem

ndash 16 ndash

2012 JINST 7 C04012

Figure 14 Interface between Blanket Module 18 and lines of sight of the Vertical Neutron Camera

An overview of ITER neutron diagnostic systems and of the associated challenging engineer-ing and integration issues has been described The design of these systems has taken into accountthe experience gained on large devices which have pointed out the importance of simultaneuousmeasurements of the neutron spatial and energy distributions

The main advantage of this complete set-up of ITER neutron diagnostics is its installation andoperation from the begin of ITER nuclear operation compared to other machines like JET LHDTFTR JT 60 where the various neutron diagnostics have been installed during different machineoperational phases

Acknowledgments

The authors wish to thank ITER Diagnostics Team and the colleagues of ITER Members of JapanKorea China Europe and Russian Federation for useful discussions and collaboration

The work described was supported and carried out by ITER Organization together with ITERMembers and Domestic Agencies of Japan Korea China Europe and Russian Federation Part ofthis activity was performed within the framework of the European Fusion Development Agreement

Disclaimer The views and opinions expressed herein do not necessarily reflect those of the ITERorganization

ndash 17 ndash

2012 JINST 7 C04012

References

[1] AJH Donne et al Progress in the ITER physics basis Chapter 7 diagnostics Nucl Fusion 47(2007) 337

[2] G Vayakis ER Hodgson and V Voitsenya Plasma diagnostics for magnetic fusion researchChapter 12 generic diagnostic issues for a burning plasma experiment Fusion Sci Technol 53(2008) 699

[3] A Encheva L Bertalot B Macklin G Vayakis and C Walker Integration of ITER in-vesseldiagnostic components in the vacuum vessel Fusion Eng Des 84 (2009) 736

[4] A Krasilnikov et al Status of ITER neutron diagnostic development Nucl Fusion 45 (2005) 1503

[5] M Sasao et al Plasma diagnostics for magnetic fusion research Chapter 9 fusion productdiagnostics Fusion Sci Technol 53 (2008) 604

[6] FP Orsitto et al Burning plasmas diagnostics AIP Conf Proc 988 Varenna Italy (2007)

[7] L Petrizzi et al Neutronic design of the ITER radial neutron camera Fusion Sci Eng 82 (2007)1308

[8] AV Krasilnikov CI Walker YA Kashchuk and DV Prosvirin A multichannel neutron collimatorfor the ITER tokamak Kluwer AcademicPlenum Publishers Instrum Exp Tech 47 (2004) 139

[9] A Encheva et al Engineering aspects of integration of ITER divertor diagnostics Fusion Eng Des86 (2011) 1323

[10] M Ishikawa et al Design of microfission chamber for ITER operations Rev Sci Instrum 79 (2008)10E507

[11] A Encheva et al Structural integrity report for ITER micro-fission chamber ITER documentITER D 3TDURL

[12] T Nishitani et al Engineering design of the ITER invessel neutron monitor using micro-fissionchambers Fusion Eng Des 82 (2007) 1192

[13] J Yang et al Fusion neutron flux monitor for ITER Plasma Sci Technol 10 (2008) 141

[14] YA Kashchuk AV Krasilrsquonikov and DV Prosvirin A conceptual project for a divertor monitor ofthe neutron yield in the ITER Instrum Exp Tech 49 (2006) 179

[15] MS Cheon et al In-vessel design of ITER diagnostic neutron activation system Rev Sci Instrum79 (2008) 10E505

[16] L Bertalot et al A strategy for calibrating the neutron systems at ITER in 35th plasma physicsconference Crete Greece 2008 EPS Europhysics Conference Abstracts 32D (2008) O2001httpepsppdepflchHersonissosstarthtm

[17] M Sasao L Bertalot M Ishikawa and S Popovichev Strategy for the absolute neutron emissionmeasurement on ITER Rev Sci Instrum 81 (2010) 10D329

[18] S Pitcher et al System Design Description Document (DDD) diagnostic generic equatorial portplug ITER document ITER D 3U8JU7

ndash 18 ndash

2012 JINST 7 C04012

Figure 1 Diagnostics locations on ITER

ITER diagnostic equipment is integrated in a total of 6 equatorial and 12 upper ports of thevacuum vessel 16 divertor cassettes and internally in many vacuum vessel locations figure 1

ITER environment is a quite harsh environment [2] The various diagnostic systems will haveto withstand high neutron flux (up to 1014 ncm2s with 14 MeV neutron energy) high temperaturesdue to plasma radiation and nuclear heating (up to 1000 C degrees) and magnetic field (up to 6 T)as well significant electromagnetic noise due to the auxiliary radiofrequency heating systems Par-ticular efforts are devoted to the maintainability of the various diagnostic systems in particular forthe In vessel ones which face the highest electromagnetic (EM) and nuclear loads [3] Differentlyfrom the diagnostics of the large tokamak devices (JET TFTR and JT 60) ITER diagnostics haveto be designed built and operated within full nuclear regulatory requirements

3 Neutron diagnostics role

Neutron measurement has been considered to be one of the major diagnostic methods to be usedsince the initiation of the ITER design phase The neutron diagnostics will provide key informationon plasma physics [4ndash6] protection and control issues

In the ITER project requirements different classes of parameters have been defined for ma-chine protection (Group 1a1) basic control (Group 1a2) and advanced control (Group 1b) Theneutron diagnostics have to measure the following parameters table 1

ndash 2 ndash

2012 JINST 7 C04012

Table 1 Neutron parameters and roles

Parameter Group

Total Neutron flux 1a1

Fusion power 1a2

Fusion density 1a2

Fluence 1a2

Neutron and alfa source 1b

Fuel ratio 1a2

Ion temperature profile 1b

Among the many plasma and first wall parameters to be measured the neutron diagnostics willallow evaluation of the neutron emissivity ie the fusion power which plays a key role for machineprotection as well for plasma optimization and for achieving ITER goals in particular the fusiongain factor Q related to the reactor performance ITER expected neutron emission strength spansover 7 decades (from 1014 up to almost 1021 ns) ITER needs various neutron diagnostic systemsable to measure the neutron emissivity within 10 accuracy with a temporal resolution of 1 msand spatial resolution of a tenth of the minor plasma radius ie 200 mm

The neutron fluence at the First Wall (FW) delivers information of the damage expected on thematerials facing the plasma

Neutron emission profile measurements deliver data on the alpha birth source Self-heating ofDT plasma by fusion-produced alpha particles is the key to realize self sustainable thermonuclearplasma in a fusion reactor

Another important parameter is the fuel ratio ie the amount of tritium and deuterium (nTnD)in the plasma measured by means of neutron spectroscopy which can provide also information onthe plasma ion temperature ITER neutron diagnostic sub systems are listed in table 2

ndash 3 ndash

2012 JINST 7 C04012

Table 2 ITER neutron diagnostics and related neutron parameters

Subsystem ParameterB1 Radial Neutron Camera Neutronalpha source profile

Total neutron source strengthIon temperature profileFuel ratioNeutron fluence on FW wall

B2 Vertical Neutron Camera Neutronalpha source profileTotal neutron source strengthIon temperature profileFuel ratioNeutron fluence on FW wall

B3 MicroFission Chambers Total neutron source strengthNeutron fluence on FW wall

B4 Neutron Flux Monitors Total neutron source strengthNeutron fluence on FW wall

B8 Neutron Activation System Neutron fluence on FW wallTotal neutron source strength

BB High Resolution Neutron Spec-trometers (Enabled)

Plasma Core Ion temperatureCore Plasma Fuel Ratio

BC Divertor Neutron Flux Monitors Total neutron source strengthNeutron fluence on the Divertor

Diagnostic subsystems responding to each measurement require measurement backup pro-vided by redundancy within the primary diagnostic by multiple primary diagnostics andor byback-up or supplementary diagnostics The role classification is as follows

bull Primary = diagnostic is well suited to the measurement

bull Backup = diagnostic provides similar data to primary but has some

limitations

bull Supplementary = diagnostic validates or calibrates the measurement but is not complete initself

The Neutron Diagnostics matrix flow down is here below shown (figure 2)

ndash 4 ndash

2012 JINST 7 C04012

Figure 2 Neutron Diagnostic matrix flow down

4 Neutron diagnostics

41 B1 Radial Neutron Camera

The Radial Neutron Camera (RNC) [7] consists of a fan-shaped array of 36 flight tubes viewingthe plasma through a vertical slot in the blanket shield module of Equatorial Port Plug 1 The sightlines intersect at a common aperture defined by the port plug and penetrate the vacuum vessel cryo-stat and biological shield through stainless steel windows (figure 3) Each flight tube culminatesin a set of detectors chosen to provide the required range of sensitivity and temporal and spectralresolution Some of the viewing chords will be equipped with compact neutron spectrometersenabling the system to provide emissivity-weighted chord-averaged measurements of ion temper-ature Appropriate spectrometers have not yet been selected but there are several (scintillatorschemical vapoured diamonds etc) that could meet the measurement requirements by further RampDactivity Because of the length of the ports the spatial coverage in the vertical direction of this partof the camera is limited Additionally 8 sight lines with collimators and detectors mounted in theport plug are included to give measurements in the outer regions of the plasma In this locationthere is reduced space for the detectors and this will limit the type and number of detectors andspectrometers that can be accommodated The maintenance of the detectors will also be more dif-ficult but the gain in spatial coverage is significant The in-port detectors have to withstand hightemperature (up to 250 degrees because of Vacuum Vessel baking)) and magnetic fields up sim 4 Tand a transient magnetic field of approx 10Ts Under these load conditions the system requiresa feasible support structure dedicated cooling and magnetic shielding Particular care is given tothe electrical connections of the in port detectors by using triax mineral insulated cables aiming tohigh noise rejection Moreover the in port detectors are enveloped in a Stainless Steel housing fornot affecting the torus vacuum due to a possible leakage of the detector filling gas

ndash 5 ndash

2012 JINST 7 C04012

Figure 3 Radial Neutron Camera with its lines of sight relative to the plasma with an additional obliqueview onto the outside of the port plug

42 B2 Vertical Neutron Camera

Because ITER does not have vertical ports it is difficult to measure the neutron emission in avertical direction (necessary for combination with the radial measurements for tomographic recon-structions of the neutron source profile) A concept for the vertically viewing camera (VNC) isbeen designed [8] This is to mount a camera adjacent to a port at the lower level The plasmawould be viewed through neutron windows in the vacuum vessel and through a slot in the divertorcassette and through the Blanket Shield Module (BSM) 18 Due to limited space only ten linesof sight are viewing the plasma with coverage up to 08 minor radius The cut outs in the Diver-tor Cassette and in BSM 18 require design modification of the interfacing components and morededicated analysis work [9] (figure 4) Mineral insulated cables will connect the detectors to thepreamplifiers unit located in the Lower Port Cell The detectors will be mounted in a box in orderto avoid detector filling gas leakage to the torus vacuum

ndash 6 ndash

2012 JINST 7 C04012

Figure 4 Vertical Neutron Camera mounted adjacent to a port at the lower level

43 B3 MicroFission Chambers

This diagnostic will provide the total neutron strength during the DT operation ie the high fusionpower phase

The neutron flux is typically measured by fission chambers containing 235U or other isotopesand filled typically with Argon gas at few atmospheres Micro-fission chambers (MFC) are de-ployed between the blanket modules and the inner shell of the Vacuum Vessel (VV) Four MFCmodules are located at two toroidal positions with two modules positioned in two different poloidallocations (figure 5) [10] By designing MFC attention has been paid to several issues such as vacuumleak rate of MFC high operational temperature tight clearance between the components and theblanket modules [11] RampD actitivity is required to ensure the proper functioning of the chamberssubjected to vibration and shock caused by various disruption events

Thermal analysis has shown that MFC can be cooled by conduction to the Vacuum Vesselreaching temperatures less than 200 ˚ C degrees if the SS module has a heat transfer coefficient gt

100 Wmminus2 Kminus1 [12]

Guard Vacuum pipes have been connected to the MFC modules to avoid detector gas entryinto the torus vacuum in the event of a fault

ndash 7 ndash

2012 JINST 7 C04012

a) b)

Figure 5 a) Two Microfission Chambers on VV Sector 1 b) detail of the Upper MFC module

44 B4 Neutron Flux Monitor

This diagnostic system will provide the total neutron strength during all phases of ITER operationFour modules containing each three Fission Chambers with different fissile content are at presentlocated in Equatorial Port 1 7 8 and 17 [13] (baseline definition of eq Port 8 and 17 has recentlychanged and as such these ports are under discussion)

The Neutron Flux Monitors (NFM) in ports 1 and 7 are used to measure DD neutron flux orthe insitu calibration flux whereas in ports 8 and 17 are used to detect DT neutron flux in bothmedium-power operation and full power operation respectively Different moderating materials(Be Graphite and B4C) with various thicknesses will be used for obtaining different sensitivities ofthe four NFMs modules with the aim of measure the total neutron strength from 1014 up to around1021 ns

RampD activities are going on to face the many implementation issues as described above (vac-uum leak high operational temperature magnetic stray fields etc)

The NFM in eq Port 7 is shown (figure 6) as example of the integration and interfaces issuesto be faced with Cryostat Thermal shield Bioshield and Neutral Beam Area

ndash 8 ndash

2012 JINST 7 C04012

VV NFM EQ7 Thermal Shield Cryostat

Figure 6 Neutron Flux Monitor integrated into Equatorial port 7

45 BC Divertor Neutron Flux Monitors

The Divertor Neutron Flux Monitors (DNFM) diagnostic [14] measures the time-resolved neutronemission from the ITER for both DD and DT plasmas providing the evaluation of the fusion power

Three DNFM modules will be installed in ITER Divertor Cassettes under the dome Thelocations of these modules are at three different toroidal positions Divertor Cassette 3 in lowerport 2 Divertor Cassette 21 in lower port 8 and Divertor Cassette 39 at lower port 14

Each module is composed of six fission chambers (FC) identical in dimension and coatedwith varying amount of 235U amp 238U fissile material

The six fission chambers are enclosed in two cylinders three U235 FC in one cylinder and threeU238 FC in the other one forming the DNFM module see figure 7

By developing a good and structuraly sound design some major challenges have been facedhigh nuclear and radiation power loads transient magnetic field causing large forces and momentsacting on the sturcture and non-negligible halo currents The Divertor water cooling system will beused also for the DNFM

ndash 9 ndash

2012 JINST 7 C04012

Figure 7 Integration of DNFM in Lower Port

Risk analysis has been carried out on the failure probability of the several DNFM weldingjoints causing water leakage in the torus vacuum Such failure event can cause the stop of theplasma operations for several weeks As mitigation action a DNFM prototype will be manufacturedfor test at high temperatures (up to 350 degrees C) and high water pressure (20 divide 40 MPa)

The use of the various time resolved flux detection systems (B3 B4 and BC) and use ofmultiple locations allow compensation of effects due to changes in plasma position or shape andprovides redundancy in case of detectors failure Together these systems give the global neutronsource strength from which the total fusion power is obtained and the measurement should beinsensitive to plasma position

46 B8 Neutron Activation System

This diagnostic system (NAS) provides time integrated measurements of the neutron fluence at theFirst Wall and total fusion power through neutronic calculations [15]

Foil samples are irradiated at positions near the FW Several irradiation ends have been po-sitioned between various Blanket Modules and on the VV inner wall as well in the Upper andEquatorial Ports (figure 8) The foils samples are transferred using a pneumatic capsule system tocounting stations through port feedthroughs

ndash 10 ndash

2012 JINST 7 C04012

a) b) c) Support IE

Figure 8 a) NAS transfer lines inside the Vacuum Vessel b) Poloidal position of the various IrradiationEnds c) Support and Irradiation End of Position F

High thermal loads are expected at the irradiation ends because of the plasma radiation andnuclear heating This fact precludes a number of materials for the capsule or sample such aspolyethylene In and Al Moreover EM forces induced by plasma disruptions require the design ofdedicated strong supports

RampD activity is on-going on the selection of material and mass of the samples in order to limitactivation and avoid counting saturation effect for the various ITER operation scenarios (from 300s up to 3000 s)

The NAS diagnostic plays a fundamental role in the ITER Neutron Calibration Strategy be-cause is the only neutron diagnostic having a dynamic range of 10 orders of magnitude due toappropriate selection of mass and foils materials

In ITER the extended nature of the plasma neutron source means that the spatial dependence ofthe sensitivity of the different neutron systems is needed and this is obtained by in-situ calibrationsin these a source of known intensity is moved inside the tokamak vacuum chamber and the responseof the neutron detectors is recorded For ITER a powerful source with an intensity sim 1011ns isneeded Account needs to be taken of the potential screening and scattering effects of the structurethat is supporting the neutron source and this is done by use of the neutron transport codes code

NAS will be absolutely calibrated during the ITER in situ neutron calibration and during theITER DD and DT phases with well-characterized plasma reference shots allowing the cross cali-bration of all other ITER neutron diagnostic systems [16 17]

ndash 11 ndash

2012 JINST 7 C04012

47 BB High Resolution Neutron Spectrometer

Provision is made for a later installation of high-resolution neutron spectrometers (HRNS) for DDand DT neutron spectroscopy by adding a collimator into the neutron camera on equatorial port 1(figure 9a b) so that instruments can be installed later

In order to measure the neutron energy distribution of DD and DT emission two or threeneutron spectroscopy instruments are required Different type of spectrometer will be considered(Time of Flight Thin Proton Recoil etc)

Because of the high neutron flux (around 109 ncm2 s) needed to meet ITER measurementrequirements (100 ms time resolution and 10divide 20 accuracy) a neutron beam dump and housingsurrounding HRNS for local shield (figure 9c) have to be installed in the Port Cell 1 in order tomeet radiation safety parameters

a) b)

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2012 JINST 7 C04012

c)

Figure 9 a b c High Resolution Neutron Spectrometers

5 Diagnostic integration

ITER neutronic diagnostics are installed within the vacuum vessel in the port plugs in the divertorand in-cryostat The installation integrations issues and loading conditions in each of these fourlocations are different and this could preclude the use of the same design for one particular systempositioned in different locations

The integration of several diagnostics in the port plugs as well in the interspaces and portcells is a key issue Several ITER systems are interfacing with the diagnostics Remote Handlingfor maintenance provision of water cooling cabling and power supply Bioshield for radiationdose reduction etc Here after some examples of integration and interface matters are reportedconcerning the neutron diagnostics at different locations The same issues are faced also by forother diagnostics systems

Diagnostics in Equatorial Ports diagnostic equipment is mounted in a port plug assembly [18]The port plug geometry consists of two basic parts -the Diagnostic Shield Module (DSM) andthe generic port plug structure figure 10a The Diagnostic Shield Module (DSM) consists ofseveral parts the Diagnostic First Wall (DFW) which is designed to handle the radiant heat fluxfrom the plasma the Diagnostic Shielding Block (DSB) which is designed to handle most of theneutronic heat load and the supporting moduledrawer which fastens the components to the portplug structure and provides a platform or housing for the diagnostic components Figure 10b showsthe drawer in eq Port 1 containing the inport detectors and collimators of B1 RNC

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a) Typical Equatorial port plug geometry b) In port RNC drawer in EqPort1

Figure 10 Equatorial port plug geometry

Figure 11 Recess of Diagnostic First Wall

The port plug assembly provides also the primary vacuum boundary at that port as well as thefeed-out for diagnostic signals (windows and feedthroughs) and feed-in for control signals

In the DSM there are a number of apertures for diagnostic viewing In designing the RNCsight lines of the inport detectors and related focal points attention has been paid to minimize theaperture (figure 10b) in the DFW which is recessed with respect to the nearby blanket modules(figure 11) This recess is needed to reduce the plasma interaction with the DFW

As an example eq Port Plug 1 is shown (figure 12) which is the most congested with diag-nostics The rational behind this is the need for being as close as possible to the plasma Followingsystems will be installed Radial Neutron Camera Divertor Impurity Monitor Bolometers Mo-tional Stark Effect Many factors have to be taken into account in optimizing the distribution ofdiagnostics within the available ports Because of neutron streaming considerations typically nomore than two systems with large labyrinths can be installed in one port with large aperture sys-tems placed near the port centres distributed systems are located evenly toroidally sometimescoordinated with the location of corresponding systems in the upper ports

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2012 JINST 7 C04012

a) b)

Figure 12 Equatorial port plug 1 a) back view of feedthroughs and connections b) front view

Diagnostics in Vacuum Vessel for the systems installed in the vacuum vessel like B3 MFC andB8 Neutron Activation System a support structure ensuring a very good thermal and mechanicalanchoring to the vacuum vessel wall is required This together with the routing and clamping of thecables and pipes adjusting the irradiation ends to the gaps between the blanket modules leads to acontinuous integration work assuring enough clearance to the neighbouring components and properdefinition of the large variety of in-vacuum vessel interfaces Even though partially shielded by theblanket modules the design of some of the components are challenged by the varying magneticfields high nuclear heat and the loop voltage created around the vessel Last but not least are theinterfacing loads like ECRH stray power and additional acceleration due to disruption events Thelatter one is more important to systems like MFC which should be tested in order to prove that theymaintain performance under shock and vibration

Diagnostics in Cryostat for the B4 Neutron flux monitor located in the in-cryostat area the loadconditions are less severe Because the system is mounted on an extended support structure attachedto the cryostat wall the major loads which should be taken into account are the acceleration due togravity acceleration due to seismic events and those during plasma disruptions and displacements

Diagnostics in Divertor the most demanding among all the mentioned locations is the divertorwhere the load conditions are very severe and it requires an active cooling of all diagnostic compo-nents This on the other hand creates an additional interface with the divertor cooling water branchof which is used for the cooling of the diagnostic components and a development of a good strategyfor a leak localization and detection

The BC Divertor Neutron Flux Monitor is mounted on a cassette body which is remote handleable through the divertor port The divertor dome provides an opportunity to place diagnosticsinside the vacuum vessel since it provides some degree of shelter from the neutron flux and plasmaradiation In the same cassette bolometers which are used for measuring the power of incidentelectromagnetic radiation are required to sit in the gap between two adjacent cassette bodies Thiscreates some integration issues as the one presented in figure 13

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2012 JINST 7 C04012

Figure 13 Integration issue bolometers and DNFM ldquosharingrdquo the same support structure

The B2 Lower Vertical Neutron Camera (LVNC) is integrated into the lower port A genericdiagnostic rack to house diagnostics or optical relays in the port is being developed which willbe customized for each diagnostic while keeping the same interfaces with the vacuum vessel Thediagnostic rack is attached to the side walls of the port and includes features for alignment to thedivertor central cassette On the basis of the recently performed neutronic analysis it became clearthat the vertical camera could not co-exist with any optical system in the same port as this is thecase now Activity is going on the possible relocation either of LVNC or of the optical systems

One of the most difficult interfaces between the blanket system and the diagnostics is pre-sented by the integration of the B2 LVNC The line of sights of the detectors need to protrude theblanket shielding module 18 and the first wall exactly in the middle where the remote handlingattachment the hydraulic connector and the cooling channels are designed as shown in figure 14This fact can bring to the reduction of number of sight lines Design work is being carried out tosort out this problem

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2012 JINST 7 C04012

Figure 14 Interface between Blanket Module 18 and lines of sight of the Vertical Neutron Camera

An overview of ITER neutron diagnostic systems and of the associated challenging engineer-ing and integration issues has been described The design of these systems has taken into accountthe experience gained on large devices which have pointed out the importance of simultaneuousmeasurements of the neutron spatial and energy distributions

The main advantage of this complete set-up of ITER neutron diagnostics is its installation andoperation from the begin of ITER nuclear operation compared to other machines like JET LHDTFTR JT 60 where the various neutron diagnostics have been installed during different machineoperational phases

Acknowledgments

The authors wish to thank ITER Diagnostics Team and the colleagues of ITER Members of JapanKorea China Europe and Russian Federation for useful discussions and collaboration

The work described was supported and carried out by ITER Organization together with ITERMembers and Domestic Agencies of Japan Korea China Europe and Russian Federation Part ofthis activity was performed within the framework of the European Fusion Development Agreement

Disclaimer The views and opinions expressed herein do not necessarily reflect those of the ITERorganization

ndash 17 ndash

2012 JINST 7 C04012

References

[1] AJH Donne et al Progress in the ITER physics basis Chapter 7 diagnostics Nucl Fusion 47(2007) 337

[2] G Vayakis ER Hodgson and V Voitsenya Plasma diagnostics for magnetic fusion researchChapter 12 generic diagnostic issues for a burning plasma experiment Fusion Sci Technol 53(2008) 699

[3] A Encheva L Bertalot B Macklin G Vayakis and C Walker Integration of ITER in-vesseldiagnostic components in the vacuum vessel Fusion Eng Des 84 (2009) 736

[4] A Krasilnikov et al Status of ITER neutron diagnostic development Nucl Fusion 45 (2005) 1503

[5] M Sasao et al Plasma diagnostics for magnetic fusion research Chapter 9 fusion productdiagnostics Fusion Sci Technol 53 (2008) 604

[6] FP Orsitto et al Burning plasmas diagnostics AIP Conf Proc 988 Varenna Italy (2007)

[7] L Petrizzi et al Neutronic design of the ITER radial neutron camera Fusion Sci Eng 82 (2007)1308

[8] AV Krasilnikov CI Walker YA Kashchuk and DV Prosvirin A multichannel neutron collimatorfor the ITER tokamak Kluwer AcademicPlenum Publishers Instrum Exp Tech 47 (2004) 139

[9] A Encheva et al Engineering aspects of integration of ITER divertor diagnostics Fusion Eng Des86 (2011) 1323

[10] M Ishikawa et al Design of microfission chamber for ITER operations Rev Sci Instrum 79 (2008)10E507

[11] A Encheva et al Structural integrity report for ITER micro-fission chamber ITER documentITER D 3TDURL

[12] T Nishitani et al Engineering design of the ITER invessel neutron monitor using micro-fissionchambers Fusion Eng Des 82 (2007) 1192

[13] J Yang et al Fusion neutron flux monitor for ITER Plasma Sci Technol 10 (2008) 141

[14] YA Kashchuk AV Krasilrsquonikov and DV Prosvirin A conceptual project for a divertor monitor ofthe neutron yield in the ITER Instrum Exp Tech 49 (2006) 179

[15] MS Cheon et al In-vessel design of ITER diagnostic neutron activation system Rev Sci Instrum79 (2008) 10E505

[16] L Bertalot et al A strategy for calibrating the neutron systems at ITER in 35th plasma physicsconference Crete Greece 2008 EPS Europhysics Conference Abstracts 32D (2008) O2001httpepsppdepflchHersonissosstarthtm

[17] M Sasao L Bertalot M Ishikawa and S Popovichev Strategy for the absolute neutron emissionmeasurement on ITER Rev Sci Instrum 81 (2010) 10D329

[18] S Pitcher et al System Design Description Document (DDD) diagnostic generic equatorial portplug ITER document ITER D 3U8JU7

ndash 18 ndash

2012 JINST 7 C04012

Table 1 Neutron parameters and roles

Parameter Group

Total Neutron flux 1a1

Fusion power 1a2

Fusion density 1a2

Fluence 1a2

Neutron and alfa source 1b

Fuel ratio 1a2

Ion temperature profile 1b

Among the many plasma and first wall parameters to be measured the neutron diagnostics willallow evaluation of the neutron emissivity ie the fusion power which plays a key role for machineprotection as well for plasma optimization and for achieving ITER goals in particular the fusiongain factor Q related to the reactor performance ITER expected neutron emission strength spansover 7 decades (from 1014 up to almost 1021 ns) ITER needs various neutron diagnostic systemsable to measure the neutron emissivity within 10 accuracy with a temporal resolution of 1 msand spatial resolution of a tenth of the minor plasma radius ie 200 mm

The neutron fluence at the First Wall (FW) delivers information of the damage expected on thematerials facing the plasma

Neutron emission profile measurements deliver data on the alpha birth source Self-heating ofDT plasma by fusion-produced alpha particles is the key to realize self sustainable thermonuclearplasma in a fusion reactor

Another important parameter is the fuel ratio ie the amount of tritium and deuterium (nTnD)in the plasma measured by means of neutron spectroscopy which can provide also information onthe plasma ion temperature ITER neutron diagnostic sub systems are listed in table 2

ndash 3 ndash

2012 JINST 7 C04012

Table 2 ITER neutron diagnostics and related neutron parameters

Subsystem ParameterB1 Radial Neutron Camera Neutronalpha source profile

Total neutron source strengthIon temperature profileFuel ratioNeutron fluence on FW wall

B2 Vertical Neutron Camera Neutronalpha source profileTotal neutron source strengthIon temperature profileFuel ratioNeutron fluence on FW wall

B3 MicroFission Chambers Total neutron source strengthNeutron fluence on FW wall

B4 Neutron Flux Monitors Total neutron source strengthNeutron fluence on FW wall

B8 Neutron Activation System Neutron fluence on FW wallTotal neutron source strength

BB High Resolution Neutron Spec-trometers (Enabled)

Plasma Core Ion temperatureCore Plasma Fuel Ratio

BC Divertor Neutron Flux Monitors Total neutron source strengthNeutron fluence on the Divertor

Diagnostic subsystems responding to each measurement require measurement backup pro-vided by redundancy within the primary diagnostic by multiple primary diagnostics andor byback-up or supplementary diagnostics The role classification is as follows

bull Primary = diagnostic is well suited to the measurement

bull Backup = diagnostic provides similar data to primary but has some

limitations

bull Supplementary = diagnostic validates or calibrates the measurement but is not complete initself

The Neutron Diagnostics matrix flow down is here below shown (figure 2)

ndash 4 ndash

2012 JINST 7 C04012

Figure 2 Neutron Diagnostic matrix flow down

4 Neutron diagnostics

41 B1 Radial Neutron Camera

The Radial Neutron Camera (RNC) [7] consists of a fan-shaped array of 36 flight tubes viewingthe plasma through a vertical slot in the blanket shield module of Equatorial Port Plug 1 The sightlines intersect at a common aperture defined by the port plug and penetrate the vacuum vessel cryo-stat and biological shield through stainless steel windows (figure 3) Each flight tube culminatesin a set of detectors chosen to provide the required range of sensitivity and temporal and spectralresolution Some of the viewing chords will be equipped with compact neutron spectrometersenabling the system to provide emissivity-weighted chord-averaged measurements of ion temper-ature Appropriate spectrometers have not yet been selected but there are several (scintillatorschemical vapoured diamonds etc) that could meet the measurement requirements by further RampDactivity Because of the length of the ports the spatial coverage in the vertical direction of this partof the camera is limited Additionally 8 sight lines with collimators and detectors mounted in theport plug are included to give measurements in the outer regions of the plasma In this locationthere is reduced space for the detectors and this will limit the type and number of detectors andspectrometers that can be accommodated The maintenance of the detectors will also be more dif-ficult but the gain in spatial coverage is significant The in-port detectors have to withstand hightemperature (up to 250 degrees because of Vacuum Vessel baking)) and magnetic fields up sim 4 Tand a transient magnetic field of approx 10Ts Under these load conditions the system requiresa feasible support structure dedicated cooling and magnetic shielding Particular care is given tothe electrical connections of the in port detectors by using triax mineral insulated cables aiming tohigh noise rejection Moreover the in port detectors are enveloped in a Stainless Steel housing fornot affecting the torus vacuum due to a possible leakage of the detector filling gas

ndash 5 ndash

2012 JINST 7 C04012

Figure 3 Radial Neutron Camera with its lines of sight relative to the plasma with an additional obliqueview onto the outside of the port plug

42 B2 Vertical Neutron Camera

Because ITER does not have vertical ports it is difficult to measure the neutron emission in avertical direction (necessary for combination with the radial measurements for tomographic recon-structions of the neutron source profile) A concept for the vertically viewing camera (VNC) isbeen designed [8] This is to mount a camera adjacent to a port at the lower level The plasmawould be viewed through neutron windows in the vacuum vessel and through a slot in the divertorcassette and through the Blanket Shield Module (BSM) 18 Due to limited space only ten linesof sight are viewing the plasma with coverage up to 08 minor radius The cut outs in the Diver-tor Cassette and in BSM 18 require design modification of the interfacing components and morededicated analysis work [9] (figure 4) Mineral insulated cables will connect the detectors to thepreamplifiers unit located in the Lower Port Cell The detectors will be mounted in a box in orderto avoid detector filling gas leakage to the torus vacuum

ndash 6 ndash

2012 JINST 7 C04012

Figure 4 Vertical Neutron Camera mounted adjacent to a port at the lower level

43 B3 MicroFission Chambers

This diagnostic will provide the total neutron strength during the DT operation ie the high fusionpower phase

The neutron flux is typically measured by fission chambers containing 235U or other isotopesand filled typically with Argon gas at few atmospheres Micro-fission chambers (MFC) are de-ployed between the blanket modules and the inner shell of the Vacuum Vessel (VV) Four MFCmodules are located at two toroidal positions with two modules positioned in two different poloidallocations (figure 5) [10] By designing MFC attention has been paid to several issues such as vacuumleak rate of MFC high operational temperature tight clearance between the components and theblanket modules [11] RampD actitivity is required to ensure the proper functioning of the chamberssubjected to vibration and shock caused by various disruption events

Thermal analysis has shown that MFC can be cooled by conduction to the Vacuum Vesselreaching temperatures less than 200 ˚ C degrees if the SS module has a heat transfer coefficient gt

100 Wmminus2 Kminus1 [12]

Guard Vacuum pipes have been connected to the MFC modules to avoid detector gas entryinto the torus vacuum in the event of a fault

ndash 7 ndash

2012 JINST 7 C04012

a) b)

Figure 5 a) Two Microfission Chambers on VV Sector 1 b) detail of the Upper MFC module

44 B4 Neutron Flux Monitor

This diagnostic system will provide the total neutron strength during all phases of ITER operationFour modules containing each three Fission Chambers with different fissile content are at presentlocated in Equatorial Port 1 7 8 and 17 [13] (baseline definition of eq Port 8 and 17 has recentlychanged and as such these ports are under discussion)

The Neutron Flux Monitors (NFM) in ports 1 and 7 are used to measure DD neutron flux orthe insitu calibration flux whereas in ports 8 and 17 are used to detect DT neutron flux in bothmedium-power operation and full power operation respectively Different moderating materials(Be Graphite and B4C) with various thicknesses will be used for obtaining different sensitivities ofthe four NFMs modules with the aim of measure the total neutron strength from 1014 up to around1021 ns

RampD activities are going on to face the many implementation issues as described above (vac-uum leak high operational temperature magnetic stray fields etc)

The NFM in eq Port 7 is shown (figure 6) as example of the integration and interfaces issuesto be faced with Cryostat Thermal shield Bioshield and Neutral Beam Area

ndash 8 ndash

2012 JINST 7 C04012

VV NFM EQ7 Thermal Shield Cryostat

Figure 6 Neutron Flux Monitor integrated into Equatorial port 7

45 BC Divertor Neutron Flux Monitors

The Divertor Neutron Flux Monitors (DNFM) diagnostic [14] measures the time-resolved neutronemission from the ITER for both DD and DT plasmas providing the evaluation of the fusion power

Three DNFM modules will be installed in ITER Divertor Cassettes under the dome Thelocations of these modules are at three different toroidal positions Divertor Cassette 3 in lowerport 2 Divertor Cassette 21 in lower port 8 and Divertor Cassette 39 at lower port 14

Each module is composed of six fission chambers (FC) identical in dimension and coatedwith varying amount of 235U amp 238U fissile material

The six fission chambers are enclosed in two cylinders three U235 FC in one cylinder and threeU238 FC in the other one forming the DNFM module see figure 7

By developing a good and structuraly sound design some major challenges have been facedhigh nuclear and radiation power loads transient magnetic field causing large forces and momentsacting on the sturcture and non-negligible halo currents The Divertor water cooling system will beused also for the DNFM

ndash 9 ndash

2012 JINST 7 C04012

Figure 7 Integration of DNFM in Lower Port

Risk analysis has been carried out on the failure probability of the several DNFM weldingjoints causing water leakage in the torus vacuum Such failure event can cause the stop of theplasma operations for several weeks As mitigation action a DNFM prototype will be manufacturedfor test at high temperatures (up to 350 degrees C) and high water pressure (20 divide 40 MPa)

The use of the various time resolved flux detection systems (B3 B4 and BC) and use ofmultiple locations allow compensation of effects due to changes in plasma position or shape andprovides redundancy in case of detectors failure Together these systems give the global neutronsource strength from which the total fusion power is obtained and the measurement should beinsensitive to plasma position

46 B8 Neutron Activation System

This diagnostic system (NAS) provides time integrated measurements of the neutron fluence at theFirst Wall and total fusion power through neutronic calculations [15]

Foil samples are irradiated at positions near the FW Several irradiation ends have been po-sitioned between various Blanket Modules and on the VV inner wall as well in the Upper andEquatorial Ports (figure 8) The foils samples are transferred using a pneumatic capsule system tocounting stations through port feedthroughs

ndash 10 ndash

2012 JINST 7 C04012

a) b) c) Support IE

Figure 8 a) NAS transfer lines inside the Vacuum Vessel b) Poloidal position of the various IrradiationEnds c) Support and Irradiation End of Position F

High thermal loads are expected at the irradiation ends because of the plasma radiation andnuclear heating This fact precludes a number of materials for the capsule or sample such aspolyethylene In and Al Moreover EM forces induced by plasma disruptions require the design ofdedicated strong supports

RampD activity is on-going on the selection of material and mass of the samples in order to limitactivation and avoid counting saturation effect for the various ITER operation scenarios (from 300s up to 3000 s)

The NAS diagnostic plays a fundamental role in the ITER Neutron Calibration Strategy be-cause is the only neutron diagnostic having a dynamic range of 10 orders of magnitude due toappropriate selection of mass and foils materials

In ITER the extended nature of the plasma neutron source means that the spatial dependence ofthe sensitivity of the different neutron systems is needed and this is obtained by in-situ calibrationsin these a source of known intensity is moved inside the tokamak vacuum chamber and the responseof the neutron detectors is recorded For ITER a powerful source with an intensity sim 1011ns isneeded Account needs to be taken of the potential screening and scattering effects of the structurethat is supporting the neutron source and this is done by use of the neutron transport codes code

NAS will be absolutely calibrated during the ITER in situ neutron calibration and during theITER DD and DT phases with well-characterized plasma reference shots allowing the cross cali-bration of all other ITER neutron diagnostic systems [16 17]

ndash 11 ndash

2012 JINST 7 C04012

47 BB High Resolution Neutron Spectrometer

Provision is made for a later installation of high-resolution neutron spectrometers (HRNS) for DDand DT neutron spectroscopy by adding a collimator into the neutron camera on equatorial port 1(figure 9a b) so that instruments can be installed later

In order to measure the neutron energy distribution of DD and DT emission two or threeneutron spectroscopy instruments are required Different type of spectrometer will be considered(Time of Flight Thin Proton Recoil etc)

Because of the high neutron flux (around 109 ncm2 s) needed to meet ITER measurementrequirements (100 ms time resolution and 10divide 20 accuracy) a neutron beam dump and housingsurrounding HRNS for local shield (figure 9c) have to be installed in the Port Cell 1 in order tomeet radiation safety parameters

a) b)

ndash 12 ndash

2012 JINST 7 C04012

c)

Figure 9 a b c High Resolution Neutron Spectrometers

5 Diagnostic integration

ITER neutronic diagnostics are installed within the vacuum vessel in the port plugs in the divertorand in-cryostat The installation integrations issues and loading conditions in each of these fourlocations are different and this could preclude the use of the same design for one particular systempositioned in different locations

The integration of several diagnostics in the port plugs as well in the interspaces and portcells is a key issue Several ITER systems are interfacing with the diagnostics Remote Handlingfor maintenance provision of water cooling cabling and power supply Bioshield for radiationdose reduction etc Here after some examples of integration and interface matters are reportedconcerning the neutron diagnostics at different locations The same issues are faced also by forother diagnostics systems

Diagnostics in Equatorial Ports diagnostic equipment is mounted in a port plug assembly [18]The port plug geometry consists of two basic parts -the Diagnostic Shield Module (DSM) andthe generic port plug structure figure 10a The Diagnostic Shield Module (DSM) consists ofseveral parts the Diagnostic First Wall (DFW) which is designed to handle the radiant heat fluxfrom the plasma the Diagnostic Shielding Block (DSB) which is designed to handle most of theneutronic heat load and the supporting moduledrawer which fastens the components to the portplug structure and provides a platform or housing for the diagnostic components Figure 10b showsthe drawer in eq Port 1 containing the inport detectors and collimators of B1 RNC

ndash 13 ndash

2012 JINST 7 C04012

a) Typical Equatorial port plug geometry b) In port RNC drawer in EqPort1

Figure 10 Equatorial port plug geometry

Figure 11 Recess of Diagnostic First Wall

The port plug assembly provides also the primary vacuum boundary at that port as well as thefeed-out for diagnostic signals (windows and feedthroughs) and feed-in for control signals

In the DSM there are a number of apertures for diagnostic viewing In designing the RNCsight lines of the inport detectors and related focal points attention has been paid to minimize theaperture (figure 10b) in the DFW which is recessed with respect to the nearby blanket modules(figure 11) This recess is needed to reduce the plasma interaction with the DFW

As an example eq Port Plug 1 is shown (figure 12) which is the most congested with diag-nostics The rational behind this is the need for being as close as possible to the plasma Followingsystems will be installed Radial Neutron Camera Divertor Impurity Monitor Bolometers Mo-tional Stark Effect Many factors have to be taken into account in optimizing the distribution ofdiagnostics within the available ports Because of neutron streaming considerations typically nomore than two systems with large labyrinths can be installed in one port with large aperture sys-tems placed near the port centres distributed systems are located evenly toroidally sometimescoordinated with the location of corresponding systems in the upper ports

ndash 14 ndash

2012 JINST 7 C04012

a) b)

Figure 12 Equatorial port plug 1 a) back view of feedthroughs and connections b) front view

Diagnostics in Vacuum Vessel for the systems installed in the vacuum vessel like B3 MFC andB8 Neutron Activation System a support structure ensuring a very good thermal and mechanicalanchoring to the vacuum vessel wall is required This together with the routing and clamping of thecables and pipes adjusting the irradiation ends to the gaps between the blanket modules leads to acontinuous integration work assuring enough clearance to the neighbouring components and properdefinition of the large variety of in-vacuum vessel interfaces Even though partially shielded by theblanket modules the design of some of the components are challenged by the varying magneticfields high nuclear heat and the loop voltage created around the vessel Last but not least are theinterfacing loads like ECRH stray power and additional acceleration due to disruption events Thelatter one is more important to systems like MFC which should be tested in order to prove that theymaintain performance under shock and vibration

Diagnostics in Cryostat for the B4 Neutron flux monitor located in the in-cryostat area the loadconditions are less severe Because the system is mounted on an extended support structure attachedto the cryostat wall the major loads which should be taken into account are the acceleration due togravity acceleration due to seismic events and those during plasma disruptions and displacements

Diagnostics in Divertor the most demanding among all the mentioned locations is the divertorwhere the load conditions are very severe and it requires an active cooling of all diagnostic compo-nents This on the other hand creates an additional interface with the divertor cooling water branchof which is used for the cooling of the diagnostic components and a development of a good strategyfor a leak localization and detection

The BC Divertor Neutron Flux Monitor is mounted on a cassette body which is remote handleable through the divertor port The divertor dome provides an opportunity to place diagnosticsinside the vacuum vessel since it provides some degree of shelter from the neutron flux and plasmaradiation In the same cassette bolometers which are used for measuring the power of incidentelectromagnetic radiation are required to sit in the gap between two adjacent cassette bodies Thiscreates some integration issues as the one presented in figure 13

ndash 15 ndash

2012 JINST 7 C04012

Figure 13 Integration issue bolometers and DNFM ldquosharingrdquo the same support structure

The B2 Lower Vertical Neutron Camera (LVNC) is integrated into the lower port A genericdiagnostic rack to house diagnostics or optical relays in the port is being developed which willbe customized for each diagnostic while keeping the same interfaces with the vacuum vessel Thediagnostic rack is attached to the side walls of the port and includes features for alignment to thedivertor central cassette On the basis of the recently performed neutronic analysis it became clearthat the vertical camera could not co-exist with any optical system in the same port as this is thecase now Activity is going on the possible relocation either of LVNC or of the optical systems

One of the most difficult interfaces between the blanket system and the diagnostics is pre-sented by the integration of the B2 LVNC The line of sights of the detectors need to protrude theblanket shielding module 18 and the first wall exactly in the middle where the remote handlingattachment the hydraulic connector and the cooling channels are designed as shown in figure 14This fact can bring to the reduction of number of sight lines Design work is being carried out tosort out this problem

ndash 16 ndash

2012 JINST 7 C04012

Figure 14 Interface between Blanket Module 18 and lines of sight of the Vertical Neutron Camera

An overview of ITER neutron diagnostic systems and of the associated challenging engineer-ing and integration issues has been described The design of these systems has taken into accountthe experience gained on large devices which have pointed out the importance of simultaneuousmeasurements of the neutron spatial and energy distributions

The main advantage of this complete set-up of ITER neutron diagnostics is its installation andoperation from the begin of ITER nuclear operation compared to other machines like JET LHDTFTR JT 60 where the various neutron diagnostics have been installed during different machineoperational phases

Acknowledgments

The authors wish to thank ITER Diagnostics Team and the colleagues of ITER Members of JapanKorea China Europe and Russian Federation for useful discussions and collaboration

The work described was supported and carried out by ITER Organization together with ITERMembers and Domestic Agencies of Japan Korea China Europe and Russian Federation Part ofthis activity was performed within the framework of the European Fusion Development Agreement

Disclaimer The views and opinions expressed herein do not necessarily reflect those of the ITERorganization

ndash 17 ndash

2012 JINST 7 C04012

References

[1] AJH Donne et al Progress in the ITER physics basis Chapter 7 diagnostics Nucl Fusion 47(2007) 337

[2] G Vayakis ER Hodgson and V Voitsenya Plasma diagnostics for magnetic fusion researchChapter 12 generic diagnostic issues for a burning plasma experiment Fusion Sci Technol 53(2008) 699

[3] A Encheva L Bertalot B Macklin G Vayakis and C Walker Integration of ITER in-vesseldiagnostic components in the vacuum vessel Fusion Eng Des 84 (2009) 736

[4] A Krasilnikov et al Status of ITER neutron diagnostic development Nucl Fusion 45 (2005) 1503

[5] M Sasao et al Plasma diagnostics for magnetic fusion research Chapter 9 fusion productdiagnostics Fusion Sci Technol 53 (2008) 604

[6] FP Orsitto et al Burning plasmas diagnostics AIP Conf Proc 988 Varenna Italy (2007)

[7] L Petrizzi et al Neutronic design of the ITER radial neutron camera Fusion Sci Eng 82 (2007)1308

[8] AV Krasilnikov CI Walker YA Kashchuk and DV Prosvirin A multichannel neutron collimatorfor the ITER tokamak Kluwer AcademicPlenum Publishers Instrum Exp Tech 47 (2004) 139

[9] A Encheva et al Engineering aspects of integration of ITER divertor diagnostics Fusion Eng Des86 (2011) 1323

[10] M Ishikawa et al Design of microfission chamber for ITER operations Rev Sci Instrum 79 (2008)10E507

[11] A Encheva et al Structural integrity report for ITER micro-fission chamber ITER documentITER D 3TDURL

[12] T Nishitani et al Engineering design of the ITER invessel neutron monitor using micro-fissionchambers Fusion Eng Des 82 (2007) 1192

[13] J Yang et al Fusion neutron flux monitor for ITER Plasma Sci Technol 10 (2008) 141

[14] YA Kashchuk AV Krasilrsquonikov and DV Prosvirin A conceptual project for a divertor monitor ofthe neutron yield in the ITER Instrum Exp Tech 49 (2006) 179

[15] MS Cheon et al In-vessel design of ITER diagnostic neutron activation system Rev Sci Instrum79 (2008) 10E505

[16] L Bertalot et al A strategy for calibrating the neutron systems at ITER in 35th plasma physicsconference Crete Greece 2008 EPS Europhysics Conference Abstracts 32D (2008) O2001httpepsppdepflchHersonissosstarthtm

[17] M Sasao L Bertalot M Ishikawa and S Popovichev Strategy for the absolute neutron emissionmeasurement on ITER Rev Sci Instrum 81 (2010) 10D329

[18] S Pitcher et al System Design Description Document (DDD) diagnostic generic equatorial portplug ITER document ITER D 3U8JU7

ndash 18 ndash

2012 JINST 7 C04012

Table 2 ITER neutron diagnostics and related neutron parameters

Subsystem ParameterB1 Radial Neutron Camera Neutronalpha source profile

Total neutron source strengthIon temperature profileFuel ratioNeutron fluence on FW wall

B2 Vertical Neutron Camera Neutronalpha source profileTotal neutron source strengthIon temperature profileFuel ratioNeutron fluence on FW wall

B3 MicroFission Chambers Total neutron source strengthNeutron fluence on FW wall

B4 Neutron Flux Monitors Total neutron source strengthNeutron fluence on FW wall

B8 Neutron Activation System Neutron fluence on FW wallTotal neutron source strength

BB High Resolution Neutron Spec-trometers (Enabled)

Plasma Core Ion temperatureCore Plasma Fuel Ratio

BC Divertor Neutron Flux Monitors Total neutron source strengthNeutron fluence on the Divertor

Diagnostic subsystems responding to each measurement require measurement backup pro-vided by redundancy within the primary diagnostic by multiple primary diagnostics andor byback-up or supplementary diagnostics The role classification is as follows

bull Primary = diagnostic is well suited to the measurement

bull Backup = diagnostic provides similar data to primary but has some

limitations

bull Supplementary = diagnostic validates or calibrates the measurement but is not complete initself

The Neutron Diagnostics matrix flow down is here below shown (figure 2)

ndash 4 ndash

2012 JINST 7 C04012

Figure 2 Neutron Diagnostic matrix flow down

4 Neutron diagnostics

41 B1 Radial Neutron Camera

The Radial Neutron Camera (RNC) [7] consists of a fan-shaped array of 36 flight tubes viewingthe plasma through a vertical slot in the blanket shield module of Equatorial Port Plug 1 The sightlines intersect at a common aperture defined by the port plug and penetrate the vacuum vessel cryo-stat and biological shield through stainless steel windows (figure 3) Each flight tube culminatesin a set of detectors chosen to provide the required range of sensitivity and temporal and spectralresolution Some of the viewing chords will be equipped with compact neutron spectrometersenabling the system to provide emissivity-weighted chord-averaged measurements of ion temper-ature Appropriate spectrometers have not yet been selected but there are several (scintillatorschemical vapoured diamonds etc) that could meet the measurement requirements by further RampDactivity Because of the length of the ports the spatial coverage in the vertical direction of this partof the camera is limited Additionally 8 sight lines with collimators and detectors mounted in theport plug are included to give measurements in the outer regions of the plasma In this locationthere is reduced space for the detectors and this will limit the type and number of detectors andspectrometers that can be accommodated The maintenance of the detectors will also be more dif-ficult but the gain in spatial coverage is significant The in-port detectors have to withstand hightemperature (up to 250 degrees because of Vacuum Vessel baking)) and magnetic fields up sim 4 Tand a transient magnetic field of approx 10Ts Under these load conditions the system requiresa feasible support structure dedicated cooling and magnetic shielding Particular care is given tothe electrical connections of the in port detectors by using triax mineral insulated cables aiming tohigh noise rejection Moreover the in port detectors are enveloped in a Stainless Steel housing fornot affecting the torus vacuum due to a possible leakage of the detector filling gas

ndash 5 ndash

2012 JINST 7 C04012

Figure 3 Radial Neutron Camera with its lines of sight relative to the plasma with an additional obliqueview onto the outside of the port plug

42 B2 Vertical Neutron Camera

Because ITER does not have vertical ports it is difficult to measure the neutron emission in avertical direction (necessary for combination with the radial measurements for tomographic recon-structions of the neutron source profile) A concept for the vertically viewing camera (VNC) isbeen designed [8] This is to mount a camera adjacent to a port at the lower level The plasmawould be viewed through neutron windows in the vacuum vessel and through a slot in the divertorcassette and through the Blanket Shield Module (BSM) 18 Due to limited space only ten linesof sight are viewing the plasma with coverage up to 08 minor radius The cut outs in the Diver-tor Cassette and in BSM 18 require design modification of the interfacing components and morededicated analysis work [9] (figure 4) Mineral insulated cables will connect the detectors to thepreamplifiers unit located in the Lower Port Cell The detectors will be mounted in a box in orderto avoid detector filling gas leakage to the torus vacuum

ndash 6 ndash

2012 JINST 7 C04012

Figure 4 Vertical Neutron Camera mounted adjacent to a port at the lower level

43 B3 MicroFission Chambers

This diagnostic will provide the total neutron strength during the DT operation ie the high fusionpower phase

The neutron flux is typically measured by fission chambers containing 235U or other isotopesand filled typically with Argon gas at few atmospheres Micro-fission chambers (MFC) are de-ployed between the blanket modules and the inner shell of the Vacuum Vessel (VV) Four MFCmodules are located at two toroidal positions with two modules positioned in two different poloidallocations (figure 5) [10] By designing MFC attention has been paid to several issues such as vacuumleak rate of MFC high operational temperature tight clearance between the components and theblanket modules [11] RampD actitivity is required to ensure the proper functioning of the chamberssubjected to vibration and shock caused by various disruption events

Thermal analysis has shown that MFC can be cooled by conduction to the Vacuum Vesselreaching temperatures less than 200 ˚ C degrees if the SS module has a heat transfer coefficient gt

100 Wmminus2 Kminus1 [12]

Guard Vacuum pipes have been connected to the MFC modules to avoid detector gas entryinto the torus vacuum in the event of a fault

ndash 7 ndash

2012 JINST 7 C04012

a) b)

Figure 5 a) Two Microfission Chambers on VV Sector 1 b) detail of the Upper MFC module

44 B4 Neutron Flux Monitor

This diagnostic system will provide the total neutron strength during all phases of ITER operationFour modules containing each three Fission Chambers with different fissile content are at presentlocated in Equatorial Port 1 7 8 and 17 [13] (baseline definition of eq Port 8 and 17 has recentlychanged and as such these ports are under discussion)

The Neutron Flux Monitors (NFM) in ports 1 and 7 are used to measure DD neutron flux orthe insitu calibration flux whereas in ports 8 and 17 are used to detect DT neutron flux in bothmedium-power operation and full power operation respectively Different moderating materials(Be Graphite and B4C) with various thicknesses will be used for obtaining different sensitivities ofthe four NFMs modules with the aim of measure the total neutron strength from 1014 up to around1021 ns

RampD activities are going on to face the many implementation issues as described above (vac-uum leak high operational temperature magnetic stray fields etc)

The NFM in eq Port 7 is shown (figure 6) as example of the integration and interfaces issuesto be faced with Cryostat Thermal shield Bioshield and Neutral Beam Area

ndash 8 ndash

2012 JINST 7 C04012

VV NFM EQ7 Thermal Shield Cryostat

Figure 6 Neutron Flux Monitor integrated into Equatorial port 7

45 BC Divertor Neutron Flux Monitors

The Divertor Neutron Flux Monitors (DNFM) diagnostic [14] measures the time-resolved neutronemission from the ITER for both DD and DT plasmas providing the evaluation of the fusion power

Three DNFM modules will be installed in ITER Divertor Cassettes under the dome Thelocations of these modules are at three different toroidal positions Divertor Cassette 3 in lowerport 2 Divertor Cassette 21 in lower port 8 and Divertor Cassette 39 at lower port 14

Each module is composed of six fission chambers (FC) identical in dimension and coatedwith varying amount of 235U amp 238U fissile material

The six fission chambers are enclosed in two cylinders three U235 FC in one cylinder and threeU238 FC in the other one forming the DNFM module see figure 7

By developing a good and structuraly sound design some major challenges have been facedhigh nuclear and radiation power loads transient magnetic field causing large forces and momentsacting on the sturcture and non-negligible halo currents The Divertor water cooling system will beused also for the DNFM

ndash 9 ndash

2012 JINST 7 C04012

Figure 7 Integration of DNFM in Lower Port

Risk analysis has been carried out on the failure probability of the several DNFM weldingjoints causing water leakage in the torus vacuum Such failure event can cause the stop of theplasma operations for several weeks As mitigation action a DNFM prototype will be manufacturedfor test at high temperatures (up to 350 degrees C) and high water pressure (20 divide 40 MPa)

The use of the various time resolved flux detection systems (B3 B4 and BC) and use ofmultiple locations allow compensation of effects due to changes in plasma position or shape andprovides redundancy in case of detectors failure Together these systems give the global neutronsource strength from which the total fusion power is obtained and the measurement should beinsensitive to plasma position

46 B8 Neutron Activation System

This diagnostic system (NAS) provides time integrated measurements of the neutron fluence at theFirst Wall and total fusion power through neutronic calculations [15]

Foil samples are irradiated at positions near the FW Several irradiation ends have been po-sitioned between various Blanket Modules and on the VV inner wall as well in the Upper andEquatorial Ports (figure 8) The foils samples are transferred using a pneumatic capsule system tocounting stations through port feedthroughs

ndash 10 ndash

2012 JINST 7 C04012

a) b) c) Support IE

Figure 8 a) NAS transfer lines inside the Vacuum Vessel b) Poloidal position of the various IrradiationEnds c) Support and Irradiation End of Position F

High thermal loads are expected at the irradiation ends because of the plasma radiation andnuclear heating This fact precludes a number of materials for the capsule or sample such aspolyethylene In and Al Moreover EM forces induced by plasma disruptions require the design ofdedicated strong supports

RampD activity is on-going on the selection of material and mass of the samples in order to limitactivation and avoid counting saturation effect for the various ITER operation scenarios (from 300s up to 3000 s)

The NAS diagnostic plays a fundamental role in the ITER Neutron Calibration Strategy be-cause is the only neutron diagnostic having a dynamic range of 10 orders of magnitude due toappropriate selection of mass and foils materials

In ITER the extended nature of the plasma neutron source means that the spatial dependence ofthe sensitivity of the different neutron systems is needed and this is obtained by in-situ calibrationsin these a source of known intensity is moved inside the tokamak vacuum chamber and the responseof the neutron detectors is recorded For ITER a powerful source with an intensity sim 1011ns isneeded Account needs to be taken of the potential screening and scattering effects of the structurethat is supporting the neutron source and this is done by use of the neutron transport codes code

NAS will be absolutely calibrated during the ITER in situ neutron calibration and during theITER DD and DT phases with well-characterized plasma reference shots allowing the cross cali-bration of all other ITER neutron diagnostic systems [16 17]

ndash 11 ndash

2012 JINST 7 C04012

47 BB High Resolution Neutron Spectrometer

Provision is made for a later installation of high-resolution neutron spectrometers (HRNS) for DDand DT neutron spectroscopy by adding a collimator into the neutron camera on equatorial port 1(figure 9a b) so that instruments can be installed later

In order to measure the neutron energy distribution of DD and DT emission two or threeneutron spectroscopy instruments are required Different type of spectrometer will be considered(Time of Flight Thin Proton Recoil etc)

Because of the high neutron flux (around 109 ncm2 s) needed to meet ITER measurementrequirements (100 ms time resolution and 10divide 20 accuracy) a neutron beam dump and housingsurrounding HRNS for local shield (figure 9c) have to be installed in the Port Cell 1 in order tomeet radiation safety parameters

a) b)

ndash 12 ndash

2012 JINST 7 C04012

c)

Figure 9 a b c High Resolution Neutron Spectrometers

5 Diagnostic integration

ITER neutronic diagnostics are installed within the vacuum vessel in the port plugs in the divertorand in-cryostat The installation integrations issues and loading conditions in each of these fourlocations are different and this could preclude the use of the same design for one particular systempositioned in different locations

The integration of several diagnostics in the port plugs as well in the interspaces and portcells is a key issue Several ITER systems are interfacing with the diagnostics Remote Handlingfor maintenance provision of water cooling cabling and power supply Bioshield for radiationdose reduction etc Here after some examples of integration and interface matters are reportedconcerning the neutron diagnostics at different locations The same issues are faced also by forother diagnostics systems

Diagnostics in Equatorial Ports diagnostic equipment is mounted in a port plug assembly [18]The port plug geometry consists of two basic parts -the Diagnostic Shield Module (DSM) andthe generic port plug structure figure 10a The Diagnostic Shield Module (DSM) consists ofseveral parts the Diagnostic First Wall (DFW) which is designed to handle the radiant heat fluxfrom the plasma the Diagnostic Shielding Block (DSB) which is designed to handle most of theneutronic heat load and the supporting moduledrawer which fastens the components to the portplug structure and provides a platform or housing for the diagnostic components Figure 10b showsthe drawer in eq Port 1 containing the inport detectors and collimators of B1 RNC

ndash 13 ndash

2012 JINST 7 C04012

a) Typical Equatorial port plug geometry b) In port RNC drawer in EqPort1

Figure 10 Equatorial port plug geometry

Figure 11 Recess of Diagnostic First Wall

The port plug assembly provides also the primary vacuum boundary at that port as well as thefeed-out for diagnostic signals (windows and feedthroughs) and feed-in for control signals

In the DSM there are a number of apertures for diagnostic viewing In designing the RNCsight lines of the inport detectors and related focal points attention has been paid to minimize theaperture (figure 10b) in the DFW which is recessed with respect to the nearby blanket modules(figure 11) This recess is needed to reduce the plasma interaction with the DFW

As an example eq Port Plug 1 is shown (figure 12) which is the most congested with diag-nostics The rational behind this is the need for being as close as possible to the plasma Followingsystems will be installed Radial Neutron Camera Divertor Impurity Monitor Bolometers Mo-tional Stark Effect Many factors have to be taken into account in optimizing the distribution ofdiagnostics within the available ports Because of neutron streaming considerations typically nomore than two systems with large labyrinths can be installed in one port with large aperture sys-tems placed near the port centres distributed systems are located evenly toroidally sometimescoordinated with the location of corresponding systems in the upper ports

ndash 14 ndash

2012 JINST 7 C04012

a) b)

Figure 12 Equatorial port plug 1 a) back view of feedthroughs and connections b) front view

Diagnostics in Vacuum Vessel for the systems installed in the vacuum vessel like B3 MFC andB8 Neutron Activation System a support structure ensuring a very good thermal and mechanicalanchoring to the vacuum vessel wall is required This together with the routing and clamping of thecables and pipes adjusting the irradiation ends to the gaps between the blanket modules leads to acontinuous integration work assuring enough clearance to the neighbouring components and properdefinition of the large variety of in-vacuum vessel interfaces Even though partially shielded by theblanket modules the design of some of the components are challenged by the varying magneticfields high nuclear heat and the loop voltage created around the vessel Last but not least are theinterfacing loads like ECRH stray power and additional acceleration due to disruption events Thelatter one is more important to systems like MFC which should be tested in order to prove that theymaintain performance under shock and vibration

Diagnostics in Cryostat for the B4 Neutron flux monitor located in the in-cryostat area the loadconditions are less severe Because the system is mounted on an extended support structure attachedto the cryostat wall the major loads which should be taken into account are the acceleration due togravity acceleration due to seismic events and those during plasma disruptions and displacements

Diagnostics in Divertor the most demanding among all the mentioned locations is the divertorwhere the load conditions are very severe and it requires an active cooling of all diagnostic compo-nents This on the other hand creates an additional interface with the divertor cooling water branchof which is used for the cooling of the diagnostic components and a development of a good strategyfor a leak localization and detection

The BC Divertor Neutron Flux Monitor is mounted on a cassette body which is remote handleable through the divertor port The divertor dome provides an opportunity to place diagnosticsinside the vacuum vessel since it provides some degree of shelter from the neutron flux and plasmaradiation In the same cassette bolometers which are used for measuring the power of incidentelectromagnetic radiation are required to sit in the gap between two adjacent cassette bodies Thiscreates some integration issues as the one presented in figure 13

ndash 15 ndash

2012 JINST 7 C04012

Figure 13 Integration issue bolometers and DNFM ldquosharingrdquo the same support structure

The B2 Lower Vertical Neutron Camera (LVNC) is integrated into the lower port A genericdiagnostic rack to house diagnostics or optical relays in the port is being developed which willbe customized for each diagnostic while keeping the same interfaces with the vacuum vessel Thediagnostic rack is attached to the side walls of the port and includes features for alignment to thedivertor central cassette On the basis of the recently performed neutronic analysis it became clearthat the vertical camera could not co-exist with any optical system in the same port as this is thecase now Activity is going on the possible relocation either of LVNC or of the optical systems

One of the most difficult interfaces between the blanket system and the diagnostics is pre-sented by the integration of the B2 LVNC The line of sights of the detectors need to protrude theblanket shielding module 18 and the first wall exactly in the middle where the remote handlingattachment the hydraulic connector and the cooling channels are designed as shown in figure 14This fact can bring to the reduction of number of sight lines Design work is being carried out tosort out this problem

ndash 16 ndash

2012 JINST 7 C04012

Figure 14 Interface between Blanket Module 18 and lines of sight of the Vertical Neutron Camera

An overview of ITER neutron diagnostic systems and of the associated challenging engineer-ing and integration issues has been described The design of these systems has taken into accountthe experience gained on large devices which have pointed out the importance of simultaneuousmeasurements of the neutron spatial and energy distributions

The main advantage of this complete set-up of ITER neutron diagnostics is its installation andoperation from the begin of ITER nuclear operation compared to other machines like JET LHDTFTR JT 60 where the various neutron diagnostics have been installed during different machineoperational phases

Acknowledgments

The authors wish to thank ITER Diagnostics Team and the colleagues of ITER Members of JapanKorea China Europe and Russian Federation for useful discussions and collaboration

The work described was supported and carried out by ITER Organization together with ITERMembers and Domestic Agencies of Japan Korea China Europe and Russian Federation Part ofthis activity was performed within the framework of the European Fusion Development Agreement

Disclaimer The views and opinions expressed herein do not necessarily reflect those of the ITERorganization

ndash 17 ndash

2012 JINST 7 C04012

References

[1] AJH Donne et al Progress in the ITER physics basis Chapter 7 diagnostics Nucl Fusion 47(2007) 337

[2] G Vayakis ER Hodgson and V Voitsenya Plasma diagnostics for magnetic fusion researchChapter 12 generic diagnostic issues for a burning plasma experiment Fusion Sci Technol 53(2008) 699

[3] A Encheva L Bertalot B Macklin G Vayakis and C Walker Integration of ITER in-vesseldiagnostic components in the vacuum vessel Fusion Eng Des 84 (2009) 736

[4] A Krasilnikov et al Status of ITER neutron diagnostic development Nucl Fusion 45 (2005) 1503

[5] M Sasao et al Plasma diagnostics for magnetic fusion research Chapter 9 fusion productdiagnostics Fusion Sci Technol 53 (2008) 604

[6] FP Orsitto et al Burning plasmas diagnostics AIP Conf Proc 988 Varenna Italy (2007)

[7] L Petrizzi et al Neutronic design of the ITER radial neutron camera Fusion Sci Eng 82 (2007)1308

[8] AV Krasilnikov CI Walker YA Kashchuk and DV Prosvirin A multichannel neutron collimatorfor the ITER tokamak Kluwer AcademicPlenum Publishers Instrum Exp Tech 47 (2004) 139

[9] A Encheva et al Engineering aspects of integration of ITER divertor diagnostics Fusion Eng Des86 (2011) 1323

[10] M Ishikawa et al Design of microfission chamber for ITER operations Rev Sci Instrum 79 (2008)10E507

[11] A Encheva et al Structural integrity report for ITER micro-fission chamber ITER documentITER D 3TDURL

[12] T Nishitani et al Engineering design of the ITER invessel neutron monitor using micro-fissionchambers Fusion Eng Des 82 (2007) 1192

[13] J Yang et al Fusion neutron flux monitor for ITER Plasma Sci Technol 10 (2008) 141

[14] YA Kashchuk AV Krasilrsquonikov and DV Prosvirin A conceptual project for a divertor monitor ofthe neutron yield in the ITER Instrum Exp Tech 49 (2006) 179

[15] MS Cheon et al In-vessel design of ITER diagnostic neutron activation system Rev Sci Instrum79 (2008) 10E505

[16] L Bertalot et al A strategy for calibrating the neutron systems at ITER in 35th plasma physicsconference Crete Greece 2008 EPS Europhysics Conference Abstracts 32D (2008) O2001httpepsppdepflchHersonissosstarthtm

[17] M Sasao L Bertalot M Ishikawa and S Popovichev Strategy for the absolute neutron emissionmeasurement on ITER Rev Sci Instrum 81 (2010) 10D329

[18] S Pitcher et al System Design Description Document (DDD) diagnostic generic equatorial portplug ITER document ITER D 3U8JU7

ndash 18 ndash

2012 JINST 7 C04012

Figure 2 Neutron Diagnostic matrix flow down

4 Neutron diagnostics

41 B1 Radial Neutron Camera

The Radial Neutron Camera (RNC) [7] consists of a fan-shaped array of 36 flight tubes viewingthe plasma through a vertical slot in the blanket shield module of Equatorial Port Plug 1 The sightlines intersect at a common aperture defined by the port plug and penetrate the vacuum vessel cryo-stat and biological shield through stainless steel windows (figure 3) Each flight tube culminatesin a set of detectors chosen to provide the required range of sensitivity and temporal and spectralresolution Some of the viewing chords will be equipped with compact neutron spectrometersenabling the system to provide emissivity-weighted chord-averaged measurements of ion temper-ature Appropriate spectrometers have not yet been selected but there are several (scintillatorschemical vapoured diamonds etc) that could meet the measurement requirements by further RampDactivity Because of the length of the ports the spatial coverage in the vertical direction of this partof the camera is limited Additionally 8 sight lines with collimators and detectors mounted in theport plug are included to give measurements in the outer regions of the plasma In this locationthere is reduced space for the detectors and this will limit the type and number of detectors andspectrometers that can be accommodated The maintenance of the detectors will also be more dif-ficult but the gain in spatial coverage is significant The in-port detectors have to withstand hightemperature (up to 250 degrees because of Vacuum Vessel baking)) and magnetic fields up sim 4 Tand a transient magnetic field of approx 10Ts Under these load conditions the system requiresa feasible support structure dedicated cooling and magnetic shielding Particular care is given tothe electrical connections of the in port detectors by using triax mineral insulated cables aiming tohigh noise rejection Moreover the in port detectors are enveloped in a Stainless Steel housing fornot affecting the torus vacuum due to a possible leakage of the detector filling gas

ndash 5 ndash

2012 JINST 7 C04012

Figure 3 Radial Neutron Camera with its lines of sight relative to the plasma with an additional obliqueview onto the outside of the port plug

42 B2 Vertical Neutron Camera

Because ITER does not have vertical ports it is difficult to measure the neutron emission in avertical direction (necessary for combination with the radial measurements for tomographic recon-structions of the neutron source profile) A concept for the vertically viewing camera (VNC) isbeen designed [8] This is to mount a camera adjacent to a port at the lower level The plasmawould be viewed through neutron windows in the vacuum vessel and through a slot in the divertorcassette and through the Blanket Shield Module (BSM) 18 Due to limited space only ten linesof sight are viewing the plasma with coverage up to 08 minor radius The cut outs in the Diver-tor Cassette and in BSM 18 require design modification of the interfacing components and morededicated analysis work [9] (figure 4) Mineral insulated cables will connect the detectors to thepreamplifiers unit located in the Lower Port Cell The detectors will be mounted in a box in orderto avoid detector filling gas leakage to the torus vacuum

ndash 6 ndash

2012 JINST 7 C04012

Figure 4 Vertical Neutron Camera mounted adjacent to a port at the lower level

43 B3 MicroFission Chambers

This diagnostic will provide the total neutron strength during the DT operation ie the high fusionpower phase

The neutron flux is typically measured by fission chambers containing 235U or other isotopesand filled typically with Argon gas at few atmospheres Micro-fission chambers (MFC) are de-ployed between the blanket modules and the inner shell of the Vacuum Vessel (VV) Four MFCmodules are located at two toroidal positions with two modules positioned in two different poloidallocations (figure 5) [10] By designing MFC attention has been paid to several issues such as vacuumleak rate of MFC high operational temperature tight clearance between the components and theblanket modules [11] RampD actitivity is required to ensure the proper functioning of the chamberssubjected to vibration and shock caused by various disruption events

Thermal analysis has shown that MFC can be cooled by conduction to the Vacuum Vesselreaching temperatures less than 200 ˚ C degrees if the SS module has a heat transfer coefficient gt

100 Wmminus2 Kminus1 [12]

Guard Vacuum pipes have been connected to the MFC modules to avoid detector gas entryinto the torus vacuum in the event of a fault

ndash 7 ndash

2012 JINST 7 C04012

a) b)

Figure 5 a) Two Microfission Chambers on VV Sector 1 b) detail of the Upper MFC module

44 B4 Neutron Flux Monitor

This diagnostic system will provide the total neutron strength during all phases of ITER operationFour modules containing each three Fission Chambers with different fissile content are at presentlocated in Equatorial Port 1 7 8 and 17 [13] (baseline definition of eq Port 8 and 17 has recentlychanged and as such these ports are under discussion)

The Neutron Flux Monitors (NFM) in ports 1 and 7 are used to measure DD neutron flux orthe insitu calibration flux whereas in ports 8 and 17 are used to detect DT neutron flux in bothmedium-power operation and full power operation respectively Different moderating materials(Be Graphite and B4C) with various thicknesses will be used for obtaining different sensitivities ofthe four NFMs modules with the aim of measure the total neutron strength from 1014 up to around1021 ns

RampD activities are going on to face the many implementation issues as described above (vac-uum leak high operational temperature magnetic stray fields etc)

The NFM in eq Port 7 is shown (figure 6) as example of the integration and interfaces issuesto be faced with Cryostat Thermal shield Bioshield and Neutral Beam Area

ndash 8 ndash

2012 JINST 7 C04012

VV NFM EQ7 Thermal Shield Cryostat

Figure 6 Neutron Flux Monitor integrated into Equatorial port 7

45 BC Divertor Neutron Flux Monitors

The Divertor Neutron Flux Monitors (DNFM) diagnostic [14] measures the time-resolved neutronemission from the ITER for both DD and DT plasmas providing the evaluation of the fusion power

Three DNFM modules will be installed in ITER Divertor Cassettes under the dome Thelocations of these modules are at three different toroidal positions Divertor Cassette 3 in lowerport 2 Divertor Cassette 21 in lower port 8 and Divertor Cassette 39 at lower port 14

Each module is composed of six fission chambers (FC) identical in dimension and coatedwith varying amount of 235U amp 238U fissile material

The six fission chambers are enclosed in two cylinders three U235 FC in one cylinder and threeU238 FC in the other one forming the DNFM module see figure 7

By developing a good and structuraly sound design some major challenges have been facedhigh nuclear and radiation power loads transient magnetic field causing large forces and momentsacting on the sturcture and non-negligible halo currents The Divertor water cooling system will beused also for the DNFM

ndash 9 ndash

2012 JINST 7 C04012

Figure 7 Integration of DNFM in Lower Port

Risk analysis has been carried out on the failure probability of the several DNFM weldingjoints causing water leakage in the torus vacuum Such failure event can cause the stop of theplasma operations for several weeks As mitigation action a DNFM prototype will be manufacturedfor test at high temperatures (up to 350 degrees C) and high water pressure (20 divide 40 MPa)

The use of the various time resolved flux detection systems (B3 B4 and BC) and use ofmultiple locations allow compensation of effects due to changes in plasma position or shape andprovides redundancy in case of detectors failure Together these systems give the global neutronsource strength from which the total fusion power is obtained and the measurement should beinsensitive to plasma position

46 B8 Neutron Activation System

This diagnostic system (NAS) provides time integrated measurements of the neutron fluence at theFirst Wall and total fusion power through neutronic calculations [15]

Foil samples are irradiated at positions near the FW Several irradiation ends have been po-sitioned between various Blanket Modules and on the VV inner wall as well in the Upper andEquatorial Ports (figure 8) The foils samples are transferred using a pneumatic capsule system tocounting stations through port feedthroughs

ndash 10 ndash

2012 JINST 7 C04012

a) b) c) Support IE

Figure 8 a) NAS transfer lines inside the Vacuum Vessel b) Poloidal position of the various IrradiationEnds c) Support and Irradiation End of Position F

High thermal loads are expected at the irradiation ends because of the plasma radiation andnuclear heating This fact precludes a number of materials for the capsule or sample such aspolyethylene In and Al Moreover EM forces induced by plasma disruptions require the design ofdedicated strong supports

RampD activity is on-going on the selection of material and mass of the samples in order to limitactivation and avoid counting saturation effect for the various ITER operation scenarios (from 300s up to 3000 s)

The NAS diagnostic plays a fundamental role in the ITER Neutron Calibration Strategy be-cause is the only neutron diagnostic having a dynamic range of 10 orders of magnitude due toappropriate selection of mass and foils materials

In ITER the extended nature of the plasma neutron source means that the spatial dependence ofthe sensitivity of the different neutron systems is needed and this is obtained by in-situ calibrationsin these a source of known intensity is moved inside the tokamak vacuum chamber and the responseof the neutron detectors is recorded For ITER a powerful source with an intensity sim 1011ns isneeded Account needs to be taken of the potential screening and scattering effects of the structurethat is supporting the neutron source and this is done by use of the neutron transport codes code

NAS will be absolutely calibrated during the ITER in situ neutron calibration and during theITER DD and DT phases with well-characterized plasma reference shots allowing the cross cali-bration of all other ITER neutron diagnostic systems [16 17]

ndash 11 ndash

2012 JINST 7 C04012

47 BB High Resolution Neutron Spectrometer

Provision is made for a later installation of high-resolution neutron spectrometers (HRNS) for DDand DT neutron spectroscopy by adding a collimator into the neutron camera on equatorial port 1(figure 9a b) so that instruments can be installed later

In order to measure the neutron energy distribution of DD and DT emission two or threeneutron spectroscopy instruments are required Different type of spectrometer will be considered(Time of Flight Thin Proton Recoil etc)

Because of the high neutron flux (around 109 ncm2 s) needed to meet ITER measurementrequirements (100 ms time resolution and 10divide 20 accuracy) a neutron beam dump and housingsurrounding HRNS for local shield (figure 9c) have to be installed in the Port Cell 1 in order tomeet radiation safety parameters

a) b)

ndash 12 ndash

2012 JINST 7 C04012

c)

Figure 9 a b c High Resolution Neutron Spectrometers

5 Diagnostic integration

ITER neutronic diagnostics are installed within the vacuum vessel in the port plugs in the divertorand in-cryostat The installation integrations issues and loading conditions in each of these fourlocations are different and this could preclude the use of the same design for one particular systempositioned in different locations

The integration of several diagnostics in the port plugs as well in the interspaces and portcells is a key issue Several ITER systems are interfacing with the diagnostics Remote Handlingfor maintenance provision of water cooling cabling and power supply Bioshield for radiationdose reduction etc Here after some examples of integration and interface matters are reportedconcerning the neutron diagnostics at different locations The same issues are faced also by forother diagnostics systems

Diagnostics in Equatorial Ports diagnostic equipment is mounted in a port plug assembly [18]The port plug geometry consists of two basic parts -the Diagnostic Shield Module (DSM) andthe generic port plug structure figure 10a The Diagnostic Shield Module (DSM) consists ofseveral parts the Diagnostic First Wall (DFW) which is designed to handle the radiant heat fluxfrom the plasma the Diagnostic Shielding Block (DSB) which is designed to handle most of theneutronic heat load and the supporting moduledrawer which fastens the components to the portplug structure and provides a platform or housing for the diagnostic components Figure 10b showsthe drawer in eq Port 1 containing the inport detectors and collimators of B1 RNC

ndash 13 ndash

2012 JINST 7 C04012

a) Typical Equatorial port plug geometry b) In port RNC drawer in EqPort1

Figure 10 Equatorial port plug geometry

Figure 11 Recess of Diagnostic First Wall

The port plug assembly provides also the primary vacuum boundary at that port as well as thefeed-out for diagnostic signals (windows and feedthroughs) and feed-in for control signals

In the DSM there are a number of apertures for diagnostic viewing In designing the RNCsight lines of the inport detectors and related focal points attention has been paid to minimize theaperture (figure 10b) in the DFW which is recessed with respect to the nearby blanket modules(figure 11) This recess is needed to reduce the plasma interaction with the DFW

As an example eq Port Plug 1 is shown (figure 12) which is the most congested with diag-nostics The rational behind this is the need for being as close as possible to the plasma Followingsystems will be installed Radial Neutron Camera Divertor Impurity Monitor Bolometers Mo-tional Stark Effect Many factors have to be taken into account in optimizing the distribution ofdiagnostics within the available ports Because of neutron streaming considerations typically nomore than two systems with large labyrinths can be installed in one port with large aperture sys-tems placed near the port centres distributed systems are located evenly toroidally sometimescoordinated with the location of corresponding systems in the upper ports

ndash 14 ndash

2012 JINST 7 C04012

a) b)

Figure 12 Equatorial port plug 1 a) back view of feedthroughs and connections b) front view

Diagnostics in Vacuum Vessel for the systems installed in the vacuum vessel like B3 MFC andB8 Neutron Activation System a support structure ensuring a very good thermal and mechanicalanchoring to the vacuum vessel wall is required This together with the routing and clamping of thecables and pipes adjusting the irradiation ends to the gaps between the blanket modules leads to acontinuous integration work assuring enough clearance to the neighbouring components and properdefinition of the large variety of in-vacuum vessel interfaces Even though partially shielded by theblanket modules the design of some of the components are challenged by the varying magneticfields high nuclear heat and the loop voltage created around the vessel Last but not least are theinterfacing loads like ECRH stray power and additional acceleration due to disruption events Thelatter one is more important to systems like MFC which should be tested in order to prove that theymaintain performance under shock and vibration

Diagnostics in Cryostat for the B4 Neutron flux monitor located in the in-cryostat area the loadconditions are less severe Because the system is mounted on an extended support structure attachedto the cryostat wall the major loads which should be taken into account are the acceleration due togravity acceleration due to seismic events and those during plasma disruptions and displacements

Diagnostics in Divertor the most demanding among all the mentioned locations is the divertorwhere the load conditions are very severe and it requires an active cooling of all diagnostic compo-nents This on the other hand creates an additional interface with the divertor cooling water branchof which is used for the cooling of the diagnostic components and a development of a good strategyfor a leak localization and detection

The BC Divertor Neutron Flux Monitor is mounted on a cassette body which is remote handleable through the divertor port The divertor dome provides an opportunity to place diagnosticsinside the vacuum vessel since it provides some degree of shelter from the neutron flux and plasmaradiation In the same cassette bolometers which are used for measuring the power of incidentelectromagnetic radiation are required to sit in the gap between two adjacent cassette bodies Thiscreates some integration issues as the one presented in figure 13

ndash 15 ndash

2012 JINST 7 C04012

Figure 13 Integration issue bolometers and DNFM ldquosharingrdquo the same support structure

The B2 Lower Vertical Neutron Camera (LVNC) is integrated into the lower port A genericdiagnostic rack to house diagnostics or optical relays in the port is being developed which willbe customized for each diagnostic while keeping the same interfaces with the vacuum vessel Thediagnostic rack is attached to the side walls of the port and includes features for alignment to thedivertor central cassette On the basis of the recently performed neutronic analysis it became clearthat the vertical camera could not co-exist with any optical system in the same port as this is thecase now Activity is going on the possible relocation either of LVNC or of the optical systems

One of the most difficult interfaces between the blanket system and the diagnostics is pre-sented by the integration of the B2 LVNC The line of sights of the detectors need to protrude theblanket shielding module 18 and the first wall exactly in the middle where the remote handlingattachment the hydraulic connector and the cooling channels are designed as shown in figure 14This fact can bring to the reduction of number of sight lines Design work is being carried out tosort out this problem

ndash 16 ndash

2012 JINST 7 C04012

Figure 14 Interface between Blanket Module 18 and lines of sight of the Vertical Neutron Camera

An overview of ITER neutron diagnostic systems and of the associated challenging engineer-ing and integration issues has been described The design of these systems has taken into accountthe experience gained on large devices which have pointed out the importance of simultaneuousmeasurements of the neutron spatial and energy distributions

The main advantage of this complete set-up of ITER neutron diagnostics is its installation andoperation from the begin of ITER nuclear operation compared to other machines like JET LHDTFTR JT 60 where the various neutron diagnostics have been installed during different machineoperational phases

Acknowledgments

The authors wish to thank ITER Diagnostics Team and the colleagues of ITER Members of JapanKorea China Europe and Russian Federation for useful discussions and collaboration

The work described was supported and carried out by ITER Organization together with ITERMembers and Domestic Agencies of Japan Korea China Europe and Russian Federation Part ofthis activity was performed within the framework of the European Fusion Development Agreement

Disclaimer The views and opinions expressed herein do not necessarily reflect those of the ITERorganization

ndash 17 ndash

2012 JINST 7 C04012

References

[1] AJH Donne et al Progress in the ITER physics basis Chapter 7 diagnostics Nucl Fusion 47(2007) 337

[2] G Vayakis ER Hodgson and V Voitsenya Plasma diagnostics for magnetic fusion researchChapter 12 generic diagnostic issues for a burning plasma experiment Fusion Sci Technol 53(2008) 699

[3] A Encheva L Bertalot B Macklin G Vayakis and C Walker Integration of ITER in-vesseldiagnostic components in the vacuum vessel Fusion Eng Des 84 (2009) 736

[4] A Krasilnikov et al Status of ITER neutron diagnostic development Nucl Fusion 45 (2005) 1503

[5] M Sasao et al Plasma diagnostics for magnetic fusion research Chapter 9 fusion productdiagnostics Fusion Sci Technol 53 (2008) 604

[6] FP Orsitto et al Burning plasmas diagnostics AIP Conf Proc 988 Varenna Italy (2007)

[7] L Petrizzi et al Neutronic design of the ITER radial neutron camera Fusion Sci Eng 82 (2007)1308

[8] AV Krasilnikov CI Walker YA Kashchuk and DV Prosvirin A multichannel neutron collimatorfor the ITER tokamak Kluwer AcademicPlenum Publishers Instrum Exp Tech 47 (2004) 139

[9] A Encheva et al Engineering aspects of integration of ITER divertor diagnostics Fusion Eng Des86 (2011) 1323

[10] M Ishikawa et al Design of microfission chamber for ITER operations Rev Sci Instrum 79 (2008)10E507

[11] A Encheva et al Structural integrity report for ITER micro-fission chamber ITER documentITER D 3TDURL

[12] T Nishitani et al Engineering design of the ITER invessel neutron monitor using micro-fissionchambers Fusion Eng Des 82 (2007) 1192

[13] J Yang et al Fusion neutron flux monitor for ITER Plasma Sci Technol 10 (2008) 141

[14] YA Kashchuk AV Krasilrsquonikov and DV Prosvirin A conceptual project for a divertor monitor ofthe neutron yield in the ITER Instrum Exp Tech 49 (2006) 179

[15] MS Cheon et al In-vessel design of ITER diagnostic neutron activation system Rev Sci Instrum79 (2008) 10E505

[16] L Bertalot et al A strategy for calibrating the neutron systems at ITER in 35th plasma physicsconference Crete Greece 2008 EPS Europhysics Conference Abstracts 32D (2008) O2001httpepsppdepflchHersonissosstarthtm

[17] M Sasao L Bertalot M Ishikawa and S Popovichev Strategy for the absolute neutron emissionmeasurement on ITER Rev Sci Instrum 81 (2010) 10D329

[18] S Pitcher et al System Design Description Document (DDD) diagnostic generic equatorial portplug ITER document ITER D 3U8JU7

ndash 18 ndash

2012 JINST 7 C04012

Figure 3 Radial Neutron Camera with its lines of sight relative to the plasma with an additional obliqueview onto the outside of the port plug

42 B2 Vertical Neutron Camera

Because ITER does not have vertical ports it is difficult to measure the neutron emission in avertical direction (necessary for combination with the radial measurements for tomographic recon-structions of the neutron source profile) A concept for the vertically viewing camera (VNC) isbeen designed [8] This is to mount a camera adjacent to a port at the lower level The plasmawould be viewed through neutron windows in the vacuum vessel and through a slot in the divertorcassette and through the Blanket Shield Module (BSM) 18 Due to limited space only ten linesof sight are viewing the plasma with coverage up to 08 minor radius The cut outs in the Diver-tor Cassette and in BSM 18 require design modification of the interfacing components and morededicated analysis work [9] (figure 4) Mineral insulated cables will connect the detectors to thepreamplifiers unit located in the Lower Port Cell The detectors will be mounted in a box in orderto avoid detector filling gas leakage to the torus vacuum

ndash 6 ndash

2012 JINST 7 C04012

Figure 4 Vertical Neutron Camera mounted adjacent to a port at the lower level

43 B3 MicroFission Chambers

This diagnostic will provide the total neutron strength during the DT operation ie the high fusionpower phase

The neutron flux is typically measured by fission chambers containing 235U or other isotopesand filled typically with Argon gas at few atmospheres Micro-fission chambers (MFC) are de-ployed between the blanket modules and the inner shell of the Vacuum Vessel (VV) Four MFCmodules are located at two toroidal positions with two modules positioned in two different poloidallocations (figure 5) [10] By designing MFC attention has been paid to several issues such as vacuumleak rate of MFC high operational temperature tight clearance between the components and theblanket modules [11] RampD actitivity is required to ensure the proper functioning of the chamberssubjected to vibration and shock caused by various disruption events

Thermal analysis has shown that MFC can be cooled by conduction to the Vacuum Vesselreaching temperatures less than 200 ˚ C degrees if the SS module has a heat transfer coefficient gt

100 Wmminus2 Kminus1 [12]

Guard Vacuum pipes have been connected to the MFC modules to avoid detector gas entryinto the torus vacuum in the event of a fault

ndash 7 ndash

2012 JINST 7 C04012

a) b)

Figure 5 a) Two Microfission Chambers on VV Sector 1 b) detail of the Upper MFC module

44 B4 Neutron Flux Monitor

This diagnostic system will provide the total neutron strength during all phases of ITER operationFour modules containing each three Fission Chambers with different fissile content are at presentlocated in Equatorial Port 1 7 8 and 17 [13] (baseline definition of eq Port 8 and 17 has recentlychanged and as such these ports are under discussion)

The Neutron Flux Monitors (NFM) in ports 1 and 7 are used to measure DD neutron flux orthe insitu calibration flux whereas in ports 8 and 17 are used to detect DT neutron flux in bothmedium-power operation and full power operation respectively Different moderating materials(Be Graphite and B4C) with various thicknesses will be used for obtaining different sensitivities ofthe four NFMs modules with the aim of measure the total neutron strength from 1014 up to around1021 ns

RampD activities are going on to face the many implementation issues as described above (vac-uum leak high operational temperature magnetic stray fields etc)

The NFM in eq Port 7 is shown (figure 6) as example of the integration and interfaces issuesto be faced with Cryostat Thermal shield Bioshield and Neutral Beam Area

ndash 8 ndash

2012 JINST 7 C04012

VV NFM EQ7 Thermal Shield Cryostat

Figure 6 Neutron Flux Monitor integrated into Equatorial port 7

45 BC Divertor Neutron Flux Monitors

The Divertor Neutron Flux Monitors (DNFM) diagnostic [14] measures the time-resolved neutronemission from the ITER for both DD and DT plasmas providing the evaluation of the fusion power

Three DNFM modules will be installed in ITER Divertor Cassettes under the dome Thelocations of these modules are at three different toroidal positions Divertor Cassette 3 in lowerport 2 Divertor Cassette 21 in lower port 8 and Divertor Cassette 39 at lower port 14

Each module is composed of six fission chambers (FC) identical in dimension and coatedwith varying amount of 235U amp 238U fissile material

The six fission chambers are enclosed in two cylinders three U235 FC in one cylinder and threeU238 FC in the other one forming the DNFM module see figure 7

By developing a good and structuraly sound design some major challenges have been facedhigh nuclear and radiation power loads transient magnetic field causing large forces and momentsacting on the sturcture and non-negligible halo currents The Divertor water cooling system will beused also for the DNFM

ndash 9 ndash

2012 JINST 7 C04012

Figure 7 Integration of DNFM in Lower Port

Risk analysis has been carried out on the failure probability of the several DNFM weldingjoints causing water leakage in the torus vacuum Such failure event can cause the stop of theplasma operations for several weeks As mitigation action a DNFM prototype will be manufacturedfor test at high temperatures (up to 350 degrees C) and high water pressure (20 divide 40 MPa)

The use of the various time resolved flux detection systems (B3 B4 and BC) and use ofmultiple locations allow compensation of effects due to changes in plasma position or shape andprovides redundancy in case of detectors failure Together these systems give the global neutronsource strength from which the total fusion power is obtained and the measurement should beinsensitive to plasma position

46 B8 Neutron Activation System

This diagnostic system (NAS) provides time integrated measurements of the neutron fluence at theFirst Wall and total fusion power through neutronic calculations [15]

Foil samples are irradiated at positions near the FW Several irradiation ends have been po-sitioned between various Blanket Modules and on the VV inner wall as well in the Upper andEquatorial Ports (figure 8) The foils samples are transferred using a pneumatic capsule system tocounting stations through port feedthroughs

ndash 10 ndash

2012 JINST 7 C04012

a) b) c) Support IE

Figure 8 a) NAS transfer lines inside the Vacuum Vessel b) Poloidal position of the various IrradiationEnds c) Support and Irradiation End of Position F

High thermal loads are expected at the irradiation ends because of the plasma radiation andnuclear heating This fact precludes a number of materials for the capsule or sample such aspolyethylene In and Al Moreover EM forces induced by plasma disruptions require the design ofdedicated strong supports

RampD activity is on-going on the selection of material and mass of the samples in order to limitactivation and avoid counting saturation effect for the various ITER operation scenarios (from 300s up to 3000 s)

The NAS diagnostic plays a fundamental role in the ITER Neutron Calibration Strategy be-cause is the only neutron diagnostic having a dynamic range of 10 orders of magnitude due toappropriate selection of mass and foils materials

In ITER the extended nature of the plasma neutron source means that the spatial dependence ofthe sensitivity of the different neutron systems is needed and this is obtained by in-situ calibrationsin these a source of known intensity is moved inside the tokamak vacuum chamber and the responseof the neutron detectors is recorded For ITER a powerful source with an intensity sim 1011ns isneeded Account needs to be taken of the potential screening and scattering effects of the structurethat is supporting the neutron source and this is done by use of the neutron transport codes code

NAS will be absolutely calibrated during the ITER in situ neutron calibration and during theITER DD and DT phases with well-characterized plasma reference shots allowing the cross cali-bration of all other ITER neutron diagnostic systems [16 17]

ndash 11 ndash

2012 JINST 7 C04012

47 BB High Resolution Neutron Spectrometer

Provision is made for a later installation of high-resolution neutron spectrometers (HRNS) for DDand DT neutron spectroscopy by adding a collimator into the neutron camera on equatorial port 1(figure 9a b) so that instruments can be installed later

In order to measure the neutron energy distribution of DD and DT emission two or threeneutron spectroscopy instruments are required Different type of spectrometer will be considered(Time of Flight Thin Proton Recoil etc)

Because of the high neutron flux (around 109 ncm2 s) needed to meet ITER measurementrequirements (100 ms time resolution and 10divide 20 accuracy) a neutron beam dump and housingsurrounding HRNS for local shield (figure 9c) have to be installed in the Port Cell 1 in order tomeet radiation safety parameters

a) b)

ndash 12 ndash

2012 JINST 7 C04012

c)

Figure 9 a b c High Resolution Neutron Spectrometers

5 Diagnostic integration

ITER neutronic diagnostics are installed within the vacuum vessel in the port plugs in the divertorand in-cryostat The installation integrations issues and loading conditions in each of these fourlocations are different and this could preclude the use of the same design for one particular systempositioned in different locations

The integration of several diagnostics in the port plugs as well in the interspaces and portcells is a key issue Several ITER systems are interfacing with the diagnostics Remote Handlingfor maintenance provision of water cooling cabling and power supply Bioshield for radiationdose reduction etc Here after some examples of integration and interface matters are reportedconcerning the neutron diagnostics at different locations The same issues are faced also by forother diagnostics systems

Diagnostics in Equatorial Ports diagnostic equipment is mounted in a port plug assembly [18]The port plug geometry consists of two basic parts -the Diagnostic Shield Module (DSM) andthe generic port plug structure figure 10a The Diagnostic Shield Module (DSM) consists ofseveral parts the Diagnostic First Wall (DFW) which is designed to handle the radiant heat fluxfrom the plasma the Diagnostic Shielding Block (DSB) which is designed to handle most of theneutronic heat load and the supporting moduledrawer which fastens the components to the portplug structure and provides a platform or housing for the diagnostic components Figure 10b showsthe drawer in eq Port 1 containing the inport detectors and collimators of B1 RNC

ndash 13 ndash

2012 JINST 7 C04012

a) Typical Equatorial port plug geometry b) In port RNC drawer in EqPort1

Figure 10 Equatorial port plug geometry

Figure 11 Recess of Diagnostic First Wall

The port plug assembly provides also the primary vacuum boundary at that port as well as thefeed-out for diagnostic signals (windows and feedthroughs) and feed-in for control signals

In the DSM there are a number of apertures for diagnostic viewing In designing the RNCsight lines of the inport detectors and related focal points attention has been paid to minimize theaperture (figure 10b) in the DFW which is recessed with respect to the nearby blanket modules(figure 11) This recess is needed to reduce the plasma interaction with the DFW

As an example eq Port Plug 1 is shown (figure 12) which is the most congested with diag-nostics The rational behind this is the need for being as close as possible to the plasma Followingsystems will be installed Radial Neutron Camera Divertor Impurity Monitor Bolometers Mo-tional Stark Effect Many factors have to be taken into account in optimizing the distribution ofdiagnostics within the available ports Because of neutron streaming considerations typically nomore than two systems with large labyrinths can be installed in one port with large aperture sys-tems placed near the port centres distributed systems are located evenly toroidally sometimescoordinated with the location of corresponding systems in the upper ports

ndash 14 ndash

2012 JINST 7 C04012

a) b)

Figure 12 Equatorial port plug 1 a) back view of feedthroughs and connections b) front view

Diagnostics in Vacuum Vessel for the systems installed in the vacuum vessel like B3 MFC andB8 Neutron Activation System a support structure ensuring a very good thermal and mechanicalanchoring to the vacuum vessel wall is required This together with the routing and clamping of thecables and pipes adjusting the irradiation ends to the gaps between the blanket modules leads to acontinuous integration work assuring enough clearance to the neighbouring components and properdefinition of the large variety of in-vacuum vessel interfaces Even though partially shielded by theblanket modules the design of some of the components are challenged by the varying magneticfields high nuclear heat and the loop voltage created around the vessel Last but not least are theinterfacing loads like ECRH stray power and additional acceleration due to disruption events Thelatter one is more important to systems like MFC which should be tested in order to prove that theymaintain performance under shock and vibration

Diagnostics in Cryostat for the B4 Neutron flux monitor located in the in-cryostat area the loadconditions are less severe Because the system is mounted on an extended support structure attachedto the cryostat wall the major loads which should be taken into account are the acceleration due togravity acceleration due to seismic events and those during plasma disruptions and displacements

Diagnostics in Divertor the most demanding among all the mentioned locations is the divertorwhere the load conditions are very severe and it requires an active cooling of all diagnostic compo-nents This on the other hand creates an additional interface with the divertor cooling water branchof which is used for the cooling of the diagnostic components and a development of a good strategyfor a leak localization and detection

The BC Divertor Neutron Flux Monitor is mounted on a cassette body which is remote handleable through the divertor port The divertor dome provides an opportunity to place diagnosticsinside the vacuum vessel since it provides some degree of shelter from the neutron flux and plasmaradiation In the same cassette bolometers which are used for measuring the power of incidentelectromagnetic radiation are required to sit in the gap between two adjacent cassette bodies Thiscreates some integration issues as the one presented in figure 13

ndash 15 ndash

2012 JINST 7 C04012

Figure 13 Integration issue bolometers and DNFM ldquosharingrdquo the same support structure

The B2 Lower Vertical Neutron Camera (LVNC) is integrated into the lower port A genericdiagnostic rack to house diagnostics or optical relays in the port is being developed which willbe customized for each diagnostic while keeping the same interfaces with the vacuum vessel Thediagnostic rack is attached to the side walls of the port and includes features for alignment to thedivertor central cassette On the basis of the recently performed neutronic analysis it became clearthat the vertical camera could not co-exist with any optical system in the same port as this is thecase now Activity is going on the possible relocation either of LVNC or of the optical systems

One of the most difficult interfaces between the blanket system and the diagnostics is pre-sented by the integration of the B2 LVNC The line of sights of the detectors need to protrude theblanket shielding module 18 and the first wall exactly in the middle where the remote handlingattachment the hydraulic connector and the cooling channels are designed as shown in figure 14This fact can bring to the reduction of number of sight lines Design work is being carried out tosort out this problem

ndash 16 ndash

2012 JINST 7 C04012

Figure 14 Interface between Blanket Module 18 and lines of sight of the Vertical Neutron Camera

An overview of ITER neutron diagnostic systems and of the associated challenging engineer-ing and integration issues has been described The design of these systems has taken into accountthe experience gained on large devices which have pointed out the importance of simultaneuousmeasurements of the neutron spatial and energy distributions

The main advantage of this complete set-up of ITER neutron diagnostics is its installation andoperation from the begin of ITER nuclear operation compared to other machines like JET LHDTFTR JT 60 where the various neutron diagnostics have been installed during different machineoperational phases

Acknowledgments

The authors wish to thank ITER Diagnostics Team and the colleagues of ITER Members of JapanKorea China Europe and Russian Federation for useful discussions and collaboration

The work described was supported and carried out by ITER Organization together with ITERMembers and Domestic Agencies of Japan Korea China Europe and Russian Federation Part ofthis activity was performed within the framework of the European Fusion Development Agreement

Disclaimer The views and opinions expressed herein do not necessarily reflect those of the ITERorganization

ndash 17 ndash

2012 JINST 7 C04012

References

[1] AJH Donne et al Progress in the ITER physics basis Chapter 7 diagnostics Nucl Fusion 47(2007) 337

[2] G Vayakis ER Hodgson and V Voitsenya Plasma diagnostics for magnetic fusion researchChapter 12 generic diagnostic issues for a burning plasma experiment Fusion Sci Technol 53(2008) 699

[3] A Encheva L Bertalot B Macklin G Vayakis and C Walker Integration of ITER in-vesseldiagnostic components in the vacuum vessel Fusion Eng Des 84 (2009) 736

[4] A Krasilnikov et al Status of ITER neutron diagnostic development Nucl Fusion 45 (2005) 1503

[5] M Sasao et al Plasma diagnostics for magnetic fusion research Chapter 9 fusion productdiagnostics Fusion Sci Technol 53 (2008) 604

[6] FP Orsitto et al Burning plasmas diagnostics AIP Conf Proc 988 Varenna Italy (2007)

[7] L Petrizzi et al Neutronic design of the ITER radial neutron camera Fusion Sci Eng 82 (2007)1308

[8] AV Krasilnikov CI Walker YA Kashchuk and DV Prosvirin A multichannel neutron collimatorfor the ITER tokamak Kluwer AcademicPlenum Publishers Instrum Exp Tech 47 (2004) 139

[9] A Encheva et al Engineering aspects of integration of ITER divertor diagnostics Fusion Eng Des86 (2011) 1323

[10] M Ishikawa et al Design of microfission chamber for ITER operations Rev Sci Instrum 79 (2008)10E507

[11] A Encheva et al Structural integrity report for ITER micro-fission chamber ITER documentITER D 3TDURL

[12] T Nishitani et al Engineering design of the ITER invessel neutron monitor using micro-fissionchambers Fusion Eng Des 82 (2007) 1192

[13] J Yang et al Fusion neutron flux monitor for ITER Plasma Sci Technol 10 (2008) 141

[14] YA Kashchuk AV Krasilrsquonikov and DV Prosvirin A conceptual project for a divertor monitor ofthe neutron yield in the ITER Instrum Exp Tech 49 (2006) 179

[15] MS Cheon et al In-vessel design of ITER diagnostic neutron activation system Rev Sci Instrum79 (2008) 10E505

[16] L Bertalot et al A strategy for calibrating the neutron systems at ITER in 35th plasma physicsconference Crete Greece 2008 EPS Europhysics Conference Abstracts 32D (2008) O2001httpepsppdepflchHersonissosstarthtm

[17] M Sasao L Bertalot M Ishikawa and S Popovichev Strategy for the absolute neutron emissionmeasurement on ITER Rev Sci Instrum 81 (2010) 10D329

[18] S Pitcher et al System Design Description Document (DDD) diagnostic generic equatorial portplug ITER document ITER D 3U8JU7

ndash 18 ndash

2012 JINST 7 C04012

Figure 4 Vertical Neutron Camera mounted adjacent to a port at the lower level

43 B3 MicroFission Chambers

This diagnostic will provide the total neutron strength during the DT operation ie the high fusionpower phase

The neutron flux is typically measured by fission chambers containing 235U or other isotopesand filled typically with Argon gas at few atmospheres Micro-fission chambers (MFC) are de-ployed between the blanket modules and the inner shell of the Vacuum Vessel (VV) Four MFCmodules are located at two toroidal positions with two modules positioned in two different poloidallocations (figure 5) [10] By designing MFC attention has been paid to several issues such as vacuumleak rate of MFC high operational temperature tight clearance between the components and theblanket modules [11] RampD actitivity is required to ensure the proper functioning of the chamberssubjected to vibration and shock caused by various disruption events

Thermal analysis has shown that MFC can be cooled by conduction to the Vacuum Vesselreaching temperatures less than 200 ˚ C degrees if the SS module has a heat transfer coefficient gt

100 Wmminus2 Kminus1 [12]

Guard Vacuum pipes have been connected to the MFC modules to avoid detector gas entryinto the torus vacuum in the event of a fault

ndash 7 ndash

2012 JINST 7 C04012

a) b)

Figure 5 a) Two Microfission Chambers on VV Sector 1 b) detail of the Upper MFC module

44 B4 Neutron Flux Monitor

This diagnostic system will provide the total neutron strength during all phases of ITER operationFour modules containing each three Fission Chambers with different fissile content are at presentlocated in Equatorial Port 1 7 8 and 17 [13] (baseline definition of eq Port 8 and 17 has recentlychanged and as such these ports are under discussion)

The Neutron Flux Monitors (NFM) in ports 1 and 7 are used to measure DD neutron flux orthe insitu calibration flux whereas in ports 8 and 17 are used to detect DT neutron flux in bothmedium-power operation and full power operation respectively Different moderating materials(Be Graphite and B4C) with various thicknesses will be used for obtaining different sensitivities ofthe four NFMs modules with the aim of measure the total neutron strength from 1014 up to around1021 ns

RampD activities are going on to face the many implementation issues as described above (vac-uum leak high operational temperature magnetic stray fields etc)

The NFM in eq Port 7 is shown (figure 6) as example of the integration and interfaces issuesto be faced with Cryostat Thermal shield Bioshield and Neutral Beam Area

ndash 8 ndash

2012 JINST 7 C04012

VV NFM EQ7 Thermal Shield Cryostat

Figure 6 Neutron Flux Monitor integrated into Equatorial port 7

45 BC Divertor Neutron Flux Monitors

The Divertor Neutron Flux Monitors (DNFM) diagnostic [14] measures the time-resolved neutronemission from the ITER for both DD and DT plasmas providing the evaluation of the fusion power

Three DNFM modules will be installed in ITER Divertor Cassettes under the dome Thelocations of these modules are at three different toroidal positions Divertor Cassette 3 in lowerport 2 Divertor Cassette 21 in lower port 8 and Divertor Cassette 39 at lower port 14

Each module is composed of six fission chambers (FC) identical in dimension and coatedwith varying amount of 235U amp 238U fissile material

The six fission chambers are enclosed in two cylinders three U235 FC in one cylinder and threeU238 FC in the other one forming the DNFM module see figure 7

By developing a good and structuraly sound design some major challenges have been facedhigh nuclear and radiation power loads transient magnetic field causing large forces and momentsacting on the sturcture and non-negligible halo currents The Divertor water cooling system will beused also for the DNFM

ndash 9 ndash

2012 JINST 7 C04012

Figure 7 Integration of DNFM in Lower Port

Risk analysis has been carried out on the failure probability of the several DNFM weldingjoints causing water leakage in the torus vacuum Such failure event can cause the stop of theplasma operations for several weeks As mitigation action a DNFM prototype will be manufacturedfor test at high temperatures (up to 350 degrees C) and high water pressure (20 divide 40 MPa)

The use of the various time resolved flux detection systems (B3 B4 and BC) and use ofmultiple locations allow compensation of effects due to changes in plasma position or shape andprovides redundancy in case of detectors failure Together these systems give the global neutronsource strength from which the total fusion power is obtained and the measurement should beinsensitive to plasma position

46 B8 Neutron Activation System

This diagnostic system (NAS) provides time integrated measurements of the neutron fluence at theFirst Wall and total fusion power through neutronic calculations [15]

Foil samples are irradiated at positions near the FW Several irradiation ends have been po-sitioned between various Blanket Modules and on the VV inner wall as well in the Upper andEquatorial Ports (figure 8) The foils samples are transferred using a pneumatic capsule system tocounting stations through port feedthroughs

ndash 10 ndash

2012 JINST 7 C04012

a) b) c) Support IE

Figure 8 a) NAS transfer lines inside the Vacuum Vessel b) Poloidal position of the various IrradiationEnds c) Support and Irradiation End of Position F

High thermal loads are expected at the irradiation ends because of the plasma radiation andnuclear heating This fact precludes a number of materials for the capsule or sample such aspolyethylene In and Al Moreover EM forces induced by plasma disruptions require the design ofdedicated strong supports

RampD activity is on-going on the selection of material and mass of the samples in order to limitactivation and avoid counting saturation effect for the various ITER operation scenarios (from 300s up to 3000 s)

The NAS diagnostic plays a fundamental role in the ITER Neutron Calibration Strategy be-cause is the only neutron diagnostic having a dynamic range of 10 orders of magnitude due toappropriate selection of mass and foils materials

In ITER the extended nature of the plasma neutron source means that the spatial dependence ofthe sensitivity of the different neutron systems is needed and this is obtained by in-situ calibrationsin these a source of known intensity is moved inside the tokamak vacuum chamber and the responseof the neutron detectors is recorded For ITER a powerful source with an intensity sim 1011ns isneeded Account needs to be taken of the potential screening and scattering effects of the structurethat is supporting the neutron source and this is done by use of the neutron transport codes code

NAS will be absolutely calibrated during the ITER in situ neutron calibration and during theITER DD and DT phases with well-characterized plasma reference shots allowing the cross cali-bration of all other ITER neutron diagnostic systems [16 17]

ndash 11 ndash

2012 JINST 7 C04012

47 BB High Resolution Neutron Spectrometer

Provision is made for a later installation of high-resolution neutron spectrometers (HRNS) for DDand DT neutron spectroscopy by adding a collimator into the neutron camera on equatorial port 1(figure 9a b) so that instruments can be installed later

In order to measure the neutron energy distribution of DD and DT emission two or threeneutron spectroscopy instruments are required Different type of spectrometer will be considered(Time of Flight Thin Proton Recoil etc)

Because of the high neutron flux (around 109 ncm2 s) needed to meet ITER measurementrequirements (100 ms time resolution and 10divide 20 accuracy) a neutron beam dump and housingsurrounding HRNS for local shield (figure 9c) have to be installed in the Port Cell 1 in order tomeet radiation safety parameters

a) b)

ndash 12 ndash

2012 JINST 7 C04012

c)

Figure 9 a b c High Resolution Neutron Spectrometers

5 Diagnostic integration

ITER neutronic diagnostics are installed within the vacuum vessel in the port plugs in the divertorand in-cryostat The installation integrations issues and loading conditions in each of these fourlocations are different and this could preclude the use of the same design for one particular systempositioned in different locations

The integration of several diagnostics in the port plugs as well in the interspaces and portcells is a key issue Several ITER systems are interfacing with the diagnostics Remote Handlingfor maintenance provision of water cooling cabling and power supply Bioshield for radiationdose reduction etc Here after some examples of integration and interface matters are reportedconcerning the neutron diagnostics at different locations The same issues are faced also by forother diagnostics systems

Diagnostics in Equatorial Ports diagnostic equipment is mounted in a port plug assembly [18]The port plug geometry consists of two basic parts -the Diagnostic Shield Module (DSM) andthe generic port plug structure figure 10a The Diagnostic Shield Module (DSM) consists ofseveral parts the Diagnostic First Wall (DFW) which is designed to handle the radiant heat fluxfrom the plasma the Diagnostic Shielding Block (DSB) which is designed to handle most of theneutronic heat load and the supporting moduledrawer which fastens the components to the portplug structure and provides a platform or housing for the diagnostic components Figure 10b showsthe drawer in eq Port 1 containing the inport detectors and collimators of B1 RNC

ndash 13 ndash

2012 JINST 7 C04012

a) Typical Equatorial port plug geometry b) In port RNC drawer in EqPort1

Figure 10 Equatorial port plug geometry

Figure 11 Recess of Diagnostic First Wall

The port plug assembly provides also the primary vacuum boundary at that port as well as thefeed-out for diagnostic signals (windows and feedthroughs) and feed-in for control signals

In the DSM there are a number of apertures for diagnostic viewing In designing the RNCsight lines of the inport detectors and related focal points attention has been paid to minimize theaperture (figure 10b) in the DFW which is recessed with respect to the nearby blanket modules(figure 11) This recess is needed to reduce the plasma interaction with the DFW

As an example eq Port Plug 1 is shown (figure 12) which is the most congested with diag-nostics The rational behind this is the need for being as close as possible to the plasma Followingsystems will be installed Radial Neutron Camera Divertor Impurity Monitor Bolometers Mo-tional Stark Effect Many factors have to be taken into account in optimizing the distribution ofdiagnostics within the available ports Because of neutron streaming considerations typically nomore than two systems with large labyrinths can be installed in one port with large aperture sys-tems placed near the port centres distributed systems are located evenly toroidally sometimescoordinated with the location of corresponding systems in the upper ports

ndash 14 ndash

2012 JINST 7 C04012

a) b)

Figure 12 Equatorial port plug 1 a) back view of feedthroughs and connections b) front view

Diagnostics in Vacuum Vessel for the systems installed in the vacuum vessel like B3 MFC andB8 Neutron Activation System a support structure ensuring a very good thermal and mechanicalanchoring to the vacuum vessel wall is required This together with the routing and clamping of thecables and pipes adjusting the irradiation ends to the gaps between the blanket modules leads to acontinuous integration work assuring enough clearance to the neighbouring components and properdefinition of the large variety of in-vacuum vessel interfaces Even though partially shielded by theblanket modules the design of some of the components are challenged by the varying magneticfields high nuclear heat and the loop voltage created around the vessel Last but not least are theinterfacing loads like ECRH stray power and additional acceleration due to disruption events Thelatter one is more important to systems like MFC which should be tested in order to prove that theymaintain performance under shock and vibration

Diagnostics in Cryostat for the B4 Neutron flux monitor located in the in-cryostat area the loadconditions are less severe Because the system is mounted on an extended support structure attachedto the cryostat wall the major loads which should be taken into account are the acceleration due togravity acceleration due to seismic events and those during plasma disruptions and displacements

Diagnostics in Divertor the most demanding among all the mentioned locations is the divertorwhere the load conditions are very severe and it requires an active cooling of all diagnostic compo-nents This on the other hand creates an additional interface with the divertor cooling water branchof which is used for the cooling of the diagnostic components and a development of a good strategyfor a leak localization and detection

The BC Divertor Neutron Flux Monitor is mounted on a cassette body which is remote handleable through the divertor port The divertor dome provides an opportunity to place diagnosticsinside the vacuum vessel since it provides some degree of shelter from the neutron flux and plasmaradiation In the same cassette bolometers which are used for measuring the power of incidentelectromagnetic radiation are required to sit in the gap between two adjacent cassette bodies Thiscreates some integration issues as the one presented in figure 13

ndash 15 ndash

2012 JINST 7 C04012

Figure 13 Integration issue bolometers and DNFM ldquosharingrdquo the same support structure

The B2 Lower Vertical Neutron Camera (LVNC) is integrated into the lower port A genericdiagnostic rack to house diagnostics or optical relays in the port is being developed which willbe customized for each diagnostic while keeping the same interfaces with the vacuum vessel Thediagnostic rack is attached to the side walls of the port and includes features for alignment to thedivertor central cassette On the basis of the recently performed neutronic analysis it became clearthat the vertical camera could not co-exist with any optical system in the same port as this is thecase now Activity is going on the possible relocation either of LVNC or of the optical systems

One of the most difficult interfaces between the blanket system and the diagnostics is pre-sented by the integration of the B2 LVNC The line of sights of the detectors need to protrude theblanket shielding module 18 and the first wall exactly in the middle where the remote handlingattachment the hydraulic connector and the cooling channels are designed as shown in figure 14This fact can bring to the reduction of number of sight lines Design work is being carried out tosort out this problem

ndash 16 ndash

2012 JINST 7 C04012

Figure 14 Interface between Blanket Module 18 and lines of sight of the Vertical Neutron Camera

An overview of ITER neutron diagnostic systems and of the associated challenging engineer-ing and integration issues has been described The design of these systems has taken into accountthe experience gained on large devices which have pointed out the importance of simultaneuousmeasurements of the neutron spatial and energy distributions

The main advantage of this complete set-up of ITER neutron diagnostics is its installation andoperation from the begin of ITER nuclear operation compared to other machines like JET LHDTFTR JT 60 where the various neutron diagnostics have been installed during different machineoperational phases

Acknowledgments

The authors wish to thank ITER Diagnostics Team and the colleagues of ITER Members of JapanKorea China Europe and Russian Federation for useful discussions and collaboration

The work described was supported and carried out by ITER Organization together with ITERMembers and Domestic Agencies of Japan Korea China Europe and Russian Federation Part ofthis activity was performed within the framework of the European Fusion Development Agreement

Disclaimer The views and opinions expressed herein do not necessarily reflect those of the ITERorganization

ndash 17 ndash

2012 JINST 7 C04012

References

[1] AJH Donne et al Progress in the ITER physics basis Chapter 7 diagnostics Nucl Fusion 47(2007) 337

[2] G Vayakis ER Hodgson and V Voitsenya Plasma diagnostics for magnetic fusion researchChapter 12 generic diagnostic issues for a burning plasma experiment Fusion Sci Technol 53(2008) 699

[3] A Encheva L Bertalot B Macklin G Vayakis and C Walker Integration of ITER in-vesseldiagnostic components in the vacuum vessel Fusion Eng Des 84 (2009) 736

[4] A Krasilnikov et al Status of ITER neutron diagnostic development Nucl Fusion 45 (2005) 1503

[5] M Sasao et al Plasma diagnostics for magnetic fusion research Chapter 9 fusion productdiagnostics Fusion Sci Technol 53 (2008) 604

[6] FP Orsitto et al Burning plasmas diagnostics AIP Conf Proc 988 Varenna Italy (2007)

[7] L Petrizzi et al Neutronic design of the ITER radial neutron camera Fusion Sci Eng 82 (2007)1308

[8] AV Krasilnikov CI Walker YA Kashchuk and DV Prosvirin A multichannel neutron collimatorfor the ITER tokamak Kluwer AcademicPlenum Publishers Instrum Exp Tech 47 (2004) 139

[9] A Encheva et al Engineering aspects of integration of ITER divertor diagnostics Fusion Eng Des86 (2011) 1323

[10] M Ishikawa et al Design of microfission chamber for ITER operations Rev Sci Instrum 79 (2008)10E507

[11] A Encheva et al Structural integrity report for ITER micro-fission chamber ITER documentITER D 3TDURL

[12] T Nishitani et al Engineering design of the ITER invessel neutron monitor using micro-fissionchambers Fusion Eng Des 82 (2007) 1192

[13] J Yang et al Fusion neutron flux monitor for ITER Plasma Sci Technol 10 (2008) 141

[14] YA Kashchuk AV Krasilrsquonikov and DV Prosvirin A conceptual project for a divertor monitor ofthe neutron yield in the ITER Instrum Exp Tech 49 (2006) 179

[15] MS Cheon et al In-vessel design of ITER diagnostic neutron activation system Rev Sci Instrum79 (2008) 10E505

[16] L Bertalot et al A strategy for calibrating the neutron systems at ITER in 35th plasma physicsconference Crete Greece 2008 EPS Europhysics Conference Abstracts 32D (2008) O2001httpepsppdepflchHersonissosstarthtm

[17] M Sasao L Bertalot M Ishikawa and S Popovichev Strategy for the absolute neutron emissionmeasurement on ITER Rev Sci Instrum 81 (2010) 10D329

[18] S Pitcher et al System Design Description Document (DDD) diagnostic generic equatorial portplug ITER document ITER D 3U8JU7

ndash 18 ndash

2012 JINST 7 C04012

a) b)

Figure 5 a) Two Microfission Chambers on VV Sector 1 b) detail of the Upper MFC module

44 B4 Neutron Flux Monitor

This diagnostic system will provide the total neutron strength during all phases of ITER operationFour modules containing each three Fission Chambers with different fissile content are at presentlocated in Equatorial Port 1 7 8 and 17 [13] (baseline definition of eq Port 8 and 17 has recentlychanged and as such these ports are under discussion)

The Neutron Flux Monitors (NFM) in ports 1 and 7 are used to measure DD neutron flux orthe insitu calibration flux whereas in ports 8 and 17 are used to detect DT neutron flux in bothmedium-power operation and full power operation respectively Different moderating materials(Be Graphite and B4C) with various thicknesses will be used for obtaining different sensitivities ofthe four NFMs modules with the aim of measure the total neutron strength from 1014 up to around1021 ns

RampD activities are going on to face the many implementation issues as described above (vac-uum leak high operational temperature magnetic stray fields etc)

The NFM in eq Port 7 is shown (figure 6) as example of the integration and interfaces issuesto be faced with Cryostat Thermal shield Bioshield and Neutral Beam Area

ndash 8 ndash

2012 JINST 7 C04012

VV NFM EQ7 Thermal Shield Cryostat

Figure 6 Neutron Flux Monitor integrated into Equatorial port 7

45 BC Divertor Neutron Flux Monitors

The Divertor Neutron Flux Monitors (DNFM) diagnostic [14] measures the time-resolved neutronemission from the ITER for both DD and DT plasmas providing the evaluation of the fusion power

Three DNFM modules will be installed in ITER Divertor Cassettes under the dome Thelocations of these modules are at three different toroidal positions Divertor Cassette 3 in lowerport 2 Divertor Cassette 21 in lower port 8 and Divertor Cassette 39 at lower port 14

Each module is composed of six fission chambers (FC) identical in dimension and coatedwith varying amount of 235U amp 238U fissile material

The six fission chambers are enclosed in two cylinders three U235 FC in one cylinder and threeU238 FC in the other one forming the DNFM module see figure 7

By developing a good and structuraly sound design some major challenges have been facedhigh nuclear and radiation power loads transient magnetic field causing large forces and momentsacting on the sturcture and non-negligible halo currents The Divertor water cooling system will beused also for the DNFM

ndash 9 ndash

2012 JINST 7 C04012

Figure 7 Integration of DNFM in Lower Port

Risk analysis has been carried out on the failure probability of the several DNFM weldingjoints causing water leakage in the torus vacuum Such failure event can cause the stop of theplasma operations for several weeks As mitigation action a DNFM prototype will be manufacturedfor test at high temperatures (up to 350 degrees C) and high water pressure (20 divide 40 MPa)

The use of the various time resolved flux detection systems (B3 B4 and BC) and use ofmultiple locations allow compensation of effects due to changes in plasma position or shape andprovides redundancy in case of detectors failure Together these systems give the global neutronsource strength from which the total fusion power is obtained and the measurement should beinsensitive to plasma position

46 B8 Neutron Activation System

This diagnostic system (NAS) provides time integrated measurements of the neutron fluence at theFirst Wall and total fusion power through neutronic calculations [15]

Foil samples are irradiated at positions near the FW Several irradiation ends have been po-sitioned between various Blanket Modules and on the VV inner wall as well in the Upper andEquatorial Ports (figure 8) The foils samples are transferred using a pneumatic capsule system tocounting stations through port feedthroughs

ndash 10 ndash

2012 JINST 7 C04012

a) b) c) Support IE

Figure 8 a) NAS transfer lines inside the Vacuum Vessel b) Poloidal position of the various IrradiationEnds c) Support and Irradiation End of Position F

High thermal loads are expected at the irradiation ends because of the plasma radiation andnuclear heating This fact precludes a number of materials for the capsule or sample such aspolyethylene In and Al Moreover EM forces induced by plasma disruptions require the design ofdedicated strong supports

RampD activity is on-going on the selection of material and mass of the samples in order to limitactivation and avoid counting saturation effect for the various ITER operation scenarios (from 300s up to 3000 s)

The NAS diagnostic plays a fundamental role in the ITER Neutron Calibration Strategy be-cause is the only neutron diagnostic having a dynamic range of 10 orders of magnitude due toappropriate selection of mass and foils materials

In ITER the extended nature of the plasma neutron source means that the spatial dependence ofthe sensitivity of the different neutron systems is needed and this is obtained by in-situ calibrationsin these a source of known intensity is moved inside the tokamak vacuum chamber and the responseof the neutron detectors is recorded For ITER a powerful source with an intensity sim 1011ns isneeded Account needs to be taken of the potential screening and scattering effects of the structurethat is supporting the neutron source and this is done by use of the neutron transport codes code

NAS will be absolutely calibrated during the ITER in situ neutron calibration and during theITER DD and DT phases with well-characterized plasma reference shots allowing the cross cali-bration of all other ITER neutron diagnostic systems [16 17]

ndash 11 ndash

2012 JINST 7 C04012

47 BB High Resolution Neutron Spectrometer

Provision is made for a later installation of high-resolution neutron spectrometers (HRNS) for DDand DT neutron spectroscopy by adding a collimator into the neutron camera on equatorial port 1(figure 9a b) so that instruments can be installed later

In order to measure the neutron energy distribution of DD and DT emission two or threeneutron spectroscopy instruments are required Different type of spectrometer will be considered(Time of Flight Thin Proton Recoil etc)

Because of the high neutron flux (around 109 ncm2 s) needed to meet ITER measurementrequirements (100 ms time resolution and 10divide 20 accuracy) a neutron beam dump and housingsurrounding HRNS for local shield (figure 9c) have to be installed in the Port Cell 1 in order tomeet radiation safety parameters

a) b)

ndash 12 ndash

2012 JINST 7 C04012

c)

Figure 9 a b c High Resolution Neutron Spectrometers

5 Diagnostic integration

ITER neutronic diagnostics are installed within the vacuum vessel in the port plugs in the divertorand in-cryostat The installation integrations issues and loading conditions in each of these fourlocations are different and this could preclude the use of the same design for one particular systempositioned in different locations

The integration of several diagnostics in the port plugs as well in the interspaces and portcells is a key issue Several ITER systems are interfacing with the diagnostics Remote Handlingfor maintenance provision of water cooling cabling and power supply Bioshield for radiationdose reduction etc Here after some examples of integration and interface matters are reportedconcerning the neutron diagnostics at different locations The same issues are faced also by forother diagnostics systems

Diagnostics in Equatorial Ports diagnostic equipment is mounted in a port plug assembly [18]The port plug geometry consists of two basic parts -the Diagnostic Shield Module (DSM) andthe generic port plug structure figure 10a The Diagnostic Shield Module (DSM) consists ofseveral parts the Diagnostic First Wall (DFW) which is designed to handle the radiant heat fluxfrom the plasma the Diagnostic Shielding Block (DSB) which is designed to handle most of theneutronic heat load and the supporting moduledrawer which fastens the components to the portplug structure and provides a platform or housing for the diagnostic components Figure 10b showsthe drawer in eq Port 1 containing the inport detectors and collimators of B1 RNC

ndash 13 ndash

2012 JINST 7 C04012

a) Typical Equatorial port plug geometry b) In port RNC drawer in EqPort1

Figure 10 Equatorial port plug geometry

Figure 11 Recess of Diagnostic First Wall

The port plug assembly provides also the primary vacuum boundary at that port as well as thefeed-out for diagnostic signals (windows and feedthroughs) and feed-in for control signals

In the DSM there are a number of apertures for diagnostic viewing In designing the RNCsight lines of the inport detectors and related focal points attention has been paid to minimize theaperture (figure 10b) in the DFW which is recessed with respect to the nearby blanket modules(figure 11) This recess is needed to reduce the plasma interaction with the DFW

As an example eq Port Plug 1 is shown (figure 12) which is the most congested with diag-nostics The rational behind this is the need for being as close as possible to the plasma Followingsystems will be installed Radial Neutron Camera Divertor Impurity Monitor Bolometers Mo-tional Stark Effect Many factors have to be taken into account in optimizing the distribution ofdiagnostics within the available ports Because of neutron streaming considerations typically nomore than two systems with large labyrinths can be installed in one port with large aperture sys-tems placed near the port centres distributed systems are located evenly toroidally sometimescoordinated with the location of corresponding systems in the upper ports

ndash 14 ndash

2012 JINST 7 C04012

a) b)

Figure 12 Equatorial port plug 1 a) back view of feedthroughs and connections b) front view

Diagnostics in Vacuum Vessel for the systems installed in the vacuum vessel like B3 MFC andB8 Neutron Activation System a support structure ensuring a very good thermal and mechanicalanchoring to the vacuum vessel wall is required This together with the routing and clamping of thecables and pipes adjusting the irradiation ends to the gaps between the blanket modules leads to acontinuous integration work assuring enough clearance to the neighbouring components and properdefinition of the large variety of in-vacuum vessel interfaces Even though partially shielded by theblanket modules the design of some of the components are challenged by the varying magneticfields high nuclear heat and the loop voltage created around the vessel Last but not least are theinterfacing loads like ECRH stray power and additional acceleration due to disruption events Thelatter one is more important to systems like MFC which should be tested in order to prove that theymaintain performance under shock and vibration

Diagnostics in Cryostat for the B4 Neutron flux monitor located in the in-cryostat area the loadconditions are less severe Because the system is mounted on an extended support structure attachedto the cryostat wall the major loads which should be taken into account are the acceleration due togravity acceleration due to seismic events and those during plasma disruptions and displacements

Diagnostics in Divertor the most demanding among all the mentioned locations is the divertorwhere the load conditions are very severe and it requires an active cooling of all diagnostic compo-nents This on the other hand creates an additional interface with the divertor cooling water branchof which is used for the cooling of the diagnostic components and a development of a good strategyfor a leak localization and detection

The BC Divertor Neutron Flux Monitor is mounted on a cassette body which is remote handleable through the divertor port The divertor dome provides an opportunity to place diagnosticsinside the vacuum vessel since it provides some degree of shelter from the neutron flux and plasmaradiation In the same cassette bolometers which are used for measuring the power of incidentelectromagnetic radiation are required to sit in the gap between two adjacent cassette bodies Thiscreates some integration issues as the one presented in figure 13

ndash 15 ndash

2012 JINST 7 C04012

Figure 13 Integration issue bolometers and DNFM ldquosharingrdquo the same support structure

The B2 Lower Vertical Neutron Camera (LVNC) is integrated into the lower port A genericdiagnostic rack to house diagnostics or optical relays in the port is being developed which willbe customized for each diagnostic while keeping the same interfaces with the vacuum vessel Thediagnostic rack is attached to the side walls of the port and includes features for alignment to thedivertor central cassette On the basis of the recently performed neutronic analysis it became clearthat the vertical camera could not co-exist with any optical system in the same port as this is thecase now Activity is going on the possible relocation either of LVNC or of the optical systems

One of the most difficult interfaces between the blanket system and the diagnostics is pre-sented by the integration of the B2 LVNC The line of sights of the detectors need to protrude theblanket shielding module 18 and the first wall exactly in the middle where the remote handlingattachment the hydraulic connector and the cooling channels are designed as shown in figure 14This fact can bring to the reduction of number of sight lines Design work is being carried out tosort out this problem

ndash 16 ndash

2012 JINST 7 C04012

Figure 14 Interface between Blanket Module 18 and lines of sight of the Vertical Neutron Camera

An overview of ITER neutron diagnostic systems and of the associated challenging engineer-ing and integration issues has been described The design of these systems has taken into accountthe experience gained on large devices which have pointed out the importance of simultaneuousmeasurements of the neutron spatial and energy distributions

The main advantage of this complete set-up of ITER neutron diagnostics is its installation andoperation from the begin of ITER nuclear operation compared to other machines like JET LHDTFTR JT 60 where the various neutron diagnostics have been installed during different machineoperational phases

Acknowledgments

The authors wish to thank ITER Diagnostics Team and the colleagues of ITER Members of JapanKorea China Europe and Russian Federation for useful discussions and collaboration

The work described was supported and carried out by ITER Organization together with ITERMembers and Domestic Agencies of Japan Korea China Europe and Russian Federation Part ofthis activity was performed within the framework of the European Fusion Development Agreement

Disclaimer The views and opinions expressed herein do not necessarily reflect those of the ITERorganization

ndash 17 ndash

2012 JINST 7 C04012

References

[1] AJH Donne et al Progress in the ITER physics basis Chapter 7 diagnostics Nucl Fusion 47(2007) 337

[2] G Vayakis ER Hodgson and V Voitsenya Plasma diagnostics for magnetic fusion researchChapter 12 generic diagnostic issues for a burning plasma experiment Fusion Sci Technol 53(2008) 699

[3] A Encheva L Bertalot B Macklin G Vayakis and C Walker Integration of ITER in-vesseldiagnostic components in the vacuum vessel Fusion Eng Des 84 (2009) 736

[4] A Krasilnikov et al Status of ITER neutron diagnostic development Nucl Fusion 45 (2005) 1503

[5] M Sasao et al Plasma diagnostics for magnetic fusion research Chapter 9 fusion productdiagnostics Fusion Sci Technol 53 (2008) 604

[6] FP Orsitto et al Burning plasmas diagnostics AIP Conf Proc 988 Varenna Italy (2007)

[7] L Petrizzi et al Neutronic design of the ITER radial neutron camera Fusion Sci Eng 82 (2007)1308

[8] AV Krasilnikov CI Walker YA Kashchuk and DV Prosvirin A multichannel neutron collimatorfor the ITER tokamak Kluwer AcademicPlenum Publishers Instrum Exp Tech 47 (2004) 139

[9] A Encheva et al Engineering aspects of integration of ITER divertor diagnostics Fusion Eng Des86 (2011) 1323

[10] M Ishikawa et al Design of microfission chamber for ITER operations Rev Sci Instrum 79 (2008)10E507

[11] A Encheva et al Structural integrity report for ITER micro-fission chamber ITER documentITER D 3TDURL

[12] T Nishitani et al Engineering design of the ITER invessel neutron monitor using micro-fissionchambers Fusion Eng Des 82 (2007) 1192

[13] J Yang et al Fusion neutron flux monitor for ITER Plasma Sci Technol 10 (2008) 141

[14] YA Kashchuk AV Krasilrsquonikov and DV Prosvirin A conceptual project for a divertor monitor ofthe neutron yield in the ITER Instrum Exp Tech 49 (2006) 179

[15] MS Cheon et al In-vessel design of ITER diagnostic neutron activation system Rev Sci Instrum79 (2008) 10E505

[16] L Bertalot et al A strategy for calibrating the neutron systems at ITER in 35th plasma physicsconference Crete Greece 2008 EPS Europhysics Conference Abstracts 32D (2008) O2001httpepsppdepflchHersonissosstarthtm

[17] M Sasao L Bertalot M Ishikawa and S Popovichev Strategy for the absolute neutron emissionmeasurement on ITER Rev Sci Instrum 81 (2010) 10D329

[18] S Pitcher et al System Design Description Document (DDD) diagnostic generic equatorial portplug ITER document ITER D 3U8JU7

ndash 18 ndash

2012 JINST 7 C04012

VV NFM EQ7 Thermal Shield Cryostat

Figure 6 Neutron Flux Monitor integrated into Equatorial port 7

45 BC Divertor Neutron Flux Monitors

The Divertor Neutron Flux Monitors (DNFM) diagnostic [14] measures the time-resolved neutronemission from the ITER for both DD and DT plasmas providing the evaluation of the fusion power

Three DNFM modules will be installed in ITER Divertor Cassettes under the dome Thelocations of these modules are at three different toroidal positions Divertor Cassette 3 in lowerport 2 Divertor Cassette 21 in lower port 8 and Divertor Cassette 39 at lower port 14

Each module is composed of six fission chambers (FC) identical in dimension and coatedwith varying amount of 235U amp 238U fissile material

The six fission chambers are enclosed in two cylinders three U235 FC in one cylinder and threeU238 FC in the other one forming the DNFM module see figure 7

By developing a good and structuraly sound design some major challenges have been facedhigh nuclear and radiation power loads transient magnetic field causing large forces and momentsacting on the sturcture and non-negligible halo currents The Divertor water cooling system will beused also for the DNFM

ndash 9 ndash

2012 JINST 7 C04012

Figure 7 Integration of DNFM in Lower Port

Risk analysis has been carried out on the failure probability of the several DNFM weldingjoints causing water leakage in the torus vacuum Such failure event can cause the stop of theplasma operations for several weeks As mitigation action a DNFM prototype will be manufacturedfor test at high temperatures (up to 350 degrees C) and high water pressure (20 divide 40 MPa)

The use of the various time resolved flux detection systems (B3 B4 and BC) and use ofmultiple locations allow compensation of effects due to changes in plasma position or shape andprovides redundancy in case of detectors failure Together these systems give the global neutronsource strength from which the total fusion power is obtained and the measurement should beinsensitive to plasma position

46 B8 Neutron Activation System

This diagnostic system (NAS) provides time integrated measurements of the neutron fluence at theFirst Wall and total fusion power through neutronic calculations [15]

Foil samples are irradiated at positions near the FW Several irradiation ends have been po-sitioned between various Blanket Modules and on the VV inner wall as well in the Upper andEquatorial Ports (figure 8) The foils samples are transferred using a pneumatic capsule system tocounting stations through port feedthroughs

ndash 10 ndash

2012 JINST 7 C04012

a) b) c) Support IE

Figure 8 a) NAS transfer lines inside the Vacuum Vessel b) Poloidal position of the various IrradiationEnds c) Support and Irradiation End of Position F

High thermal loads are expected at the irradiation ends because of the plasma radiation andnuclear heating This fact precludes a number of materials for the capsule or sample such aspolyethylene In and Al Moreover EM forces induced by plasma disruptions require the design ofdedicated strong supports

RampD activity is on-going on the selection of material and mass of the samples in order to limitactivation and avoid counting saturation effect for the various ITER operation scenarios (from 300s up to 3000 s)

The NAS diagnostic plays a fundamental role in the ITER Neutron Calibration Strategy be-cause is the only neutron diagnostic having a dynamic range of 10 orders of magnitude due toappropriate selection of mass and foils materials

In ITER the extended nature of the plasma neutron source means that the spatial dependence ofthe sensitivity of the different neutron systems is needed and this is obtained by in-situ calibrationsin these a source of known intensity is moved inside the tokamak vacuum chamber and the responseof the neutron detectors is recorded For ITER a powerful source with an intensity sim 1011ns isneeded Account needs to be taken of the potential screening and scattering effects of the structurethat is supporting the neutron source and this is done by use of the neutron transport codes code

NAS will be absolutely calibrated during the ITER in situ neutron calibration and during theITER DD and DT phases with well-characterized plasma reference shots allowing the cross cali-bration of all other ITER neutron diagnostic systems [16 17]

ndash 11 ndash

2012 JINST 7 C04012

47 BB High Resolution Neutron Spectrometer

Provision is made for a later installation of high-resolution neutron spectrometers (HRNS) for DDand DT neutron spectroscopy by adding a collimator into the neutron camera on equatorial port 1(figure 9a b) so that instruments can be installed later

In order to measure the neutron energy distribution of DD and DT emission two or threeneutron spectroscopy instruments are required Different type of spectrometer will be considered(Time of Flight Thin Proton Recoil etc)

Because of the high neutron flux (around 109 ncm2 s) needed to meet ITER measurementrequirements (100 ms time resolution and 10divide 20 accuracy) a neutron beam dump and housingsurrounding HRNS for local shield (figure 9c) have to be installed in the Port Cell 1 in order tomeet radiation safety parameters

a) b)

ndash 12 ndash

2012 JINST 7 C04012

c)

Figure 9 a b c High Resolution Neutron Spectrometers

5 Diagnostic integration

ITER neutronic diagnostics are installed within the vacuum vessel in the port plugs in the divertorand in-cryostat The installation integrations issues and loading conditions in each of these fourlocations are different and this could preclude the use of the same design for one particular systempositioned in different locations

The integration of several diagnostics in the port plugs as well in the interspaces and portcells is a key issue Several ITER systems are interfacing with the diagnostics Remote Handlingfor maintenance provision of water cooling cabling and power supply Bioshield for radiationdose reduction etc Here after some examples of integration and interface matters are reportedconcerning the neutron diagnostics at different locations The same issues are faced also by forother diagnostics systems

Diagnostics in Equatorial Ports diagnostic equipment is mounted in a port plug assembly [18]The port plug geometry consists of two basic parts -the Diagnostic Shield Module (DSM) andthe generic port plug structure figure 10a The Diagnostic Shield Module (DSM) consists ofseveral parts the Diagnostic First Wall (DFW) which is designed to handle the radiant heat fluxfrom the plasma the Diagnostic Shielding Block (DSB) which is designed to handle most of theneutronic heat load and the supporting moduledrawer which fastens the components to the portplug structure and provides a platform or housing for the diagnostic components Figure 10b showsthe drawer in eq Port 1 containing the inport detectors and collimators of B1 RNC

ndash 13 ndash

2012 JINST 7 C04012

a) Typical Equatorial port plug geometry b) In port RNC drawer in EqPort1

Figure 10 Equatorial port plug geometry

Figure 11 Recess of Diagnostic First Wall

The port plug assembly provides also the primary vacuum boundary at that port as well as thefeed-out for diagnostic signals (windows and feedthroughs) and feed-in for control signals

In the DSM there are a number of apertures for diagnostic viewing In designing the RNCsight lines of the inport detectors and related focal points attention has been paid to minimize theaperture (figure 10b) in the DFW which is recessed with respect to the nearby blanket modules(figure 11) This recess is needed to reduce the plasma interaction with the DFW

As an example eq Port Plug 1 is shown (figure 12) which is the most congested with diag-nostics The rational behind this is the need for being as close as possible to the plasma Followingsystems will be installed Radial Neutron Camera Divertor Impurity Monitor Bolometers Mo-tional Stark Effect Many factors have to be taken into account in optimizing the distribution ofdiagnostics within the available ports Because of neutron streaming considerations typically nomore than two systems with large labyrinths can be installed in one port with large aperture sys-tems placed near the port centres distributed systems are located evenly toroidally sometimescoordinated with the location of corresponding systems in the upper ports

ndash 14 ndash

2012 JINST 7 C04012

a) b)

Figure 12 Equatorial port plug 1 a) back view of feedthroughs and connections b) front view

Diagnostics in Vacuum Vessel for the systems installed in the vacuum vessel like B3 MFC andB8 Neutron Activation System a support structure ensuring a very good thermal and mechanicalanchoring to the vacuum vessel wall is required This together with the routing and clamping of thecables and pipes adjusting the irradiation ends to the gaps between the blanket modules leads to acontinuous integration work assuring enough clearance to the neighbouring components and properdefinition of the large variety of in-vacuum vessel interfaces Even though partially shielded by theblanket modules the design of some of the components are challenged by the varying magneticfields high nuclear heat and the loop voltage created around the vessel Last but not least are theinterfacing loads like ECRH stray power and additional acceleration due to disruption events Thelatter one is more important to systems like MFC which should be tested in order to prove that theymaintain performance under shock and vibration

Diagnostics in Cryostat for the B4 Neutron flux monitor located in the in-cryostat area the loadconditions are less severe Because the system is mounted on an extended support structure attachedto the cryostat wall the major loads which should be taken into account are the acceleration due togravity acceleration due to seismic events and those during plasma disruptions and displacements

Diagnostics in Divertor the most demanding among all the mentioned locations is the divertorwhere the load conditions are very severe and it requires an active cooling of all diagnostic compo-nents This on the other hand creates an additional interface with the divertor cooling water branchof which is used for the cooling of the diagnostic components and a development of a good strategyfor a leak localization and detection

The BC Divertor Neutron Flux Monitor is mounted on a cassette body which is remote handleable through the divertor port The divertor dome provides an opportunity to place diagnosticsinside the vacuum vessel since it provides some degree of shelter from the neutron flux and plasmaradiation In the same cassette bolometers which are used for measuring the power of incidentelectromagnetic radiation are required to sit in the gap between two adjacent cassette bodies Thiscreates some integration issues as the one presented in figure 13

ndash 15 ndash

2012 JINST 7 C04012

Figure 13 Integration issue bolometers and DNFM ldquosharingrdquo the same support structure

The B2 Lower Vertical Neutron Camera (LVNC) is integrated into the lower port A genericdiagnostic rack to house diagnostics or optical relays in the port is being developed which willbe customized for each diagnostic while keeping the same interfaces with the vacuum vessel Thediagnostic rack is attached to the side walls of the port and includes features for alignment to thedivertor central cassette On the basis of the recently performed neutronic analysis it became clearthat the vertical camera could not co-exist with any optical system in the same port as this is thecase now Activity is going on the possible relocation either of LVNC or of the optical systems

One of the most difficult interfaces between the blanket system and the diagnostics is pre-sented by the integration of the B2 LVNC The line of sights of the detectors need to protrude theblanket shielding module 18 and the first wall exactly in the middle where the remote handlingattachment the hydraulic connector and the cooling channels are designed as shown in figure 14This fact can bring to the reduction of number of sight lines Design work is being carried out tosort out this problem

ndash 16 ndash

2012 JINST 7 C04012

Figure 14 Interface between Blanket Module 18 and lines of sight of the Vertical Neutron Camera

An overview of ITER neutron diagnostic systems and of the associated challenging engineer-ing and integration issues has been described The design of these systems has taken into accountthe experience gained on large devices which have pointed out the importance of simultaneuousmeasurements of the neutron spatial and energy distributions

The main advantage of this complete set-up of ITER neutron diagnostics is its installation andoperation from the begin of ITER nuclear operation compared to other machines like JET LHDTFTR JT 60 where the various neutron diagnostics have been installed during different machineoperational phases

Acknowledgments

The authors wish to thank ITER Diagnostics Team and the colleagues of ITER Members of JapanKorea China Europe and Russian Federation for useful discussions and collaboration

The work described was supported and carried out by ITER Organization together with ITERMembers and Domestic Agencies of Japan Korea China Europe and Russian Federation Part ofthis activity was performed within the framework of the European Fusion Development Agreement

Disclaimer The views and opinions expressed herein do not necessarily reflect those of the ITERorganization

ndash 17 ndash

2012 JINST 7 C04012

References

[1] AJH Donne et al Progress in the ITER physics basis Chapter 7 diagnostics Nucl Fusion 47(2007) 337

[2] G Vayakis ER Hodgson and V Voitsenya Plasma diagnostics for magnetic fusion researchChapter 12 generic diagnostic issues for a burning plasma experiment Fusion Sci Technol 53(2008) 699

[3] A Encheva L Bertalot B Macklin G Vayakis and C Walker Integration of ITER in-vesseldiagnostic components in the vacuum vessel Fusion Eng Des 84 (2009) 736

[4] A Krasilnikov et al Status of ITER neutron diagnostic development Nucl Fusion 45 (2005) 1503

[5] M Sasao et al Plasma diagnostics for magnetic fusion research Chapter 9 fusion productdiagnostics Fusion Sci Technol 53 (2008) 604

[6] FP Orsitto et al Burning plasmas diagnostics AIP Conf Proc 988 Varenna Italy (2007)

[7] L Petrizzi et al Neutronic design of the ITER radial neutron camera Fusion Sci Eng 82 (2007)1308

[8] AV Krasilnikov CI Walker YA Kashchuk and DV Prosvirin A multichannel neutron collimatorfor the ITER tokamak Kluwer AcademicPlenum Publishers Instrum Exp Tech 47 (2004) 139

[9] A Encheva et al Engineering aspects of integration of ITER divertor diagnostics Fusion Eng Des86 (2011) 1323

[10] M Ishikawa et al Design of microfission chamber for ITER operations Rev Sci Instrum 79 (2008)10E507

[11] A Encheva et al Structural integrity report for ITER micro-fission chamber ITER documentITER D 3TDURL

[12] T Nishitani et al Engineering design of the ITER invessel neutron monitor using micro-fissionchambers Fusion Eng Des 82 (2007) 1192

[13] J Yang et al Fusion neutron flux monitor for ITER Plasma Sci Technol 10 (2008) 141

[14] YA Kashchuk AV Krasilrsquonikov and DV Prosvirin A conceptual project for a divertor monitor ofthe neutron yield in the ITER Instrum Exp Tech 49 (2006) 179

[15] MS Cheon et al In-vessel design of ITER diagnostic neutron activation system Rev Sci Instrum79 (2008) 10E505

[16] L Bertalot et al A strategy for calibrating the neutron systems at ITER in 35th plasma physicsconference Crete Greece 2008 EPS Europhysics Conference Abstracts 32D (2008) O2001httpepsppdepflchHersonissosstarthtm

[17] M Sasao L Bertalot M Ishikawa and S Popovichev Strategy for the absolute neutron emissionmeasurement on ITER Rev Sci Instrum 81 (2010) 10D329

[18] S Pitcher et al System Design Description Document (DDD) diagnostic generic equatorial portplug ITER document ITER D 3U8JU7

ndash 18 ndash

2012 JINST 7 C04012

Figure 7 Integration of DNFM in Lower Port

Risk analysis has been carried out on the failure probability of the several DNFM weldingjoints causing water leakage in the torus vacuum Such failure event can cause the stop of theplasma operations for several weeks As mitigation action a DNFM prototype will be manufacturedfor test at high temperatures (up to 350 degrees C) and high water pressure (20 divide 40 MPa)

The use of the various time resolved flux detection systems (B3 B4 and BC) and use ofmultiple locations allow compensation of effects due to changes in plasma position or shape andprovides redundancy in case of detectors failure Together these systems give the global neutronsource strength from which the total fusion power is obtained and the measurement should beinsensitive to plasma position

46 B8 Neutron Activation System

This diagnostic system (NAS) provides time integrated measurements of the neutron fluence at theFirst Wall and total fusion power through neutronic calculations [15]

Foil samples are irradiated at positions near the FW Several irradiation ends have been po-sitioned between various Blanket Modules and on the VV inner wall as well in the Upper andEquatorial Ports (figure 8) The foils samples are transferred using a pneumatic capsule system tocounting stations through port feedthroughs

ndash 10 ndash

2012 JINST 7 C04012

a) b) c) Support IE

Figure 8 a) NAS transfer lines inside the Vacuum Vessel b) Poloidal position of the various IrradiationEnds c) Support and Irradiation End of Position F

High thermal loads are expected at the irradiation ends because of the plasma radiation andnuclear heating This fact precludes a number of materials for the capsule or sample such aspolyethylene In and Al Moreover EM forces induced by plasma disruptions require the design ofdedicated strong supports

RampD activity is on-going on the selection of material and mass of the samples in order to limitactivation and avoid counting saturation effect for the various ITER operation scenarios (from 300s up to 3000 s)

The NAS diagnostic plays a fundamental role in the ITER Neutron Calibration Strategy be-cause is the only neutron diagnostic having a dynamic range of 10 orders of magnitude due toappropriate selection of mass and foils materials

In ITER the extended nature of the plasma neutron source means that the spatial dependence ofthe sensitivity of the different neutron systems is needed and this is obtained by in-situ calibrationsin these a source of known intensity is moved inside the tokamak vacuum chamber and the responseof the neutron detectors is recorded For ITER a powerful source with an intensity sim 1011ns isneeded Account needs to be taken of the potential screening and scattering effects of the structurethat is supporting the neutron source and this is done by use of the neutron transport codes code

NAS will be absolutely calibrated during the ITER in situ neutron calibration and during theITER DD and DT phases with well-characterized plasma reference shots allowing the cross cali-bration of all other ITER neutron diagnostic systems [16 17]

ndash 11 ndash

2012 JINST 7 C04012

47 BB High Resolution Neutron Spectrometer

Provision is made for a later installation of high-resolution neutron spectrometers (HRNS) for DDand DT neutron spectroscopy by adding a collimator into the neutron camera on equatorial port 1(figure 9a b) so that instruments can be installed later

In order to measure the neutron energy distribution of DD and DT emission two or threeneutron spectroscopy instruments are required Different type of spectrometer will be considered(Time of Flight Thin Proton Recoil etc)

Because of the high neutron flux (around 109 ncm2 s) needed to meet ITER measurementrequirements (100 ms time resolution and 10divide 20 accuracy) a neutron beam dump and housingsurrounding HRNS for local shield (figure 9c) have to be installed in the Port Cell 1 in order tomeet radiation safety parameters

a) b)

ndash 12 ndash

2012 JINST 7 C04012

c)

Figure 9 a b c High Resolution Neutron Spectrometers

5 Diagnostic integration

ITER neutronic diagnostics are installed within the vacuum vessel in the port plugs in the divertorand in-cryostat The installation integrations issues and loading conditions in each of these fourlocations are different and this could preclude the use of the same design for one particular systempositioned in different locations

The integration of several diagnostics in the port plugs as well in the interspaces and portcells is a key issue Several ITER systems are interfacing with the diagnostics Remote Handlingfor maintenance provision of water cooling cabling and power supply Bioshield for radiationdose reduction etc Here after some examples of integration and interface matters are reportedconcerning the neutron diagnostics at different locations The same issues are faced also by forother diagnostics systems

Diagnostics in Equatorial Ports diagnostic equipment is mounted in a port plug assembly [18]The port plug geometry consists of two basic parts -the Diagnostic Shield Module (DSM) andthe generic port plug structure figure 10a The Diagnostic Shield Module (DSM) consists ofseveral parts the Diagnostic First Wall (DFW) which is designed to handle the radiant heat fluxfrom the plasma the Diagnostic Shielding Block (DSB) which is designed to handle most of theneutronic heat load and the supporting moduledrawer which fastens the components to the portplug structure and provides a platform or housing for the diagnostic components Figure 10b showsthe drawer in eq Port 1 containing the inport detectors and collimators of B1 RNC

ndash 13 ndash

2012 JINST 7 C04012

a) Typical Equatorial port plug geometry b) In port RNC drawer in EqPort1

Figure 10 Equatorial port plug geometry

Figure 11 Recess of Diagnostic First Wall

The port plug assembly provides also the primary vacuum boundary at that port as well as thefeed-out for diagnostic signals (windows and feedthroughs) and feed-in for control signals

In the DSM there are a number of apertures for diagnostic viewing In designing the RNCsight lines of the inport detectors and related focal points attention has been paid to minimize theaperture (figure 10b) in the DFW which is recessed with respect to the nearby blanket modules(figure 11) This recess is needed to reduce the plasma interaction with the DFW

As an example eq Port Plug 1 is shown (figure 12) which is the most congested with diag-nostics The rational behind this is the need for being as close as possible to the plasma Followingsystems will be installed Radial Neutron Camera Divertor Impurity Monitor Bolometers Mo-tional Stark Effect Many factors have to be taken into account in optimizing the distribution ofdiagnostics within the available ports Because of neutron streaming considerations typically nomore than two systems with large labyrinths can be installed in one port with large aperture sys-tems placed near the port centres distributed systems are located evenly toroidally sometimescoordinated with the location of corresponding systems in the upper ports

ndash 14 ndash

2012 JINST 7 C04012

a) b)

Figure 12 Equatorial port plug 1 a) back view of feedthroughs and connections b) front view

Diagnostics in Vacuum Vessel for the systems installed in the vacuum vessel like B3 MFC andB8 Neutron Activation System a support structure ensuring a very good thermal and mechanicalanchoring to the vacuum vessel wall is required This together with the routing and clamping of thecables and pipes adjusting the irradiation ends to the gaps between the blanket modules leads to acontinuous integration work assuring enough clearance to the neighbouring components and properdefinition of the large variety of in-vacuum vessel interfaces Even though partially shielded by theblanket modules the design of some of the components are challenged by the varying magneticfields high nuclear heat and the loop voltage created around the vessel Last but not least are theinterfacing loads like ECRH stray power and additional acceleration due to disruption events Thelatter one is more important to systems like MFC which should be tested in order to prove that theymaintain performance under shock and vibration

Diagnostics in Cryostat for the B4 Neutron flux monitor located in the in-cryostat area the loadconditions are less severe Because the system is mounted on an extended support structure attachedto the cryostat wall the major loads which should be taken into account are the acceleration due togravity acceleration due to seismic events and those during plasma disruptions and displacements

Diagnostics in Divertor the most demanding among all the mentioned locations is the divertorwhere the load conditions are very severe and it requires an active cooling of all diagnostic compo-nents This on the other hand creates an additional interface with the divertor cooling water branchof which is used for the cooling of the diagnostic components and a development of a good strategyfor a leak localization and detection

The BC Divertor Neutron Flux Monitor is mounted on a cassette body which is remote handleable through the divertor port The divertor dome provides an opportunity to place diagnosticsinside the vacuum vessel since it provides some degree of shelter from the neutron flux and plasmaradiation In the same cassette bolometers which are used for measuring the power of incidentelectromagnetic radiation are required to sit in the gap between two adjacent cassette bodies Thiscreates some integration issues as the one presented in figure 13

ndash 15 ndash

2012 JINST 7 C04012

Figure 13 Integration issue bolometers and DNFM ldquosharingrdquo the same support structure

The B2 Lower Vertical Neutron Camera (LVNC) is integrated into the lower port A genericdiagnostic rack to house diagnostics or optical relays in the port is being developed which willbe customized for each diagnostic while keeping the same interfaces with the vacuum vessel Thediagnostic rack is attached to the side walls of the port and includes features for alignment to thedivertor central cassette On the basis of the recently performed neutronic analysis it became clearthat the vertical camera could not co-exist with any optical system in the same port as this is thecase now Activity is going on the possible relocation either of LVNC or of the optical systems

One of the most difficult interfaces between the blanket system and the diagnostics is pre-sented by the integration of the B2 LVNC The line of sights of the detectors need to protrude theblanket shielding module 18 and the first wall exactly in the middle where the remote handlingattachment the hydraulic connector and the cooling channels are designed as shown in figure 14This fact can bring to the reduction of number of sight lines Design work is being carried out tosort out this problem

ndash 16 ndash

2012 JINST 7 C04012

Figure 14 Interface between Blanket Module 18 and lines of sight of the Vertical Neutron Camera

An overview of ITER neutron diagnostic systems and of the associated challenging engineer-ing and integration issues has been described The design of these systems has taken into accountthe experience gained on large devices which have pointed out the importance of simultaneuousmeasurements of the neutron spatial and energy distributions

The main advantage of this complete set-up of ITER neutron diagnostics is its installation andoperation from the begin of ITER nuclear operation compared to other machines like JET LHDTFTR JT 60 where the various neutron diagnostics have been installed during different machineoperational phases

Acknowledgments

The authors wish to thank ITER Diagnostics Team and the colleagues of ITER Members of JapanKorea China Europe and Russian Federation for useful discussions and collaboration

The work described was supported and carried out by ITER Organization together with ITERMembers and Domestic Agencies of Japan Korea China Europe and Russian Federation Part ofthis activity was performed within the framework of the European Fusion Development Agreement

Disclaimer The views and opinions expressed herein do not necessarily reflect those of the ITERorganization

ndash 17 ndash

2012 JINST 7 C04012

References

[1] AJH Donne et al Progress in the ITER physics basis Chapter 7 diagnostics Nucl Fusion 47(2007) 337

[2] G Vayakis ER Hodgson and V Voitsenya Plasma diagnostics for magnetic fusion researchChapter 12 generic diagnostic issues for a burning plasma experiment Fusion Sci Technol 53(2008) 699

[3] A Encheva L Bertalot B Macklin G Vayakis and C Walker Integration of ITER in-vesseldiagnostic components in the vacuum vessel Fusion Eng Des 84 (2009) 736

[4] A Krasilnikov et al Status of ITER neutron diagnostic development Nucl Fusion 45 (2005) 1503

[5] M Sasao et al Plasma diagnostics for magnetic fusion research Chapter 9 fusion productdiagnostics Fusion Sci Technol 53 (2008) 604

[6] FP Orsitto et al Burning plasmas diagnostics AIP Conf Proc 988 Varenna Italy (2007)

[7] L Petrizzi et al Neutronic design of the ITER radial neutron camera Fusion Sci Eng 82 (2007)1308

[8] AV Krasilnikov CI Walker YA Kashchuk and DV Prosvirin A multichannel neutron collimatorfor the ITER tokamak Kluwer AcademicPlenum Publishers Instrum Exp Tech 47 (2004) 139

[9] A Encheva et al Engineering aspects of integration of ITER divertor diagnostics Fusion Eng Des86 (2011) 1323

[10] M Ishikawa et al Design of microfission chamber for ITER operations Rev Sci Instrum 79 (2008)10E507

[11] A Encheva et al Structural integrity report for ITER micro-fission chamber ITER documentITER D 3TDURL

[12] T Nishitani et al Engineering design of the ITER invessel neutron monitor using micro-fissionchambers Fusion Eng Des 82 (2007) 1192

[13] J Yang et al Fusion neutron flux monitor for ITER Plasma Sci Technol 10 (2008) 141

[14] YA Kashchuk AV Krasilrsquonikov and DV Prosvirin A conceptual project for a divertor monitor ofthe neutron yield in the ITER Instrum Exp Tech 49 (2006) 179

[15] MS Cheon et al In-vessel design of ITER diagnostic neutron activation system Rev Sci Instrum79 (2008) 10E505

[16] L Bertalot et al A strategy for calibrating the neutron systems at ITER in 35th plasma physicsconference Crete Greece 2008 EPS Europhysics Conference Abstracts 32D (2008) O2001httpepsppdepflchHersonissosstarthtm

[17] M Sasao L Bertalot M Ishikawa and S Popovichev Strategy for the absolute neutron emissionmeasurement on ITER Rev Sci Instrum 81 (2010) 10D329

[18] S Pitcher et al System Design Description Document (DDD) diagnostic generic equatorial portplug ITER document ITER D 3U8JU7

ndash 18 ndash

2012 JINST 7 C04012

a) b) c) Support IE

Figure 8 a) NAS transfer lines inside the Vacuum Vessel b) Poloidal position of the various IrradiationEnds c) Support and Irradiation End of Position F

High thermal loads are expected at the irradiation ends because of the plasma radiation andnuclear heating This fact precludes a number of materials for the capsule or sample such aspolyethylene In and Al Moreover EM forces induced by plasma disruptions require the design ofdedicated strong supports

RampD activity is on-going on the selection of material and mass of the samples in order to limitactivation and avoid counting saturation effect for the various ITER operation scenarios (from 300s up to 3000 s)

The NAS diagnostic plays a fundamental role in the ITER Neutron Calibration Strategy be-cause is the only neutron diagnostic having a dynamic range of 10 orders of magnitude due toappropriate selection of mass and foils materials

In ITER the extended nature of the plasma neutron source means that the spatial dependence ofthe sensitivity of the different neutron systems is needed and this is obtained by in-situ calibrationsin these a source of known intensity is moved inside the tokamak vacuum chamber and the responseof the neutron detectors is recorded For ITER a powerful source with an intensity sim 1011ns isneeded Account needs to be taken of the potential screening and scattering effects of the structurethat is supporting the neutron source and this is done by use of the neutron transport codes code

NAS will be absolutely calibrated during the ITER in situ neutron calibration and during theITER DD and DT phases with well-characterized plasma reference shots allowing the cross cali-bration of all other ITER neutron diagnostic systems [16 17]

ndash 11 ndash

2012 JINST 7 C04012

47 BB High Resolution Neutron Spectrometer

Provision is made for a later installation of high-resolution neutron spectrometers (HRNS) for DDand DT neutron spectroscopy by adding a collimator into the neutron camera on equatorial port 1(figure 9a b) so that instruments can be installed later

In order to measure the neutron energy distribution of DD and DT emission two or threeneutron spectroscopy instruments are required Different type of spectrometer will be considered(Time of Flight Thin Proton Recoil etc)

Because of the high neutron flux (around 109 ncm2 s) needed to meet ITER measurementrequirements (100 ms time resolution and 10divide 20 accuracy) a neutron beam dump and housingsurrounding HRNS for local shield (figure 9c) have to be installed in the Port Cell 1 in order tomeet radiation safety parameters

a) b)

ndash 12 ndash

2012 JINST 7 C04012

c)

Figure 9 a b c High Resolution Neutron Spectrometers

5 Diagnostic integration

ITER neutronic diagnostics are installed within the vacuum vessel in the port plugs in the divertorand in-cryostat The installation integrations issues and loading conditions in each of these fourlocations are different and this could preclude the use of the same design for one particular systempositioned in different locations

The integration of several diagnostics in the port plugs as well in the interspaces and portcells is a key issue Several ITER systems are interfacing with the diagnostics Remote Handlingfor maintenance provision of water cooling cabling and power supply Bioshield for radiationdose reduction etc Here after some examples of integration and interface matters are reportedconcerning the neutron diagnostics at different locations The same issues are faced also by forother diagnostics systems

Diagnostics in Equatorial Ports diagnostic equipment is mounted in a port plug assembly [18]The port plug geometry consists of two basic parts -the Diagnostic Shield Module (DSM) andthe generic port plug structure figure 10a The Diagnostic Shield Module (DSM) consists ofseveral parts the Diagnostic First Wall (DFW) which is designed to handle the radiant heat fluxfrom the plasma the Diagnostic Shielding Block (DSB) which is designed to handle most of theneutronic heat load and the supporting moduledrawer which fastens the components to the portplug structure and provides a platform or housing for the diagnostic components Figure 10b showsthe drawer in eq Port 1 containing the inport detectors and collimators of B1 RNC

ndash 13 ndash

2012 JINST 7 C04012

a) Typical Equatorial port plug geometry b) In port RNC drawer in EqPort1

Figure 10 Equatorial port plug geometry

Figure 11 Recess of Diagnostic First Wall

The port plug assembly provides also the primary vacuum boundary at that port as well as thefeed-out for diagnostic signals (windows and feedthroughs) and feed-in for control signals

In the DSM there are a number of apertures for diagnostic viewing In designing the RNCsight lines of the inport detectors and related focal points attention has been paid to minimize theaperture (figure 10b) in the DFW which is recessed with respect to the nearby blanket modules(figure 11) This recess is needed to reduce the plasma interaction with the DFW

As an example eq Port Plug 1 is shown (figure 12) which is the most congested with diag-nostics The rational behind this is the need for being as close as possible to the plasma Followingsystems will be installed Radial Neutron Camera Divertor Impurity Monitor Bolometers Mo-tional Stark Effect Many factors have to be taken into account in optimizing the distribution ofdiagnostics within the available ports Because of neutron streaming considerations typically nomore than two systems with large labyrinths can be installed in one port with large aperture sys-tems placed near the port centres distributed systems are located evenly toroidally sometimescoordinated with the location of corresponding systems in the upper ports

ndash 14 ndash

2012 JINST 7 C04012

a) b)

Figure 12 Equatorial port plug 1 a) back view of feedthroughs and connections b) front view

Diagnostics in Vacuum Vessel for the systems installed in the vacuum vessel like B3 MFC andB8 Neutron Activation System a support structure ensuring a very good thermal and mechanicalanchoring to the vacuum vessel wall is required This together with the routing and clamping of thecables and pipes adjusting the irradiation ends to the gaps between the blanket modules leads to acontinuous integration work assuring enough clearance to the neighbouring components and properdefinition of the large variety of in-vacuum vessel interfaces Even though partially shielded by theblanket modules the design of some of the components are challenged by the varying magneticfields high nuclear heat and the loop voltage created around the vessel Last but not least are theinterfacing loads like ECRH stray power and additional acceleration due to disruption events Thelatter one is more important to systems like MFC which should be tested in order to prove that theymaintain performance under shock and vibration

Diagnostics in Cryostat for the B4 Neutron flux monitor located in the in-cryostat area the loadconditions are less severe Because the system is mounted on an extended support structure attachedto the cryostat wall the major loads which should be taken into account are the acceleration due togravity acceleration due to seismic events and those during plasma disruptions and displacements

Diagnostics in Divertor the most demanding among all the mentioned locations is the divertorwhere the load conditions are very severe and it requires an active cooling of all diagnostic compo-nents This on the other hand creates an additional interface with the divertor cooling water branchof which is used for the cooling of the diagnostic components and a development of a good strategyfor a leak localization and detection

The BC Divertor Neutron Flux Monitor is mounted on a cassette body which is remote handleable through the divertor port The divertor dome provides an opportunity to place diagnosticsinside the vacuum vessel since it provides some degree of shelter from the neutron flux and plasmaradiation In the same cassette bolometers which are used for measuring the power of incidentelectromagnetic radiation are required to sit in the gap between two adjacent cassette bodies Thiscreates some integration issues as the one presented in figure 13

ndash 15 ndash

2012 JINST 7 C04012

Figure 13 Integration issue bolometers and DNFM ldquosharingrdquo the same support structure

The B2 Lower Vertical Neutron Camera (LVNC) is integrated into the lower port A genericdiagnostic rack to house diagnostics or optical relays in the port is being developed which willbe customized for each diagnostic while keeping the same interfaces with the vacuum vessel Thediagnostic rack is attached to the side walls of the port and includes features for alignment to thedivertor central cassette On the basis of the recently performed neutronic analysis it became clearthat the vertical camera could not co-exist with any optical system in the same port as this is thecase now Activity is going on the possible relocation either of LVNC or of the optical systems

One of the most difficult interfaces between the blanket system and the diagnostics is pre-sented by the integration of the B2 LVNC The line of sights of the detectors need to protrude theblanket shielding module 18 and the first wall exactly in the middle where the remote handlingattachment the hydraulic connector and the cooling channels are designed as shown in figure 14This fact can bring to the reduction of number of sight lines Design work is being carried out tosort out this problem

ndash 16 ndash

2012 JINST 7 C04012

Figure 14 Interface between Blanket Module 18 and lines of sight of the Vertical Neutron Camera

An overview of ITER neutron diagnostic systems and of the associated challenging engineer-ing and integration issues has been described The design of these systems has taken into accountthe experience gained on large devices which have pointed out the importance of simultaneuousmeasurements of the neutron spatial and energy distributions

The main advantage of this complete set-up of ITER neutron diagnostics is its installation andoperation from the begin of ITER nuclear operation compared to other machines like JET LHDTFTR JT 60 where the various neutron diagnostics have been installed during different machineoperational phases

Acknowledgments

The authors wish to thank ITER Diagnostics Team and the colleagues of ITER Members of JapanKorea China Europe and Russian Federation for useful discussions and collaboration

The work described was supported and carried out by ITER Organization together with ITERMembers and Domestic Agencies of Japan Korea China Europe and Russian Federation Part ofthis activity was performed within the framework of the European Fusion Development Agreement

Disclaimer The views and opinions expressed herein do not necessarily reflect those of the ITERorganization

ndash 17 ndash

2012 JINST 7 C04012

References

[1] AJH Donne et al Progress in the ITER physics basis Chapter 7 diagnostics Nucl Fusion 47(2007) 337

[2] G Vayakis ER Hodgson and V Voitsenya Plasma diagnostics for magnetic fusion researchChapter 12 generic diagnostic issues for a burning plasma experiment Fusion Sci Technol 53(2008) 699

[3] A Encheva L Bertalot B Macklin G Vayakis and C Walker Integration of ITER in-vesseldiagnostic components in the vacuum vessel Fusion Eng Des 84 (2009) 736

[4] A Krasilnikov et al Status of ITER neutron diagnostic development Nucl Fusion 45 (2005) 1503

[5] M Sasao et al Plasma diagnostics for magnetic fusion research Chapter 9 fusion productdiagnostics Fusion Sci Technol 53 (2008) 604

[6] FP Orsitto et al Burning plasmas diagnostics AIP Conf Proc 988 Varenna Italy (2007)

[7] L Petrizzi et al Neutronic design of the ITER radial neutron camera Fusion Sci Eng 82 (2007)1308

[8] AV Krasilnikov CI Walker YA Kashchuk and DV Prosvirin A multichannel neutron collimatorfor the ITER tokamak Kluwer AcademicPlenum Publishers Instrum Exp Tech 47 (2004) 139

[9] A Encheva et al Engineering aspects of integration of ITER divertor diagnostics Fusion Eng Des86 (2011) 1323

[10] M Ishikawa et al Design of microfission chamber for ITER operations Rev Sci Instrum 79 (2008)10E507

[11] A Encheva et al Structural integrity report for ITER micro-fission chamber ITER documentITER D 3TDURL

[12] T Nishitani et al Engineering design of the ITER invessel neutron monitor using micro-fissionchambers Fusion Eng Des 82 (2007) 1192

[13] J Yang et al Fusion neutron flux monitor for ITER Plasma Sci Technol 10 (2008) 141

[14] YA Kashchuk AV Krasilrsquonikov and DV Prosvirin A conceptual project for a divertor monitor ofthe neutron yield in the ITER Instrum Exp Tech 49 (2006) 179

[15] MS Cheon et al In-vessel design of ITER diagnostic neutron activation system Rev Sci Instrum79 (2008) 10E505

[16] L Bertalot et al A strategy for calibrating the neutron systems at ITER in 35th plasma physicsconference Crete Greece 2008 EPS Europhysics Conference Abstracts 32D (2008) O2001httpepsppdepflchHersonissosstarthtm

[17] M Sasao L Bertalot M Ishikawa and S Popovichev Strategy for the absolute neutron emissionmeasurement on ITER Rev Sci Instrum 81 (2010) 10D329

[18] S Pitcher et al System Design Description Document (DDD) diagnostic generic equatorial portplug ITER document ITER D 3U8JU7

ndash 18 ndash

2012 JINST 7 C04012

47 BB High Resolution Neutron Spectrometer

Provision is made for a later installation of high-resolution neutron spectrometers (HRNS) for DDand DT neutron spectroscopy by adding a collimator into the neutron camera on equatorial port 1(figure 9a b) so that instruments can be installed later

In order to measure the neutron energy distribution of DD and DT emission two or threeneutron spectroscopy instruments are required Different type of spectrometer will be considered(Time of Flight Thin Proton Recoil etc)

Because of the high neutron flux (around 109 ncm2 s) needed to meet ITER measurementrequirements (100 ms time resolution and 10divide 20 accuracy) a neutron beam dump and housingsurrounding HRNS for local shield (figure 9c) have to be installed in the Port Cell 1 in order tomeet radiation safety parameters

a) b)

ndash 12 ndash

2012 JINST 7 C04012

c)

Figure 9 a b c High Resolution Neutron Spectrometers

5 Diagnostic integration

ITER neutronic diagnostics are installed within the vacuum vessel in the port plugs in the divertorand in-cryostat The installation integrations issues and loading conditions in each of these fourlocations are different and this could preclude the use of the same design for one particular systempositioned in different locations

The integration of several diagnostics in the port plugs as well in the interspaces and portcells is a key issue Several ITER systems are interfacing with the diagnostics Remote Handlingfor maintenance provision of water cooling cabling and power supply Bioshield for radiationdose reduction etc Here after some examples of integration and interface matters are reportedconcerning the neutron diagnostics at different locations The same issues are faced also by forother diagnostics systems

Diagnostics in Equatorial Ports diagnostic equipment is mounted in a port plug assembly [18]The port plug geometry consists of two basic parts -the Diagnostic Shield Module (DSM) andthe generic port plug structure figure 10a The Diagnostic Shield Module (DSM) consists ofseveral parts the Diagnostic First Wall (DFW) which is designed to handle the radiant heat fluxfrom the plasma the Diagnostic Shielding Block (DSB) which is designed to handle most of theneutronic heat load and the supporting moduledrawer which fastens the components to the portplug structure and provides a platform or housing for the diagnostic components Figure 10b showsthe drawer in eq Port 1 containing the inport detectors and collimators of B1 RNC

ndash 13 ndash

2012 JINST 7 C04012

a) Typical Equatorial port plug geometry b) In port RNC drawer in EqPort1

Figure 10 Equatorial port plug geometry

Figure 11 Recess of Diagnostic First Wall

The port plug assembly provides also the primary vacuum boundary at that port as well as thefeed-out for diagnostic signals (windows and feedthroughs) and feed-in for control signals

In the DSM there are a number of apertures for diagnostic viewing In designing the RNCsight lines of the inport detectors and related focal points attention has been paid to minimize theaperture (figure 10b) in the DFW which is recessed with respect to the nearby blanket modules(figure 11) This recess is needed to reduce the plasma interaction with the DFW

As an example eq Port Plug 1 is shown (figure 12) which is the most congested with diag-nostics The rational behind this is the need for being as close as possible to the plasma Followingsystems will be installed Radial Neutron Camera Divertor Impurity Monitor Bolometers Mo-tional Stark Effect Many factors have to be taken into account in optimizing the distribution ofdiagnostics within the available ports Because of neutron streaming considerations typically nomore than two systems with large labyrinths can be installed in one port with large aperture sys-tems placed near the port centres distributed systems are located evenly toroidally sometimescoordinated with the location of corresponding systems in the upper ports

ndash 14 ndash

2012 JINST 7 C04012

a) b)

Figure 12 Equatorial port plug 1 a) back view of feedthroughs and connections b) front view

Diagnostics in Vacuum Vessel for the systems installed in the vacuum vessel like B3 MFC andB8 Neutron Activation System a support structure ensuring a very good thermal and mechanicalanchoring to the vacuum vessel wall is required This together with the routing and clamping of thecables and pipes adjusting the irradiation ends to the gaps between the blanket modules leads to acontinuous integration work assuring enough clearance to the neighbouring components and properdefinition of the large variety of in-vacuum vessel interfaces Even though partially shielded by theblanket modules the design of some of the components are challenged by the varying magneticfields high nuclear heat and the loop voltage created around the vessel Last but not least are theinterfacing loads like ECRH stray power and additional acceleration due to disruption events Thelatter one is more important to systems like MFC which should be tested in order to prove that theymaintain performance under shock and vibration

Diagnostics in Cryostat for the B4 Neutron flux monitor located in the in-cryostat area the loadconditions are less severe Because the system is mounted on an extended support structure attachedto the cryostat wall the major loads which should be taken into account are the acceleration due togravity acceleration due to seismic events and those during plasma disruptions and displacements

Diagnostics in Divertor the most demanding among all the mentioned locations is the divertorwhere the load conditions are very severe and it requires an active cooling of all diagnostic compo-nents This on the other hand creates an additional interface with the divertor cooling water branchof which is used for the cooling of the diagnostic components and a development of a good strategyfor a leak localization and detection

The BC Divertor Neutron Flux Monitor is mounted on a cassette body which is remote handleable through the divertor port The divertor dome provides an opportunity to place diagnosticsinside the vacuum vessel since it provides some degree of shelter from the neutron flux and plasmaradiation In the same cassette bolometers which are used for measuring the power of incidentelectromagnetic radiation are required to sit in the gap between two adjacent cassette bodies Thiscreates some integration issues as the one presented in figure 13

ndash 15 ndash

2012 JINST 7 C04012

Figure 13 Integration issue bolometers and DNFM ldquosharingrdquo the same support structure

The B2 Lower Vertical Neutron Camera (LVNC) is integrated into the lower port A genericdiagnostic rack to house diagnostics or optical relays in the port is being developed which willbe customized for each diagnostic while keeping the same interfaces with the vacuum vessel Thediagnostic rack is attached to the side walls of the port and includes features for alignment to thedivertor central cassette On the basis of the recently performed neutronic analysis it became clearthat the vertical camera could not co-exist with any optical system in the same port as this is thecase now Activity is going on the possible relocation either of LVNC or of the optical systems

One of the most difficult interfaces between the blanket system and the diagnostics is pre-sented by the integration of the B2 LVNC The line of sights of the detectors need to protrude theblanket shielding module 18 and the first wall exactly in the middle where the remote handlingattachment the hydraulic connector and the cooling channels are designed as shown in figure 14This fact can bring to the reduction of number of sight lines Design work is being carried out tosort out this problem

ndash 16 ndash

2012 JINST 7 C04012

Figure 14 Interface between Blanket Module 18 and lines of sight of the Vertical Neutron Camera

An overview of ITER neutron diagnostic systems and of the associated challenging engineer-ing and integration issues has been described The design of these systems has taken into accountthe experience gained on large devices which have pointed out the importance of simultaneuousmeasurements of the neutron spatial and energy distributions

The main advantage of this complete set-up of ITER neutron diagnostics is its installation andoperation from the begin of ITER nuclear operation compared to other machines like JET LHDTFTR JT 60 where the various neutron diagnostics have been installed during different machineoperational phases

Acknowledgments

The authors wish to thank ITER Diagnostics Team and the colleagues of ITER Members of JapanKorea China Europe and Russian Federation for useful discussions and collaboration

The work described was supported and carried out by ITER Organization together with ITERMembers and Domestic Agencies of Japan Korea China Europe and Russian Federation Part ofthis activity was performed within the framework of the European Fusion Development Agreement

Disclaimer The views and opinions expressed herein do not necessarily reflect those of the ITERorganization

ndash 17 ndash

2012 JINST 7 C04012

References

[1] AJH Donne et al Progress in the ITER physics basis Chapter 7 diagnostics Nucl Fusion 47(2007) 337

[2] G Vayakis ER Hodgson and V Voitsenya Plasma diagnostics for magnetic fusion researchChapter 12 generic diagnostic issues for a burning plasma experiment Fusion Sci Technol 53(2008) 699

[3] A Encheva L Bertalot B Macklin G Vayakis and C Walker Integration of ITER in-vesseldiagnostic components in the vacuum vessel Fusion Eng Des 84 (2009) 736

[4] A Krasilnikov et al Status of ITER neutron diagnostic development Nucl Fusion 45 (2005) 1503

[5] M Sasao et al Plasma diagnostics for magnetic fusion research Chapter 9 fusion productdiagnostics Fusion Sci Technol 53 (2008) 604

[6] FP Orsitto et al Burning plasmas diagnostics AIP Conf Proc 988 Varenna Italy (2007)

[7] L Petrizzi et al Neutronic design of the ITER radial neutron camera Fusion Sci Eng 82 (2007)1308

[8] AV Krasilnikov CI Walker YA Kashchuk and DV Prosvirin A multichannel neutron collimatorfor the ITER tokamak Kluwer AcademicPlenum Publishers Instrum Exp Tech 47 (2004) 139

[9] A Encheva et al Engineering aspects of integration of ITER divertor diagnostics Fusion Eng Des86 (2011) 1323

[10] M Ishikawa et al Design of microfission chamber for ITER operations Rev Sci Instrum 79 (2008)10E507

[11] A Encheva et al Structural integrity report for ITER micro-fission chamber ITER documentITER D 3TDURL

[12] T Nishitani et al Engineering design of the ITER invessel neutron monitor using micro-fissionchambers Fusion Eng Des 82 (2007) 1192

[13] J Yang et al Fusion neutron flux monitor for ITER Plasma Sci Technol 10 (2008) 141

[14] YA Kashchuk AV Krasilrsquonikov and DV Prosvirin A conceptual project for a divertor monitor ofthe neutron yield in the ITER Instrum Exp Tech 49 (2006) 179

[15] MS Cheon et al In-vessel design of ITER diagnostic neutron activation system Rev Sci Instrum79 (2008) 10E505

[16] L Bertalot et al A strategy for calibrating the neutron systems at ITER in 35th plasma physicsconference Crete Greece 2008 EPS Europhysics Conference Abstracts 32D (2008) O2001httpepsppdepflchHersonissosstarthtm

[17] M Sasao L Bertalot M Ishikawa and S Popovichev Strategy for the absolute neutron emissionmeasurement on ITER Rev Sci Instrum 81 (2010) 10D329

[18] S Pitcher et al System Design Description Document (DDD) diagnostic generic equatorial portplug ITER document ITER D 3U8JU7

ndash 18 ndash

2012 JINST 7 C04012

c)

Figure 9 a b c High Resolution Neutron Spectrometers

5 Diagnostic integration

ITER neutronic diagnostics are installed within the vacuum vessel in the port plugs in the divertorand in-cryostat The installation integrations issues and loading conditions in each of these fourlocations are different and this could preclude the use of the same design for one particular systempositioned in different locations

The integration of several diagnostics in the port plugs as well in the interspaces and portcells is a key issue Several ITER systems are interfacing with the diagnostics Remote Handlingfor maintenance provision of water cooling cabling and power supply Bioshield for radiationdose reduction etc Here after some examples of integration and interface matters are reportedconcerning the neutron diagnostics at different locations The same issues are faced also by forother diagnostics systems

Diagnostics in Equatorial Ports diagnostic equipment is mounted in a port plug assembly [18]The port plug geometry consists of two basic parts -the Diagnostic Shield Module (DSM) andthe generic port plug structure figure 10a The Diagnostic Shield Module (DSM) consists ofseveral parts the Diagnostic First Wall (DFW) which is designed to handle the radiant heat fluxfrom the plasma the Diagnostic Shielding Block (DSB) which is designed to handle most of theneutronic heat load and the supporting moduledrawer which fastens the components to the portplug structure and provides a platform or housing for the diagnostic components Figure 10b showsthe drawer in eq Port 1 containing the inport detectors and collimators of B1 RNC

ndash 13 ndash

2012 JINST 7 C04012

a) Typical Equatorial port plug geometry b) In port RNC drawer in EqPort1

Figure 10 Equatorial port plug geometry

Figure 11 Recess of Diagnostic First Wall

The port plug assembly provides also the primary vacuum boundary at that port as well as thefeed-out for diagnostic signals (windows and feedthroughs) and feed-in for control signals

In the DSM there are a number of apertures for diagnostic viewing In designing the RNCsight lines of the inport detectors and related focal points attention has been paid to minimize theaperture (figure 10b) in the DFW which is recessed with respect to the nearby blanket modules(figure 11) This recess is needed to reduce the plasma interaction with the DFW

As an example eq Port Plug 1 is shown (figure 12) which is the most congested with diag-nostics The rational behind this is the need for being as close as possible to the plasma Followingsystems will be installed Radial Neutron Camera Divertor Impurity Monitor Bolometers Mo-tional Stark Effect Many factors have to be taken into account in optimizing the distribution ofdiagnostics within the available ports Because of neutron streaming considerations typically nomore than two systems with large labyrinths can be installed in one port with large aperture sys-tems placed near the port centres distributed systems are located evenly toroidally sometimescoordinated with the location of corresponding systems in the upper ports

ndash 14 ndash

2012 JINST 7 C04012

a) b)

Figure 12 Equatorial port plug 1 a) back view of feedthroughs and connections b) front view

Diagnostics in Vacuum Vessel for the systems installed in the vacuum vessel like B3 MFC andB8 Neutron Activation System a support structure ensuring a very good thermal and mechanicalanchoring to the vacuum vessel wall is required This together with the routing and clamping of thecables and pipes adjusting the irradiation ends to the gaps between the blanket modules leads to acontinuous integration work assuring enough clearance to the neighbouring components and properdefinition of the large variety of in-vacuum vessel interfaces Even though partially shielded by theblanket modules the design of some of the components are challenged by the varying magneticfields high nuclear heat and the loop voltage created around the vessel Last but not least are theinterfacing loads like ECRH stray power and additional acceleration due to disruption events Thelatter one is more important to systems like MFC which should be tested in order to prove that theymaintain performance under shock and vibration

Diagnostics in Cryostat for the B4 Neutron flux monitor located in the in-cryostat area the loadconditions are less severe Because the system is mounted on an extended support structure attachedto the cryostat wall the major loads which should be taken into account are the acceleration due togravity acceleration due to seismic events and those during plasma disruptions and displacements

Diagnostics in Divertor the most demanding among all the mentioned locations is the divertorwhere the load conditions are very severe and it requires an active cooling of all diagnostic compo-nents This on the other hand creates an additional interface with the divertor cooling water branchof which is used for the cooling of the diagnostic components and a development of a good strategyfor a leak localization and detection

The BC Divertor Neutron Flux Monitor is mounted on a cassette body which is remote handleable through the divertor port The divertor dome provides an opportunity to place diagnosticsinside the vacuum vessel since it provides some degree of shelter from the neutron flux and plasmaradiation In the same cassette bolometers which are used for measuring the power of incidentelectromagnetic radiation are required to sit in the gap between two adjacent cassette bodies Thiscreates some integration issues as the one presented in figure 13

ndash 15 ndash

2012 JINST 7 C04012

Figure 13 Integration issue bolometers and DNFM ldquosharingrdquo the same support structure

The B2 Lower Vertical Neutron Camera (LVNC) is integrated into the lower port A genericdiagnostic rack to house diagnostics or optical relays in the port is being developed which willbe customized for each diagnostic while keeping the same interfaces with the vacuum vessel Thediagnostic rack is attached to the side walls of the port and includes features for alignment to thedivertor central cassette On the basis of the recently performed neutronic analysis it became clearthat the vertical camera could not co-exist with any optical system in the same port as this is thecase now Activity is going on the possible relocation either of LVNC or of the optical systems

One of the most difficult interfaces between the blanket system and the diagnostics is pre-sented by the integration of the B2 LVNC The line of sights of the detectors need to protrude theblanket shielding module 18 and the first wall exactly in the middle where the remote handlingattachment the hydraulic connector and the cooling channels are designed as shown in figure 14This fact can bring to the reduction of number of sight lines Design work is being carried out tosort out this problem

ndash 16 ndash

2012 JINST 7 C04012

Figure 14 Interface between Blanket Module 18 and lines of sight of the Vertical Neutron Camera

An overview of ITER neutron diagnostic systems and of the associated challenging engineer-ing and integration issues has been described The design of these systems has taken into accountthe experience gained on large devices which have pointed out the importance of simultaneuousmeasurements of the neutron spatial and energy distributions

The main advantage of this complete set-up of ITER neutron diagnostics is its installation andoperation from the begin of ITER nuclear operation compared to other machines like JET LHDTFTR JT 60 where the various neutron diagnostics have been installed during different machineoperational phases

Acknowledgments

The authors wish to thank ITER Diagnostics Team and the colleagues of ITER Members of JapanKorea China Europe and Russian Federation for useful discussions and collaboration

The work described was supported and carried out by ITER Organization together with ITERMembers and Domestic Agencies of Japan Korea China Europe and Russian Federation Part ofthis activity was performed within the framework of the European Fusion Development Agreement

Disclaimer The views and opinions expressed herein do not necessarily reflect those of the ITERorganization

ndash 17 ndash

2012 JINST 7 C04012

References

[1] AJH Donne et al Progress in the ITER physics basis Chapter 7 diagnostics Nucl Fusion 47(2007) 337

[2] G Vayakis ER Hodgson and V Voitsenya Plasma diagnostics for magnetic fusion researchChapter 12 generic diagnostic issues for a burning plasma experiment Fusion Sci Technol 53(2008) 699

[3] A Encheva L Bertalot B Macklin G Vayakis and C Walker Integration of ITER in-vesseldiagnostic components in the vacuum vessel Fusion Eng Des 84 (2009) 736

[4] A Krasilnikov et al Status of ITER neutron diagnostic development Nucl Fusion 45 (2005) 1503

[5] M Sasao et al Plasma diagnostics for magnetic fusion research Chapter 9 fusion productdiagnostics Fusion Sci Technol 53 (2008) 604

[6] FP Orsitto et al Burning plasmas diagnostics AIP Conf Proc 988 Varenna Italy (2007)

[7] L Petrizzi et al Neutronic design of the ITER radial neutron camera Fusion Sci Eng 82 (2007)1308

[8] AV Krasilnikov CI Walker YA Kashchuk and DV Prosvirin A multichannel neutron collimatorfor the ITER tokamak Kluwer AcademicPlenum Publishers Instrum Exp Tech 47 (2004) 139

[9] A Encheva et al Engineering aspects of integration of ITER divertor diagnostics Fusion Eng Des86 (2011) 1323

[10] M Ishikawa et al Design of microfission chamber for ITER operations Rev Sci Instrum 79 (2008)10E507

[11] A Encheva et al Structural integrity report for ITER micro-fission chamber ITER documentITER D 3TDURL

[12] T Nishitani et al Engineering design of the ITER invessel neutron monitor using micro-fissionchambers Fusion Eng Des 82 (2007) 1192

[13] J Yang et al Fusion neutron flux monitor for ITER Plasma Sci Technol 10 (2008) 141

[14] YA Kashchuk AV Krasilrsquonikov and DV Prosvirin A conceptual project for a divertor monitor ofthe neutron yield in the ITER Instrum Exp Tech 49 (2006) 179

[15] MS Cheon et al In-vessel design of ITER diagnostic neutron activation system Rev Sci Instrum79 (2008) 10E505

[16] L Bertalot et al A strategy for calibrating the neutron systems at ITER in 35th plasma physicsconference Crete Greece 2008 EPS Europhysics Conference Abstracts 32D (2008) O2001httpepsppdepflchHersonissosstarthtm

[17] M Sasao L Bertalot M Ishikawa and S Popovichev Strategy for the absolute neutron emissionmeasurement on ITER Rev Sci Instrum 81 (2010) 10D329

[18] S Pitcher et al System Design Description Document (DDD) diagnostic generic equatorial portplug ITER document ITER D 3U8JU7

ndash 18 ndash

2012 JINST 7 C04012

a) Typical Equatorial port plug geometry b) In port RNC drawer in EqPort1

Figure 10 Equatorial port plug geometry

Figure 11 Recess of Diagnostic First Wall

The port plug assembly provides also the primary vacuum boundary at that port as well as thefeed-out for diagnostic signals (windows and feedthroughs) and feed-in for control signals

In the DSM there are a number of apertures for diagnostic viewing In designing the RNCsight lines of the inport detectors and related focal points attention has been paid to minimize theaperture (figure 10b) in the DFW which is recessed with respect to the nearby blanket modules(figure 11) This recess is needed to reduce the plasma interaction with the DFW

As an example eq Port Plug 1 is shown (figure 12) which is the most congested with diag-nostics The rational behind this is the need for being as close as possible to the plasma Followingsystems will be installed Radial Neutron Camera Divertor Impurity Monitor Bolometers Mo-tional Stark Effect Many factors have to be taken into account in optimizing the distribution ofdiagnostics within the available ports Because of neutron streaming considerations typically nomore than two systems with large labyrinths can be installed in one port with large aperture sys-tems placed near the port centres distributed systems are located evenly toroidally sometimescoordinated with the location of corresponding systems in the upper ports

ndash 14 ndash

2012 JINST 7 C04012

a) b)

Figure 12 Equatorial port plug 1 a) back view of feedthroughs and connections b) front view

Diagnostics in Vacuum Vessel for the systems installed in the vacuum vessel like B3 MFC andB8 Neutron Activation System a support structure ensuring a very good thermal and mechanicalanchoring to the vacuum vessel wall is required This together with the routing and clamping of thecables and pipes adjusting the irradiation ends to the gaps between the blanket modules leads to acontinuous integration work assuring enough clearance to the neighbouring components and properdefinition of the large variety of in-vacuum vessel interfaces Even though partially shielded by theblanket modules the design of some of the components are challenged by the varying magneticfields high nuclear heat and the loop voltage created around the vessel Last but not least are theinterfacing loads like ECRH stray power and additional acceleration due to disruption events Thelatter one is more important to systems like MFC which should be tested in order to prove that theymaintain performance under shock and vibration

Diagnostics in Cryostat for the B4 Neutron flux monitor located in the in-cryostat area the loadconditions are less severe Because the system is mounted on an extended support structure attachedto the cryostat wall the major loads which should be taken into account are the acceleration due togravity acceleration due to seismic events and those during plasma disruptions and displacements

Diagnostics in Divertor the most demanding among all the mentioned locations is the divertorwhere the load conditions are very severe and it requires an active cooling of all diagnostic compo-nents This on the other hand creates an additional interface with the divertor cooling water branchof which is used for the cooling of the diagnostic components and a development of a good strategyfor a leak localization and detection

The BC Divertor Neutron Flux Monitor is mounted on a cassette body which is remote handleable through the divertor port The divertor dome provides an opportunity to place diagnosticsinside the vacuum vessel since it provides some degree of shelter from the neutron flux and plasmaradiation In the same cassette bolometers which are used for measuring the power of incidentelectromagnetic radiation are required to sit in the gap between two adjacent cassette bodies Thiscreates some integration issues as the one presented in figure 13

ndash 15 ndash

2012 JINST 7 C04012

Figure 13 Integration issue bolometers and DNFM ldquosharingrdquo the same support structure

The B2 Lower Vertical Neutron Camera (LVNC) is integrated into the lower port A genericdiagnostic rack to house diagnostics or optical relays in the port is being developed which willbe customized for each diagnostic while keeping the same interfaces with the vacuum vessel Thediagnostic rack is attached to the side walls of the port and includes features for alignment to thedivertor central cassette On the basis of the recently performed neutronic analysis it became clearthat the vertical camera could not co-exist with any optical system in the same port as this is thecase now Activity is going on the possible relocation either of LVNC or of the optical systems

One of the most difficult interfaces between the blanket system and the diagnostics is pre-sented by the integration of the B2 LVNC The line of sights of the detectors need to protrude theblanket shielding module 18 and the first wall exactly in the middle where the remote handlingattachment the hydraulic connector and the cooling channels are designed as shown in figure 14This fact can bring to the reduction of number of sight lines Design work is being carried out tosort out this problem

ndash 16 ndash

2012 JINST 7 C04012

Figure 14 Interface between Blanket Module 18 and lines of sight of the Vertical Neutron Camera

An overview of ITER neutron diagnostic systems and of the associated challenging engineer-ing and integration issues has been described The design of these systems has taken into accountthe experience gained on large devices which have pointed out the importance of simultaneuousmeasurements of the neutron spatial and energy distributions

The main advantage of this complete set-up of ITER neutron diagnostics is its installation andoperation from the begin of ITER nuclear operation compared to other machines like JET LHDTFTR JT 60 where the various neutron diagnostics have been installed during different machineoperational phases

Acknowledgments

The authors wish to thank ITER Diagnostics Team and the colleagues of ITER Members of JapanKorea China Europe and Russian Federation for useful discussions and collaboration

The work described was supported and carried out by ITER Organization together with ITERMembers and Domestic Agencies of Japan Korea China Europe and Russian Federation Part ofthis activity was performed within the framework of the European Fusion Development Agreement

Disclaimer The views and opinions expressed herein do not necessarily reflect those of the ITERorganization

ndash 17 ndash

2012 JINST 7 C04012

References

[1] AJH Donne et al Progress in the ITER physics basis Chapter 7 diagnostics Nucl Fusion 47(2007) 337

[2] G Vayakis ER Hodgson and V Voitsenya Plasma diagnostics for magnetic fusion researchChapter 12 generic diagnostic issues for a burning plasma experiment Fusion Sci Technol 53(2008) 699

[3] A Encheva L Bertalot B Macklin G Vayakis and C Walker Integration of ITER in-vesseldiagnostic components in the vacuum vessel Fusion Eng Des 84 (2009) 736

[4] A Krasilnikov et al Status of ITER neutron diagnostic development Nucl Fusion 45 (2005) 1503

[5] M Sasao et al Plasma diagnostics for magnetic fusion research Chapter 9 fusion productdiagnostics Fusion Sci Technol 53 (2008) 604

[6] FP Orsitto et al Burning plasmas diagnostics AIP Conf Proc 988 Varenna Italy (2007)

[7] L Petrizzi et al Neutronic design of the ITER radial neutron camera Fusion Sci Eng 82 (2007)1308

[8] AV Krasilnikov CI Walker YA Kashchuk and DV Prosvirin A multichannel neutron collimatorfor the ITER tokamak Kluwer AcademicPlenum Publishers Instrum Exp Tech 47 (2004) 139

[9] A Encheva et al Engineering aspects of integration of ITER divertor diagnostics Fusion Eng Des86 (2011) 1323

[10] M Ishikawa et al Design of microfission chamber for ITER operations Rev Sci Instrum 79 (2008)10E507

[11] A Encheva et al Structural integrity report for ITER micro-fission chamber ITER documentITER D 3TDURL

[12] T Nishitani et al Engineering design of the ITER invessel neutron monitor using micro-fissionchambers Fusion Eng Des 82 (2007) 1192

[13] J Yang et al Fusion neutron flux monitor for ITER Plasma Sci Technol 10 (2008) 141

[14] YA Kashchuk AV Krasilrsquonikov and DV Prosvirin A conceptual project for a divertor monitor ofthe neutron yield in the ITER Instrum Exp Tech 49 (2006) 179

[15] MS Cheon et al In-vessel design of ITER diagnostic neutron activation system Rev Sci Instrum79 (2008) 10E505

[16] L Bertalot et al A strategy for calibrating the neutron systems at ITER in 35th plasma physicsconference Crete Greece 2008 EPS Europhysics Conference Abstracts 32D (2008) O2001httpepsppdepflchHersonissosstarthtm

[17] M Sasao L Bertalot M Ishikawa and S Popovichev Strategy for the absolute neutron emissionmeasurement on ITER Rev Sci Instrum 81 (2010) 10D329

[18] S Pitcher et al System Design Description Document (DDD) diagnostic generic equatorial portplug ITER document ITER D 3U8JU7

ndash 18 ndash

2012 JINST 7 C04012

a) b)

Figure 12 Equatorial port plug 1 a) back view of feedthroughs and connections b) front view

Diagnostics in Vacuum Vessel for the systems installed in the vacuum vessel like B3 MFC andB8 Neutron Activation System a support structure ensuring a very good thermal and mechanicalanchoring to the vacuum vessel wall is required This together with the routing and clamping of thecables and pipes adjusting the irradiation ends to the gaps between the blanket modules leads to acontinuous integration work assuring enough clearance to the neighbouring components and properdefinition of the large variety of in-vacuum vessel interfaces Even though partially shielded by theblanket modules the design of some of the components are challenged by the varying magneticfields high nuclear heat and the loop voltage created around the vessel Last but not least are theinterfacing loads like ECRH stray power and additional acceleration due to disruption events Thelatter one is more important to systems like MFC which should be tested in order to prove that theymaintain performance under shock and vibration

Diagnostics in Cryostat for the B4 Neutron flux monitor located in the in-cryostat area the loadconditions are less severe Because the system is mounted on an extended support structure attachedto the cryostat wall the major loads which should be taken into account are the acceleration due togravity acceleration due to seismic events and those during plasma disruptions and displacements

Diagnostics in Divertor the most demanding among all the mentioned locations is the divertorwhere the load conditions are very severe and it requires an active cooling of all diagnostic compo-nents This on the other hand creates an additional interface with the divertor cooling water branchof which is used for the cooling of the diagnostic components and a development of a good strategyfor a leak localization and detection

The BC Divertor Neutron Flux Monitor is mounted on a cassette body which is remote handleable through the divertor port The divertor dome provides an opportunity to place diagnosticsinside the vacuum vessel since it provides some degree of shelter from the neutron flux and plasmaradiation In the same cassette bolometers which are used for measuring the power of incidentelectromagnetic radiation are required to sit in the gap between two adjacent cassette bodies Thiscreates some integration issues as the one presented in figure 13

ndash 15 ndash

2012 JINST 7 C04012

Figure 13 Integration issue bolometers and DNFM ldquosharingrdquo the same support structure

The B2 Lower Vertical Neutron Camera (LVNC) is integrated into the lower port A genericdiagnostic rack to house diagnostics or optical relays in the port is being developed which willbe customized for each diagnostic while keeping the same interfaces with the vacuum vessel Thediagnostic rack is attached to the side walls of the port and includes features for alignment to thedivertor central cassette On the basis of the recently performed neutronic analysis it became clearthat the vertical camera could not co-exist with any optical system in the same port as this is thecase now Activity is going on the possible relocation either of LVNC or of the optical systems

One of the most difficult interfaces between the blanket system and the diagnostics is pre-sented by the integration of the B2 LVNC The line of sights of the detectors need to protrude theblanket shielding module 18 and the first wall exactly in the middle where the remote handlingattachment the hydraulic connector and the cooling channels are designed as shown in figure 14This fact can bring to the reduction of number of sight lines Design work is being carried out tosort out this problem

ndash 16 ndash

2012 JINST 7 C04012

Figure 14 Interface between Blanket Module 18 and lines of sight of the Vertical Neutron Camera

An overview of ITER neutron diagnostic systems and of the associated challenging engineer-ing and integration issues has been described The design of these systems has taken into accountthe experience gained on large devices which have pointed out the importance of simultaneuousmeasurements of the neutron spatial and energy distributions

The main advantage of this complete set-up of ITER neutron diagnostics is its installation andoperation from the begin of ITER nuclear operation compared to other machines like JET LHDTFTR JT 60 where the various neutron diagnostics have been installed during different machineoperational phases

Acknowledgments

The authors wish to thank ITER Diagnostics Team and the colleagues of ITER Members of JapanKorea China Europe and Russian Federation for useful discussions and collaboration

The work described was supported and carried out by ITER Organization together with ITERMembers and Domestic Agencies of Japan Korea China Europe and Russian Federation Part ofthis activity was performed within the framework of the European Fusion Development Agreement

Disclaimer The views and opinions expressed herein do not necessarily reflect those of the ITERorganization

ndash 17 ndash

2012 JINST 7 C04012

References

[1] AJH Donne et al Progress in the ITER physics basis Chapter 7 diagnostics Nucl Fusion 47(2007) 337

[2] G Vayakis ER Hodgson and V Voitsenya Plasma diagnostics for magnetic fusion researchChapter 12 generic diagnostic issues for a burning plasma experiment Fusion Sci Technol 53(2008) 699

[3] A Encheva L Bertalot B Macklin G Vayakis and C Walker Integration of ITER in-vesseldiagnostic components in the vacuum vessel Fusion Eng Des 84 (2009) 736

[4] A Krasilnikov et al Status of ITER neutron diagnostic development Nucl Fusion 45 (2005) 1503

[5] M Sasao et al Plasma diagnostics for magnetic fusion research Chapter 9 fusion productdiagnostics Fusion Sci Technol 53 (2008) 604

[6] FP Orsitto et al Burning plasmas diagnostics AIP Conf Proc 988 Varenna Italy (2007)

[7] L Petrizzi et al Neutronic design of the ITER radial neutron camera Fusion Sci Eng 82 (2007)1308

[8] AV Krasilnikov CI Walker YA Kashchuk and DV Prosvirin A multichannel neutron collimatorfor the ITER tokamak Kluwer AcademicPlenum Publishers Instrum Exp Tech 47 (2004) 139

[9] A Encheva et al Engineering aspects of integration of ITER divertor diagnostics Fusion Eng Des86 (2011) 1323

[10] M Ishikawa et al Design of microfission chamber for ITER operations Rev Sci Instrum 79 (2008)10E507

[11] A Encheva et al Structural integrity report for ITER micro-fission chamber ITER documentITER D 3TDURL

[12] T Nishitani et al Engineering design of the ITER invessel neutron monitor using micro-fissionchambers Fusion Eng Des 82 (2007) 1192

[13] J Yang et al Fusion neutron flux monitor for ITER Plasma Sci Technol 10 (2008) 141

[14] YA Kashchuk AV Krasilrsquonikov and DV Prosvirin A conceptual project for a divertor monitor ofthe neutron yield in the ITER Instrum Exp Tech 49 (2006) 179

[15] MS Cheon et al In-vessel design of ITER diagnostic neutron activation system Rev Sci Instrum79 (2008) 10E505

[16] L Bertalot et al A strategy for calibrating the neutron systems at ITER in 35th plasma physicsconference Crete Greece 2008 EPS Europhysics Conference Abstracts 32D (2008) O2001httpepsppdepflchHersonissosstarthtm

[17] M Sasao L Bertalot M Ishikawa and S Popovichev Strategy for the absolute neutron emissionmeasurement on ITER Rev Sci Instrum 81 (2010) 10D329

[18] S Pitcher et al System Design Description Document (DDD) diagnostic generic equatorial portplug ITER document ITER D 3U8JU7

ndash 18 ndash

2012 JINST 7 C04012

Figure 13 Integration issue bolometers and DNFM ldquosharingrdquo the same support structure

The B2 Lower Vertical Neutron Camera (LVNC) is integrated into the lower port A genericdiagnostic rack to house diagnostics or optical relays in the port is being developed which willbe customized for each diagnostic while keeping the same interfaces with the vacuum vessel Thediagnostic rack is attached to the side walls of the port and includes features for alignment to thedivertor central cassette On the basis of the recently performed neutronic analysis it became clearthat the vertical camera could not co-exist with any optical system in the same port as this is thecase now Activity is going on the possible relocation either of LVNC or of the optical systems

One of the most difficult interfaces between the blanket system and the diagnostics is pre-sented by the integration of the B2 LVNC The line of sights of the detectors need to protrude theblanket shielding module 18 and the first wall exactly in the middle where the remote handlingattachment the hydraulic connector and the cooling channels are designed as shown in figure 14This fact can bring to the reduction of number of sight lines Design work is being carried out tosort out this problem

ndash 16 ndash

2012 JINST 7 C04012

Figure 14 Interface between Blanket Module 18 and lines of sight of the Vertical Neutron Camera

An overview of ITER neutron diagnostic systems and of the associated challenging engineer-ing and integration issues has been described The design of these systems has taken into accountthe experience gained on large devices which have pointed out the importance of simultaneuousmeasurements of the neutron spatial and energy distributions

The main advantage of this complete set-up of ITER neutron diagnostics is its installation andoperation from the begin of ITER nuclear operation compared to other machines like JET LHDTFTR JT 60 where the various neutron diagnostics have been installed during different machineoperational phases

Acknowledgments

The authors wish to thank ITER Diagnostics Team and the colleagues of ITER Members of JapanKorea China Europe and Russian Federation for useful discussions and collaboration

The work described was supported and carried out by ITER Organization together with ITERMembers and Domestic Agencies of Japan Korea China Europe and Russian Federation Part ofthis activity was performed within the framework of the European Fusion Development Agreement

Disclaimer The views and opinions expressed herein do not necessarily reflect those of the ITERorganization

ndash 17 ndash

2012 JINST 7 C04012

References

[1] AJH Donne et al Progress in the ITER physics basis Chapter 7 diagnostics Nucl Fusion 47(2007) 337

[2] G Vayakis ER Hodgson and V Voitsenya Plasma diagnostics for magnetic fusion researchChapter 12 generic diagnostic issues for a burning plasma experiment Fusion Sci Technol 53(2008) 699

[3] A Encheva L Bertalot B Macklin G Vayakis and C Walker Integration of ITER in-vesseldiagnostic components in the vacuum vessel Fusion Eng Des 84 (2009) 736

[4] A Krasilnikov et al Status of ITER neutron diagnostic development Nucl Fusion 45 (2005) 1503

[5] M Sasao et al Plasma diagnostics for magnetic fusion research Chapter 9 fusion productdiagnostics Fusion Sci Technol 53 (2008) 604

[6] FP Orsitto et al Burning plasmas diagnostics AIP Conf Proc 988 Varenna Italy (2007)

[7] L Petrizzi et al Neutronic design of the ITER radial neutron camera Fusion Sci Eng 82 (2007)1308

[8] AV Krasilnikov CI Walker YA Kashchuk and DV Prosvirin A multichannel neutron collimatorfor the ITER tokamak Kluwer AcademicPlenum Publishers Instrum Exp Tech 47 (2004) 139

[9] A Encheva et al Engineering aspects of integration of ITER divertor diagnostics Fusion Eng Des86 (2011) 1323

[10] M Ishikawa et al Design of microfission chamber for ITER operations Rev Sci Instrum 79 (2008)10E507

[11] A Encheva et al Structural integrity report for ITER micro-fission chamber ITER documentITER D 3TDURL

[12] T Nishitani et al Engineering design of the ITER invessel neutron monitor using micro-fissionchambers Fusion Eng Des 82 (2007) 1192

[13] J Yang et al Fusion neutron flux monitor for ITER Plasma Sci Technol 10 (2008) 141

[14] YA Kashchuk AV Krasilrsquonikov and DV Prosvirin A conceptual project for a divertor monitor ofthe neutron yield in the ITER Instrum Exp Tech 49 (2006) 179

[15] MS Cheon et al In-vessel design of ITER diagnostic neutron activation system Rev Sci Instrum79 (2008) 10E505

[16] L Bertalot et al A strategy for calibrating the neutron systems at ITER in 35th plasma physicsconference Crete Greece 2008 EPS Europhysics Conference Abstracts 32D (2008) O2001httpepsppdepflchHersonissosstarthtm

[17] M Sasao L Bertalot M Ishikawa and S Popovichev Strategy for the absolute neutron emissionmeasurement on ITER Rev Sci Instrum 81 (2010) 10D329

[18] S Pitcher et al System Design Description Document (DDD) diagnostic generic equatorial portplug ITER document ITER D 3U8JU7

ndash 18 ndash

2012 JINST 7 C04012

Figure 14 Interface between Blanket Module 18 and lines of sight of the Vertical Neutron Camera

An overview of ITER neutron diagnostic systems and of the associated challenging engineer-ing and integration issues has been described The design of these systems has taken into accountthe experience gained on large devices which have pointed out the importance of simultaneuousmeasurements of the neutron spatial and energy distributions

The main advantage of this complete set-up of ITER neutron diagnostics is its installation andoperation from the begin of ITER nuclear operation compared to other machines like JET LHDTFTR JT 60 where the various neutron diagnostics have been installed during different machineoperational phases

Acknowledgments

The authors wish to thank ITER Diagnostics Team and the colleagues of ITER Members of JapanKorea China Europe and Russian Federation for useful discussions and collaboration

The work described was supported and carried out by ITER Organization together with ITERMembers and Domestic Agencies of Japan Korea China Europe and Russian Federation Part ofthis activity was performed within the framework of the European Fusion Development Agreement

Disclaimer The views and opinions expressed herein do not necessarily reflect those of the ITERorganization

ndash 17 ndash

2012 JINST 7 C04012

References

[1] AJH Donne et al Progress in the ITER physics basis Chapter 7 diagnostics Nucl Fusion 47(2007) 337

[2] G Vayakis ER Hodgson and V Voitsenya Plasma diagnostics for magnetic fusion researchChapter 12 generic diagnostic issues for a burning plasma experiment Fusion Sci Technol 53(2008) 699

[3] A Encheva L Bertalot B Macklin G Vayakis and C Walker Integration of ITER in-vesseldiagnostic components in the vacuum vessel Fusion Eng Des 84 (2009) 736

[4] A Krasilnikov et al Status of ITER neutron diagnostic development Nucl Fusion 45 (2005) 1503

[5] M Sasao et al Plasma diagnostics for magnetic fusion research Chapter 9 fusion productdiagnostics Fusion Sci Technol 53 (2008) 604

[6] FP Orsitto et al Burning plasmas diagnostics AIP Conf Proc 988 Varenna Italy (2007)

[7] L Petrizzi et al Neutronic design of the ITER radial neutron camera Fusion Sci Eng 82 (2007)1308

[8] AV Krasilnikov CI Walker YA Kashchuk and DV Prosvirin A multichannel neutron collimatorfor the ITER tokamak Kluwer AcademicPlenum Publishers Instrum Exp Tech 47 (2004) 139

[9] A Encheva et al Engineering aspects of integration of ITER divertor diagnostics Fusion Eng Des86 (2011) 1323

[10] M Ishikawa et al Design of microfission chamber for ITER operations Rev Sci Instrum 79 (2008)10E507

[11] A Encheva et al Structural integrity report for ITER micro-fission chamber ITER documentITER D 3TDURL

[12] T Nishitani et al Engineering design of the ITER invessel neutron monitor using micro-fissionchambers Fusion Eng Des 82 (2007) 1192

[13] J Yang et al Fusion neutron flux monitor for ITER Plasma Sci Technol 10 (2008) 141

[14] YA Kashchuk AV Krasilrsquonikov and DV Prosvirin A conceptual project for a divertor monitor ofthe neutron yield in the ITER Instrum Exp Tech 49 (2006) 179

[15] MS Cheon et al In-vessel design of ITER diagnostic neutron activation system Rev Sci Instrum79 (2008) 10E505

[16] L Bertalot et al A strategy for calibrating the neutron systems at ITER in 35th plasma physicsconference Crete Greece 2008 EPS Europhysics Conference Abstracts 32D (2008) O2001httpepsppdepflchHersonissosstarthtm

[17] M Sasao L Bertalot M Ishikawa and S Popovichev Strategy for the absolute neutron emissionmeasurement on ITER Rev Sci Instrum 81 (2010) 10D329

[18] S Pitcher et al System Design Description Document (DDD) diagnostic generic equatorial portplug ITER document ITER D 3U8JU7

ndash 18 ndash

2012 JINST 7 C04012

References

[1] AJH Donne et al Progress in the ITER physics basis Chapter 7 diagnostics Nucl Fusion 47(2007) 337

[2] G Vayakis ER Hodgson and V Voitsenya Plasma diagnostics for magnetic fusion researchChapter 12 generic diagnostic issues for a burning plasma experiment Fusion Sci Technol 53(2008) 699

[3] A Encheva L Bertalot B Macklin G Vayakis and C Walker Integration of ITER in-vesseldiagnostic components in the vacuum vessel Fusion Eng Des 84 (2009) 736

[4] A Krasilnikov et al Status of ITER neutron diagnostic development Nucl Fusion 45 (2005) 1503

[5] M Sasao et al Plasma diagnostics for magnetic fusion research Chapter 9 fusion productdiagnostics Fusion Sci Technol 53 (2008) 604

[6] FP Orsitto et al Burning plasmas diagnostics AIP Conf Proc 988 Varenna Italy (2007)

[7] L Petrizzi et al Neutronic design of the ITER radial neutron camera Fusion Sci Eng 82 (2007)1308

[8] AV Krasilnikov CI Walker YA Kashchuk and DV Prosvirin A multichannel neutron collimatorfor the ITER tokamak Kluwer AcademicPlenum Publishers Instrum Exp Tech 47 (2004) 139

[9] A Encheva et al Engineering aspects of integration of ITER divertor diagnostics Fusion Eng Des86 (2011) 1323

[10] M Ishikawa et al Design of microfission chamber for ITER operations Rev Sci Instrum 79 (2008)10E507

[11] A Encheva et al Structural integrity report for ITER micro-fission chamber ITER documentITER D 3TDURL

[12] T Nishitani et al Engineering design of the ITER invessel neutron monitor using micro-fissionchambers Fusion Eng Des 82 (2007) 1192

[13] J Yang et al Fusion neutron flux monitor for ITER Plasma Sci Technol 10 (2008) 141

[14] YA Kashchuk AV Krasilrsquonikov and DV Prosvirin A conceptual project for a divertor monitor ofthe neutron yield in the ITER Instrum Exp Tech 49 (2006) 179

[15] MS Cheon et al In-vessel design of ITER diagnostic neutron activation system Rev Sci Instrum79 (2008) 10E505

[16] L Bertalot et al A strategy for calibrating the neutron systems at ITER in 35th plasma physicsconference Crete Greece 2008 EPS Europhysics Conference Abstracts 32D (2008) O2001httpepsppdepflchHersonissosstarthtm

[17] M Sasao L Bertalot M Ishikawa and S Popovichev Strategy for the absolute neutron emissionmeasurement on ITER Rev Sci Instrum 81 (2010) 10D329

[18] S Pitcher et al System Design Description Document (DDD) diagnostic generic equatorial portplug ITER document ITER D 3U8JU7

ndash 18 ndash