Post on 12-Nov-2021
WA104 - NESSiE R&D Plan1
Abstract2
The WA104-NESSiE Collaboration operating at the CERN Neutrino Facility3
aims at developing innovative solutions for the determination of the momentum4
and charge state of low energy muons. The ultimate goal is to provide high5
efficiency detectors and analysis tools for the study of neutrino interactions in6
the 1-10 GeV energy range.7
The NESSiE Collaboration8
A. Anokhina10, A. Bagulya9, M. Benettoni11, P. Bernardini7,6, R. Brugnera12,11,9
M. Calabrese6, S. Cecchini3, M. Chernyavskiy9, P. Creti6, O. Dalkarov9, A. Del Prete8,10
G. De Robertis1, M. De Serio2,1, L. Degli Esposti3, D. Di Ferdinando3, S. Dusini11,11
T. Dzhatdoev10, R. A. Fini1, G. Fiore6, G. Galati2, A. Garfagnini12,11, S. Golovanov9,12
C. Guandalini3, M. Guerzoni3, B. Klicek14, U. Kose11∗, K. Jakovcic14, G. Laurenti3,13
M. Laveder12,11, I. Lippi11, F. Loddo1, A. Longhin5, M. Malenica14, G. Mancarella7,6,14
G. Mandrioli3, A. Margiotta4,3, G. Marsella7,6, N. Mauri5, E. Medinaceli12,11,15
A. Mengucci5, M. Mezzetto11, R. Michinelli3, R. Mingazheva9, O. Morgunova10,16
A. Paoloni5, G. Papadia8, L. Paparella2,1, A. Pastore1, L. Patrizii3, N. Polukhina9,17
M. Pozzato4,3, M. Roda12,11, T. Roganova10, G. Rosa13, Z. Sahnoun3‡, S. Simone2,1,18
C. Sirignano12,11, G. Sirri3, M. Spurio4,3, L. Stanco11,a, N. Starkov9, M. Stipcevic14,19
A. Surdo6, M. Tenti4,3, V. Togo3 and M. Vladymyrov9.20
(a) Spokesperson21
1. INFN, Sezione di Bari, 70126 Bari, Italy22
2. Dipartimento di Fisica dell’Universita di Bari, 70126 Bari, Italy23
3. INFN, Sezione di Bologna, 40127 Bologna, Italy24
4. Dipartimento di Fisica dell’Universita di Bologna, 40127 Bologna, Italy25
5. Laboratori Nazionali di Frascati dell’INFN, 00044 Frascati (Roma), Italy26
6. INFN, Sezione di Lecce, 73100 Lecce, Italy27
7. Dipartimento di Matematica e Fisica dell’Universita del Salento, 73100 Lecce, Italy28
8. Dipartimento di Ingegneria dell’Innovazione dell’Universita del Salento, 73100 Lecce,29
Italy30
9. Lebedev Physical Institute of Russian Academy of Science, Leninskie pr., 53, 11933331
Moscow, Russia.32
10. Lomonosov Moscow State University (MSU SINP), 1(2) Leninskie gory, GSP-1,33
119991 Moscow, Russia34
11. INFN, Sezione di Padova, 35131 Padova, Italy35
12. Dipartimento di Fisica e Astronomia dell’Universita di Padova, 35131 Padova, Italy36
13. Dipartimento di Fisica dell’Universita di Roma “La Sapienza” and INFN, 00185 Roma,37
Italy38
14. Rudjer Boskovic Institute, Bijenicka 54, 10002 Zagreb, Croatia39
** Now at CERN, CH-1211 Geneva 23, Switzerland40
Preprint submitted to Elsevier February 28, 2014
‡ Also at Centre de Recherche en Astronomie Astrophysique et Gophysique, Alger, Algeria1
1. Introduction2
The WA104 activity is part of the CERN Neutrino platform that moving from3
the recommendation of the European Strategy Group to ”[...] develop a neu-4
trino programme to pave the way for a substantial European role in future long-5
baseline experiments” [1], includes neutrino detectors R&D and the study of a6
new neutrino beam [2].7
WA104-NESSiE aims at developing innovative solutions for the precise de-8
termination of the momentum and charge state of muons in the energy range9
from few hundreds MeV to several GeV.10
The immediate goal is the applications of identified solutions in the exper-11
imental search for sterile neutrinos beyond the Standard Model with a new12
CERN-SPS neutrino beam, as proposed in [3, 4].13
Two different approaches will be followed, a conservative one based on a14
light spectrometer seated in a 20 − 30 m3 magnetized air volume (Air Core15
Magnet), and an advanced one exploiting the novel superconducting (SC) cable16
technique for the magnetization of several hundreds cubic meter volumes. A17
novel intermediate system is also sketched for a SC-ACM.18
In the following we shall briefly recall the design of the NESSiE Air Core19
Magnet (Section 2), the required performances of the ACM Spectrometer (Sec-20
tion 2.1), the detectors to be used to instrument it (Section 3). The main21
features of the charged test beam are summarized in Section 6 while in Sec-22
tion 7 the EHN1 experimental hall facility is described. Our test program is23
outlined in Section 8. In Section 9 a proposal is advanced for a combined anal-24
ysis between ACM and liquid-Argon detector put in front of. In Section 10 we25
discuss the planned R&D on superconducting magnets for neutrino detectors.26
2. ACM for WA10427
The design of the Air Core Magnet (ACM) is optimized for the determination28
of the momentum and charge state of muons in the 0.5 - 3 GeV/c range (the mis-29
ID is required to be less than 3% at 0.5 GeV/c). Therefore a global small budget30
of low-density material along the beam direction should be envisaged. Provided31
the eventual use in a neutrino beam, a magnetic field over a relatively large32
volume is required as well. The ACM design has also to satisfy the requirements33
of large acceptance, modularity of construction, low power consumption and34
reduced costs.35
The ACM has been designed as a compromise between all these requirements36
and the measurement capability, the latter being maximized by the quantity37
B×∆z (magnetic field and size along the beam axis, respectively). The chosen38
ACM features are reported in Table 1. A suitable power supply can be the high39
current switch mode power converter PS-SMH57 [5]. It is extensively used in40
LHC, with output in the ranges 4-10 kA, 8-16 V. We may ask CERN to provide41
it.42
2
B ∆z Coils Single coil length Current density Power0.12 T 1.30 m 39 17.2 m 1.9 A/mm2 270 kW
Table 1: Values of the ACM design parameters.
In Fig. 1 and Fig. 2 the ACM 3D view and single coil view are shown,1
respectively. The mechanical structure contrasting the magnetic forces and the2
conductors are both made of Aluminum, which is a low density material. The3
volume of the bending magnetic field is in air. Single coils are all made in4
the same way and can be assembled one on top of the other. The tie-rods5
in the internal volume are placed in such a way to minimize the material in6
the magnetic volume available and to maximize the effective volume for the7
detectors.8
In Fig. 3 a sketch of the ACM equipped with a cage structure to allow safe9
and easy displacements with crane is shown. The single coil section is reported10
in Fig. 4. The heat due to the Joule effect is extracted from the coils by a water11
flow. Assuming the flow is 20 m3/h an increase of ∼ 10◦ C is expected for the12
water temperature going through the circuit.13
3
Figure 3: ACM with the structure used for moving it by crane.
Figure 4: Section of the single ACM coil. The hole for the water flow is visible.
5
2.1. Expected performances of the ACM1
The mechanical stress due to the magnetic and gravitational forces have been2
carefully studied by means of finite element analyses. We have verified that3
Von Mises stress is always lower than the yield strength, thus the ACM (coils4
and load-bearing structure) is everywhere in the elastic range. Furthermore5
the strains induced by the forces on the ACM are lower than some tenth of6
millimeter.7
The magnetic field in the ACM volume is expected to be almost uniform. Its8
value versus different axes is shown in Fig. 5. In Fig. 6 the field value is shown9
also outside the ACM volume assuming a magnetic shielding (see Sec. 2.2 for10
details). The rapid change of the field magnitude at the two vertical edges11
forces a measurement of the non-bending coordinate(y). The y-coordinate can12
be coarsely measured via e.g. scintillator strips (see Section 4.2). We observe13
that it is lower than 10 G at few meters from the ACM. Indeed the fringe field14
value must be low in order to avoid any interference with the operation of the15
LAr detector.16
Fig. 7 shows the displacement with respect to the original path expected17
for a muon crossing different magnetic volume depths for different values of the18
magnetic field. In Fig. 8 the displacement versus incidence angle for the chosen19
130 cm volume depth and 0.12 T magnetic field is reported.20
Many simulations have been performed to foresee the capability of the ACM21
to distinguish the particle charge and to measure the momentum. The charge22
mis-identification shown in Fig. 9 as a function of the muon momentum is the23
result of a simulation assuming a realistic neutrino beam and CC interaction in24
the LAr detector. Twelve detector planes are used in the ACM volume with a25
resolution of 1 mm, a Kalman filter is applied for the charge measurement. The26
momentum measurement are expected with a resolution of the order of 30% or27
less, as depicted in the right plot of Fig. 9.28
6
Figure 5: The magnetic field in the ACM volume versus the vertical axis (left)and the beam axis (right).
7
Figure 6: Side view of the magnetic field. The white color corresponds to regionswith B > 50 G, the color palette is instead for B < 50 G. The shield and theACM are clearly visible.
8
Figure 7: Displacement of the muon path in the bending plane, as a functionof the momentum, for different values of magnetic field and its depth along thebeam axis. Particles are assumed to enter the ACM volume perpendicularly tothe detector planes.
9
)°angle in XY plane (50 100 150 200 250 300 350
)°
an
gle
wit
h r
esp
ect
to Z
axis
(
5
10
15
20
25
30
35
40
45
dis
pla
cem
en
t (c
m)
8
10
12
14
16
18
displacement (cm)
Figure 8: Shift of charged particle tracks with 0.5 GeV/c momentum versusimpinging angle (B = 0.12 T , ∆z = 130 cm).
Figure 9: Charge misidentification and momentum resolution as a function ofthe muon momentum. The ACM features are B = 0.12 T , ∆z = 130 cm, thespatial resolution of the assumed 5 detector planes is 1 mm. The error barscorrespond to the spread due to the multiple scattering and the intrinsic spatialresolution.
10
2.2. Magnetic shielding1
The experimental setup will be completed with a magnetic shield system2
made of iron and vacoflux-50 slabs. Vacoflux-50 is a cobalt-iron alloy widely3
used for magnetic shielding due to the high magnetic saturation (2.35 T).4
The aim of this configuration is to have a magnetic fringe-field lower than5
0.5 G where the LAr detector is. Many shield configurations have been studied6
taking into account also the request that the material in-between LAr and ACM7
must be as low as possible. It turned out that the magnetic shield shown in8
Fig. 10 is a suitable set-up. One iron slab (5 cm thick) is put in-between two9
vacoflux-50 slabs (each 1.5 cm thick). Another iron slab (50 cm thick) is put10
downstream the ACM to close the magnetic field lines.11
The magnetic field with this shielding has been already shown in Fig. 6. A12
zoom of the fringe field in the LAr detector position is shown in Fig. 11 and it13
results fully compatible with the standard PMT operation.14
Figure 10: The magnetic shield is made by iron and vacoflux-50 slabs. Thethickness of iron slabs is 5 (in front of the ACM) and 50 cm (behind), that ofvacoflux-50 slabs is 1.5 cm.
11
Figure 11: Magnetic field as a function of the distance from the ACM. The LAractive detector is expected to be at 2 m from the ACM (-2 m in this figure)where the fringe field is lower than 0.5 G (the 3 curves are referred to differenty heights).
3. Precision detectors1
The charge identification of low momentum muons cannot be done using an2
iron core magnet because of the multiple scattering they would undergo. This3
limitation is avoided if the magnetic field is in air. In Sec. 2.1 the expected4
effect of the magnetic field on muon tracks and the possible measurements are5
presented. As a consequence the resolution of the detectors to be used is of the6
order of 1 mm.7
Taking into account the beam energy and the short distance of the ACM8
detectors from the neutrino interaction point, a wide muon angular distribution9
with respect to the beam axis (z) is expected. Therefore two independent views10
(x, z and y, z) are necessary for a full reconstruction of the muon track bending11
and to check the association of the ACM-track with the LAr-track.12
The ACM will be instrumented with high precision tracking devices. Differ-13
ent detector options are being considered, which are discussed in the following.14
Also a combination of different detectors is possible in order to get a two-views15
reconstruction. Detailed Montecarlo simulations and test-beams are mandatory16
for the final choice of the precision trackers and of their configuration in the17
ACM volume.18
12
3.1. Scintillator Bar Tracking System1
The tracking detector comprises 5 planes of scintillator bar (SciBar) detec-2
tors 2 × 2 m2 size. The planes are equi-spaced inside the ACM depth of 1.33
m. Each plane is made of triangular shape scintillator bars aligned along two4
orthogonal directions (x,y when the beam is along the z direction). Two addi-5
tional planes are foreseen in order to resolve ambiguities in the hit position. The6
scintillator bar cross-section is a triangle 17 mm heigh and 33 mm wide, with a7
central hole 2.6 mm diameter to lodge the wavelength shifting fiber 12). Each8
bar is read by SiPMs, that can operate in a magnetic field; the hit position is9
determined by analog pulse readout and analysis. Preliminary R&D carried out10
on prototypes using laser beams, radioactive sources and cosmic ray particles11
for was aimed at12
• studying characteristics of different SiPMs;13
• determining their working conditions and efficiency dependence on vari-14
ables like temperature, Vbias etc;15
• calibrating;16
• determining the spatial resolution achievable with this tracking system.17
Results of the measurements made with a laboratory set-up that triggered on18
cosmic rays are shown in Figs.13; the corresponding predictions obtained by a19
pure geometrical Montecarlo reproducing the experimental tracking system is20
plotted in 14.21
Figure 12: Left: triangular scintillator bar and WLS fibers. Right: sketch of a2 plane scintillator bar tracker.
13
!Figure 13: Distribution of the reconstructed positions for cosmic rays selectedwithin 5.0 mm window trigger displaced by 4 mm is shown.
!Figure 14: Reconstructed position for cosmic rays selected within a 2.5 mmwindow (left): RMS 2.0 mm. Geometrical MC simulation (right): RMS 1.0mm
14
3.2. Resistive Plate Chambers with analog read-out1
Resistive Plate Chambers (RPCs) are suitable to reach the required 1-mm2
resolution for the charge ID. They are gas detectors [9] widely used in high3
energy and astroparticle experiments. Single gas gap delimited by bakelite re-4
sistive electrodes is the simpler set-up commonly used in streamer mode and5
digital read-out. The main operation features are excellent time resolution and6
high counting rate. Also the spatial resolution is very good. In particular con-7
ditions the centroid of the induced charge profile has been determined [10] with8
a FWHM resolution of ∼ 120 µm. In the case of the NESSIE experiment such9
resolution is not necessary and a simpler and cheaper set-up can be used.10
The analog read-out of RPC has been used in many experiments [13]. This11
technique allows to read the total amount of charge induced on the strips, so to12
get a more detailed information on the streamer charge distribution across the13
strips, resulting in a better estimate of the particle track across the detector.14
The charge profile has a Gaussian shape. The total charge depends strongly15
on the RPC high voltage and on the gas mixture. The width of the profile is16
∼ 5 mm and constant.17
The charge collected on the strips is proportional to the area and the solid18
angle involved. Then the choice of an adequate strip size allows to reach a19
mm resolution in the charge position determination. Also the dynamic range20
is improved, making possible to extend the capability to detect particle at a21
density of the order of 1000 particles/m2.22
We are willing to test the performances of these detectors in the WA104-23
NESSiE program. New electronics for the analog read-out will be implemented24
thanks to the expertise acquired in the ARGO-YBJ experiment [12]. A 10-bit25
5-kHz ADC should fit the required resolution with 1-cm strips. Strips of 0.5 cm26
would be more effective but the number of channels may come out to be too27
large.28
The gas system can be recovered from the OPERA experiment in Gran Sasso29
Laboratory. We will require to CERN the supply of the gas mixture and the30
security assistance.31
15
4. The Ancillary Systems1
4.1. The Iron-RPC System2
A mock-up of the iron core magnet of the NESSiE experiment instrumented3
with bakelite RPCs will be installed downstream of the ACM. It will be act4
mainly as muon range detector.5
The iron structure 1 was developed in 2003 for a CERN test-beam with6
glass RPCs in the context of the Monolith proposal. It is composed by a stack7
of twenty 5 cm thick iron plates separated by 2 cm wide gaps (total depth of8
138 cm). The cross section is 1 × 1 m2. The structure is held by a quadruplet9
of I-beams welded with the stack of slabs on two sides (Fig. 15).10
Figure 15: The Iron-RPC ancillary system.
The RPCs will be used also as trackers in the ancillary iron system. In this11
case the analog read-out and the signal amplification are not necessary and the12
digital operation in streamer regime is enough.13
This operation mode does not require a devoted R&D activity because it is14
widely used. Furthermore the NESSiE people acquired a lot of experience using15
digital RPCs in OPERA and ARGO-YBJ experiments. Standard 2-mm single-16
gap RPCs in streamer mode reach 3 MHz/m2 and this rate is fully compatible17
with the test-beam.18
In the ancillary device each RPC plane will be readout in two views by19
means of inductive strips. Therefore the tracks will be fully reconstructed to20
make easier an univocal association with LAr and ACM tracks.21
4.1.1. The Iron RPC FrontEnd22
A fully new front-end electronics of the RPCs instrumenting the iron mag-23
nets of the NESSiE Spectrometers has been designed to operate with an event24
rate of the order of several tens of events per spill. A trigger-less logic has been25
1The setup is currenly at the Laboratori Nazionali di Frascati (INFN).
16
implemented. According to the same design scheme adopted for the OPERA ex-1
periment, groups of 64 signals coming from the RPCs working in streamer mode2
are read-out by means of front-end boards (FEB) equipped with 4 16 -channel3
LVDS receivers and an Ethernet configurable Field Programmable Gate Array4
(FPGA). The LVDS receivers act as discriminators with programmable thresh-5
olds that can be set via Ethernet by 4 integrated 10-bit DACs. The output6
of each discriminator is sampled with a resolution of 10 ns and continuously7
stored in a 4096-sample circular buffer whenever a write-enable signal is ac-8
tive. A time stamp with a 10 ns resolution is provided for each stored signal.9
Each FEB provides 2 FAST - OR signals implementing the trigger of groups10
of 32 channels. FEBs are housed in crates controlled by a FPGA-based Crate11
Controller Board (CCB) with several tasks such as power supply management12
and monitoring, control signal distribution, masking, FAST-OR collection and13
management. Each CCB is able to manage up to 19 FEBs. The FAST-OR14
signals coming from the FEBs are stored in a circular buffer in a similar way as15
described above for the discriminated RPC signals in each FEB. The CCB pro-16
vides 4 configurable FAST-OR signals as input to a Trigger Supervisor Board17
(TSB) able to generate a programmable trigger which can be used for the acqui-18
sition of cosmic ray muons as well as for monitoring and calibration purposes.19
Prototypes of FEBs and CCB are currently under test in connection with a20
RPC set - up collecting cosmic rays.21
4.2. The scintillator sandwich system22
The incoming/outgoing directions of particles entering/exiting the ACM will23
be determined by planes of plastic scintillator strips placed upstream and down-24
stream of the ACM. The strips are arranged in horizontal and vertical planes25
(transverse to the beam direction) thus providing 3D track information. The26
scintillator strips are 2.5 cm wide, read on both sides using WLS fibers and27
multi-anode photomultipliers. (If made available we may re-use part of the28
target tracker system of the OPERA experiment.)29
17
5. Data Acquisition System1
The Data Acquisition system is built like an Ethernet network whose nodes2
are the FEB equipped with an Ethernet controller. The Ethernet network is3
used to collect the data from the FEB, send them to the event building worksta-4
tion and dispatch the commands to the FEBs for configuration, monitoring and5
slow control. This scheme implies the distribution of a global clock to synchro-6
nize the local counters running on the FEBs that are used to time stamp the7
data. The clock signal can be distributed either using a dedicated network or8
with the same Ethernet network implementing a White Rabbit protocol2. The9
DAQ clock is synchronized with the CERN General Time Machine signal in or-10
der to start the DAQ readout cycle during particle extraction time. Given the11
long duration (order of second) of the beam still a trigger system is needed to12
acquire the data associated with the passage of the beam particles and typically13
several FEB read-out cycle are performed within the same particle extraction14
time.15
Along the spill duration the FEBs store the status of the discriminators or16
the pulse height of the input signals, for digital and analog readout, respectively,17
in a circular buffer driven by an external clock. The readout of the buffer by the18
DAQ is triggered by a signal generated by a programmable logic (Trigger Board)19
on the basis of the FAST-OR signals generated by the FEBs. The trigger signal20
causes the FEB to disable the writing and the buffer content is transferred to21
the Ethernet controller. Here data are time stamped, eventually zero suppressed22
and sent through Ethernet to the event building. At the end of the read-out23
cycle an enable signal is used to reset the FEBs and start a new read-out cycle.24
In the inter-spill time the acquisition of cosmic ray muons and calibration data25
is triggered by a fake spill gate, possibly validated by a programmable logic26
(Trigger Board) on the basis of the FAST-OR signals generated by the FEBs.27
The start-of-spill signal is used to abort all the readout process on the FEBs28
and to start new data read-out.29
6. The charged beam30
The primary beam of 400 GeV/c protons are slowly extracted from the SPS.31
Typical SPS spill length varies from 4.8 to 9.6 s, while spills are repeated every32
14.8 s to 48 s depending on the number of SPS users. The extracted beam is33
transported over about 1 km by bending and focusing magnets and then split34
into three parts. Each one is directed towards the primary targets T2, T4 and35
T6 to provide secondary beam for experimental building in the North Area.36
EHN1 experimental hall hosts four secondary particle beam lines: the beam37
from target T2 splits into the lines H2 and H4, while T4 splits into the beam38
lines H6 and H8 (Figure 17). The H2, H4 and H8 beam lines can provide39
secondary hadrons, electrons or muons up to 400 GeV/c or primary protons of40
2http://www.ohwr.org/projects/white-?rabbit
19
up to 450 GeV/c. The height of the beam lines from the floor level is in the1
range 2.0-2.8 m.2
Since the detectors will be placed in the pit 9 m deep in the extended part,3
the beam lines have to be extended to transport the low energy particles. The4
length of H4 beam line is about 659 m, a few tens meter of extension is foreseen5
to provide tertiary beam to the experiment.6
Muons and pions test beams of positive and negative polarity and momenta7
between 0.5 and 5 GeV/c (with possibility of extending up to 7 GeV/c) are8
required to evaluate the ACM performances in a standalone configuration. An9
intensity of 1-2 kHz for each given momentum in a beam size of 10 × 10 cm210
would be required. A particle composition of > 99% for muon beams and ≥ 90%11
for pion beams is preferable. If the beam is a mixture of π and µ, particle tagging12
information from the Cherenkov counters or TOF is required to determine the13
ACM response separately to each particle type. Moreover, the π/µ, separation14
can be evaluated in the Iron-RPC system (see Section 4.1).15
Figure 17: Beam lines in EHN1 experimental hall.
20
7. EHN1 Experimental hall1
The NESSiE detectors will be placed in the extended part of the Exper-2
imental Hall 1 (EHN1) at the Super Proton Synchrotron (SPS) North Area3
(Figure 18) as agreed in the CERN Neutrino Platform and with a layout com-4
patible to the neutrino beam option. The total length of the extension is about5
70 m along the direction of beam lines. It includes two large pits of 7.3 and6
9.0 m deep devoted to WA105 and WA104, respectively. The extended EHN17
hall must be equipped with electrical power, air ventilation, water cooling and8
cranes. Depending on the test beam activity to be carried out, the detector will9
be moved downstream or upstream the LAr-TPC detector. Power converters10
of PS-SMH57&61 or LHC13kA-190V type could be used. They will be located11
in the vicinity of the detector setup. The power required to run the ACM, at12
the nominal field of 0.12 Tesla, is 8100 Amps for 35 Volts. Estimated power13
consumption would be around 270 kW plus 5% power loss in the supply for14
ACM and 30 kW for the electronic of the detector.15
The ACM coils are kept at a temperature of ∼ 20 0C by a water cooling16
system. A demineralised water flow of about 20 m3/h is required.17
Figure 18: EHN1 hall layout in neutrino beam configuration with NESSiE de-tectors placed downstream ICARUS-T150.
21
8. Test Program1
We plan to perform tests related to the structure and magnetic field of the2
ACM as well as to the performances of the spectrometer.3
8.1. Test on the ACM mechanical structure and magnetic fields4
The 39 coils ACM structure will be tested against5
• mechanical deformations under magnetic forces and weights6
• thermal expansion.7
Mapping of the magnetic fields in the ACM volume and the external fringe field8
will be performed by means of Hall probes, in different shielding configurations.9
8.2. Test beam10
The test will be performed using the 39-coils ACM. Different phases with11
the test-beam are foreseen. At the beginning the detectors will be tested on12
the charged beam. In a second phase the ancillary iron system will be used as13
a target upstream the ACM, finally the test will be performed with the muons14
emerging from the LAr volume.15
The ACM will be equipped with two different detectors (scintillator bars,16
analog RPCs) on the two sides. By means of the cranes the ACM will be moved17
in order to center the beam on scintillator or RPC part and to change the18
arrival angle of the charged particles. The scintillator sandwiches will be used19
to compare the tracks reconstructed inside the ACM with the tracks upstream20
and downstream the ACM. When necessary the addition of a copper plane will21
allow to enhance the pion/muon separation at low energy.22
The test-beam will be devoted to:23
• Check of DAQ, trigger and detector performances.24
• Optimization of the detector setup (number of planes and position in the25
ACM, scintillator bar geometry, RPC operation point and so on).26
• Estimate of the charge ID percentage as a function of detectors, energy,27
beam angle. This measurement is based on the track bending.28
• Measurement of the particle momentum as a function of detectors, energy,29
beam angle. This measurement is based on the bending in magnetic field30
complemented by the range measurement in the ancillary device.31
• Combined analysis of LAr-ACM events (see Sec. 9).32
22
9. Combined analysis of LAr-TPC - ACM events1
The following test program is foreseen to evaluate the global performance2
of ACM and LAr-TPC detectors. In this configuration the ACM is located3
downstream the LAr-TPC. The positioning of the setup with respect to the4
LAr-TPC detector is shown in Figure 18. We do not request any special beam5
operation. Beacuse of the average energy loss of the muon in argon (about6
210 MeV/m for a minimum ionizing particle), muons with Pµ > 3 GeV/c are7
energetic enough to emerge from the LAr volume (the length of T150 is about8
10 m), Figure 19.9
The momentum and sign of the tracks will be measured in ACM for each10
beam spill. This information will be provided to LAr-TPC data from the same11
spill using a timestamps common in both detectors. Therefore we need to access12
time stamp information as well as beam timing signal. All the tracks identified13
by ACM and LAr-TPC are then searched to identify the corresponding tracks14
in the two detectors.15
LAr-TPC tracks will be extrapolated along their directional three-vector16
from their exit position in the TPC to the ACM. The matching between two17
projections, by comparing the angle of the tracks and radial difference between18
the projected track, will be applied. Multiple scattering at the exits and entering19
to the detectors will be also taken into account.20
Assuming a beam spot of 5×5 cm2 containing 10 K muons with a momentum21
range 0f 2.5 to 5.5 GeV/c at the entrance of LAr-TPC, 1 m2 surface of ACM22
would be illuminated, as shown in Figure 20. In Figure 21 an example of the23
distribution of the reconstructed slopes in ACM is shown.24
In order to take detector resolution in account, gaussian smearing (1 mm)25
around the hits in ACM for all coordinates have been applied. All the hits26
recorded in the ACM within a time window would be used to form a track27
candidates in (x,z) and (y,z) planes. Charged particle tracks are bent in the28
ACM region due to presence of magnetic field, therefore a parabolic fit is applied.29
The track element in the LArTPC have been extracted by linear fit of muon30
hits at last 2 m.31
The angular matching for given momentum spectrum is found to be about32
50 mrad. Knowing the last point and slope of the track at LAr-TPC, the33
predicted position of the track on ACM evaluated. The position resolution34
(positions in ACM smeared) for a given momentum spectrum is found to be35
60 mm.36
The charge ID will be available at high sensitivity for all these kinds of37
tracks, allowing a substantial up-till-now unmeasured test of the possible charge38
identification in LAr.39
In case the neutrino beam will be granted, we would be ready to include40
ICM to exploit the full performances of the extended NESSiE system.41
23
Z (mm)-12000 -10000 -8000 -6000 -4000 -2000 0 2000 4000
X (
mm
)
-2500
-2000
-1500
-1000
-500
0
500
1000
1500
2000
2500
TOP ViEW
Z (mm)-12000 -10000 -8000 -6000 -4000 -2000 0 2000 4000
Y (
mm
)
-2500
-2000
-1500
-1000
-500
0
500
1000
1500
2000
2500
SIDE ViEW
Figure 19: Muon tracks with a momentum of 2.1, 2.8 and 3.5 GeV/c penetratingLAr-TPC. The track with Pµ > 3 GeV/c crossing ACM as well. Gray blocksrepresent passive materials (5 cm and 50 cm iron slabs).
x [cm]-100 -80 -60 -40 -20 0 20 40 60 80 100
y [c
m]
-100
-80
-60
-40
-20
0
20
40
60
80
100
0
1
2
3
4
5
6
7
8
9
10
Beam spot on ACM
Figure 20: Beam spot on the ACM.
24
xθ-0.5 -0.4 -0.3 -0.2 -0.1 0 0.1 0.2 0.3 0.4 0.5
Trac
ks
0
50
100
150
200
250
300
350
400
450
in ACMXθ
xθδ
-0.2 -0.15 -0.1 -0.05 0 0.05 0.1 0.15 0.2
Trac
ks
0
50
100
150
200
250
Xθδ
in ACMXθ
yθ-0.5 -0.4 -0.3 -0.2 -0.1 0 0.1 0.2 0.3 0.4 0.5
Trac
ks
0
50
100
150
200
250
300
350
400
450
in ACMYθ
yθδ-0.2 -0.15 -0.1 -0.05 0 0.05 0.1 0.15 0.2
Trac
ks
0
50
100
150
200
250
Yθδ
in ACMYθ
Figure 21: The angular resolution in the bending corrdinate of the ACM isreported for muon tracks of < Pµ >= 1.0GeV/c. The bias of about 50 mrad isclearly due to the effect of the magnetic field and the simplified reconstructionalgorithm, and it can properly accounted for.
25
10. R&D on Superconducting Magnets for Neutrino Detectors1
We will investigate the use of and feasibility of incorporating Superconduct-2
ing (SC) magnet systems in the design of the Air Core Magnet called SC-ACM,3
as well as magnet systems for Liquid Argon Chamber-like detectors. Several4
types of superconducting materials such as Niobium-Titanium (NbTi), operat-5
ing temperature 4.2 K, Magnesium-di-Boride (MgB2), operating at 20 K and6
Rare Earth Barium-Copper-Oxide (REBCO), operating at around 50 K will be7
investigated by considering the various options for coil design such as solenoids8
with rectangular section or sets of racetrack coils. Based on this study a con-9
ductor technology will be chosen.10
For the different superconductors the required operating conditions in terms11
of critical current density as function of peak magnetic field, forces, stress and12
thermal stability requirements will be optimized and evaluated. Crucial proper-13
ties like effective temperature margin for safe operation and quench protection14
options to handle the stored energy will be analysed in more detail. A second15
key issue is the choice of conductor technology and the impact on the coil wind-16
ing technology and cryogenic requirements. Depending on the Lorentz force17
produced due to magnetic field, a sufficiently rigid coil support structure has to18
be designed.19
Various tests to qualify the conductor technology are foreseen. Once the20
conductor technology is frozen, the construction of a short model coil is foreseen21
to validate the coil winding technology under realistic operating conditions in22
order to mitigate project risks.23
The magnetic and mechanical designs will be analysed using FEM codes like24
ANSYS and FIELD. The comprehensive R&D program on the use of supercon-25
ducting magnet technology will allow us to evaluate the options to reach a cost26
effective solution providing the best possible performance.27
We envisage to perform this activity in conjunction and supporting the28
CERN and ICARUS foreseen plans.29
10.1. A toroidal Super Conducting ACM30
We are studying the possibility to use a SC toroidal magnet to produce an31
average magnetic field of 1 T in air, by considering standard techniques already32
developed for the LHC experiments. It will be made by 8 Niobium-Titanium33
superconducting coils arranged in a toroidal configuration, as depicted in Fig. 22.34
The system owns an external diameter of 8 m. Detector can be inserted in front,35
inside and behind the toroid. It provides a large measuring surface free of any36
material, thus freeing of any limitation induced by multiple scattering. It can37
be operated with liquid Helium at 4.2 K.38
The sketched new system, provided its currently workable element-configuration,39
will allow to construct a magnetized setup for muons in a relatively short time,40
to provide large surfaces of measurements, and to couple in a standard way to41
Liquid Argon tanks. Needless to say this kind of configuration will have no42
outgoing fringe field.43
26
11. Conclusions1
The WA104 activity that is foreseen by the NESSiE Collaboration has been2
extensively described in this document. It will be part of the general frame3
endowed by the CERN Neutrino platform, which moves from the recommen-4
dation of the European Strategy Group to ... develop a neutrino program to5
pave the way for a substantial European role in future long–baseline experiments.6
R&D on neutrino detectors and the study of a new neutrino beam at CERN is7
therefore part of this program.8
WA104–NESSiE aims at developing innovative solutions for the precise de-9
termination of the momentum and charge state of muons in the energy range10
from few hundreds MeV to several GeV. The immediate goal is the applications11
of identified solutions in the experimental search for sterile neutrinos beyond12
the Standard Model with a new CERN-SPS neutrino beam, as already pro-13
posed. The two different approaches that we aim to develop, a conservative14
one based on a light–Z spectrometer (Air Core Magnet), and an advanced one15
exploiting the novel superconducting cable technique for the magnetization of16
several hundreds cubic meter volumes, have been described. In the latter case17
a relevant guideline will be taken into account, namely the overall cost for both18
its construction and the running mode.19
The foreseen prototyping of an ACM will allow to check the construction20
issues, in term of mechanical feasibility, optimization of the servicing modes21
and robustness. The magnetic system is foreseen to be operated in a standalone22
mode. In such a way it will be possible to place it in different positions, following23
different test–patterns and with different detectors, mainly Liquid–Argon ones.24
The R&D activity on the super–conducting cable will go all along the fore-25
seen time period and it will be conducted in parallel.26
The overall time schedule is reported in Figure 23.27
28
Figure 23: The foreseen time-table of the WA104-NESSiE activities.
Floor load capacity: 20 tons (concentrated loads 2 t/300 cm2)A crane of small capacity (5 t)A crane of large capacity (at least 30 t with auxiliary hook of 5 t)Control room, about 20 m2
General safety conditionsACM power supplyCooling services: heat exchangers, pumps and valvesDemineralized water (20 m3/h flow)Gas mixing, distribution and recirculation plant
Table 2: Required technical infrastructures at CERN
12. References1
[1] ...ref a documento strategy Group2
[2] ref a P5 Nov20133
[3] P. Bernardini et al., Prospect for Charge Current Neutrino Interactions4
Measurements at the CERN-PS, SPSC-P-343 (2011).5
[4] ICARUS and NESSiE Collaborations, M. Antonello et al.,6
[5] http://te-epc-lpc.web.cern.ch/te-epc-lpc/converters/SMH57-7
61/general.stm.8
[6] CERN - SBLNF - Study, EDMS Document No. 1260131 v. 10.09
[7] ...10
[8] G. Bari et al. Analysis of the performance of the MONOLITH prototype11
Nucl. Instr. and Meth. A 508 (2003) 170-17412
29
[9] R. Santonico, R. Cardarelli, Nucl. Instr. and Meth. A 187 (1981) 377.1
R. Santonico, R. Cardarelli, Nucl. Instr. and Meth. A 263 (1988) 20.2
[10] E. Ceron Zeballos et al, Nucl. Instr. and Meth. A 392 (1997) 150.3
[11] R. Arnaldi et al, Nucl. Instr. and Meth. A 490 (2002) 51.4
[12] G. Aielli et al, Nucl. Instr. and Meth. A 661 (2012) S56.5
[13] D. Autiero et al, RPC 2001 Workshop, Coimbra, November 2001.6
[14] P.K.F. Grieder ”Cosmic rays at earth”, Elsevier (Amsterdam, 2011).7
[15] ...8
30