Austrian Fusion RTD Activities · sheath, weighing altogether 120 tons. Assembled like slices of...

Association EURATOM-ÖAW

ANNUAL REPORT 2013

Austrian Fusion RTD Activities

Cover page

Top left: Coordinated Activities on ITER Physics – gyrofluid computations of turbulent and ELMy SOL transport

Turbulent dispersion of a cloud of impurity ions in the scrape-off layer

(SOL) after being hit by an edge localized ideal ballooning mode burst. The impurity density n is shown at four poloidal positions (z=0: inboard side; z=8: outboard side) in a radial-toroidal section. The black dashed lines denote the position of the edge-SOL separation. Impurity density is both blown outwards by ELM fingers and also sucked inside by respective holes.

Graph: Institute of Ion Physics and Applied Physics, University of

Innsbruck

Top right: Coordinated Activities on ITER Physics – multi-device research to understand the pedestal stability

(a) Typical input diffusion coefficient profile for ASTRA modelling with variable core and edge values. The neoclassical diffusion coefficient profile is shown in blue. The diffusive transport is anomalous. (b) Input convective velocity profile estimated from the ne profile and a variable edge value. The neoclassical convective velocity profile is shown in blue. Graph: Institute of Applied Physics, Vienna University of Technology in

cooperation with the ASDEX Upgrade Team (IPP Garching)

Bottom: Coordinated Activities on Power Plant Physics and Technology – High Heat Flux Materials

SEM micrograph of W-25wt%Cu: the material was annealed at 720°C in vacuum for 1 hour and 30 turns were applied at room temperature.

In order to improve ductility and strength of high heat flux materials, samples of copper and tungsten based materials were subjected to high-pressure torsion and various heat treatments. The materials were then inspected by a scanning electron microscope (SEM) in order to analyse the effects of the various treatments.

Graph: Erich-Schmid Institute of Materials Science at ÖAW


ANNUAL REPORT 2013

Austrian Fusion RTD Activities

Vienna March 2014

The Annual Report 2013 of the Association EURATOM-ÖAW covers the period 1 January to 31 December 2013

Compiled by Monika Fischer

This work, supported by the European Commission under the Contract of Association between EURATOM and ÖAW, was carried out within the framework of the European Fusion Development Agreement (EFDA). The views and opinions expressed

herein do not necessarily reflect those of the European Commission.

Supported by


Kegelgasse 27/13 1030 Wien

Austria

Tel. +43-1-51581-2675

http://www.oeaw.ac.at/fusion

Copyright © 2014 by Austrian Academy of Sciences

Vienna Printed in Austria

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CONTENTS

Introduction 2On the road to fusion energy 4Executive summary 6Participation of Austrian Scientists in the EFDA Work Programme 2013 12

Distribution of scientific competencies – participation in EFDA task areas 13

I. COORDINATED ACTIVITIES ON ITER PHYSICS 14

I.1. Modelling and simulation of plasma phenomena 14

Contributions to Integrated Tokamak Modelling S. Kuhn, D. Tskhakaya jun. et al. (University of Innsbruck)

14

Tokamak fast-ion confinement based on 3D Fokker Planck modelling K. Schöpf et al. (University of Innsbruck)

18

I.2. Participation in ITER Support Projects 24

Plasma-wall interaction and transport in edge plasmas F. Aumayr et al. (Vienna University of Technology)

24

Molecular dynamics simulations of mixed materials M. Probst et al. (University of Innsbruck)

29

Investigation of plasma-wall interaction processes: chemical erosion, deposition and transport P. Scheier et al. (University of Innsbruck)

32

Transport and heating in toroidal devices W. Kernbichler et al. (Graz University of Technology)

39

Computational plasma dynamics A. Kendl et al. (University of Innsbruck)

44

Edge plasma turbulence and transport phenomena R. Schrittwieser et al. (University of Innsbruck)

48

II. COORDINATED ACTIVITIES ON POWER PLANT PHYSICS AND TECHNOLOGY

55

II.1. Materials R & D 55

Characterization of high-heat flux materials R. Pippan et al. (Erich-Schmid Institute of Materials Science)

55

II.2. Design assessment studies 65

High-temperature superconducting materials for fusion magnets M. Eisterer et al. (Vienna University of Technology)

65

II.3. Socio-Economic Research on Fusion (SERF) 73

Energy scenario development with EFDA-TIMES M. Biberacher et al. (Research Studios Austria)

73

Abbreviations and acronyms 75Austrian representatives in European committees relevant for fusion R and D 79Contact information 80Management structure 81

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INTRODUCTION

I am honoured to present the Annual Report 2013 of the Association EURATOM-ÖAW on

Austrian Fusion Research and Development activities. In 2013, research groups from the

Austrian Academy of Sciences, the Graz University of Technology, the University of

Innsbruck, the Research Studio iSPACE in Salzburg and the Vienna University of Technology

contributed to several tasks in the areas Integrated Tokamak Modelling, ITER Support Projects

and Power Plant Physics and Technology in the framework of the Contract of Association

between EURATOM and ÖAW and in close cooperation with EFDA. Like in previous years,

frequent use has been made of Staff Mobility, an important instrument for a university-based

Association without its own fusion laboratory.

I am especially proud to report on the assignment of the 2013 Lifetime Achievement Award to

Professor Harald Weber (Vienna University of Technology) at the International Cryogenic

Materials Conference in Anchorage (Alaska) and the nomination of Professor Roman

Schrittwieser as Fellow of the American Physical Society “... for outstanding experimental

contributions to the physics of double layers, potential relaxation instabilities, fireballs and

probe diagnostics in tokamaks”.

The year 2013 was characterized by a vigorous effort by the EFDA Leader and the chair of the

EFDA Steering Committee with their respective teams and all Heads of Research Unit of the

Fusion Associations to achieve a smooth transition from the system of bilateral contracts

between fusion laboratories and the European Commission to a new consortium structure for

H2020. On the basis of the Roadmap to the Realization of Fusion Energy a proposal for a

European Joint Programme Co-fund Action was drafted and a Memorandum of Understanding

was concluded among the prospective participants. Despite some open administrative issues I

am optimistic that the successful participation of Austrian fusion researchers in the European

Fusion Programme will smoothly continue in Horizon 2020.

In Austria fusion research is almost exclusively performed at university institutes, with

approximately 15 active PhD students per year. Education and training has been a major

priority of the Association EURATOM-ÖAW throughout its existence and will continue to be

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an important objective in the future. The framework conditions of Horizon 2020 will hopefully

help us to ensure the long-term perspective required for the successful implementation of the

Roadmap objectives.

The Commission for the Coordination of Fusion Research in Austria at ÖAW (KKKÖ) has

continued its support for PhD students contributing to the Austrian Fusion Programme and for

graduates who intend to apply for employment with Fusion for Energy or the ITER

Organization. At its meeting on 19th November 2013 KKKÖ adapted the internal eligibility

criteria for support to the future structure of the European Joint Programme.

The involvement of industry in the European Fusion Programme and the accessibility of

business opportunities triggered by the construction of ITER are of vital importance for the

ITER project. In this respect, valuable support is provided by the Industrial Liaison Officer

(ILO) at the Austrian Chamber of Commerce who circulates information about calls and

specialized meetings for industry to qualified companies and organizes the participation of

industrial delegations in specialized meetings.

Last, but not least I wish to thank all individuals and institutions who have offered continuous

support to the Association and will help to ensure the continuity of the Austrian Fusion

Programme:

the Austrian Minister for Science and Research and his representatives,

the President, Presiding Committee and staff of ÖAW,

the Austrian Commission for the Coordination of Fusion Research at ÖAW,

the responsible officers of the European Fusion Programme,

the EU and ÖAW delegates of the Association Steering Committee,

the staff of the ÖAW-EURATOM Coordination Office and all scientists actively participating in Austrian fusion RTD.

Vienna, March 2014 (Friedrich Aumayr, Head of Research Unit)

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ON THE ROAD TO FUSION ENERGY

A roadmap to the realization of fusion energy

A long-term perspective on fusion is essential to defend Europe’s leading position in the field. As a compendium of guidelines for a focussed research effort in Horizon 2020 and beyond, EFDA published the Roadmap to the Realization of Fusion Energy which had been elaborated in cooperation of the EFDA partners at the beginning of 2013. The Roadmap is considered to be a living document setting the pace for fusion becoming a source of base-load energy generation.

ITER – the key facility of the Roadmap

ITER, currently under construction in the South of France, will be the first magnetic confinement device to produce a net surplus of fusion energy. In 2013, the infrastructure of the ITER work site was further developed. The coil winding facility was completed in 2012. In 2013, work started on the assembly building, where large components will be assembled on site. Pipes for the precipitation drainage system and cooling water release were installed and a restaurant, infirmary and parking spaces were added.

The European Domestic Agency - Fusion for Energy (F4E)

Fusion for Energy (F4E) is the organization responsible for providing Europe’s contribution to ITER. One of the main tasks of the organization is to cooperate with European industry, SMEs and research organizations to develop and provide a wide range of high technology components together with engineering, maintenance and support services for the ITER project.

In 2013 Director Henrik Bindslev initiated a renewed dialogue with the Industrial Liaison Officers of Member States to seek opportunities for greater engagement by industry in F4E’s business opportunities and seeking an optimal sharing of risk between F4E and contractors which will help to control costs. “We want to understand how to incentivize industry to participate in contracts with F4E and to have an equitable sharing of the risks”, said Professor Bindslev. The Governing Board has adopted an industrial policy and guidelines on intellectual property rights and endorsed proposals from F4E on how to implement them.

Calls for tender, vacancies, events etc. are published at http://fusionforenergy.europa.eu .

Information for Austrian industry

Harnessing fusion energy is an industrial effort to be backed up by targeted research. It is the task of the network of Industrial Liaison Officers (ILOs) to raise awareness among qualified companies and advise them on ways to get involved in the ITER project. In cooperation with the ILOs, F4E plans a series of information days and seminars to report on the roadmap of different procurement packages and facilitate partnerships between companies. In Austria the function of ILO is performed by the Austrian Chamber of Commerce which acts as a contact forum for Austrian companies qualified for participating in high-tech industrial projects.

Foundation of the ITER tokamak complex: the round shape of the tokamak is already visible.

Source: http://www.iter.org/

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JET – the testing ground for ITER operation

JET (Culham, UK) is presently the world’s largest magnetic fusion device. It is the only experiment capable of using tritium and special wall materials. Since 1999 it has been operated in cooperation between the EFDA partners. With its recent upgrade with the installation of the ITER-like wall it has become an ideal ITER test ground. Recognizing this capability, the possibility of continuing the operation of JET in wider, world-wide collaboration is being pursued.

The Wendelstein 7-X stellarator – testing a long-term alternative to the tokamak

When completed, Wendelstein 7-X will be the world’s largest fusion device of the stellarator type. It is a ring-shaped device being installed as five almost structurally identical modules: Each of the five sections of the plasma vessel, along which 14 magnet coils are strung, is enclosed by a steel outer sheath, weighing altogether 120 tons. Assembled like slices of cake on the machine’s foundation, the five modules form a steel ring from which numerous connection ports protrude – inlets for diagnostic systems, heating facilities and pumps.

Transition from EFDA to a new governance structure in Horizon 2020

A dedicated effort has been undertaken by F. Romanelli (EFDA Leader), S. Günter (Head of IPP and chair of the EFDA Steering Committee) and the respective teams in cooperation with the Heads of Research Unit of the Fusion Associations to draft a Memorandum of Understanding for the transition to H2020 and to agree on a work plan for the period from 2014 to 2018 and a work programme for 2014 in line with the objectives of the Roadmap. These endeavours were undertaken in order to ensure a smooth transition from the system of bilateral contracts between fusion laboratories and the European Commission (Contracts of Association) to the new consortium structure.

The 254th and last port was brazed in between the plasma vessel and outer vessel with millimeter precision on 28 May 2013.

Photo: http://www.ipp.mpg.de

JET celebrated its 30th anniversary on 24 and 25 June 2013. A number of renowned journalists attended the event to report about progress and prospects of JET. Among the visitors were also four former directors of JET.

Source: http://www.efda.org

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Association EURATOM-ÖAW – Annual Report 2013 - Austrian Fusion RTD

EXECUTIVE SUMMARY

Research activities in 2013

I. COORDINATED ACTIVITIES ON ITER PHYSICS

I.1. Modelling and simulation of plasma phenomena in cooperation with the EFDA Task-Force Integrated Tokamak Modelling (ITM)

The main goals of the EFDA ITM work programme 2013 were the development of workflows towards a single validated suite of integrated modelling codes suitable for supporting the ITER Physics activi-ties, the validation of workflows developed in the course of the EFDA Work Programme 2013 and their application to physics problems of relevance to the ITER Scenario Modelling activity, the Inter-national Tokamak Physics Activity (ITPA) and/or for regular interpretative/predictive modelling of experimental data from present devices by modelers/experimentalists in the Fusion Associations.

D. Tskhakaya jun. (University of Innsbruck / Vienna University of Technology) contributed to the validation and implementation of AMNS data into the ITM platform. Atomic and molecular data (col-lision cross sections) were obtained with the code BIT1 and prepared for integration into the AMNS database. In particular, the influence of double ionization of tungsten on the ion distribution in the plasma edge was studied in the framework of task WP13-ITM-AMNS.

As part of Task WP13-ITM-IMP3, the code BIT1 was further adapted for use on the ITM platform. The input/output of the code was significantly simplified (e.g. the number of parameters for typical JET SOL simulation was reduced from more than 1,000 to 50) and flexible routines were developed for initializing atomic, molecular and plasma-surface interaction (PSI) processes during simulation runs. D. Tskhakaya jun. also participated in the coordination of task WP13-ITM-IMP3 (Transport code and discharge evolution) under activity WP13-ITM-TFL-PL.

K. Schöpf et al. (University of Innsbruck) model fast-ion behaviour in tokamak plasmas to explain specific transport mechanisms as well as loss of charged fusion products and injected ions in JET. Under task WP13-ITM-IMP5 the neutron beam injection (NBI) source module SNBI was further adapted to the ITM code platform.

In the framework of task WP13-IPH-A09-P1 the fusion alpha density before and after the redistribu-tion caused by toroidicity-induced Alfvén Eigenmodes (TAEs) was simulated with the coupled code system FIDIS/HAGIS.

The capability of gamma ray diagnostics to measure confined high-energy alphas in ITER was evalu-ated in the framework of task WP13-IPH-A09-P2. New detector possibilities for fast ion diagnostics in ITER were examined. The group has intensified its collaboration with JET with the purpose of sup-porting the development of gamma ray diagnostics and new detector systems with modelling and sim-ulation.

Figure 1. Simulated temporal evolution of flux surface averaged distribution functions of NBI deuterons (left) and NBI tritons (right) at the normal-ized flux surface ra-dius r/a=0.15 in JET shot #40214

7

In cooperation with CCFE (Culham, UK), CEA (Cadarache, France), ITER and F4E F. Köchl (Vien-na University of Technology) contributed to integrated simulations of the ITER baseline scenario and its variants.

I.2. Participation in ITER Support Projects

F. Aumayr et al. (Vienna University of Technology) investigate pedestal formation after L-H transi-tions and subsequent evolution in steady H-mode and perform fluctuation measurements across the edge transport barrier at ASDEX Upgrade with a Li diagnostic beam. In addition, the group special-izes in processes of plasma wall-interaction, in particular wall erosion, deposition and fuel retention. In 2013, the group contributed to ITER Support Projects WP13-IPH-A01-P2 (Formation of re-erosion dynamics of ITER-relevant mixed materials: erosion of mixed Be-N layers by D-species and compari-son to pure Be-layers, using the Vienna quartz crystal microbalance (QCM) setup - F. Aumayr, K. Dobes et al. in cooperation with IPP Garching and FZ Jülich), WP13-IPH-A08-P2 (multi-device re-search to understand the pedestal stability through the study of the edge barrier evolution between ELMs (short, recurrent instabilities of the edge plasma): characterization of edge pedestal density with the upgraded Li-beam diagnostics at ASDEX Upgrade and predictive modelling of experimental pro-files throughout the density build-up after the L-H transition with the code ASTRA - M. Willensdorfer, F. Laggner, F. Aumayr). State-selective cross sections for collisions of hydrogen (deu-terium) atoms with seeding impurity ions (N, Ne, Ar) were calculated with the improved AO-CC code in cooperation with IPP Garching (H. Veiter in cooperation with A. Schweinzer – IPP) under task WP13-ITM-AMNS-ACT1.

.

.

M. Probst et al. (University of Innsbruck) calculate energy profiles and atomistic reaction details by means of quantum chemical methods. Quantum chemical calculations of particle-Be interactions are used to obtain information on ion/atom bonding at Be surfaces. In 2013 the group participated in ITER Support Projects WP13-IPH-A01-P2 (Collision processes and electronic interaction between D, N and other atoms and Be, Be/W and W surfaces) and WP13-IPH-A01-P3-01 (Modelling and interpretation of the mechanisms of Be-H species formation).

Figure 2. (a) Typical input diffusion coefficient profile for ASTRA modelling with variable core and edge values. The neoclas-sical diffusion coefficient pro-file is shown in blue. The diffu-sive transport is anomalous. (b) Input convective velocity pro-file estimated from the ne pro-file and a variable edge value. The neoclassical convective ve-locity profile is shown in blue (M. Willensdorfer and the ASDEX Upgrade Team, “Par-ticle transport analysis of the density build-up after the L-H transition in ASDEX Upgrade", Nuclear Fusion 53 (2013), 093020).

8

P. Scheier et al. (University of Innsbruck) investigate erosion and deposition interactions of the in-volved plasma constituents with the materials used in plasma-facing components. In 2013 they con-tributed to ITER Support Project WP13-IPH-A01-P2 (Chemical erosion of beryllium by deuterium ions colliding with pure Be and Be/W mixture surface samples) and ITM Task WP13-ITM-AMNS-ACT1 (Molecular and surface data). In the framework of the latter task, inelastic electron scattering processes of the epoxy resin ethylidene bis-4.1-phenylene dicyanate were studied (used as an insulator of the superconductive magnetic coils in fusion devices). This material is less susceptible to radiation damage than conventional glue materials

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W. Kernbichler et al. (Graz University of Technology) investigate the numerical evaluation of toroidal viscosity and evolution of equilibrium plasma parameters under the action of external reso-nant magnetic perturbation fields. In 2013 they participated in ITER Support Projects WP13-IPH-A04-P1 (Predictive capabilities of the plasma rotation profile) and WP13-IPH-A06-P2 (Active control of ELMs and the associated divertor heat loads). In addition, they contribute to stellarator optimization in the framework of a collaboration of major stellarator laboratories.

Figure 3. Minimum-energy structures of (a) BeH and (b) BeH2 from Quadratic Configura-tion Interaction with Single and Double Excitations QCISD/aug-cc-pVTZ calcula-tions.

Figure 4. Electron ionization mass spectrum of ethylidene bis-4.1-pheny-lene dicyanate between m/z 165 and 330 at three different sample tem-peratures: 55°C, 74°C and 100°C. All peaks are inde-pendent of the sample tem-perature, i.e. no heavy fragment ions and no parent ion can be observed upon ionization of ethylidene bis-4.1-pheny-lene dicyanate.

Figure 5. Cross-sections of surfaces which are im-portant for computa-tions of the magnetic field of W7-X

9

A. Kendl and the Complex Systems Group (University of Innsbruck) specialize in the computation of plasma turbulence and modelling of impurity transport, with an emphasis on non-linear gyrofluid sim-ulations of plasma edge turbulence and edge localized ideal ballooning modes.

In 2013 the group prepared the existing gyrofluid GEMR and TOEFL codes for suitable perturbation field scenarios. In the future TOEFL should include a full-f global density evolution model together with a global (non-linear) polarization solver for realistic flux surface geometry (consistently crossing the separatrix) with multiple (non-trace) species. In addition, the group is working on the comparison with edge and SOL turbulence and blob measurements on ASDEX Upgrade. R. Schrittwieser and the Innsbruck Experimental Plasma Physics Group (University of Innsbruck) investigate plasma turbulence and related plasma phenomena, especially ELMs by various methods (specifically designed probe systems). In 2013, transport measurements have been performed in ASDEX Upgrade and COMPASS. This work has been performed in cooperation with IPP Garching (ASDEX Upgrade), JET, Consortio RFX, MESCS, IPP.CR and DTU.

Figure 6. Turbulent dispersion of a cloud of impurity ions in the scrape-off layer (SOL) after being hit by an edge localized ideal ballooning mode burst. The impurity density n is shown at four poloidal positions (z=0: inboard side; z=8: outboard side) in a radial-toroidal section. The black dashed lines denote the position of the edge-SOL separa-tion. Impurity density is both blown outwards by ELM fingers and also sucked inside by respective holes.

Figure 7. Temporal evolution of the floating potentials of BPP2 (red) and LP2 (blue) during the probe head re-ciprocation in COMPASS. The black line shows the radial position of the probe with respect to the separa-trix. The transition from the cold to the self-emitting LP2 starts at t = 1125 ms. It is radially 25 mm inside the separatrix.

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II.1. Materials

Characterization of high-heat flux materials

Applications in fusion technology require materials with high thermal conductivity and acceptable ductility and strength both at room temperature and higher temperatures. Additionally, the materials must be resistant to activation by neutron bombardment. In 2013, R. Pippan et al. (ErichSchmid In-stitute of Materials Science at ÖAW, Leoben) characterized the mechanical and thermal properties of high heat flux materials such as chromium and tungsten alloys with the goal of optimizing these mate-rials by suitable processing techniques.. The group contributed to several subtasks of WP13-MAT-HHFM (High heat flux materials).

Figure 8. SEM micrographs of W-25wt%Cu. Left side: 400 turns and right side: 30 turns were applied at room temperature. Both materials were annealed at 720°C in vacuum for 1 hour.

II.2. Design assessment studies

High-temperature superconductors

High-temperature superconducting (HTS) materials offer a considerable potential for magnet applica-tions because of their extremely high upper critical magnetic fields and their excellent current carrying capabilities at low temperatures. In the framework of this project, the material properties of HTS mate-rials developed and optimized by industry are characterized at different temperatures and magnetic fields before and after neutron irradiation. In 2013, M. Eisterer, H.W. Weber et al. (Vienna University of Technology) contributed to Task WP13-DAS-01 (Superconducting magnets).

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Figure 9. Irreversibility lines of new tapes developed by dif-ferent companies. Neutron irradiation was carried out in the TRIGA MARK II re-actor, Vienna, from July to September. The samples were exposed to a target fast neutron fluence of 2.5x1022 m-2 (E>0.1 MeV). At the reporting date, post-irradiation data were only available for the ASC-40 sample.

11

II. 3. Socio-economic research on fusion (SERF)

Energy scenario modelling

For several years M. Biberacher et al. (Research Studios Austria / Salzburg) contributed to the de-velopment of the EFDA Times Model in order to anticipate the future share of fusion power in the global energy mix. In 2013, a final report was prepared under EFDA (WP13-SER-ETM (Energy sce-narios - EFDA-TIMES).

The communication and presentation of the background, scope and achieved results with the EFDA-TIMES model (ETM), however, remains a major goal of ETM community. The model and its findings should not only be spread within the scientific community, but also be made available to an interested public community. Therefore the development of a first prototype of an ETM internet platform has been realized. Scope of this website is the interactive presentation of motivation, scope, scenarios and results of ETM to a wide public community. The website will be accessible from the future EUROfusion platform.

III. TRAINING AND EDUCATION

The Association EURATOM-ÖAW consists of a network of scientific contributors at three universi-ties, the Austrian Academy of Sciences and Research Studio Salzburg. Training and education of young researchers is a predominant goal within this network. Efforts to keep young researchers in the programme and to enable the continuation and / or completion of several studies described in the An-nual Report 2013 have been supported by special incentives of the Commission for the Coordination of Fusion Research in Austria (KKKÖ) at the Austrian Academy of Sciences.

IV. RESEARCH GRANTS IN COOPERATION WITH ITER AND F4E

Two small research grants were carried out in the fields of ITER Scenario Modelling and Nuclear Data.

V. MEETINGS AND PUBLIC OUTREACH

The Association EURATOM-ÖAW organized its 28th Association Day at Research Studio Salzburg on 18 October 2013. At this meeting, young researchers and their mentors met with groups from the other participating institutions in Austria and presented the topics of their PhD theses.

A popular scientific lecture on nuclear fusion was given by W. Kernbichler at the EXPI hands-on sci-ence center (St. Margareten, Carinthia) on 21 November 2013.

Several lectures for schools were organized at the Vienna University of Technology.

Visit of a group of high-school students to the Institute of Applied Physics of the Vienna University of Technology

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Participation of Austrian scientists in the EFDA Work Programme 2013 List of Task Agreements

COORDINATED ACTIVITIES ON ITER PHYSICS Integrated Tokamak Modelling Atomic, molecular, nuclear and surface physics data WP13-ITM-AMNS TU Wien,

UIBK Transport code and discharge evolution WP13-ITM-IMP3 TU Wien,

UIBK Heating, current drive and fast particle physics WP13-ITM-IMP5 UIBK Task Force Leadership WP13-ITM-TFL UIBK ITER scenario modelling WP13-ITM-ISM TU Wien ITER Support Projects Prediction of material migration and mixed material formation

WP13-IPH-A01 TU Wien, UIBK

Plasma rotation WP13-IPH-A04 TU Graz Pedestal instabilities (ELMs) mitigation and heat loads

WP13-IPH-A06 TU Graz, UIBK

Physics of the pedestal and H-mode WP13-IPH-A08 TU Wien, UIBK

Fast particles WP13-IPH-A09 UIBK COORDINATED ACTIVITIES ON POWER PLANT PHYSICS AND TECHNOLOGY Materials R & D High heat flux materials WP13-MAT-01-

HHFM ÖAW-ESI

Design Assessment Studies Superconducting magnets WP13-DAS-01 TU Wien Socio-Economic Research on Fusion (SERF) Energy scenarios EFDA-TIMES WP13-SER-ETM Research Studio

Salzburg

Participation in the EFDA-JET Work Programme 2013

Participation in EFDA-JET Campaigns C31 and C32

JW12-O-OAW12 TU Wien, UIBK

Number of publications in 2013

Publications in scientific journals 45 Publications in conference proceedings 14 Posters / presentations at conferences 10

Abbreviations: TU Wien = Vienna University of Technology

TU Graz = Graz University of Technology UIBK = University of Innsbruck ÖAW-ESI = Erich Schmid Institute of Materials Science

13

Distribution of scientific competencies - participation in EFDA task areas

Source: Fusion@ÖAW

Distribution of national funding

Source: Federal Ministry for Transport, Innovation and Technology (bmvit) http://www.nachhaltigwirtschaften.at/iea_pdf/1338_energieforschungserhebung_2012.pdf

Federal Ministries

Research institutions

Universities

22.5 %

9.5 %

68 %

Association EURATOM-ÖAW – Annual Report 2013 – Coordinated Activities on ITER Physics – Integrated Tokamak Modelling

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I. COORDINATED ACTIVITIES ON ITER PHYSICS

I.1. Modelling and simulation of plasma phenomena

Institute for Theoretical Physics, University of Innsbruck/ Institute of Applied Physics, Vienna University of Technology (TU Wien)

CONTRIBUTIONS TO INTEGRATED TOKAMAK MODELLING

S. Kuhn; N. Jelić, D. Tskhakaya jun. and D.D. Tskhakaya sen.

PROJECT SUMMARY

This project is intended to respond to the next-step needs of European Integrated Tokamak Modelling (ITM) by providing standardized “plug-in” physics and code modules for the new generation of European Integrated Tokamak Modelling (ITM) fluid codes.

1. WORK PERFORMED IN 2013 Task Agreement No. /

Tasks Milestones / Objectives Participants

Integrated Tokamak Modelling (ITM)

WP13-ITM-AMNS-ACT1-01/ÖAW

Further development, maintenance and documentation of modules to provide AMNS data to ITM-TF codes as well as support for the use of the modules

D. Tskhakaya jun.

WP13-ITM-IMP3-ACT2-01/ÖAW

Validation and productive runs of keplerized BIT1

D. Tskhakaya jun.

WP13-ITM-TFL-PL-01/ÖAW

Deputy leadership of IMP3 D. Tskhakaya jun.

Theoretical Support Improved boundary-layer theory and conditions for SOL simulation codes

S. Kuhn D. Tskhakaya sen. N. Jelic

WP13-ITM-AMNS-ACT1-01/ÖAW

Task description

1. Further development, maintenance and documentation of the user callable interface to the AMNS library

2. Support for the implementation of the AMNS interface in ITM codes

Deliverables / milestones

Maintenance and further development of the user-callable interface; Updates to the AMNS interface modules as needed by new data and new capabilities and

related documentation Implementation report on codes converted to use the AMNS interface Support in validation and implementation of the AMNS data in the ITM platform.


15

Progress of work

1. In collaboration with R. Mayo Garcia and A. Alberto Morillas the first version of the AMNS data-reader was developed and checked. This routine searches for available AMNS data and retrieves the queried data.

2. AMNS data production and management [1-3].

3. The code BIT1 was updated to simulate different models of metastable excited molecules which will be used to decide on how to bundle complex systems of metastables. We will start the corresponding simulations when the required molecular data become available.

4. Atomic and molecular data (collision cross sections) were extracted from the BIT1 code and the corresponding documentation for possible use in the AMNS database was provided.

5. Simulation runs were carried out in order to study the contribution of tungsten double ionization to tungsten impurity concentration.

Results

The simulations indicated that double ionization of tungsten can significantly influence the tungsten ion distribution in the plasma edge and cannot be neglected. For this reason the corresponding AMNS data have to be updated. It was further demonstrated that the BIT1 code can be successfully used for the identification of important atomic and molecular processes in the plasma edge.

WP13-ITM-IMP3-ACT2-01/ÖAW Task description

Implementation and release (including verification and validation) of a number of edge codes using consistent physical objects (CPOs) - phase V of the “ITM modules release cycle”.

Progress of work

For the ITM version of the BIT 1 code [4] (i) a new physics module for coupling of the code at the separatrix was developed and tested; (ii) the input/output of the code was significantly simplified (e.g. the number of parameters for typical JET SOL simulation was reduced from >1000 to 50); (iii) flexible routines were developed for initializing atomic, molecular and plasma-surface interaction (PSI) processes during the simulation runs.

New features compared to the original BIT1 code include:

(i) Automatic selection of the atomic, molecular and plasma-surface interaction (PSI) processes after specifying the simulated particle species;

(ii) It can be coupled with code/pedestal simulating codes;

(iii) A number of complex diagnostics (e.g. potential oscillation spectrums) or flexible inputs (e.g. the possibility to deactivate some types of collision, or other processes) are deactivated. If required, these capabilities can be activated.

Improved boundary-layer theory and conditions for SOL simulation codes (N. Jelic and D. Tskhakaya sen. in co-operation with the Association EURATOM-MESCS)

Publications under this topic are referred to in the list of publications below.


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2. OUTLOOK FOR 2014 AND BEYOND

D. Tskhakaya jun. Intends to continue his research activities in Horizon 2020 in the framework of the European joint fusion research programme.

REFERENCES

[1] G. Langer, G. Erdélyi, A. Csik, D. Tskhakaya, D. Coster and K. Tőkési, “Interaction of low energy carbon ions with tungsten surface”, poster P108, 28th International Conference on Photonic, Electronic and Atomic Collisions (ICPEAC) 2013, Lanzhou, China, 24-30 July, 2013.

[2] K. Tőkési, P. Salamon, D. Tskhakaya and D. Coster, “Universal functional formula of atomic elastic cross sections. The case of the hydrogen target”, poster P43, 28th International Conference on Photonic, Electronic and Atomic Collisions (ICPEAC) 2013, Lanzhou, China, 24-30 July 2013.

[3] K. Tőkési, D. Tskhakaya and D. Coster, “Atomic data for integrated tokamak modelling”, talk T2-OL6 given at the Third European Energy Conference (E2C 2013), Budapest, Hungary, October 27-30, 2013.

[4] D. Tskhakaya, D. Coster and ITM-TF Contributors, “Implementation of PIC/MC code BIT1 in ITM platform”, poster P1-8, PET 14 workshop, Krakow, Poland, 23-25 September 2013. Accepted for publication in Contributions to Plasma Physics.

OTHER PUBLICATIONS

Journal articles

Duras, J., K. Matyash, D.Tskhakaya, O. Kalentev and R. Schneider, “Self-force in 1D electrostatic particle-in-cell codes for nonequidistant grids”, accepted for publication in Contributions to Plasma Physics.

Grünwald, J., D. Tskhakaya, J. Kovacic, M. Cercek, T. Gyergyek, C. Ionita and R. Schrittwieser, “Comparison of measured and simulated electron energy distribution functions in low-pressure helium plasmas”, Plasma Sources of Science and Technology 22 (2013), 015023 (7 pages).

Järvinen, A., M. Groth, D. Moulton, J. Strachan, S. Wiesen, P. Belo, M. Beurskens, G. Corrigan, T. Eich, C. Giroud, E. Havlickova, S. Jachmich, M. Lehnen, J. Lönnroth, D. Tskhakaya and JET EFDA Contributors, “Simulations of tungsten transport in the edge of JET ELMy H-mode plasmas”, Journal of Nuclear Materials 438 (2013), 1005-1009.

Jelic, N. and L. Kos, “Ion-sound velocity at the plasma edge in fusion-relevant plasmas”, Nuclear Engineering and Design 261 (2013), 269-274.

Krek, J., N. Jelic and J. Duhovnik, “Grid-free treecode method in diode simulation”, Nuclear Engineering and Design 261 (2013), 238-243.

Moulton, D., Ph. Ghendrih, W. Fundamenski, G. Manfredi and D. Tskhakaya, “Quasineutral plasma expansion into infinite vacuum as a model for parallel ELM transport”, Plasma Physics and Controlled Fusion 55 (2013), 085003 (21pages).

Moulton, D., W. Fundamenski, G. Manfredi, S. Hirstoaga and D. Tskhakaya, “Comparison of free-streaming ELM formulae to a Vlasov simulation”, Journal of Nuclear Materials 438, (2013), 633-637.


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Tskhakaya, D., M. Groth and JET EFDA Contributors, “1D kinetic modelling of the JET SOL with tungsten divertor plates”, Journal of Nuclear Materials 438 (2013), 522-525.

Conference contributions

Brida, D. and D. Tskhakaya, “Investigation of plasma sheath oscillations”, Poster P1-21, PET 14 workshop, Krakow, Poland, 23-25 September 2013, accepted for publication in Contributions to Plasma Physics.

Eisenstecken, Th. and D. Tskhakaya, “On ion sound speed in a high recycling plasma edge”, Poster P1-22, PET 14 workshop, Krakow, Poland, 23-25 September 2013, accepted for publication in Contributions to Plasma Physics.

Gasteiger, M. and D. Tskhakaya, “On the electron distribution function in the plasma edge”, Poster P2-11, PET 14 workshop, Krakow, Poland, 23-25 September 2013, accepted for publication in Contributions to Plasma Physics.

Kuhn. S. and D.D. Tskhakaya (sen.), “The non-marginal Bohm condition in the collisionless plasma diode”, 40th EPS Conference on Plasma Physics, Espoo, Finland, 1-5 July 2013.


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Institute for Theoretical Physics, University of Innsbruck

TOKAMAK FAST ION CONFINEMENT BASED ON 3D FOKKER-PLANCK MODELLING

K. Schöpf; T. Gassner, V. Goloborod’ko, M. Khan, E. Reiter, V. Yavorskij

PROJECT SUMMARY

K. Schöpf and his group model fast-ion behaviour in tokamak plasmas to explain specific transport mechanisms as well as loss measurements of neutron beam injection (NBI) generated ions and of charged fusion products. They analyse results on confinement and loss distributions of energetic particles in JET and predict energetic-particle behaviour in ITER.

1. WORK PERFORMED IN 2013

Task Agreement No. /


ITER Support Projects WP13-IPH-A09-P1-01/BS/ÖAW WP13-IPH-A09-P1-02/PS/ÖAW

Behaviour and consequences of alpha-particle driven modes in ITER

K. Schöpf V. Yavorskij V. Goloborod'ko T. Gassner E. Reiter

WP13-IPH-A09-P2-01/BS/ÖAW

Diagnosing fast-ion behaviour in ITER K. Schöpf V. Yavorskij V. Goloborod'ko T. Gassner E. Reiter


WP13-ITM-IMP5-ACT1-02/ÖAW/PS

Maintenance, testing and benchmarking of Kepler Actors from HCD and fast particle codes and adaptation of new codes

K. Schöpf V. Goloborod'ko E. Reiter

ITER Support Projects

WP13-IPH-A09-P1-01/BS/ÖAW, WP13-IPH-A09-P1-02/PS/ÖAW Behaviour and consequences of alpha-particle driven modes in ITER Evolution of TAE amplitudes in ITER and corresponding fast alpha redistribution

We investigated the evolution of an ensemble of toroidicity-induced Alfvén Eigenmodes (TAEs) in the presence of fusion alphas and studied the emerging particle and energy transport effects [1]. A plasma configuration based on ITER Scenario 2 was assumed for our calculations. For our simulations we used the codes FIDIT and HAGIS coupled via a (de)stabilization switch [2]. A suitable fusion alpha source term for FIDIT was derived from the distributions of background deuterons and tritons. External heating methods like ion cyclotron resonant heating (ICRH) or neutral beam injection of deuterium were not considered in our simplified case. For the simulations performed with HAGIS the equilibrium reconstruction was calculated with HELENA. The radial eigenfunctions of 15 TAEs supported by the equilibrium were computed with CASTOR. As illustrated in figure 1, TAE


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modes with toroidal mode numbers ranging from n=4 to n=15 where found to occur, and two distinct eigenmodes were identified for each toroidal mode number in the range n=12-14.

Figure 1. HAGIS-simulated temporal evolution of the relative amplitudes B /B0 of 15 TAE

modes in the second ITER Scenario, starting with a stationary alpha distribution delivered by FIDIT.

The simulation was designed as a test case for the coupled code system FIDIT/HAGIS, with a TAE (in)stability criterion acting as a switch between the codes. Starting our simulation without any fusion alphas present in the plasma, the fusion source was switched on and the build-up phase of the alpha distribution was simulated. The TAE growth rates achieved in our simulation were comparable to those predicted in [3]. In the beginning of our simulation the fast ion pressure was relatively low and, in addition, the distribution function featured a significant portion with / 0f E which had some damping effect on the TAEs. However as the fast ion pressure reached a high enough value for driving TAEs to significant amplitudes, a corresponding outward redistribution and loss of fusion born alphas was demonstrated in the simulation. In the FIDIT calculation following this redistribution a substantial transport of the precedently relocated alphas was observed [4, 5]. The highly energetic alphas were shifted to the outer plasma edge in the wake of the wave-particle interaction, where stronger collisional transport – further enhanced by the magnetic field ripples – caused the loss of a significant portion of fast ions. Figure 2 shows the fusion alpha density just before the TAE redistribution, as well as the redistributed and fast alpha density some time after the TAE event. The wave-induced redistribution of alphas towards the low field side is evident, as well as the subsequent loss of alphas in the following time period. The alpha fusion source was acting all the time and continuously delivered new particles into the plasma. Nevertheless the particle number is found to decrease at first due to enhanced transport. Only after about 100 ms the total alpha number increases again.


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Figure 2. Fusion alpha density before and at various times after the redistribution caused by TAEs

Inspecting the energy content of the plasma as associated with fusion alphas, their transport towards the low B-field side is equally evident. It is observed that the synergy of wave-induced redistribution and collisional ripple transport leads to the loss of predominantly high-energetic alphas.

Figure 3. Top: time evolution of the total number of fusion alphas after the TAE event.

Bottom: time evolution of the total energy content associated with fusion alphas.

A comparison of the time evolution of the total number of fusion alphas in the plasma and of the total energy content in the plasma carried by the alphas is provided in figure 3. Following the loss by the redistribution caused by the interaction with TAEs, an additional decrease in particle number and energy is observed which results in a total loss of about 20 per cent in particle number and energy content of fusion alphas. An interesting feature in this comparison is the location of the minimum in those numbers. While the energy content increases again

Total fast alpha population varying with time

Corresponding alpha energy content varying with time

TAE induced redistribution + losses

losses mostly TFR induced

minimum alpha population but with many newly born high-energy alphas

minimum alpha energy content due to lost and decelerating alphas

Total fast alpha population varying with time

Corresponding alpha energy content varying with time

TAE induced redistribution + losses

losses mostly TFR induced

minimum alpha population but with many newly born high-energy alphas

minimum alpha energy content due to lost and decelerating alphas


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after about 45 ms, the total particle number is still decreasing until about 100 ms after the redistribution. Thus one can deduce that the alphas with the highest energy are removed first from the plasma due to ripple-enhanced diffusion at the plasma edge. This transport happens more slowly for particles with lower energies. Since the fusion source is active all the time and new alphas with 3.5 MeV are continuously born, the alpha energy content increases earlier, as only redistributed alphas with lower energies are removed from the plasma.

Further, the alpha particle distribution function was calculated for ITER Scenario 2 with off-axis NBI injection of tritons using the Fokker-Planck code FIDIT. The calculated fast ion distribution results in the destabilization of TAE modes in the central region of the ITER plasma column. The evolution of TAE amplitudes and the corresponding fast ion redistribution in the vicinity of the resonant point was calculated with the orbit following code HAGIS.

Effect of the evolution of NBI ion distribution on TAE modes in tokamak reactors

In preparation of the study of DT fusion alpha driven TAEs in the envisaged similarity DT experiments on JET we modelled the temporal behaviour of neutron beam injection (NBI) generated deuteron and triton distributions in JET and investigated their impact on the evolution of Alfvénic modes [6]. These experiments aim at finding the conditions required to destabilize alpha driven TAE modes in ITER. We note that the knowledge of NBI ion distributions is of crucial importance in this context because of the dominant dissipation of the TAE modes on beam ions [7, 8]. The modelling is based on our 3D Fokker-Planck code FIDIT incorporating also the recently developed SNBI module for NBI sources [9]. JET shot #40214 was used as a reference discharge for equilibrium and plasma parameters. Figure 4 displays the modelled distribution functions of beam deuterons and tritons in a plane spanned by the particle velocity components perpendicular and parallel to the magnetic field. Clearly seen are the substantial time variations of (v, v//)-distributions for both D and T beam ions, as well as the non-similarity of deuteron and triton distribution functions. Attention is drawn to the fact that these modelled distribution functions are differentiable in the constants-of-motion space and, correspondingly, are suitable for calculations of the TAE mode damping on the beam ions [1, 2].

Figure 4. Simulated temporal evolution of flux surface averaged distribution functions of NBI

deuterons (left) and NBI tritons (right) at the normalised flux surface radius r/a=0.15 in JET shot #40214


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References

[1] T. Gassner, “Time-evolution of fast ion distributions in MHD-active tokamak plasmas based on HAGIS/Fokker-Planck code coupling”, PhD thesis, University of Innsbruck, Austria (May 2013).

[2] T. Gassner, “Time evolution of fast ion distributions in MHD-active tokamak plasmas by FIDIT/HAGIS coupling”, Third International Workshop on Fast Ion Modelling and Diagnostics (FIMAD-3), Innsbruck, Austria, February 2013.

[3] N.N. Gorelenkov, “Study of thermonuclear Alfven instabilities in next step burning plasma proposals”, Nuclear Fusion 43 (2003), 594.

[4] K. Schoepf, M. Khan, E. Reiter et. al., “Synergetic transport effects by the co-action of MHD modes and collisional ripple transport in ITER”, Third International Workshop on Fast Ion Modelling and Diagnostics, Innsbruck, Austria, February 2013.

[5] M. Khan, K. Schoepf and V. Goloborodko, “Resonance and synergy effects on fast transport in tokamaks”, Monograph, Lambert Academic Publishing (2012),

[6] V. Goloborod’ko, S. Sharapov, K. Schoepf and V. Yavorskij, “Influence of NBI ions distribution function evolution on TAE modes behaviour in tokamak-reactors”, Ukrainian Conference on Plasma Physics and Nuclear Fusion, Kiev, Ukraine, 24-25 September 2013, paper C12.

[7] G.Y. Fu, C.Z.Cheng, R.Budnz et al., “Analysis of alpha particle driven toroidal Alfven eigenmodes in Tokamak Fusion Test Reactor deuterium-tritium experiments”, Physics of Plasmas 3 (1996), 4036.

[8] S.E. Sharapov, D. Borba, A.Fasoli et al., “Stability of alpha particle driven Alfven eigenmodes in high performance JET DT plasmas”, Nuclear Fusion, 39/3 (1999), 373.

[9] V. Goloborod’ko and K. Schoepf, “SNBI and FIDIT modules”, final report on WP13-ITM-IMP5-ACT1-02/ÖAW/PS (2013).

WP13-IPH-A09-P2-01/BS/ÖAW Diagnosing fast-ion behaviour in ITER Capability of gamma diagnostics

We evaluated the capability of gamma ray diagnostics of confined high-energy alphas in ITER. We compared the profiles of -emission rates with the density profiles of partly thermalized alphas, which showed good agreement and confirmed the attractiveness of -diagnostics of energetic alphas in ITER.

Diagnostic tools

New detector possibilities for fast ion diagnostics in ITER were examined. To optimize the detector’s operation a new orbit following code was developed which calculates the fast ion traces inside the detector. This code uses a numerically defined realistic equilibrium and considers resonant magnetic perturbations (RMPs) from error field correction coils (EFCC) and radial electric fields. Based on these calculations a new ITER detector prototype is designed and envisaged to be installed on JET.


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Predictive modelling of fusion alpha effects in ITER

Predictive Fokker-Planck modelling of fusion alphas in ITER was carried out on the basis of the code FIDIT. A prominent sensitivity of alpha particle phase space distributions to the plasma scenarios was demonstrated. A significant dissimilarity of distributions over spatial coordinates (R, Z) and over the longitudinal energy was observed for the second and fourth ITER scenario. In particular, the longitudinal anisotropy of alpha distributions in the fourth scenario results in a rather strong alpha driven current, causing a sizable redistribution of density of the plasma current in the poloidal cross section. The poloidal profiles of alpha density as well as of the fusion power deposition to electrons and ions were calculated. Coulomb collisions result in a substantial (about 25-30 %) loss of partly thermalized fusion alphas (E > 0.32MeV). The energy spectra of lost alphas is shown to be sensitive to the chosen plasma scenario. The current driven by fusion alphas can noticeably affect the profiles of safety factor and Shafranov shift, especially in the case of the reversed shear plasma in the fourth Scenario. Fokker-Planck modelling of convective and diffusive loss of fast ions

Predictive Fokker-Planck modelling of fusion alpha effects in ITER and fast-ion loss distributions at the first wall were carried out, wherein a prominent sensitivity of alpha particle phase space distributions to the ITER plasma scenarios was demonstrated.. Integrated Tokamak Modelling (ITM)

WP13-ITM-IMP5-ACT1-02/ÖAW/PS Maintenance, testing and benchmarking of Kepler Actors from HCD (heating an current drive) and fast particle codes and adaptation of new codes

SNBI and FIDIT modules

The NBI source module SNBI installed on the ITM Gateway has been updated to use NBI geometry data from NBI consistent physical objects (CPOs). This module was tested with ITER and JET NBI layouts. The migration of the Fokker-Planck fast ion distribution function module FIDIT on the ITM Gateway to the 4.10a version of CPO data structure was carried out. Both SNBI and FIDIT KEPLER actors were generated for 4.10a CPOs. A test KEPLER workflow with SNBI and FIDIT actors was created and successfully tested on the new Gateway for the latest version of CPOs. The next step is benchmarking against other NBI modules.


The group intends to continue the research activities described above in Horizon 2020 in the framework of the European joint fusion research programme.

Association EURATOM-ÖAW – Annual Report 2013 – Coordinated Activities on ITER Physics – ITER Support Projects

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I.2. Participation in ITER Support Projects

Institute of Applied Physics, Vienna University of Technology (TU Wien)

PLASMA WALL INTERACTION AND TRANSPORT IN EDGE PLASMAS

F. Aumayr; K. Dobes, E. Gruber, F. Laggner, R. Ritter, A. Veiter, M. Willensdorfer

PROJECT SUMMARY

F. Aumayr et al. investigate pedestal formation after L-H transitions and subsequent evolution in steady H-mode and perform fluctuation measurements across the edge transport barrier at ASDEX Upgrade with a Li diagnostic beam. In addition, the group specializes in processes of plasma wall-interaction, in particular wall erosion, deposition and fuel retention, using a highly sensitive quartz crystal microbalance technique. The group’s major collaboration partners are the ASDEX Upgrade Team at IPP Garching and FZ Jülich.


Task Agreement No./ Tasks

Milestones / Objectives Participants


WP13-ITM-AMNS/ACT1-01/ÖAW

Calculate state selective cross sections for collisions of hydrogen (deuterium) atoms using the AO-CC method; calculate effective charge exchange emission rate coefficients of ArXVI to ArXVIII optical line emission (collaboration with A. Schweinzer, IPP Garching)

F. Aumayr A. Veiter


WP13-IPH-A01-P2-01/ÖAW/BS

Formation and re-erosion dynamics of ITER relevant mixed materials:

Erosion of mixed Be-N layers by D-species and comparison to pure Be-layers, using the Vienna quartz crystal microbalance (QCM) setup (collaboration with C. Linsmeier et al., FZ Jülich)

F. Aumayr K. Dobes E. Gruber R. Ritter


Multi device research to understand the pedestal stability through the study of the edge barrier evolution between ELMs:

Characterization of edge pedestal density for with the upgraded Li-beam diagnostics at ASDEX Upgrade. Predictive modelling of experimental profiles throughout the density build-up after the L-H transition with the code ASTRA to identify the role of diffusive and convective particle transport in the plasma edge (collaboration with E. Wolfrum et al., IPP Garching).

F. Aumayr M. Willensdorfer F. Laggner


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Integrated Tokamak Modelling WP13-ITM-AMNS/ACT1-01/ÖAW Atomic and molecular cross section data

Our AO-CC code was improved to handle up to 1000 atomic states. This required new approaches of the computational implementation of the task. Calculations are currently being performed at the Vienna Scientific Cluster VLC2.

Figure 1. Comparison of AOCC (full circles) and CTMC (square contours) of n-resolved charge

exchange cross sections for Ar18+ + H(1s) collisions. The left plot shows total CX cross sections as well as cross sections for capture into subshells 5 ≤ n ≤ 9 where the agreement is excellent The plot on the right side compares n-resolved cross sections for 10 ≤ n ≤ 15. It can be seen that the results differ at energies below 30 keV/amu.

ITER Support Projects WP13-IPH-A01-P2-01/ÖAW/BS Formation and re-erosion dynamics of ITER relevant mixed materials

We studied total sputtering yields of Be surfaces under deuterium and nitrogen impact, using a highly sensitive quartz crystal microbalance (QCM) technique. With our experimental approach we are able to not only investigate steady state erosion, but also transient phenomena for the interaction of ions with surfaces in situ and in real-time.

The Be samples were provided by C. Lungu (National Institute for Laser, Plasma and Radiation Physics, Association EURATOM-MEdC). 500 nm thick Be layers were deposited onto one side of the quartz crystal by a thermionic vacuum arc deposition technique. They were transferred to Garching in air and therefore show a native oxide layer.

Sputtering experiments were performed at IPP Garching. The experimental setup was first prepared and tested at TU Vienna and then transferred to Garching. The quartz crystal microbalance was mounted in an ultra high vacuum (UHV) chamber at a base pressure of about 10-10 mbar. All investigations were performed at an elevated temperature of 192°C, where the quartz crystal is least sensitive to temperature fluctuations. The projectiles used were produced by an electron impact ion source equipped with a Wien filter for ion mass separation. Mass selected ion beams of N2

+ and D2+ were used to study the dynamics of the

transient behaviour of Be sputtering. Areal atomic concentrations of the involved species were investigated after the sputtering experiment by nuclear reaction analysis.

The evolution of the total mass change per incident projectile of a Be sample as a function of the applied ion fluence was determined for both, N2

+ and D2+ impact. For this purpose an ion


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beam with an energy of 5 keV was used. It was found that for both target projectile combinations, the observed mass change depends strongly on the applied ion fluence (at constant flux).

When bombarding a virgin Be sample with N, the interaction is at first dominated by a high net erosion which can be attributed to the removal of loosely bound surface adsorbates. For applied ion fluences of 4·1015≤ ≤1.2·1017 N/cm2, this initially very fast mass loss is followed by a regime of net mass increase due to dominant N implantation. It is superseded by dominant erosion for fluences of ≥1.2·1017 N/cm2. At ~ 8.3·1017 N/cm2 steady state surface conditions are established and the erosion of the resulting N containing surface layer is no longer changing with ion fluence. Subsequent post mortem nuclear reaction analysis (NRA) revealed a retained N areal density of ~ 1.4·1017 N/cm2.

In addition surface oxidation of the Be sample was investigated for various N saturation levels. Oxide growth due to the ambient oxygen pressure in the UHV chamber was monitored with the QCM. It was found that for N containing Be surfaces the oxidation rate decreases and falls below any detectable limit when N saturation is reached.

Similar investigations were performed with D2+ projectiles. The D saturation behaviour of an

N containing surface was compared to the saturation behaviour of a virgin Be sample. In both cases, for low D fluences again a regime of net mass uptake due to dominant D implantation was found. However for the N containing Be surface, this mass increase was more pronounced than for the virgin Be surface. After a fluence of some 1017 D/cm2, the D retention starts to saturate and additional D is implanted less efficiently. Net erosion conditions are reached after a total ion fluence of 1.2·1018 D/cm2 in the N containing Be surface and only after approximately twice this fluence for the pure Be sample. The retained amount of D is higher for the N containing Be surface with an areal density as determined by NRA of approximately 6.2·1018 D/cm2 compared to 4·1018 D/cm2 for the pure Be surface, respectively.

In addition, sputtering of nitrogen saturated W surfaces under Ar and Ne impact was studied. Particular emphasis was put on testing any charge state dependency of the sputtering yield, as various non conducting materials have shown enhanced erosion rates under highly charged ion bombardment (potential sputtering) in the past. N saturated W surfaces were prepared by irradiating a W sample with a cumulated fluence of ~ 3.5·1017 N/cm2. N bombardment was stopped after an integrated surface recession of approximately 70 Å, which clearly exceeds the mean ion range in the surface as estimated by TRIDYN. The observed sputtering yields were found to be independent of the charge state of the projectiles. Total sputtering yields of N saturated W surfaces were found to be very similar to pure W, with N erosion apparently balancing the reduction of the partial W sputtering yield.

This work was presented at the 14th International Conference on Plasma-Facing Materials and Components for Fusion Applications, Jülich, Germany, 13-17 May 2013 and the 29th International Conference on Ion Surface Interactions, Yaroslavl, Russia, 22-26 August 2013 (see also list of publications).

WP13-IPH-A08-P2-01/ÖAW/BS Multi device research to understand the pedestal stability through the study of the edge barrier evolution between edge localized modes (ELMs)

The recent upgrade of the Li-beam diagnostics at ASDEX Upgrade allows the routine delivery of edge electron density profiles with a temporal resolution of 5 µs and thus an accurate characterization of the edge pedestal density. Due to enhanced photon statistics, measurements of density recovery after the ELM crash and ELM filaments are possible with improved time resolution.


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The role of convective and diffusive particle transport in the edge during the density build-up after the L–H transition was investigated on the basis of predictive-iterative modelling, using the 1.5D radial transport code ASTRA for the time-dependent modelling. The convective velocity, diffusion coefficient and particle source profiles were parameterized to reach the best match of modelling to the density measurements. Extensive parameter scans show that the density build-up can be reproduced by assuming only a diffusive edge transport barrier (ETB) with reduced diffusion coefficient at the edge with respect to the core values. The replacement of the diffusive ETB by a strong inwards directed convective velocity at the edge (edge pinch) did not lead to a successful data description, which indicates that a diffusive ETB is required to explain the density build-up. However, the addition of an edge pinch to the diffusive ETB slightly enhances the agreement between modelling and experiment. The best agreement was found with an edge diffusion coefficient of 0.031 m2 s−1 and an edge convective velocity of −0.5 m s−1. Because of the large uncertainties in the source, it is not possible to determine the exact value for the additional edge pinch. An upper limit for a possible edge convective velocity of −5 m s−1 was estimated. These findings were confirmed by analysing H-mode phases of a collisionality scan, in which the normalized collisionality varied from 3.5 to 5.5 at the pedestal top.

Results of this work were published in M. Willensdorfer, E. Fable, E. Wolfrum, L. Aho-Mantila, F. Aumayr, R. Fischer, F. Reimold, F. Ryter and the ASDEX Upgrade Team, “Particle transport analysis of the density build-up after the L-H transition in ASDEX Upgrade", Nuclear Fusion 53/9 (2013), 0930201- 09302011.


The group intends to continue its research activities in Horizon 2020 in the framework of the European joint fusion research programme.

3. PUBLICATIONS

Articles in journals

Garcia-Munoz, M., S. Äkäslompolo, E. Viezzer, M. Willensdorfer, E. Wolfrum et al., “Fast-ion redistribution and loss due to edge perturbations in the ASDEX Upgrade, DIII-D and KSTAR tokamaks”, Nuclear Fusion 53/12 (2013), 1230081 - 1230089.

Rathgeber, S., L. Barrera Orte, T. Eich, R. Fischer, B. Nold, W. Suttrop, M. Willensdorfer, E. Wolfrum and the ASDEX Upgrade Team, “Estimation of edge electron temperature profiles via forward modelling of the electron cyclotron radiation transport at ASDEX Upgrade” , Plasma Physics and Controlled Fusion 55 (2013), 0250041 - 02500415.

Ryter F., S. Rathgeber, L. Barrera Orte, M. Bernert, G. Conway, R. Fischer, T. Happel, B. Kurzan, R. McDermott, A. Scarabosio, W. Suttrop, E. Viezzer, M. Willensdorfer, E. Wolfrum and the ASDEX Upgrade Team, "Survey of the H-mode power threshold and transition physics studies in ASDEX Upgrade"; Nuclear Fusion 53/11 (2013), 1130031 - 11300312.

Stroth, U., M. Willensdorfer, E. Wolfrum et al., "Overview of ASDEX Upgrade results", Nuclear Fusion 53/10 (2013), 1040031 – 1040039.

Viezzer, T. Pütterich, G. Conway, R. Dux, T. Happel, J. Fuchs, R. McDermott, F. Ryter, B. Sieglin, W. Suttrop, M. Willensdorfer, E. Wolfrum and the ASDEX Upgrade Team, "High-accuracy characterization of the edge radial electric field at ASDEX Upgrade", Nuclear Fusion 53/5 (2013), 0530051 - 05300513.


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Willensdorfer, M., E. Fable, E. Wolfrum, L. Aho-Mantila, F. Aumayr, R. Fischer, F. Reimold, F. Ryter and the ASDEX Upgrade Team, “Particle transport analysis of the density build-up after the L-H transition in ASDEX Upgrade", Nuclear Fusion 53/9 (2013), 0930201- 09302011.

Willensdorfer, M., G. Birkenmeier, R. Fischer, F. Laggner, E. Wolfrum, G. Veres, F. Aumayr, D. Carralero, L. Guimaräis, B. Kurzan and the ASDEX Upgrade Team, "Characterization of the Li-BES at ASDEX Upgrade", Plasma Physics and Controlled Fusion 56 (2014), 0250081 - 02500810.

Conference contributions

Birkenmeier, G., T. Kobayashi, F. Laggner, M. Willensdorfer, E. Wolfrum, D. Carralero, P. Manz, H. Müller, R. Fischer, U. Stroth and the ASDEX Upgrade Team, "Investigations of the magnetic field dependence of blob velocity and size with Li-BES at ASDEX Upgrade"; in: Proceedings of the 40th EPS Conference on Plasma Physics, Europhys. Conf. Abstracts, European Physical Society (EPS), 2013, ISBN: 2-914771-84-3, 1 - 4.

Dobes, K., M. Köppen, M. Oberkofler, C. P. Lungu and C. Porosnicu, Ch. Linsmeier and F. Aumayr, “Erosion of beryllium under nitrogen impact – investigations of transient and steady state conditions”, 14th International Conference on Plasma-Facing Materials and Components for Fusion Applications, Jülich, Germany, 13-17 May 2013.

Dobes, K., M. Köppen, M. Oberkofler, C.P. Lungu, C. Porosnicu, T. Höschen, Ch. Linsmeier and F. Aumayr, “Studies on the interaction of nitrogen and deuterium with beryllium surfaces; 29th International Conference on Ion Surface Interactions, Yaroslavl, Russia, 22-26 August 2013. Poster Presentation

Laggner, F., G. Birkenmeier, M. Willensdorfer, E. Wolfrum, F. Aumayr and the ASDEX Upgrade Team, "Determination of blob-filament sizes using lithium beam emission spectroscopy at ASDEX Upgrade"; Poster: Sokendai Asian Winter School 2013, Toki/Japan, 11 December 2013.

Laggner, F., E. Wolfrum, M. Willensdorfer, G. Birkenmeier, T. Kobayashi, F. Aumayr and the ASDEX Upgrade Team, „Reconstruction of electron density perturbations using lithium beam emission spectroscopy”, Poster: Deutsche Physikalische Gesellschaft (DPG) Frühjahrstagung 2013, Jena, Germany, 27 February 2013.


29

Institute of Ion Physics and Applied Physics, University of Innsbruck

MOLECULAR DYNAMICS SIMULATIONS OF MIXED MATERIALS

M. Probst; S. Huber, A. Kaiser, A. Mauracher

PROJECT SUMMARY M. Probst et al. calculate energy profiles and atomistic reaction details by means of quantum chemical methods. Quantum chemical calculations of particle-Be interactions are used to obtain information on ion / atom bonding at Be surfaces.





WP13-IPH-A01-P2-01/ÖAW

Collision processes and electronic interaction between D, N and other atoms and Be, Be/W and W surfaces: model Be and Be/W chemical erosion under

relevant plasma conditions (erosion from D/N/O) Model the collision processes leading to the

formation of molecular species like BeH on the surfaces and of the properties of these species

M. Probst S. Huber A. Kaiser

WP13-IPH-A01-P3-01/ÖAW

Modelling and interpretation of the mechanisms of Be-H species formation: Evaluate information on Be-substituent materials

(proxies) like Al from electronic structure, simulation and other sources

Augment the available information of electron-impact cross sections for Be-containing species (molecules, ions, excited states)

M. Probst S. Huber A. Kaiser

ITER Support Projects WP13-IPH-A01-P2-01/ÖAW Collision processes and electronic interaction between D, N and other atoms and Be, Be/W and W surfaces

We studied collision processes and electronic interaction between deuterium, neutrogen and other atoms and beryllium, Be/tungsten and tungsten surfaces as well as the collision dynamics and reaction mechanisms for the formation of BeH and other species and investigated the properties of these molecules.

A variety of molecular dynamics simulations were carried out in collaboration with J. Urban and I. Sukuba at the Comenius university Bratislava on the sputtering of D on Be surfaces and Be/W alloy surfaces. The collision dynamics was investigated in terms of sputtering yields, surface saturation, depth profile and many other features. The investigated energy range (D kinetic energy) was between 0 to 50 eV. Concerning nitrogen, the interaction of Be with N was studied quantum mechanically. Key results were the good agreement of the sputtering yields as a function of the energy of the impinging particle with former completely independent and methodically different simulations carried out with empirical formulas and the following observations:


30

‐ Within the investigated energy range D penetrates within a shallow range of a few Å mostly into W and its alloys.

‐ Only Be was sputtered from the allows, not W.

‐ A stepwise formation is favoured and the impinging H is normally not the one forming the hydride at the end.

‐ Several new candidate molecules containing Be, H and N were investigated by means of quantum chemical calculation. Some of them are surprisingly stable and will be present in the plasma.

WP13-IPH-A01-P3-01/ÖAW Modelling and interpretation of the mechanisms of Be-H species formation

Modelling and interpretation of the mechanisms of Be-H species formation was performed and information on Be-substituent materials (proxies) such as aluminium was gathered from electronic structure, simulation and other sources. The available information of electron-impact cross sections for Be-containing species (molecules, ions, excited states) was augmented.

Molecular dynamics simulations specified were used to elucidate the mechanisms of BeH2 formation. This work was also carried out in collaboration with J. Urban and I. Sukuba (Comenius University Bratislava): The following observations were made:

‐ No other species except BeH and BeH2 were found.

‐ The bonding of D in the Be bulk was studied with respect to coordination numbers, volume change and molecule formation.

‐ The mechanisms of Be-H and H-Be-H formation were investigated in detail for the first. ime.A stepwise formation is favoured and the impinging H is normally not the one forming the hydride at the end.

‐ Extensive property calculations on Be-hydrides of the BexHx and BexH2x series were performed which are described in T. Maihom et al.

‐ Information was gathered on the use of Be-proxies. Aluminium is the best overall choice next to magnesium and scandium.

Figure 1. Electron impact cross sections of several Be-hydrides


31



3. PUBLICATIONS

Maihom, T., M. Probst et al., “Electron impact ionization cross sections of beryllium and beryllium hydrides”, European Physics Journal D 67:2 (2013). Huber, S., M. Probst et. al, “Scattering of hydrogen and helium on graphite (0001) surfaces at beam energies of 1 to 4 eV using a split-step Fourier method”, Theoretical Chemistry Accounts 132 (2013). Huber, S. and M. Probst, “Modeling the intrusion of molecules into graphite: origin and shape of the barriers”, International Journey of Mass Spectrometry (2013), http://dx.doi.org/10.1016/j.ijms.2013.12.015.


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INVESTIGATION OF PLASMA WALL INTERACTION PROCESSES: CHEMICAL EROSION, DEPOSITION AND TRANSPORT

P. Scheier; P. Bartl, M. Daxner, S. Denifl, M. Harnisch, A. Keim, A. Mauracher, J. Postler, B. Puschnigg, S. Ralser, K. Tanzer, S. Zöttl

PROJECT SUMMARY

Modelling and computational science for ITER strongly depend on the determination of ero-sion and deposition interactions of the involved plasma constituents with the materials used in plasma-facing components such as beryllium and tungsten. Material studies are now shifting to impurity seeding with gases such as argon or nitrogen for divertor cooling. Therefore, pro-found knowledge on interactions between these possible projectiles and the tiles of the inner wall is essential. P. Scheier et al. collect data on electron scattering and chemical erosion.





WP13-ITM-AMNS-ACT1

Study of inelastic electron scattering processes (dissociative excitation, dissociative electron ionization, and dissociative electron attach-ment) with fusion relevant molecules such as hydrocarbon molecules as well as the epoxy resin ethylidene bis-4.1-phenylene dicyanate used as an insulator of the superconductive magnetic coils in fusion devices. This material is known to be less susceptible to radiation damage than conventional glue materials. Some of the studies were carried out in collab-oration with Š. Matejčik, Comenius Universi-ty, Bratislava, utilizing a crossed electron mo-lecular beam experiment.

S. Denifl M. Harnisch A. Keim S. Zöttl et al.

ITER Support Projects WP13-IPH-A01-P2-01-ÖAW/BS

Investigate the chemical erosion of beryllium by deuterium ions colliding with pure Be and Be/W mixture surface samples (in collabora-tion with Z. Herman, Prague and C.P. Lungu, Bucharest). Similar experiments with nitrogen ions allow to identify the reaction products from the interaction of such ions with the same surfaces.

M. Harnisch A. Keim S. Denifl P. Scheier S. Zöttl et al.

Integrated Tokamak Modelling WP13-ITM-AMNS-ACT1 Study of ineleastic electron scattering processes

Electron ionization and electron attachment measurements with ethylidene bis-4,1-phenylene dicyanate were carried out by S. Denifl during a visit at the Department of Experimental Physics of the Comenius University, Bratislava (S. Matejcik). The apparatus used for these measurements was a crossed neutral/electron beams instrument with a quadrupole mass spec-


33

trometer. Two ion sources were available: (i) a trochoidal electron monochromator (electron currents of ~250 nA with an electron energy resolution during the measurements of about 200 meV) and (ii) a standard ion source without monochromatizing element (electron currents ~0.5 mA with an energy resolution of about 1 eV). The former ion source was used to study negative ion formation and the latter was used to study electron ionization.

For positive ions several mass spectra were recorded at the electron energy of about ~ 70 eV. Mass scans were measured at different temperatures of the sample container. Mass peaks in-dependent of temperature can be assigned to the background ion yield arising from ionization of background gas in the main chamber and gas inlet. Figures 1 and 2 show the resulting mass spectra between m/z 50 and m/z 170, and between m/z 165 and m/z 330, respectively. Below m/z 50 only mass peaks arising from the background were obtained. Figures 1 and 2 show the mass spectra obtained for 55°C, 74°C and 100°C, respectively. Several mass peaks like m/z 69, 127, etc. are not affected by the increase of temperature, i.e. these ion signals can be as-cribed to the background. Mass peaks ascribed to the ionization of ethylidene bis-4,1-phenylene dicyanate are m/z 55 (C3H3O

+), 61 (C5H+), 73 (C6H

+), 83 (C5H7O+) and 98

(C6CN+), as shown in figure 1. These peaks are formed in complex dissociation reactions in-cluding multiple bond breaks as well as molecular rearrangement in some cases. In the mass range between m/z 165 and m/z 330 (see figure 2), no temperature dependent mass peaks were observed, i.e. no heavy fragment ions and also no parent ion were observable within the detection limit of the apparatus.

40 60 80 100 120 140 160 180

0.0

0.5

1.0

1.5

****

Ion

yiel

d (a

rb. u

nits

)

m/z (Thomson)

55°C 74°C 100°C

*

Figure 1. Electron ionization mass spectrum of ethylidene bis-4,1-phenylene dicyanate between m/z 50

and 170 at three different sample temperatures, 55°C, 74°C and 100°C. Mass peaks arising from the ionization of the molecule are marked with stars.


34

160 180 200 220 240 260 280 300 320 340

0.000

0.005

0.010

0.015

55°C 74°C 100°C

Ion

yiel

d (a

rb. u

nits

)

m/z (Thomson)

Figure 2. Electron ionization mass spectrum of ethylidene bis-4.1-phenylene dicyanate between m/z 165 and 330 at three different sample temperatures: 55°C, 74°C and 100°C. All peaks are inde-pendent of the sample temperature, i.e. no heavy fragment ions and no parent ion can be ob-served upon ionization of ethylidene bis-4.1-phenylene dicyanate.

In the course of the experiments concerning anion formation the apparatus was optimized by first using SF6

–/SF6 [E. Illenberger and J. Momigny, Gaseous Molecular Ions. An Introduction to Elementary Processes Induced by Ionization, Steinkopff, Darmstadt, Springer, New York (1992)]. The latter measurement shows a zero eV peak formed in an s-wave attachment reaction. This peak can be used for calibration of the energy scale as well as for determination of the elec-tron beam resolution. Within the detection limit of the apparatus only one negative ion at mass m/z 42 is formed upon electron attachment to ethylidene bis-4.1-phenylene dicyanate. The ion signal can be ascribed to the cyanate anion NCO. NCO has a very high electron affin-ity and corresponds to a pseudo halogen. The ion yield of NCO– is shown in figure 3 meas-ured in an electron energy range between about 0 and 9 eV. NCO– is formed in a single peak at about 157 meV, i.e. the resonance can be most likely ascribed to a shape resonance. The high electron affinity of NCO (3.6 eV [NIST Chemistry Web-Book, http://webbook.nist.gov]) seems to reduce the reaction threshold of the dissociative electron attachment (DEA) reaction to very low energies.

In summary, ethylidene bis-4.1-phenylene dicyanate seems to have rather low electron scav-enging properties. Since chemical transformation of material can also be ascribed to the action of low energy electrons, the present results support the observation of the high resistance to-wards radiative degradation in bulk material [R. Prokopec, K. Humer, R.K. Maix, H. Fillunger and H.W. Weber, Fusion Engineering and Design 85 (2010), 227].


35

0 2 4 6 8 10

0

5

10

15

20

Ion

yie

ld (

arb

. un

its)

Electron energy (eV)

NCO-

SF6

- (/25000)

Figure 3. Ion yield of NCO– formed upon DEA to ethylidene bis-4.1-phenylene dicyanate (black line). For comparison the SF6

–/SF6 used for calibration of the electron energy scale is also shown.

ITER Support Projects WP13-IPH-A01-P2-01-ÖAW/BS Formation and dissociation processes of Be-W thin film materials The group investigated formation and dissociation processes of Be-W thin film materials of different composition. Results were compiled in A. Keim, M. Harnisch, P. Scheier and Z. Herman, “Collisions of low-energy ions Ar+, N2+ with room-temperature and heated surfaces of tungsten, beryllium, and a mixed beryllium-tungsten thin film”, International Journal of Mass Spectrometry 354-355 (2013), 78-86.

The experiments were carried out on the ion-surface apparatus BESTOF at the University of Innsbruck. A detailed description can be found in C. Mair, T. Fiegele, F. Biasioli, R. Wörgötter, V. Grill, M. Lezius and T.D. Märk, Plasma Source Science and Technology 8 (1999), 191. Ion-surface interactions of Ar+, N2

+, and D2+ ions (incident energies 20-100 eV)

with thin mixed beryllium-tungsten films of different composition (BeW(90:10), BeW(50:50), BeWO (60:22:11)) were investigated at different sample temperatures (room temperature (RT), 150°C, 300°C). The results were compared under three different aspects:

1. Comparison of different BeW surfaces (BeW(50:50), BeW(90:10), BeWO(60:22:11)) in collisions with Ar+ ions

2. Comparison of different projectiles Ar+ vs. N2+ (measurements with BeW(50:50))

3. Comparison of seeding gas projectiles to D2+ projectiles (measurements with

BeW(50:50)) 1.1. Comparison of different BeW surfaces - BeW (50:50), BeW (90:10), BeWO (60:22:11) -

in collisions with Ar+ ions

Collisions of Ar+ with different BeW thin films on a silicon wafer, namely BeW(50:50) (50%Be, 50% W), BeW(90:10) (90% Be, 10% W) and BeWO (60:22:11) (60% Be, 22% W, 10.5% O, 7.5% C), were investigated at different temperatures of the surface sample (room temperature (RT), 150°C, 300°C) and different incident energies ranging from 20 to 100 eV. Figure 4 shows the interaction at an incident energy of 70 eV and at RT. While the total ion


36

yields of BeW (50:50) and BeW (90:10) seem to be comparable, the ion yield of BeWO (60:22:11) is smaller by a factor of 9.

The most substantial difference between the samples BeW (50:50) and BeW (90:10) can be found in the sputtering of surface material Be+ and its compounds BeH+ and BeOH+, which show clear peaks for all temperatures in the BeW (50:50) measurements and are almost negli-gible in the BeW (90:10) measurements. All ions of the basic material of the sample show an increase with increasing incident energy of the Ar+ projectile, more dramatic at higher inci-dent energies and elevated temperatures of the sample. For BeWO (60:22:11) the ratios of the different sputter products are similar to those of BeW (50:50).

Figure 5. Mass spectra of product ions from collisions of D2+ of incident energies of 30 eV

and 70 eV with the BeW (50:50) surface kept at a temperature of 450°C.

Figure 4. Mass spectra of product ions from collisions of Ar+ (incident energy 70 eV) with surfaces of different Be-W thin mixed films kept at RT: BeW (90:10); BeW (50:50); BeWO (60:22:11).


37

Unfortunately, the yield of the basic material of the sample, Be+, does not correspond to the content of the Be in the film material, thus the original idea of using the ion yields of Be+ as a quantitative measure of the Be content in the films does not seem to be possible.

The other component of the surface film, tungsten, unfortunately does not produce any meas-urable yields of sputtered ions at the incident energies of this experiment (up to 100 eV). 1.2. Comparison of different projectiles Ar+ vs. N2

+

Collisions of N2+ with BeW (50:50) at different sample temperatures (RT, 150°C, 300°C) and

different incident energies ranging from 20 to 100 eV were compared to measurements using Ar+ as a projectile. The spectra show similar product ion spectra for both incident ions (see figure 5 below).

The most notable differences are shown in the more pronounced hydrocarbon background for the Ar+-projectile and higher alkali metal peaks in the N2

+ measurements. However, these differences can be explained by the measuring order. They are less pronounced at higher sur-face temperatures, showing very similar yields in the spectra for both incident ions at 300°C. Surface induced dissociation of molecular N2

+ to N+ cannot be detected. 1.3. Comparison of seeding gas projectiles to D2

+ projectiles

Collisions of D2+ with BeW (50:50) at different temperatures of the sample (RT, 150°C,

300°C, 400°C, 450°C) and different incident energies ranging from 20 to 100 eV were com-pared to measurements using Ar+ as a projectile (see figure 5).

The main difference can be seen in the much lower ion yield of the product ions in the D2+-

collisions in comparison with the Ar+-collisions. Furthermore all the spectra show a strong surface-induced dissociation of the projectile D2

+ to D+. Up to a temperature of 300°C Be+ is hardly detectable in the spectra and the ion yields of the different hydrocarbons are much lower than those in the spectra of Ar+-collisions. However, when increasing the temperature even further (400°C, 450°C) Be+ starts to increase and ion-chemical reactions of the projectile with the surface material producing BeD+ can be detected. This indicates that the reaction already takes place at lower surface temperatures but cannot be detected due to the low sput-tering efficiency and the resulting low ion yields of the compounds.

The ratio of the sputtering products Be+/BeD+ depends on the incident energy of the projectile ion. Both Be+ and BeD+ increase with rising incident energy of the projectile, but the increase of Be+ is much stronger. While at lower incident energies (e.g. 30 eV) the ratio (Be+/BeD+) is about 1.6, at higher incident energies (70eV) it increases to a value of about 40.

Figure 5. Mass spectra of product ions from collisions of N2+ and Ar+ of incident ener-gy 70 eV with the BeW(50:50) surface kept at RT


38


The group intends to continue its research activities in Horizon 2020 in the framework of the European joint fusion research programme, in particular specializing on educating young spe-cialists in the field of plasma-wall interaction.

3. PUBLICATIONS

Danko, M., J. Orszagh, M. Durian, J. Kocisek, M. Daxner, S. Zöttl, J.B. Maljkovic, J. Fedor, P. Scheier, S. Denifl and S. Matejcik, “Electron impact excitation of methane: determination of appearance energies for dissociation products.”, Journal Of Physics B: Atomic Molecular And Optical Physics 46/4, (2013) 045203. Harnisch, M., A. Keim, P. Scheier and Z. Herman, “Collisions of low-energy Ar+, N2

+, and D2

+ ions with room-temperature and heated surfaces of mixed beryllium-tungsten thin films of different composition”, International Journal of Mass Spectrometry (2014), in press. Harnisch, M., A. Keim, P. Scheier and Z. Herman, ”Formation of HCN+ in heterogeneous reactions of N2+ and N+ with surface hydrocarbons”, The Journal of Physical Chemistry A, 117 (39) (2013), 9653. Keim, A., M. Harnisch, P. Scheier and Z. Herman, “Collisions of low-energy ions Ar+, N2+ with room-temperature and heated surfaces of tungsten, beryllium, and a mixed beryllium-tungsten thin films”, International Journal of Mass Spectrometry 354-355 (2013), 78-86.


39

Institute of Theoretical and Computational Physics, Graz University of Technology

TRANSPORT AND HEATING IN TOROIDAL DEVICES

W. Kernbichler; M.F. Heyn, G. Kapper, S.V. Kasilov, P. Leitner, A. Martitsch, V.V. Nemov, I. Ivanov

PROJECT SUMMARY

W. Kernbichler et al. investigate the numerical evaluation of toroidal viscosity and evolution of equilibrium plasma parameters under the action of external resonant magnetic perturbation (RMP) fields. In addition, they contribute to stellarator optimization in the framework of a collaboration of major stellarator laboratories.


Task Agreement No. / Tasks



WP13-IPH-A04-P1-01/ÖAW/BS WP13-IPH-A04-P1-02/ÖAW/PS

Achieve predictive capabilities of the plasma rotation profile: Numerical evaluation of neoclassical

toroidal viscosity due to non-resonant magnetic perturbations using the drift kinetic equation solver NEO-2

Implementation of realistic perturbation fields into NEO-2

computation of the additional contribution to neoclassical toroidal viscosity (NTV) from the toroidal torque acting on the plasma driven by external magnetic field perturbations will be implemented into NEO-2

W. Kernbichler S. Kasilov P. Leitner

WP13-IPH-A06-P2-01/ ÖAW/BS

Active control of ELMs and the associated divertor heat loads: Self-consistent modelling of the

shielding of resonant magnetic field perturbations by the plasma and the evolution of plasma parameters, using the code KILCA

W. Kernbichler M. Heyn S. Kasilov P. Leitner

WP13-IPH-A04-P1-01/ÖAW/BS Objectives

The general objective of the work performed at TU Graz is the development of a numerical model for the computation of the toroidal torque acting on the plasma driven by external magnetic field perturbations (neoclassical toroidal viscosity - NTV). This model is based on the drift kinetic equation solver NEO-2, which does not use any model assumptions on device geometry and Coulomb collision model. The only assumption is that the perturbation field is small enough to exclude the non-linear regimes, which is a condition fulfilled in most cases of practical interest. A milestone pursued by this work was the development of a version of NEO-2 using a 2-D adaptive finite difference discretization in velocity space. This is required for modelling regimes with very low collisionality where resonances in velocity space are


40

important (superbanan -‐plateau and drift - orbit resonance). Realistic perturbation fields will be implemented in NEO-2 using the interface developed earlier for the purpose of ELM-mitigation studies with resonant magnetic perturbations (RMPs), using experimental data on rotation and on perturbation magnetic fields.

Achievements

In 2013, the existing version of NEO-2 was significantly improved and benchmarked with analytical and numerical models. NEO-2 stays in good agreement with asymptotical models of Shaing et al. in regimes where the banana kinetic equation (bounce averaged equation), which is the starting point for the theory of Shaing et al and Sun et al., can be used. In addition, the regimes, which cannot be described by the banana kinetic equation, such as ripple-plateau (Boozer 1989), resonant diffusion (Yushmanov 1982) and regimes similar to stochastic diffusion (Goldstone et al., 1983) are well reproduced. In cases where resonant diffusion is important, passing particles play a significant role (they do not play any role in regimes described by the banana kinetic equation) and the correct account of the toroidal torque acting on the plasma driven by external magnetic field perturbations is of crucial importance. This is taken into account automatically in the set of quasilinear equations solved within NEO-2. In addition, benchmarking with the drift kinetic equation solver (DKES) was done in cooperation with MPI Greifswald (H. Maassberg). For the case of the Lorentz collision model used within DKES both codes stay in good agreement in particular in regimes where the banana kinetic equation is not valid. (The Lorentz collision model is a simplified model which provides a good representation of most of the long-mean-free-path regimes but needs a momentum correction technique for regimes with medium and high collisionality where momentum conservation and diffusion over energy is important. NEO-2 contains the Lorentz model as a particular option but generally uses a full collision operator.)

The benchmarking described above shows that the present version of NEO-2 is already sufficient for modelling experimentally relevant regimes because it provides a sufficient resolution of super-banana-plateau and resonant diffusion regimes and therefore the application to the analysis of experiments on real devices is fully possible. The version with improved resolution of the phase space in case of resonant regimes will be further developed, but as a secondary goal. The main objective of this work is the analysis of experimental data on plasma rotation in ASDEX Upgrade.

For this purpose, data on magnetic perturbations in ASDEX Upgrade were provided by IPP Garching in Boozer coordinates computed from VMEC equilibria (E. Strumberger). This data form can be used in NEO-2 directly, avoiding the use of an interface, which has been developed earlier for the analysis of RMP experiments. Preliminary results were reported at the Joint 19th International Single Helicity Workshop (ISHW) and 16th RFP workshop (S.V. Kasilov, W. Kernbichler, A.F. Martitsch, “Evaluation of non-ambipolar particle fluxes driven by non-resonant magnetic perturbations in a tokamak”, 16 - 20 September 2013, Padova, Italy) and at the “Theorieseminar” of Max Planck Institut für Plasmaphysik at Damerow, Germany, 18-23. November 2013.

Conclusion and general perspective

The work described above has resulted in a code version which is already covering most of the experimentally relevant cases.

The quasi-linear version of the code NEO-2 which describes the torque from the external non- resonant magnetic field perturbations was successfully benchmarked against analytical and numerical models which cover particular transport regimes. Unlike these models, NEO-2 covers all those regimes except non-linear regimes. In 2014 we plan to analyze toroidal rotation driven by external magnetic field perturbation (due to toroidal field ripple and ELM


41

mitigation coils) in ASDEX Upgrade. The intrinsic toroidal rotation velocity will be computed for experimentally relevant plasma parameter profiles. WP13-IPH-A06-P2-01/ÖAW/BS Objectives

One of the most promising methods for controlling edge localized modes (ELMs) in a tokamak is the creation of an ergodic field region near the separatrix with the help of RMPs from special external or internal coils. These perturbations are strongly influenced by plasma response currents, which typically shield them and prevent them from penetrating deep into the core plasma. Our activity focuses on the proper description of the penetration of RMPs into the tokamak plasma and the study of their effect on plasma transport.

The penetration of RMPs into the plasma is very sensitive to plasma parameter profiles, especially to the toroidal and poloidal rotation velocities. On the other hand, the torque introduced by RMPs can modify these velocities significantly. Therefore the computation of the electromagnetic field in the plasma must be performed for the background plasma parameter profiles evolving under the action of RMPs. For such self-consistent computations, the code KiLCA (Kinetic Linear Cylindrical Approximation) [I.B. Ivanov, M. Heyn, S.V. Kasilov, W. Kernbichler, “Kinetic linear model of the interaction of helical magnetic perturbations with cylindrical plasmas”, Physics of Plasmas 18 (2011)] for computation of the electromagnetic field based on a 1-D straight cylinder model was combined with a 1-D transport code into a QL-BALANCE code for computation of the evolution of plasma parameter profiles. The effect of RMPs on rotation velocity, density and temperature profiles is described in QL-BALANCE by a set of quasi-linear transport equations.

Achievements

First experiments on ELM mitigation with the help of ITER-like coils on ASDEX Upgrade have been analyzed, using linear and quasilinear kinetic models to describe the interaction of RMPs with the plasma. A detailed gyrokinetic derivation of RMP-driven transport coefficients was provided. The role of fluid resonances was studied, in particular the role of the drift resonance associated with zero E × B drift, V_E = 0. Like the electron fluid resonance associated with the zero of the total perpendicular electron fluid velocity, the V_E = 0 resonance may lead to enhanced transport due to the reduction of RMP shielding in the pedestal region where the RMP field can even be amplified by this resonance.

To test the model, the same DIII-D shot which had already been analyzed in 2008 was evaluated with original parameters and with the upgraded code with the corrected toroidal rotation velocity. Results were then compared to ASDEX Upgrade discharges. The comparison of several ASDEX Upgrade shots with DIII-D Shot 126006, which has a significantly smaller plasma collisionality, shows a rather different behaviour of the RMPs in the plasma. In contrast to the DIII-D shot where the strong shielding of most of the perturbation spectral modes prevents the formation of an ergodic layer, the shielding of the perturbations in ASDEX Upgrade is rather weak - by a factor ten or even less. Such weak shielding does not prevent the formation of an ergodic layer but rather reduces its size to approximately the size of the pedestal region. The optimum performance in ASDEX Upgrade is achieved when this layer simply covers the whole pedestal, whereas a wider layer already leads to a degradation of the electron temperature.

The ELM mitigation mechanism for such high collisionality scenarii appears to be the same as the mechanism originally considered by the original authors of the method - a reduction of the pedestal pressure due to an enhanced transport in the ergodic field. Basically, the properties of the shielded ergodic layer are pre-determined by the properties of the ergodic


42

layer in vacuum and the main role is not played by the modes resonant in the core plasma (these modes have a rather deleterious effect) but by the modes resonant in the pedestal. Since the magnetic shear is high in the pedestal, spectral modes with relatively low amplitudes but high poloidal mode numbers are required because the Chirikov overlapping criterion scales as a square root of the amplitude, but linearly with the poloidal number. In order to fulfil the resonance conditions for high poloidal mode numbers, higher toroidal numbers are desirable that are not commensurable among each other. In recent ASDEX Upgrade experiments the main toroidal mode number was n = 2. This is lower than in DIII-D and is closer to the experiments on JET where higher toroidal numbers were hardly achievable due to the limitation of the coil design.

Figure 1. Electron collision frequencies of DIII-D and ASDEX Upgrade.

In low collisionality discharges, the ELM mitigation mechanism is quite different. Instead of the formation of an ergodic field region, a few or even a single mode of the spectrum is resonant - the mode which is close to the fluid resonance, V_e = 0. This type of resonance can explain the narrow window of plasma parameters where ELMs are mitigated in the experiments. It has been shown that another fluid resonance, connected to the equilibrium electric field reversal resonance E_r = 0, can also be responsible for ELM mitigation with a similar narrow parameter window. This resonance is not so strongly affected by anomalous transport in a collisional plasma with parameters close to those of ASDEX Upgrade. The V_E = 0 point is also present in DIII-D Shot 126006 and is located within the pedestal region. Actually, an enhanced transport in the region with strong density gradient pertinent to the pedestal would have a stronger effect on the plasma parameters. In particular, it would cause a stronger density pump-out than a resonance at the pedestal top where the gradients are smaller. An additional argument in favour of this resonance comes from the observations of amplification of the RMPs in relevant experiments. Such an amplification is also demonstrated in current numerical modelling. It should be noted that the conditions for an optimal use of fluid resonances are actually the same as the conditions for ergodic layer


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formation in the pedestal. Since those resonances are rather narrow in parameter space, the coil spectrum must be rather dense, and it is not so important that the amplitudes of the resonant modes are high. This is similar to the required conditions for the formation of ergodic magnetic field layers: small distances between the resonant surfaces are more important than amplitudes because the non-resonant modes are shielded by two orders of magnitude and are practically eliminated from the spectrum. Thus, a preferable perturbation spectrum is achieved if many relatively high toroidal mode numbers which are not commensurable with each other are excited so that they provide the maximum possible density of resonances in the pedestal region. On the other hand, due to high values of the safety factor in the pedestal, very high toroidal mode numbers lead to even higher poloidal mode numbers in order to be resonant there. Those modes are already strongly attenuated by the vacuum opacity barrier, i.e. the amplitude scales with the poloidal mode number as r^|m|-1. Thus, a compromise is needed between the requirement of a dense spectrum and the attenuation in such a barrier.

Conclusions and general perspectives

We plan to continue the computations of RMP shielding by the plasma in tokamaks with a linear kinetic plasma response model and the calculation of RMP effects on plasma parameter profiles (RMP induced torques, particle and heat transport). Because the mechanism of RMP action on the plasma appears to be quite different in plasmas with moderate collisionality (dominated by RMP-induced heat transport in ergodic magnetic fields) and with low collisionality (fluid resonances play an important role), the role of fluid resonances must be studied within a further improved version of our theoretical model.



3. PUBLICATIONS

Heyn, M.F., I.B. Ivanov, S.V. Kasilov, W. Kernbichler and P. Leitner, “Quasilinear kinetic modelling of RMP penetration into a tokamak plasma”, Problems of Atomic Science and Technology/Series Plasma Physics 1 Vol. 83/51 (2013). Heyn, M.F., I.B. Ivanov, S.V. Kasilov, W. Kernbichler, P. Leitner, V.V. Nemov, W. Suttrop and the ASDEX Upgrade Team, “Quasilinear modelling of RMP interaction with a tokamak plasma: Application to ASDEX upgrade ELM mitigation experiments”, Nuclear Fusion (2014), in press. Nemov, V., S. Kasilov, W. Kernbichler, V.N. Kalyuzhnyi and M.F. Heyn, “Calculations of collisionless high-energy particle losses for heliotron/torsatron devices in real space coordinates.”, 40th EPS Conference on Plasma Physics, Espoo, Finland, 1-5 July 2013, paper P2.112. Heyn, M.F., I.B. Ivanov, S. Kasilov, W. Kernbichler, P. Leitner and V.V. Nemov, “Kinetic modelling of shielding and amplification of RMPs by the tokamak plasma”, 40th EPS Conference on Plasma Physics, Espoo, Finland, 1-5 July 2013, paper P4.134.


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COMPUTATIONAL PLASMA DYNAMICS

A. Kendl; F. Gennrich, M. Held, O. Meyer, J. Peer, M. Wiesenberger

PROJECT SUMMARY

The Complex Systems Group at the University of Innsbruck specializes in the computation of plasma turbulence and modelling of impurity transport, with an emphasis on non-linear gyrofluid simulations of plasma edge turbulence and edge localized ideal ballooning modes.





WP13-IPH-A06-1-P1-01/ÖAW/BS

SOL transport measurements by probes in L-mode, inter-ELMs and ELMs: Realistic gyrofluid computations of

turbulent and ELMy SOL transport – development of suitable nonlinear polarization solvers

Simulations of turbulence in steady L-mode like state and unmitigated ballooning-mode ELMs

A.Kendl J. Peer F. Gennrich O. Meyer

WP13-IPH-A06-1-P2-01/ÖAW/PS

Active control of ELMs and the associated divertor heat loads: Application of the non-linear

polarization solvers described above to the RMP field module developed for GEMR, testing and application suitable perturbation field scenarios.

A. Kendl J. Peer F. Gennrich O. Meyer

Non-linear gyrofluid simulations of ideal ballooning in ELM dynamics and inter-ELM/L-mode turbulence with the GEMR code including magnetic perturbation fields

Nonlinear gyrofluid modelling with the GEMR code has been continued in collaboration with B. Scott and T. Ribeiro (IPP Garching) to support the understanding of complete suppression versus destabilization of ELMs. Previous results were published in Nuclear Fusion [1] and new results were presented at the 6th International Workshop on Stochasticity in Fusion Plasmas [2] and in a journal article [3].

The vacuum resonant magnetic perturbation (RMP) fields in our GEMR simulation were found by screening plasma response currents, so that magnetic transport by perturbed parallel motion was not significantly changed. Radial transport of both particles and heat is dominated by turbulent convection even for large RMP amplitudes, where the formation of stationary convective structures leads to edge profile degradation. As the plasma adjusts to the RMP-induced three-dimensional magnetic equilibrium, convective transport is reorganized in terms


45

of convection cells which are resonant with the toroidal and poloidal mode numbers of the perturbation fields.

Accordingly, the radial convective transport exhibits a stationary component which increases with increasing RMP amplitude. For the same reason, RMPs give rise to a decrease of the turbulent fluctuations in the thermal state variables, whereas the stationary contributions to the fluctuations increase. Moreover, the RMP-induced stationary structures decelerate the poloidal plasma rotation. Except for the imposed stationary structures, the drift-wave mode structure of the turbulent fluctuations is widely preserved [2, 3].

Modelling of ideal ballooning mode: unstable edge profiles for single bursts including RMP fields cause resonant mode locking and destabilization. If RMPs are applied to an ideal ballooning unstable "H-mode"-like initial configuration, the profiles adjust to the RMP-induced three-dimensional magnetic equilibrium and form resonant perturbations in the dependent variables. The interchange-ballooning drive increases the resonant perturbations so that they can grow faster than the most unstable mode of the perturbation-free case. If, on the other hand, this scenario is extended to include a bi-directional shear flow layer in the closed-flux surface region, the ballooning blow-out is delayed or, above a given threshold of the shear rate, suppressed. By combining the opposite effects of RMPs and artificially imposed shear flows, the time of the ballooning blow-out can be controlled.

The dynamics change if a shear flow layer is combined with sources in the equations for densities and temperatures: the resulting quasi-saturated H-mode-like state undergoes quasi-periodic relaxations of the edge transport barrier. The relaxations are associated with intermittent low toroidal mode number transport bursts exhibiting ballooning character. If RMPs are applied in this setup, the repetitive transport bursts are mitigated even though the fluctuations in the thermal state variables, and consequently the total radial transport are still dominated by the temporally fluctuating parts. The mitigation mechanism is not completely clear. A possible explanation could be the RMP-induced stabilization of the pressure gradient to values below the ideal ballooning threshold. By contrast, a modification of the magnetic transport by an RMP induced formation of ergodic field regions can be excluded as RMPs do not significantly change the intrinsic magnetic flutter [2, 3].

We initially intended to use the nonlinear polarization solvers described in A06-P1 with our RMP field module developed for GEMR, and test and apply these on suitable perturbation field scenarios. This goal has not yet been achieved, as the present nonlinear / global polarization implementation by a discontinous Galerkin approach in our TOEFL test code [4, 5] has resulted in the need for a complete re-structuring of the code, which is not (yet) easily compatible with a straightforward implementation into the classically finite-difference discretized gyrofluid codes. Several development versions of our versatile multi-species (isothermal) TOEFL code (described in [6, 7]) have, however, matured to a point where we are able to independently achieve ideal ballooning mode simulations including finite temperature evolution in the near future. We therefore plan to implement our GEMR RMP field module [1] into a TOEFL version including full profile gradient evolution.

On the aspect of virtual diagnostics for improved comparisons to experiments we have performed numerical investigations with the GEMR code on the validity of ion temperature measurements with a retarding field analyzer (RFA) [8, 9].

Further work was devoted to the development of methods for the implementation of a realistic tokamak edge geometry in simulations that couple the closed-field line edge region with the scrape-off layer region. For the ELM computations reported above only circular flux surface geometry had been considered. In 2013 we analyzed and tested several approaches that had recently been suggested in literature (e.g. the conformal coordinates by T. Ribeiro et al. or the flux-independent coordinates by Ottaviani et al.). These geometry models will be


46

implemented and applied in the near future in the TOEFL and GEMR codes for future edge turbulence and ELM computations.

Another aspect was the consistent inclusion of a third non-trace species ("impurity" ions) in our gyrofluid code TOEFL. We started to study isotope effects on zonal flows and turbulence (simulating mixed H-D and D-T plasmas with non-trace mixtures in the local flux-tube version of TOEFL) and also investigated the passive convection of trace impurities from the outer scrape-off-layer into the main plasma (with the profile-evolving version of TOEFL) with an emphasis on inward convection by (outward propagating) blobs, (inward propagating) holes and ideal-ballooning mode ELM models [6, 7]. So far we have not yet included RMP fields into these impurity and blob computations. This aspect will be treated in the near future.

Figure 1. Turbulent dispersion of a cloud of impurity ions in the scrape-off layer (SOL) after being hit by an edge localized ideal ballooning mode burst. The impurity density n is shown at four poloidal positions (z=0: inboard side; z=8: outboard side) in a radial-toroidal section. The black dashed lines denote the position of the edge-SOL separation. Impurity density is both blown outwards by ELM fingers and also sucked inside by respective holes.

Conclusions and general perspectives

We will continue both the application of the existing GEMR code and the further development of our TOEFL gyrofluid code. In the future TOEFL should include a full-f global density evolution model together with a global (non-linear) polarization solver for realistic flux surface geometry (consistently crossing the separatrix) with multiple (non-trace) species. The comparison with edge and SOL turbulence and blob measurements on ASDEX Upgrade will continue.




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3. REFERENCES [1] J. Peer, A. Kendl and B.D. Scott, “Ergodicity of gyrofluid edge localised ideal

ballooning modes”. Plasma Physics and Controlled Fusion 55 (2013), 015002.

[2] J. Peer, A. Kendl and T.T. Ribeiro, “Non-axisymmetric resonant magnetic perturbations in gyrofluid simulations of tokamak edge plasmas”, 6th International Workshop on Stochasticity in Fusion Plasmas, Jülich, Germany, 18-21 March 2013.

[3] J. Peer, T. Ribeiro, A. Kendl and B.D. Scott, “Gyrofluid computation of magnetic perturbation effects on turbulence and edge localized bursts”, submitted to Nuclear Fusion (2014).

[4] M. Wiesenberger and A. Kendl, “Global nonlinear gyrofluid computation of interchange blobs in tokamak edge plasmas”, 15th European Fusion Theory Conference, Oxford, UK, 23-26 September 2013.

[5] L. Einkemmer and M. Wiesenberger, “A conservative discontinuous Galerkin scheme for the 2D incompressible Navier-Stokes equations”, submitted to Computer Physics Communications (2013); arXiv:1311.7477.

[6] A. Kendl, M. Wiesenberger, O. Meyer and M. Held, “Gyrofluid computation of impurity convection in tokamak edge turbulence”, 15th European Fusion Theory Conference, Oxford, UK, 23-26 September 2013.

[7] A. Kendl, “Modelling of turbulent impurity transport in fusion edge plasmas using measured and calculated ionization cross sections”, International Journal of Mass Spectromertry (special issue, 2014).

[8] M. Kočan, H.W. Müller, B. Nold, T. Lunt, J. Adámek, S.Y. Allan, M. Bernert, G.D. Conway, P. de Marné, T. Eich, S. Elmore, F.P Gennrich, A. Herrmann, J. Horacek, Z. Huang, A. Kallenbach, M. Komm, M. Maraschek, F. Mehlmann, S. Müller, T.T. Ribeiro, V. Rohde, R. Schrittwieser, B. Scott, U. Stroth, W. Suttrop, E. Wolfrum and the ASDEX Upgrade Team, “Intermittent transport across the scrape-off layer: latest results from ASDEX Upgrade”, Nuclear Fusion 53 (2013), 073047.

[9] F. Gennrich, M. Kocan, A. Kendl, H.W. Müller and the ASDEX Upgrade Team, “Numerical investigations on the validity of ion temperature measurements with a retarding field analyser in turbulent plasma”, International Workshop on Electric Probes in Magnetized Plasmas (IWEP 2013), Madrid, Spain, 9-12 July 2013.


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EDGE PLASMA TURBULENCE AND TRANSPORT PHENOMENA

R. Schrittwieser; S. Costea, C. Lux, F. Mehlmann, C. Ioniţă-Schrittwieser

PROJECT SUMMARY

R. Schrittwieser, C. Ionita, S. Costea et al. investigate plasma turbulence and related plasma phenomena, especially ELMs (short, recurrent instabilities of the edge plasma) by various methods (specifically designed probe systems). In 2013, transport measurements were performed in ASDEX Upgrade and COMPASS. This work has been performed in cooperation with IPP Garching (ASDEX Upgrade), JET, Consortio RFX, MESCS, IPP.CR and DTU.






Scrape-off layer (SOL) transport measurements by probes in L-mode, inter ELMs and and ELMs

R. Schrittwieser C. Ionita-Schrittwieser F. Mehlmann S. Costea

WP13-IPH-A06-P1-02/ÖAW/PS

Development of a probe head with emissive probes for electric field measurements

R. Schrittwieser C. Ionita-Schrittwieser F. Mehlmann S. Costea

WP13-IPH-A06-P1-01/ÖAW/BS SOL transport measurements by probes in L-mode, inter ELMs and ELMs

SOL transport measurements with the Innsbruck-Padua probe

We determined the poloidal velocity in the ASDEX Upgrade scrape-off layer (SOL) and further inside with three different methods, using the Innsbruck-Padua probe with six pins by which the radial electric field, the cross-correlation (CC) and the conditional-averaging (CA) of signals were determined in the SOL up to the shear layer (SL) and a few mm further inside. The poloidal velocity was determined (i) from the E×B drift, (ii) from the CC of the floating potential and the ion saturation currents of two poloidally separated probes and (iii) from the CA of the same signals as for the CC. Detailed benchmarking was carried out, using synthetic data obtained from simulations with ASDEX Upgrade parameters applying the ESEL code. Based on the probe data we also determined the position of the shear layer.

Figure 1 shows the front side of the "Innsbruck-Padua“ probe head as seen from the plasma, with graphite probe pins of 1 mm diameter and 2 mm length. One pin (#6) protrudes by 3 mm from the other five pins and is inserted more deeply inside the plasma.


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The difference between the floating potentials of pins #6 and #8, divided by their radial separation of d6, 8 = 3 mm, yields an approximation of the radial electric field: Er = (Vfl,6 – Vfl,8)/d6,8 from which the poloidal velocity vp is de-rived under the assumption that it is due to the Er×Bt-drift (Bt is the toroidal magnetic field). The toroidal distance of 20 mm between pins #6 and #8 does not have an effect since the toroidal electric field can be neglected for this distance.

Although measurements were performed in a region with a steep gradient of Te, we had to assume equal electron temperatures Te on both pin positions, due to the absence of a diagnostic tool measuring the plasma potential directly from which all relevant electric field components could be derived, and/or a reliable diagnostic for Te with sufficient temporal resolution to resolve also Te fluctuations. In addition, the ion saturation currents Isat7,10 of probe pins #7 and #10 and the floating potentials Vfl8,11 measured by pins #8 and #11 were evaluated by cross correlation and conditional averaging.

To derive the poloidal velocity vp three methods were used:

Method 1: From the E×B drift and using Er = (Vfl,6 – Vfl,8)/d 6,8, while Bt is known: vp = Er/Bt .

Method 2: From the cross correlation of the signals of the two ion-biased probe pins (#7 and #10) and of the two floating probe pins (#8 and #11) which deliver the time lag for maximum CC. For each time window, respectively radial probe position, we obtain: vp = d7,10/tlag,sat and vp = d8,11/tlag,fl. For this method we have to assume that the E×B velocity is dominating any phase velocity of the structures we use for cross correlation.

Method 3: From conditional averaging of the same signals as for the CC method, which deliver the time lag for maximum CA, and obtaining vp the same way and under the same assumption.

For the experimental data, the CC and CA methods have been performed on moving-window samples of 4096 points (≅ 2 ms). Each sample has its mean value removed for an improved correlation map and a 200 kHz low-pass filter is applied in order to remove the high frequency noise which produces high velocity spikes that have no physical meaning. For the CA method, the condition used was signal > 2 standard deviation (signal). The velocity is computed from the maximum of a second order polynomial fit around the maximum of both CC and CA curves.

By magnetic reconstruction, the separatrix was found at –47.6 mm with respect to the ion cyclotron resonant heating (ICRH) limiter for the first insertion of the probe shown in figure 2 (2.11 ≤ t ≤ 2.14 s). Thus the probe head stopped 2.5 mm in front of the separatrix. Earlier findings showed that steep gradients in the radial profiles of electron temperature and density of several diagnostics which mark the position of the separatrix were found 5 mm outwards

Figure 1. Front side of the ”Innsbruck-Padua“ probe head (50 mm diameter, 115 mm long), as seen from the plasma with six probe pins of 1 mm diameter and a length of 2 mm each, mounted on the mid-plane manipulator of ASDEX Upgrade.


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with respect to the position of the separatrix by magnetic reconstruction. We thus conclude that the determination of the separatrix by magnetic reconstruction has an uncertainty of at least ±5 mm.

The experimental results obtained show that all three methods indicate the same point of change of vp which marks the shear layer. Methods 2 and 3 do not indicate a smooth transition, but a sudden jump in the flow reversal. This was well reproduced during multiple insertions. Methods 2 and 3 are in very good agreement in the determination of vp at the shear layer (≅ 4 km/s), but do not at agree with the E×B method, which even indicates an opposite poloidal velocity inside the shear layer. This could be explained by the fact that there is a maximum growth rate for pressure-gradient-driven instabilities at the separatrix and the CC and CA methods are sensitive to both phase velocity of turbulence and drift velocity of plasma. Nevertheless, we still have to assume that the phase velocities are small compared to the E×B velocity. There could also be a turbulence-driven shear layer. Another factor is the influence of electron temperature fluctuations on the probe pins close to the separatrix, which we see as the main reason for the strong discrepancy between the E×B method and the CC / CA methods. We understand this as another corroboration of our endeavours to use emissive probes for a more precise measurement of the plasma potential / electric fields.

The EDGE-SOL region in the radial-poloidal plane of ASDEX Upgrade was also simulated with the ESEL code. A virtual probe head consisting of poloidally and radially separated point-probes was used to simulate the tips of the pins of our experimental probe head and the recorded signals. In the case of synthetic data from the simulated probe head in ESEL, all three methods described above are in good agreement in the determination of the position of the shear layer, marked by the steep gradient of poloidal velocity. Furthermore, all three methods applied on the synthetic probe head show the same direction of the poloidal flow, which is in good agreement with the directly simulated flow and with the experimental E×B drift flow measured by the probes.

Figure 2. Radial probe position with respect to the ICRH limiter (top plot), temporal evolution of the cross correlation (centre plot) of the ion saturation current, temporal evolution of poloidal velocity deter-mined from the maximum of the cross-correlation (bottom-plot, red), from the ExB method (bottom plt, blue) and conditional-average method (bottom plot, black)


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WP13-IPH-A06-P1-02/ÖAW/PS Development of a probe head with emissive probes for electric field measurements

Ball-pen probe measurements in ASDEX Upgrade and COMPASS

Ball-pen probes (BPP) were used for systematic measurements of the plasma potential Φpl in ASDEX Upgrade and in COMPASS. For the first time we performed comparative measurements of Φpl with a BPP and a self-emissive Langmuir probe (LP). In both experiments, an electrically floating LP significantly changed its potential Vfl during deep insertion into the SOL. The transition from the cold to the emissive floating potential was observed close to the moment of maximum insertion of the probe. Both techniques provided similar values of Φpl and its fluctuations. The plasma and floating potential fluctuations of the BPP and the hot and cold Langmuir probe were investigated by power spectral analysis and conditional averaging techniques. The temperature of the self-emitting LP was simulated by 3D modeling, taking into account the real geometry of the graphite pin and the heat flux.

Self-emissive Langmuir probes have been used on ASDEX Upgrade before. The heating mechanism of such a probe, however, differs from an electrically heated emissive probe or laser-heated emissive probe used on smaller devices (ISTTOK, CASTOR or VINETA). Emissive probe measurements can, in general, be affected by a space charge effect induced by emission current from the hot probe surface. The BPP method, on the other hand, is based on non-heating processes. The comparison of these two probe techniques could help to prove BPPs as a routine tool for direct measurements of Φpl in magnetized plasmas.

The COMPASS and ASDEX Upgrade midplane manipulators were used to insert the probe heads shown in figures 3a and b below. In COMPASS, the plasma and floating potential were measured with the central BPP2 (figure 3a) with a retraction depth of –0.5 mm and one of the Langmuir probes (LP1 or LP2). The BBP collectors are made of stainless steel with diameters of 2 mm and an alumina shielding tube of 5 mm inner diameter. The graphite Langmuir probe pins have the same design as on ASDEX Upgrade with diameters of 0.9 mm and protruding by 1.5 mm. The poloidal distance between the LP and BPP is around 4 mm.

Similar measurements were performed on ASDEX Upgrade, using BPP1 (figure 3b) and two neighbouring Langmuir probes (LP2 and LP4). The BPPs used in ASDEX Upgrade consist of stainless steel collectors with diameters of 4 mm fixed at –0.5 mm and boron nitride shielding tubes with inner diameters of 6 mm. BPP1, LP2 and LP4 are located on different poloidal and radial position due to the inclination of the magnetic flux surface with respect to the probe surface, which is roughly 12°. The ASDEX Upgrade probe head has a diameter of 50 mm. The temporal resolution of the potential measurements is limited by the sampling frequency of 2 MHz of the data acquisition system.

Figure 4 shows the temporal evolution of the floating potentials of one BPP (red) and one LP (blue), which becomes emissive shortly before the point of deepest insertion, 25 mm inside

(a) (b)

Figure 3. (a) BPP head used in the COMPASS midplane manipulator consisting of three ball-pen probes with stainless steel collectors and alumina shielding tube and two graphite Langmuir probes. The front side of the probe head has a diameter of 3 cm. (b) BPP head used in ASDEX Upgrade with four ball pen probes with stainless steel collectors and boron nitride shielding tubes. In addition, there are four graphite Langmuir probes.


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Figure 4 shows the temporal evolution of the floating potentials of one BPP (red) and one LP (blue), which becomes emissive shortly before the point of deepest insertion, 25 mm inside the separatrix, i.e. for t = 1125 ms. In this case we see a sudden jump of the floating potential of the LP from about –150 V to +30 V, becoming almost identical to the BPP floating potential.

Assuming that the BPP floating potential Vfl,BPP is always more or less equal to Φpl, we understand this as confirmation that: (i) in the SOL and further inside of medium sized tokamaks a graphite LP can indeed be heated to such a strong electron emission that it becomes emissive, (ii) the floating potential Vfl,em of such a probe becomes indeed identical to Φpl although the plasma electron temperature Te is at least two orders of magnitude higher than the temperature of the emitted electrons (Tem ≅ 0.2 eV). This seems to contradict earlier results which indicated that Vfl,em will always remain below Φpl by a value up to Te if Te > Tem. Statistical analysis of the fluctuations of Vfl,BPP and Vfl,em‘showed very similar properties, which confirms the above assumption.

The results described above have encouraged us to develop an emissive probe for COMPASS and ASDEX Upgrade which can be heated electrically in a controlled way from the start of the probe head insertion. We expect that some contradictory results delivered by emissive probes could be clarified with this method.

In several COMPASS and ASDEX Upgrade shots similar results were obtained, although sometimes the transition from the cold to the self-emitting state of the Langmuir probe occurred less suddenly. Therefore 3D modeling of heat conduction in a graphite probe pin was performed, using the real values of the heat flux from COMPASS measurements to clarify what is really heating a self-emissive LP. Modeling results indicate that plasma heating alone cannot be responsible for the sudden transition from the cold to the self-emissive state of a LP as shown in figure 4. On the other hand, the slow transition (about 10 ms) might be slow enough to create a self-emitting LP by plasma heating. Nevertheless, both techniques demonstrated the capability of the probes to measure similar signals which can be used as direct measurements of the plasma potential. Development of a probe head with emissive probes for electric field measurements

Based on our experience with emissive probes in laboratory plasmas and small tokamaks such as CASTOR and ISTTOK and considering the great advantages of emissive probes over cold probes for the determination of the plasma potential Φpl and of electric fields we plan to develop a graphite probe head with one electrically heatable emissive probe and several cold probes. This array should be tested in the SOL of COMPASS and ASDEX Upgrade to

Figure 4. Temporal evolution of the floating potentials of BPP2 (red) and LP2 (blue) during the probe head re-ciprocation in COMPASS. The black line shows the radial position of the probe with respect to the separa-trix. The transition from the cold to the self-emitting LP2 starts at t = 1125 ms. It is radially 25 mm inside the separatrix.


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ascertain whether an emissive probe (EP) will be able to produce sufficient electron emission for the plasma in the deep SOL and hopefully even inside the last closed flux surface (LCFS). An externally heated EP can also be tested as an alternative to BBPs.

An electrically heatable EP may have decisive advantages compared to a self-emissive probe, since the electron emission of the latter cannot be controlled. The shift of the floating potential of a self-emissive probe towards Φpl starts at an unpredictable moment when the probe is already inside the SOL; it depends very strongly on plasma density and electron temperature and therefore also on the depths of insertion, whether the probe will start to become emissive at all and when this will happen. We therefore prefer to use a probe that is already heated before the first insertion into the plasma.

The design of an externally electrically heated emissive probe for hot and dense plasmas has to take into account the effect of additional heating by the plasma to avoid over-heating. The most suitable materials would be LaB6 or CeB6, which is also resistant to high temperatures. Slight contamination with La or Ce sputtered off from such a probe in the SOL plasma of COMPASS or ASDEX Upgrade is tolerable. We calculated that at a temperature of 2100 K the electron emission would be comparable to a typical electron current density in the SOL of ASDEX Upgrade. The simplest way would be the use of a single-crystal electron source of LaB6 or CeB6 which is commercially available. In case of probe materials with positive temperature resistance coefficients a constant voltage source has to be used to compensate additional external heating by the plasma. This will limit the electric heating power and avoid overheating.

A graphite probe head for COMPASS and ASDEX Upgrade with one electrically heated emissive probe has been designed. The cathode of LaB6 protrudes from the centre of the front side of the head. With the circular ceramic base with a diameter of 12 mm several conventional ASDEX Upgrade cold probes can be mounted as closely as possible to the emissive probe (6 mm) to protrude from the front surface of the probe head by about 2 mm. This will allow the direct comparison of the floating potentials Vfl of the cold probes and the emissive probe Vfl,em so that it can be tested when the emission current from the emissive probe will be sufficient to reach a floating potential equal to Φpl. For reliable comparison, Φpl can also be determined from one of the cold probes when its bias is swept and its I-V characteristic recorded. Experiments with armoured probes

Due to their significance for future work, mention should be made of first measurements in the deep SOL and beyond the separatrix in EAST (Hefei, People's Republic of China) with armoured probe heads. These investigations have been carried out in collaboration with the Sino-Danish-Center for Education and Research.

Two graphite probe heads of EAST were coated with a layer of electrically insulating ultra nano-crystalline diamond (UNCD) utilizing a chemical vapour deposition (CVD) method. The thickness of the UNCD layer was in the range of 10 to 15 μm. The coating extended over the front side and up to about 3 cm towards the rear sides of the probe heads. The probe heads with 3 and 5 graphite pins, respectively, were mounted on the reciprocating probe manipulator of EAST. Transport parameters, plasma density, temperature, potential, as well as toroidal rotation near the separatrix were determined up to a distance of 15 mm inside the LCFS in high confinement regimes. Results show that the UNCD coating could almost completely prevent the sputtering of graphite from the probe head and the subsequent deposition of a layer of conductive graphite on the boron nitride.


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3. PUBLICATIONS

Adámek, J., J. Horacek, J. Seidl, H.W. Müller, R. Schrittwieser, F. Mehlmann, P. Vondracek, S. Ptak and the COMPASS and ASDEX Upgrade Teams, "Direct plasma potential measurements by ball-pen probe and self-emitting Langmuir probe on COMPASS and ASDEX Upgrade", oral presentation, 10th International Workshop on Electric Probes in Magnetized Plasmas (IWEP 2013), Madrid, Spain, 9-12 July 2013.

Gruenwald, J., D. Tskhakaya, J. Kovačič, M. Čerček, T. Gyergyek, C. Ionita and R. Schrittwieser, "Comparison of measured and simulated electron energy distribution functions in various plasmas", Plasma Source Science and Technology 22 (2013), 015023 (7pp) (doi:10.1088/0963-0252/22/1/015023).

Ionita, C., V. Naulin, F. Mehlmann, J.J. Rasmussen, H.W. Müller, R. Schrittwieser, V. Rohde, A.H. Nielsen, Ch. Maszl, P. Balan, A. Herrmann and the ASDEX Upgrade Team, "Radial transport in the far SOL of ASDEX Upgrade during L-mode and ELMy H-mode", Nuclear Fusion 53 (2013), 043021 (14pp) (doi:10.1088/0029-5515/53/4/043021).

Kocan, M., H.W. Müller, B. Nold, T. Lunt, J. Adámek, S.Y. Allan, M. Bernert, G.D. Conway, P. de Marné, T. Eich, S. Elmore, F.P. Gennrich, A. Herrmann, J. Horacek, Z. Huang, A. Kallenbach, M. Komm, M. Maraschek, F. Mehlmann, S. Müller, T.T. Ribeiro, V. Rohde, R. Schrittwieser, B. Scott, U. Stroth, W. Suttrop, E. Wolfrum and the ASDEX Upgrade Team, "Intermittent transport across the scrape-off layer: latest results from ASDEX Upgrade", Nucear Fusion 53 (2013), 073047 (9pp) (doi:10.1088/0029-5515/53/7/073047).

Mehlmann, F., R. Schrittwieser, S. Costea, V. Naulin, J.J. Rasmussen, H.W. Müller, A.H. Nielsen, N. Vianello, D. Carralero, V. Rohde, C. Lux, C. Ionita and the ASDEX Upgrade Team, "Electric probe measurements in the scrape-off layer of ASDEX Upgrade and inside the last closed flux surface", oral presentation at the 10th Int. Workshop Electric Probes in Magnetized Plasmas (IWEP 2013), Madrid, Spain, 9-12 July 2013.

Mehlmann, F., S. Costea, V. Naulin, J.J. Rasmussen, H.W. Müller, A.H. Nielsen, N. Vianello, D. Carralero, V. Rohde, C. Lux, R. Schrittwieser, C. Ionita and the ASDEX Upgrade Team, "Radial profiles of transport parameters in ASDEX Upgrade", 40th European Conference on Plasma Physics (EPS),Espoo, Finland, 1-5 July 2013, P5.187.

Schrittwieser, R., C. Ionita, K. Rahbarnia, J. Gruenwald, T. Windisch, R. Stärz, O. Grulke and T. Klinger, "Measurements of HF-plasma oscillations by means of a laser-heated emissive probe", Contributions to Plasma Physics 53 (2013), 92-95 (doi: 10.1002/ctpp201310016).

Schrittwieser, R., G.S. Xu, N. Yan, V. Naulin, J.J. Rasmussen, P. Schrittwieser, D. Steinmüller-Nethl, F. Mehlmann and C. Ionita, "Diamond-coated probe head for measurements in the deep SOL and beyond", 40th European Conference on Plasma Physics (EPS), Satellite Conf. on Plasma Diagnostics 2013, Espoo, Finland, 6 July 2013, P6.017.

Schrittwieser, R., S. Costea, F. Mehlmann, A.H. Nielsen, V. Naulin, J.J. Rasmussen, H.W. Müller, N. Vianello, D. Carralero, V. Rohde, C. Lux, C. Ionita and the ASDEX Upgrade Team, "On the determination of the poloidal velocity and the shear layer in the SOL of ASDEX Upgrade", 55th Annual Meeting of the American Physical Society, Division Plasma Physics, Denver, Colorado, USA, 11-15 November 2013, Bulletin of the American Physical Society 58 (2013), p. 119, GP8 6.

Association EURATOM-ÖAW – Annual Report 2013 – Coordinated Activities on Power Plant Physics and Technology - Materials

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II.1. Materials

Erich-Schmid-Institute of Materials Science at ÖAW

CHARACTERIZATION OF HIGH-HEAT FLUX MATERIALS

R. Pippan; D. Firneis, L. Krämer, P. Kutlesa, V. Nikolic, S. Wurster

PROJECT SUMMARY

Applications in fusion technology require materials with high thermal conductivity and acceptable ductility and strength both at room temperature and higher temperatures. Additionally, the materials must be resistant to activation by neutron bombardment. The goal of this work is to characterize the mechanical and thermal properties of high heat flux materials such as chromium and tungsten alloys and to optimize these materials by suitable processing techniques.




Power Plant Physics and Technology (PPPT) - Materials

WP13MAT-HHFM-02-01/ÖAW/BS

Production of several batches of ultrafine-grained and oxide dispersion strengthened copper materials (Cu-Xwt%Y2O3, …) using severe plastic deformation (high pressure torsion - HPT); investigation of the long-term high-temperature stability of the processed materials; material parameters of suitable materials

R. Pippan L. Krämer P. Kutlesa S. Wurster

WP13-MAT-HHFM-02-02/ÖAW/BS

Fabrication of copper alloys R. Pippan L. Krämer P. Kutlesa S. Wurster

WP13-MAT-HHFM-03-01/ÖAW/BS

Material characterization in terms of ductility by using differently manufactured base materials (plate, rod, foil) and annealing treatments for determination of the temperature ranges of long-term applicability

R. Pippan D. Firneis V. Nikolic P. Kutlesa S. Wurster

WP13-MAT-HHFM-03-02/ÖAW/PS

Study of long-term structural materials; development of W sheet materials (thin plates together with specific high temperature characterization of these materials


WP13-MAT-IREMEV-04-01/ÖAW/BS

Material science and simulation of armour materials and joints



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WP13-MAT-HHFM-02=01 and 02/ÖAW/BS Fabrication of copper materials and characterization of nanocrystalline samples

Introduction

Applications in fusion technology require materials with high thermal conductivity and acceptable ductility and strength both at room temperature and higher temperatures. Additionally, the materials must be resistant to activation by neutron bombardment. Copper fulfils these requirements and is one of the metals with the highest thermal conductivity.

Nanocrystalline materials show improved properties such as high strength at acceptable ductility. At high temperatures, however, the grain size will increase and the properties will change. In the framework of this task we therefore tried to produce materials with a nanocrystalline matrix (copper) which is stabilized by fine particles (W [1–3], Fe, yttria) to slow down the motion of grain boundaries and to improve the microstructural stability at high annealing temperatures [3]. Nanocrystalline materials produced by severe plastic deformation (SPD) using HPT [4, 5] are free of pores and the output can be in the range of cm³. Due to the high hydrostatic pressure [6], the HPT method is suitable for deforming high-strength and brittle materials at room temperature as well as at low and high temperatures [5]. The anvils used for HPT deformation are cylinders with cavities of a certain shape where the specimens are inserted. The form of the anvil allows the material to flow out, but the friction forces increase until the flow stops and the material inside the anvils is under hydrostatic pressure [7].

This process also enables the mixing of immiscible elements and particles such as W and Y2O3 or elements with a poor solubility such as Fe. For the task described here, the elemental powder and particles were mixed, compacted and deformed by HPT. The immiscibility of the elements is important for stabilizing the material at higher temperatures as the particles cannot dissolve in the matrix and are thereby capable of hindering the movement of grain boundaries and suppressing grain growth.

In the framework of this task, the mechanical properties of several non-annealed and annealed nanocrystalline Cu materials stabilized with different particles were investigated.

1. Fabrication of samples

Most specimens were produced from powder. Three industrially produced materials (W10wt%Cu, W20wt%Cu and W25wt%Cu) and one pure Cu-bulk material were used as reference materials to ascertain the influence of powder with its large specific surface and increased impurity conten.

After mixing, the powders are filled into a Cu-ring with an outer diameter larger than the cavity of the anvils, which is glued on the lower anvil of the large HPT-device. The inner diameter of the Cu-ring is as large as the cavity in the anvils. Thereby the amount of material that can be processed is maximized. The anvils are closed, a pressure of ~210 kN is applied and one anvil is rotated for 2° to 3° against each other. The compacted disc has to be removed so that the flattened Cu-ring can be cut off. This is a very important step in order to prevent cracks from growing from the edge to the center of the copper disc and to prevent mixing of the copper of the ring with the powder and thereby changing the concentration of the material within the specimen. The disc is placed again in the anvil and it is deformed for 10 turns at room temperature. The finished sample has a diameter of 40 mm and is 7 mm high.

Afterwards, the disc is cut in half and 2-mm thick slices are produced which can be used for hardness measurements. For the second HPT-step two pieces (8 mm thick) are cut off


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parallel to the first cut and formed into a cylinder with a diameter of 8 mm. These two cylinders are sliced to pieces which are 0.8 mm thick. An overview on the two-step HPT process as used by Bachmaier et al. is shown in figure 1 below.

Figure 1. Two-step HPT deformation process of powder compacts according to Bachmaier et al. [8]

The second HPT-step using the smaller HPT-device varies from sample to sample. The number of turns and rotation velocity (hence, the strain rate) are subject to change, but also the applied pressure during deformation and the deformation temperature can be adjusted. The samples are heated inductively by placing a water-cooled coil around the anvil; the temperature is measured with a pyrometer. The diameter of the final specimens can be varied by using anvils of different geometry.

For all but one sample anvils with a cavity diameter of 8 mm were used; the applied pressure range was from 5 to 7 GPa to ensure the comparability of the specimens. For further investigation the samples were cut into half to obtain a fully tangential view at a radius of 3 mm which offers a fully radial view in the center of the cut-off piece. Those pieces were embedded, ground and polished. 2. Thermal treatment of HPT-processed materials

Thermal treatments were either conducted in a vacuum furnace or inductively in vacuum or atmosphere. Temperatures within the vacuum furnace were 720°C, 800°C and 900°C. The inductively achieved temperatures measured with a pyrometer were 580°C, 850°C, 900°C and 1000°C. In the vacuum furnace the heating rate was 10°C/min and the holding time was one hour. The furnace cooling in vacuum was slow. With inductive heating, the end temperature was reached very fast after approximately 1 min and the temperature was kept constant for approximately 30 seconds to 1 minute. In the vacuum furnace the pressure was 10-6 mbar at room temperature and approximately 10-5 mbar at higher temperatures and during inductive heating the minimal pressure was 10-4 mbar. 3. Characterization of processed materials

The microstructure was characterized in a light microscope and in a scanning electron microscope (SEM) type LEO 1525 using secondary detectors or a backscattered electrons detector. To determine the chemical composition of the processed materials, energy dispersive X-ray analysis (EDX) was performed at the SEM LEO 1525.

The Vicker hardness was measured with BUEHLER Microsmet using 500 g or 1000 g along the radii of the specimen divided in half. By this method the hardness can be seen in correlation with the applied strain. The distance between the indents was 250 µm for small indentations and 500 µm for larger ones. The HPT-discs were cut into halves, so that material closer to the edge of the specimen that experienced larger strains could be tested.


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A circular grinding tool (G. Rathmayr et al [9]) was used for the production of sub-sized tensile specimens. This tool consists of a grinding disc, an adjustable specimen holder, a liquid cooling system and a dial gauge. There are two shafts with a fixation for the samples in the specimen holder. The shafts are synchronically driven by one motor. Thus, there is no twisting moment on the sample, because no side can slow down or accelerate. To measure the position of the specimen holder on the linear bearing, a dial gauge is used. The linear bearing is perpendicular to the axes of the grinding disc, so that the rotation axis of the specimen is perpendicular to the shoulder. For the liquid cooling system, water with a grinding additive is used.

As the specimen and the grinding disc rotate, the diameter is adjusted by moving the specimen holder along the linear bearing. The polishing step after grinding was omitted to avoid the danger of breaking the very thin specimens (diameter ~ 300 µm) during the polishing process. Before tensile testing, the diameter of the specimens was measured using transmitted light on an optical microscope and it was also controlled whether the samples were completely circular.

Testing was performed at a Kammrath & Weiss miniature tensile testing machine (for a description of the process see [9]). Two different load cells were used: 200 N and 10 kN. A diode provided the light from underneath, so that the pictures – recorded in top view – show a very strong contrast between the dark tensile specimen and the light background.

The specimens were simply lying on the holder to avoid bending and only plasticine was used to absorb the energy released upon final fracture. The speed of testing was 2.5 µm/s. During testing, pictures of the samples were taken with a single lens flex camera to monitor the changing specimen geometry. From the resulting thickness reduction and length increase stress-strain curves can be calculated using a Matlab package written by G. Rathmayr [9]. Hardness

The hardness strongly depends on the composition (i.e. additions of yttria, tungsten, iron or no additions) of the materials and the applied strain. For Cu25wt%W and Cu4wt% Y2O3, hardness increases with increasing strain. This is contrary to the behaviour of HPT-processed single-phase bulk material, where a saturation of hardness would occur equivalent to the saturation in the microstructural evolution. This does not imply that the microstructure does not change upon further deformation, but certain important parameters such as grain size, grain aspect ratio and texture reach a dynamic equilibrium.

Figure 2. SEM micrographs of W-25wt%Cu. Left side: 400 turns and right side: 30 turns were applied at room temperature. Both materials were annealed at 720°C in vacuum for 1 hour.


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4. Summary of results

The best result in terms of ductility and strength for a material containing additions was obtained if it was first deformed at room temperature and then - with fewer turns - at elevated temperature (500°C). This material shows a higher strength compared to the pure bulk copper and reaches about the same strain at fracture.

Yttria is more brittle than tungsten and cannot be deformed within the copper matrix, even at high strains. Thus, the form of the particles does not change, but they become smaller as the yttria agglomerates break down. In contrast, Fe and Cu are more similar in strength; thus, not only the Cu-grains refine quickly, but also the Fe-particles become smaller. It can be shown that after 30 turns the size of the large particles decreases from 2 µm in the center of the HPT-disc to 500 nm at the edge.

Not only the mechanical properties influence the behaviour of deformation, but also the ratio (volume, weight percentage) of the harder to the softer phase. Harder particles are floating within the matrix because the harder phase is so small. As soon as the volume of the harder phase increases, however, the strain in the harder phase increases too. Thus, a higher share of W has two effects: larger areas of the tungsten particles are torn apart (i.e. destruction of the agglomerations during deformation), and the grain sizes of Cu and W decrease strongly. In order to achieve a co-deformation of a non-copper phase, it is either necessary that the difference in strength is not too high or that the volume percentage of a harder phase is high. In the latter case it is possible to deform e.g. tungsten.

Tensile tests show that the ductility decreases, if large and brittle particles are added (e.g. W and yttria). The fracture strain of HPT-processed copper powder is smaller than that of HPT-processed bulk material, because the bulk material contains less impurities. The most important conclusion of this work is that the ductility of the samples can be increased by additional deformation at higher temperatures.

References

[1] I. Sabirov and R. Pippan, "Formation of a W–25%Cu nanocomposite during high pressure torsion", Scripta Materialia 52 (2005), 1293–1298.

[2] I. Sabirov and R. Pippan, "Characterization of tungsten fragmentation in a W–25%Cu composite after high-pressure torsion", Materials Charactization 58 (2007), 848–853.

[3] D. Edwards, I. Sabirov, W. Sigle and R. Pippan, "Microstructure and thermostability of a W–Cu nanocomposite produced via high-pressure torsion", Philosophical Magazine 92 (2012), 4151–4166.

[4] R. Valiev, R. Islamgaliev and I. Alexandrov, "Bulk nanostructured materials from severe plastic deformation", Progess in Materials Science 45 (2000), 103–189.

[5] R. Pippan, S. Scheriau, A. Taylor, M. Hafok, A. Hohenwarter and A. Bachmaier, "Saturation of fragmentation during severe plastic deformation", Annual Review of Materials Research 40 (2010), 319–343.

[6] S. Wurster, B. Gludovatz, A. Hoffmann and R. Pippan, "Fracture behaviour of tungsten-vanadium and tungsten-tantalum alloys and composites", Journal of Nuclear Materials 413 (2011), 166–176.

[7] A. Hohenwarter, A. Bachmaier, B. Gludovatz, S. Scheriau and R. Pippan, "Technical parameters affecting grain refinement by high pressure torsion", International Journal of Materials Research 100 (2009), 1653–1661.

[8] A. Bachmaier, M. Kerber, D. Setman and R. Pippan, "The formation of supersaturated solid solutions in Fe–Cu alloys deformed by high-pressure torsion", Acta Materialia 60 (2012), 860–871.


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[9] G.B. Rathmayr, A. Bachmaier and R. Pippan, "Development of a new testing procedure for performing tensile tests on specimens with sub-millimeter dimensions, Journal of Testing and Evaluation 41 (2013), 20120175.

WP13-MAT-HHFM-03-01/ÖAW/BS, WP13-MAT-HHFM-03-02/ÖAW/PS Development of W sheet materials (thin plates) and high-temperature characterization of these materials

1. Introduction

Tungsten and tungsten-based materials are promising candidates for fusion applications. However, the inherent brittleness of the material at low temperatures and at high testing speeds large-scale application as structural and armor materials. it was reported in several publications [1–8] that setting a beneficial microstructure, i.e. applying appropriate manufacturing steps, is a promising way to make tungsten tougher and more ductile. The exact value of the ductile-brittle transition temperature – normally found at several hundred degree Celsius – strongly depends on the strain rate of the applied experiment [9–12].

One possibility to overcome the low toughness is alloying with d-band filling elements. Especially rhenium has shown a ductilizing effect on tungsten [13–15], resulting in increased fracture toughness even at room temperature [16, 17]. For large-scale industrial production, however, alloying with expensive and rare elements is not a viable option. The only way to produce tough and ductile tungsten and tungsten-based materials on an industrial scale therefore seems to be the application of adequate manufacturing techniques. It is widely accepted that the microstructural design, i.e. changing the grain size, grain shape, texture, dislocation density, etc., has a significant influence on fracture behaviour [2, 6, 18–20], and a very recent proposal for fusion-ready tungsten-based materials is the application of thin and ductile tungsten foils featuring a high degree of deformation [21–24]. Results suggest that plate-like grains which are interlocked with each other present the highest number of testing directions featuring high fracture toughness.

In the framework of this task fracture experiments were carried out on potassium-doped tungsten tested in different annealed conditions, taking into account two different testing directions. The results show a very pronounced influence of annealing temperature on fracture toughness, which notably decreases as soon as recrystallization starts.

The low toughness and ductility of tungsten and tungsten-based materials at low temperatures define the lower temperature limit for their application as structural material. At higher temperatures, the operational temperature limit is defined by the recrystallization temperature, where a possible beneficial microstructure would be destroyed and material properties degrade. This work aims at an exact description of the influence of thermal treatments to potassium doped tungsten in terms of changes of fracture properties. 2. Experiments and results

The starting material is an industrially produced plate made of potassium doped tungsten (WVM), 1.4 mm thick.

The as-received material is subjected to thermal treatments in a vacuum furnace at different temperatures. During all thermal treatments, the temperature is kept constant for 60 min. The pressure is at least as 10-4 mbar. Fracture experiments have been performed in the as-received condition and on material annealed at 1200°C, 1400°C and 1600°C.

For taking into account a possible anisotropy in grain size and grain shape due to the rolling process, specimens for fracture experiments were extracted from the plate: first, with the crack propagating parallel to the rolling direction and second, with the crack


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propagating perpendicular to the rolling direction. Using the standard test method for plane-strain fracture toughness measurements of metallic materials (ASTM E 399, see fFigure 3), the specimens can be denominated (T-L) with crack propagation parallel to the rolling direction and (L-T) with crack propagation perpendicular to the rolling direction. Test arrangements with the crack plane parallel to the rolling plane were not used, as they would require sophisticated brazing methods to make the specimen bigger or to use smaller sub-sized specimens [25, 26]. Previous experience gained on pure tungsten and other tungsten based materials suggests that the fracture toughness is low when the crack plane is parallel to the rolling plane.

Compact tension (CT) specimens were cut out of the thin plate. A crack was introduced by consecutively using a diamond wire saw, a razor blade and finally fatigue pre-cracking under compressive loading. The set-up used [17] is not only suitable for testing specimens in vacuum at high temperatures, but also for room temperature experiments. The testing speed was kept constant for all experiments in order to avoid an influence of the loading rate on the fracture toughness [7, 11].

The calculated fracture toughness values were compared with the data from hardness measurements. Hardness was determined with the loading direction perpendicular to the plate and showed a gradual decrease from high values (> 480 HV) for the as-received material up to an annealing temperature of 1400°C. This is mainly due to recovery processes. The hardness at 1400°C was tested in the outer region of the material where the material is not yet recrystallized. Between annealing temperatures of 1400°C and 1600°C hardness decrease dramatically. The deformed, rolled material vanishes completely, and a fully recrystallized microstructure consisting of globular grains is formed.

A very prominent feature of the fracture surface of the specimen of as-received material and tested in (L-T) configuration is the existence of a lot of cracks perpendicular to the original fracture surface. These cracks open along planes that are parallel to the rolling plane, indicating that these planes are of lower toughness. The cracks, seem to improve the fracture toughness in (L-T) configuration. They are, however, not visible in (T-L) configuration and the fracture toughness of (T-L) is lower by about 4 MPa m1/2.

Figure 3. Nomenclature for specimens used in fracture experiments, taking into account rolling direction, short and long transverse direction. The two crack systems investigated are (T-L) and (L-T).


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Figure 4. Left: SEM micrograph of the fracture surface of as-received material in (L-T)

configuration. On the very top, the razor blade sharpened notch is visible with the adjacent region of fatigue pre-cracking. In both the fatigue pre-cracked area and the final fracture surface opening cracks are visible (parallel to the rolling plane). The picture on the right shows a SEM micrograph of the same material in (T-L) configuration. Less cracks are visible in parallel direction to the rolling plane and the cracks are smaller.

The reason for crack opening in the rolling plane could be the aspect ratio of the grains in the rolling plane. If grains are longer in rolling direction, it would be “easier” for the crack in the (T-L) system to circumvent the grain interior and follow brittle grain boundaries. This is supported by figure 5 below, showing the fracture surface of the material annealed at 1200°C. The fracture surface is rougher in the right picture (L-T configuration) than in the picture on the left (T-L configuration) and the fracture toughness is higher.

Figure 5. Fracture surface of the specimen made of material annealed at 1200°C (left: tested in T-L configuration, right: tested in L-T configuration.)

Closer investigations of the fracture surfaces of the specimens made of the annealed material have not shown any cracks forming in the rolling plane, neither in (L-T) nor in (T-L) configuration. 3. Summary and conclusion

In the framework of this task the influence of microstructure-changing annealing treatments on the fracture behaviour of potassium bubbles–stabilized tungsten material was investigated. The material was tested in the as-received state (WVM, industrially produced plate, 1.4 mm thick) as well as in three different annealed states. Fracture experiments show a drop in room-temperature fracture toughness with increasing annealing temperature, with the material in the as-received state having the highest toughness in both


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investigated testing direction. As soon as a marked microstructural change occurs (between 1200°C and 1400°C in the center of the plate), there is a decrease in fracture toughness by approximately 4 MPa m1/2. As previous investigations of potassium-doped material have shown, the fracture toughness of the recrystallized material stays about constant – at least up to annealing temperatures of 2400°C (for one hour). There is a slight difference of fracture toughness between crack systems propagating perpendicular and parallel to the rolling direction. This could be due to the elongation of grains in the rolling direction leading to easier crack opening along the rolling plane for the (L-T) configuration. The larger fracture surface possibly increases fracture toughness.

In a smart design of the tungsten microstructure “predetermined breaking points” could be introduced which consume energy in case of fracture. This would lead to increased toughness and would reduce the risks of catastrophic failure.

In its present form, the WVM-plate material is not adequate for final application. Higher degrees of deformation during processing of the plate would lead to a better distribution of potassium bubbles, resulting in improved overall material behaviour. The recrystallization temperature would be higher (in all regions of the plate), thermal stability would be better and fracture toughness is expected to increase in both testing directions. References

[1] M. Faleschini, H. Kreuzer, D. Kiener and R. Pippan, "Fracture toughness investigations of tungsten alloys and SPD tungsten alloys", Journal of Nuclear Materials 367-370 A (2007), 800–805.

[2] B. Gludovatz, S. Wurster, A. Hoffmann and R. Pippan, "Fracture toughness of polycrystalline tungsten alloys", International Journal of Refractory Metals and Hard Materials 28 (2010), 674–678.

[3] S. Wurster, B. Gludovatz and R. Pippan, "High temperature fracture experiments on tungsten-rhenium alloys", International Journal of Refractory Metals and Hard Materials 28 (2010), 692–697.

[4] S. Wurster, B. Gludovatz, A. Hoffmann and R. Pippan, "Fracture behaviour of tungsten-vanadium and tungsten-tantalum alloys and composites", Journal of Nuclear Materials 413 (2011), 166–176.

[5] B. Gludovatz, S. Wurster, A. Hoffmann and R. Pippan, "A study into the crack propagation resistance of pure tungsten", Engineering Fracture Mechnics 100 (2013), 76–85.

[6] D. Rupp, R. Mönig, P. Gruber and S.M. Weygand, "Fracture toughness and microstructural characterization of polycrystalline rolled tungsten", International Journal of Refractory Metals and Hard Materials 28 (2010), 669–673.

[7] D. Rupp and S.M. Weygand, "Loading rate dependence of the fracture toughness of polycrystalline tungsten", Journal of Nuclear Materials 417 (2011), 477–480.

[8] J. Reiser, M. Rieth, B. Dafferner and A. Hoffmann, "Charpy impact properties of pure tungsten plate material in as-received and recrystallized condition (1 h at 2000°C (2273 K)", Journal of Nuclear Materials.442 (2013), 204-207.

[9] P. Gumbsch, J. Riedle, A. Hartmaier and H.F. Fischmeister, "Controlling factors for the brittle-to-ductile transition in tungsten single crystals", Science 282 (1998), 1293–1295.

[10] P. Gumbsch, "Brittle fracture and the brittle-to-ductile transition of tungsten", Journal of Nuclear Materials 323 (2003), 304–312.

[11] A. Giannattasio and S.G. Roberts, "Strain-rate dependence of the brittle-to-ductile transition temperature in tungsten", Philosophical Magazine 87 (2007), 2589–2598.


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[12] A. Giannattasio, Z. Yao, E. Tarleton and S.G. Roberts, "Brittle-ductile transitions in polycrystalline tungsten", Philosophical Magazine 90 (2010), 3947–3959.

[13] G.A. Geach and J.E. Hughes, "The alloys of rhenium with molybdenum or with tungsten and having good high temperature properties", Proceedings of the 2nd Int. Plansee Seminar (1955), 245–253.

[14] R.I. Jaffee, C.T. Sims and J.J. Harwood, "The effect of rhenium on the fabricability and ductility of molybdenum and tungsten", Proceedings of the 3rd Int. Plansee Seminar (1958), 380–411.

[15] P.L. Raffo, "Yielding and fracture in tungsten and tungsten-rhenium alloys", Journal of -Common Metals 17 (1969), 133–149.

[16] Y. Mutoh, K. Ichikawa, K. Nagata and M. Takeuchi, "Effect of rhenium addition on fracture toughness of tungsten at elevated temperatures", Journal of Materials Science 30 (1995), 770–775.

[17] S. Wurster, B. Gludovatz and R. Pippan, "High temperature fracture experiments on tungsten-rhenium alloys", International Journal of Refractory Metals and Hard Materials 28 (2010), 692–697.

[18] J. Neges, B. Ortner, G. Leichtfried and H.P. Stüwe, "On the 45° embrittlement of tungsten sheets", Materials and Science Engineering 196 (1995), 129–133.

[19] M. Rieth and A. Hoffmann, "Influence of microstructure and notch fabrication on impact bending properties of tungsten materials", International Journal of Refractory Metals and Hard Materials 28 (2010), 679–686.

[20] B. Gludovatz, S. Wurster, A. Hoffmann and R. Pippan, "A study into the crack propagation resistance of pure tungsten", Engineering Fracture Mechanics 100 (2013), 76-85.

[21] J. Reiser, M. Rieth, B. Dafferner and A. Hoffmann, "Tungsten foil laminate for structural divertor applications – Basics and outlook", Journal of Nuclear Materials 423 (2012), 1–8.

[22] J. Reiser, M. Rieth, A. Möslang, B. Dafferner, J. Hoffmann, T. Mrotzek et al., "Tungsten foil laminate for structural divertor applications – Joining of tungsten foils", Journal of Nuclear Materials 436 (2013), 47–55.

[23] J. Reiser, M. Rieth, B. Dafferner, A. Hoffmann, X. Yi and D.E.J. Armstrong, "Tungsten foil laminate for structural divertor applications – analyses and characterisation of tungsten foil", J. of Nuclear Materials 424 (2012), 197–203.

[24] J. Reiser, M. Rieth, A. Möslang, B. Dafferner, A. Hoffmann, X. Yi et al., "Tungsten foil laminate for structural divertor applications – Tensile test properties of tungsten foil", Journal of Nuclear Materials 434 (2013), 357–366.

[25] D. Di Maio and S.G. Roberts, "Measuring fracture toughness of coatings using focused-ion-beam-machined microbeams", Journal of Materials Research 20 (2005), 299–302.

[26] S. Wurster, C. Motz and R. Pippan, "Characterization of the fracture toughness of micro-sized tungsten single crystal notched specimens", Philosophical Magazine 92 (2012), 1803–1825.



Association EURATOM-ÖAW – Annual Report 2013 – Coordinated Activities on Power Plant Physics and Technology – Design Assessment Studies

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II.2. Design Assessment Studies

Institute of Atomic and Subatomic Physics, Vienna University of Technology

HIGH-TEMPERATURE SUPERCONDUCTING MATERIALS FOR FUSION MAGNETS

R. Prokopec, M. Eisterer, T. Baumgartner, J. Hecher, V. Mishev, F.M. Sauerzopf, M. Zehetmayer, H.W. Weber

PROJECT SUMMARY

High-temperature superconducting (HTS) materials offer a considerable potential for magnet applications because of their extremely high upper critical magnetic fields and their excellent current carrying capabilities at low temperatures. In the framework of this project, the material properties of HTS materials developed and optimized by industry are characterized at different temperatures and magnetic fields before and after neutron irradiation.




Design Assessment Studies

WP13-DAS-01-T08-01- 02/ÖAW

Characterization of HTS tapes before and after irradiation, assessing the following characteristics: a) Critical temperature (Tc) b) Critical current (Ic), including angular

dependence c) Strain (test of selected samples) d) Homogeneity of supercurrent flow by

magnetoscan

R. Prokopec J. Hecher V. Mishev M. Zehetmayer T. Baumgartner F.M. Sauerzopf

1.1 Overview

Our work is aiming at the characterization of state-of-the-art superconducting tapes under realistic operation conditions in future fusion magnets. Well known results on commercial coated conductors obtained under standard conditions are complemented by measurements simulating the exceptionally hard conditions in fusion devices: neutron radiation, high hoop stresses and inclined magnetic fields.

All data collected refer to direct transport measurements in helium gas flow or in liquid nitrogen evaluated by the widely used 1 µV/cm electric field criterion. Prior to the transport measurements, each sample was checked by the Hall scan technique in order to detect defects caused by the fabrication process. The studies on the SuperPower tape shielded with a gadolinium foil during neutron irradiation were completed in order to explain the unexpected high degradation reported last year.

Recently developed tapes from American Superconductor, SuperPower and SuNam (delivered in 2013), were characterized prior to irradiation and will be characterized after irradiation to a fast neutron target fluence of 2.5x1022 m-2. The re-characterization was started in January 2014 with a tape from American Superconductors.


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1.2 Shielding of HTS coated conductors against thermal neutrons

Additional irradiation experiments were carried out in order to clarify the reason for the previously reported high degradation of SuperPower tapes after neutron irradiation. It was supposed that the unexpected behaviour was the result of additional defects created by neutron capture reactions of Gd in the low neutron energy regime. The superconducting layer in the latest generation of SuperPower tapes consists of Gd-123 instead of Y-123. The neutron capture cross section of Gd in the low energy region is higher by several orders of magnitude than that of Y. However, low energy neutrons are hardly present in a fusion spectrum contrary to the fission spectrum. Therefore, the samples were covered with gadolinium foil which should prevent the low energy neutrons from creating defects in the superconductor. Also one tape from American Superconductor (AMSC) which does not contain Gd was included in order to investigate whether the shielding also affects Y-123 tapes. 1.2.1 Results

Figure 1. Irreversibility lines of SCS4050 before and after irradiation

Figure 1 shows the irreversibility lines of the SCS4050 tape. The critical temperature Tc drops by 5.9 K in case of irradiation without shielding to a fast neutron fluence of 0.6x1022 m-2. For the Gd shielded sample the Tc reduction is significantly smaller (1.1 K), which is in good agreement with previously obtained results on Y-123 based tapes.

The data on the critical currents confirms this behaviour (see figure 2). Ic of the unshielded sample is heavily reduced in the investigated temperature range between 85 K and 50 K, especially at high temperatures the reduction is dramatic. The shielded sample shows only an Ic reduction at 85 K mainly caused by the decreased Tc. At 77 K and below, the tape shows the expected Ic enhancement resulting from the additional pinning centers created by high energy neutrons.


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0 2 4 6 8 10 12 14 16

0.1

1

10

100

SCS4050 H tape

unirr. 85 K 77 K 64 K 50 K

irr. 85 K 77 K 64 K 50 K

irr. + Gd-shield 85 K 77 K 64 K 50 K

I c (A

)

µ0H (T)

Figure 2. Critical currents of the SCS4050 tape in magnetic fields perpendicular to the

tape at different temperatures

The properties of the irradiated AMSC tape are not affected by the Gd-layer surrounding the sample during irradiation. The Tc reduction is nearly the same for both irradiated samples, i.e. 1.4 K for the un-shielded and 1.5 K for the shielded sample. Also the irreversibility lines are overlapping.

1.3 Characterization of HTS coated conductors delivered in 2013

1.3.1 Sample details

New HTS tapes from SuperPower, American Superconductor (AMSC) and SuNam were delivered at the beginning of 2013. The tapes consist of a REBCO layer with a thickness of ~ 1 µm. The superconducting layers were produced by different fabrication techniques and on different substrates. An overview of the various tapes is given in table 1.

Table 1. Overview of the investigated HTS tapes SCS4050-AP ASC-40 SuNam2G

HCN04150 Manufacturer SuperPower American

Superconductors SuNam

Cross-section 4 x 0.1 mm² 4 x 0.4 mm² 4 x 0.1 mm² SC GdBCO by MOD REBCO by MOD

(Y:Dy:Ba:Cu=1:0.5:2:3)GdBCO by RCE-DR

SC- layer thickness 1 µm 1.2 µm 1.35 µm Substrate Hastelloy MgO-

IBAD RABITS Ni, 5wt% W

Hastelloy MgO-IBAD

Some particularities of the tapes should be pointed out: The SuperPower tape contains artificial pinning centers of a few nanometers in order to increase the pinning efficiency. These pinning centers are presumably made by the addition of zirconium (Zr), which forms BZO nanocolumns. The AMSC tape has an improved mechanical stability. The additional brass lamination offers an extremely robust structure resulting in a four times higher thickness of the tape compared to the other two conductors.


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1.3.2 Neutron irradiation

The neutron irradiation was carried out in the TRIGA MARK II reactor, Vienna, from July to September. The samples were exposed to a target fast neutron fluence of 2.5x1022 m-2 (E>0.1 MeV). The GdBCO tapes (SuperPower, SuNam) were enclosed by a Cd-foil in order to prevent low energy neutrons which are hardly present in a fusion spectrum, from defect creation via absorption by Gd. In addition, a small piece of a Ni-foil was included in the irradiation capsule, in order to calculate the fast neutron fluence from the induced activity of Co-58. The re-characterization of the tapes was started in January 2014 with the AMSC tapes due to its lower radioactivity. The Co-58 activity of the Ni-foil was measured and the fast neutron fluence was calculated to be 2.3x1022 m-2

. 1.3.3 Irreversibility lines of the new tapes

The SuNam tape has the highest Tc of 94.0 K indicating a very clean superconducting layer, while the critical temperatures of the other two tapes are ~ 90 K. Their superconducting transition is sharp with a width Tc of 0.25 K. Figure 3 shows the irreversibility lines of the tapes in the main field orientations. The irradiation to a fast neutron fluence of 2.3x1022 m-2 leads to a Tc reduction of 5.6 K in the ASC-40 conductor. Also the slopes of the irreversibility lines are significantly affected, especially when the field is oriented perpendicular to the tape. Hirr (T) becomes steeper after irradiation.

0

2

4

6

8

10

12

14

16

70 75 80 85 90 95

SuNAM H tape H tape

SCS-4050AP H tape H tape

ASC-40unirr.

H tape H tape

2.3x1022

m-2

H tape H tape

T (K)

µ0H

(T

)

Figure 3. Irreversibility lines of the SCS4050-AP, ASC-40 and SuNam tapes. Post-irradiation data are currently available only for the ASC-40 sample.

1.3.4 Critical currents of the SuNam tape

In general, the tape has an extremely good performance at low magnetic fields, e.g. 222 A at 77 K and 0 T, which is equal to a critical current density of 4.1x1010 A/m2. However, this situation changes significantly with increasing magnetic fields, where the critical currents decrease rapidly. This is not unexpected because of the obvious clean nature of the superconductor. In the fusion-relevant field of 15 T, an Ic of 50 A (9.25x109 A/m2) for H || tape and 21.4 A (3.96x109 A/m2) for H tape was measured at 40 K, which is significantly lower than for the other two tapes.


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Figure 4. Critical currents of the SuNam tape in magnetic fields applied parallel and

perpendicular to the sample surface

1.3.5 Critical currents of the SuperPower tape

Figure 5. Critical currents of the SCS4050-AP tape in magnetic fields applied parallel

and perpendicular to the sample surface

The critical currents of the SuperPower tape in the main field orientations show a cross-over at high temperatures and low magnetic fields, below which the critical currents are higher when the magnetic field is applied perpendicular to the tape surface. The additional nano-particles seem to be extremely effective in this low field regime. The critical currents are higher for H tape than for H || tape below 3.5 T at 77 K and below 6 T at 64 K. At 15 T an Ic of 247 A (6.18x1010 A/m2) for H || tape and 54.9 A (1.37x1010 A/m2) for H tape was measured at 40 K. 1.3.6 Critical currents of the AMSC tape

The AMSC tape also shows a cross-over at high temperatures and low magnetic fields. However, this behaviour is less pronounced than in the SuperPower tape. An Ic of 220 A (4.17x1010 A/m2) for H || tape and 41 A (7.77x109 A/m2) for H tape was measured at 40 K and 14 T.


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0 2 4 6 8 10 12 14 160.1

1

10

100

H || tape 77 K 64 K 50 K 40 K

H tape 77 K 64 K 50 K 40 K 20 K

I c (A

)

µ0H (T)

Figure 6. Critical currents of the ASC-40 tape in magnetic fields applied parallel and

perpendicular to the sample surface

After irradiation to a fast neutron fluence of 2.3x1022 m-2, Ic for H tape is reduced at 64 K and above presumably due to the lower Tc, whereas at 50 K and below the situation is reversed, because the additional pinning centers created by neutron irradiation enhance the current carrying capability. At a magnetic field of 15 T, the critical current is ~ 50 % higher at 50 K after irradiation and more than twice as high (130 A) at 30 K.

For H || tape, the irradiation reduced the critical currents over the entire range of investigated temperatures and magnetic fields. The added defects disturb the intrinsic pinning properties of the superconductor and, therefore, reduce the critical currents. Ic decreases by ~ 50 % at a magnetic field of 15 T and 64 K as well as at 50 K. 1.3.7 Angular dependence of critical currents

The tapes from SuperPower and SuNam - both consist of an IBAD-MgO template - show a shift of the intrinsic ab-peak by ~2 ° compared to the tape surface indicating a slightly tilted substrate.

50 100 150 2000

10

20

30

40

50

60

H tape H || tape

77 K 64 K

I C (

A)

Angle (°)

50 100 150 2000

10

20

30

40

H tape H || tape

5.5 T 2 T

I c (A

)

Angle (°)

Figure 7. Angular dependence of Ic of the SuNam tape at 5 T (left) and of the SCS4050-AP

tape at 77 K (right) Figure 7 shows two extreme cases. The SuNam tape has a nearly constant critical current over a wide range with respect to the field orientation, e.g. 15 A at 64 K. The intrinsic ab-peak is very sharp and pronounced. Only a small enhancement of Ic occurs, when the tape is oriented parallel to the c-axis. We assume that the lack of effective pinning centers causes the highly


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anisotropic properties as well as the Ic reduction when the field orientation deviates from the ab-plane.

For the SuperPower tape, only a small peak was found at 5.5 T, when the magnetic field was oriented parallel to the c-axis, while a significant peak was found at 2 T, which is even higher than the ab-peak. In general, the anisotropy is much smaller compared to the SuNam tape due to the additional pinning centers. 1.3.8 Stress dependence of critical currents

Ic measurements were also made under tensile load. As an example, Figure 8 presents the results obtained on the SuNam tape. The tape shows a very homogeneous behaviour with respect to the total investigated tape length of 15 cm, which was cut into three pieces. The stress level was increased in steps of 25 MPa (figure 8, left). The force was reduced to 25 MPa after each measurement, in order to check whether the superconductor had been irreversibly damaged (figure 8, right).

0 200 400 600 800 10000

50

100

150

200

250

#1 #2 #3

I c (A

)

(MPa)

0 200 400 600 800 10000

50

100

150

200

250

#1 #2 #3

I c (A

)

Maximum applied stress

max (MPa)

Figure 8. Stress dependence of critical currents at 77 K (left) and critical currents after

reducing the stress to 25 MPa (right)

The results do not show any significant variation among the individual pieces. The critical current decreases continuously with increasing stress. The reduction of Ic is less than 10 % up to an applied stress of 830 MPa. The tapes are irreversibly damaged above 860 MPa. This transition is relatively sharp, which can be seen especially for sample 2 and 3, where the step size was reduced in the transition area. If the applied stress exceeds the reversible point by more than 25 MPa, no macroscopic loss-free current could be detected anymore.

Similar results were obtained on the SuperPower tape, which also has a Hastelloy substrate. However, a sample to sample variation was found, and stresses of more than 1000 MPa do not cause irreversible damage in some pieces.

Due to the robust architecture of the AMSC tape it was decided to stop the measurements after a maximum applied stress of 500 MPa, in order to avoid damage of the experimental setup. Up to this stress level, Ic remains nearly constant.

The tapes were scanned after the measurement using the Hall scanning technique. A trapped magnetic field was only measured in areas, where the tape had been fixed, while the superconductor is damaged in between shown by the area with no trapped field.


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Figure 9. Hall scan of an irreversibly damaged sample



The characterization of the remaining samples will be completed and the tapes will be further irradiated afterwards. The goal is to characterize these materials up to a fast neutron fluence of at least 5x1022 m-2. A comparison with the radiation resistance of Nb3Sn is envisaged. Monitoring the conductors developed by industry will be continued to assess the state-of-the-art performance.

3. PUBLICATION

J. Emhofer, M. Eisterer and H.W. Weber, “Stress dependence of the critical currents in neutron irradiated (RE)BCO coated conductors”, Superconductor Science and Technology 26 (2013) 035009.

Association EURATOM-ÖAW – Annual Report 2013 – Coordinated Activities on Power Plant Physics and Technology - Socio-Economic Research on Fusion

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II.3. Socio-Economic Research on Fusion (SERF)

Research Studios Austria

ENERGY SCENARIO DEVELOPMENT WITH EFDA-TIMES

M. Biberacher; S. Gadocha

PROJECT SUMMARY

Fusion represents a key technological option for future energy system, with the concern for climate change as the key driver for future market penetration. The adoption of environmental measures, even in the weaker form of a CO2 tax differentiated among regions and with a moderate path of growth, is sufficient to push fusion into the electricity market at the end of the century. Fusion results seem robust against different paths of economic growth. The role of fusion is also linked to the tightness of environmental constraints.




Socio-Economic Research on Fusion (SERF)

WP13-SER-ETM-T04-ÖAW/BS

Update and maintenance of the ETM base scenario tree and common dissemination materials

Analysis of fusion – comparison among different periods and model regions

New ETM internet platform

M. Biberacher S. Gadocha

Development of a new ETM internet platform

The EFDA-TIMES Model (ETM) is an economic model of the global energy system based on The Integrated MARKAL-EFOM System (TIMES) Framework. The development of the EFDATIMES model within EFDA Socio Economic Research on Fusion (SERF) started in 2004.

The development of the future world energy system is triggered by many different aspects. Global economical and population development will influence our energy system as well as climate change issues, resource depletion or political commitments. Since we do not have perfect knowledge about these developments in the future, the purpose of ETM scenarios is to show correlations between assumptions on future constraints and the development of the future energy system development. These assumptions on future constraints are represented by the following aspects:

climate change

demand development

technological development

political commitments

Association EURATOM-ÖAW – Annual Report 2013 – Coordinated Activities on Power Plant Physics and Technology - Socio-Economic Research on Fusion

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ETM scenarios are addressing these aspects in the possible future development of the global energy system. Fusion power is one possible future technology amongst others. The scope of the ETM scenario analysis is to show how it would evolve under different circumstances.

Figure 1. Anlysis of policy scenarios with EFDA Times

In 2013 a prototype of an internet platform for ETM - which is at present only available as a draft and not yet accessible for the public - was developed to provide general information about future energy scenarios obtained with the EFDA-TIMES model. Information will be provided about the underlying methodology and assumptions used. It will be possible to download previous analyses and there will be an interactive section where the distribution of energy sources can be looked up by world region, year and scenario (with different model assumptions, e.g. CO2 reduction policies).

2. OUTLOOK FOR 2014

M. Biberacher et al. intend to continue their research and dissemination activities in Horizon 2020 in the framework of the European joint fusion research programme.

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ABBREVIATIONS AND ACRONYMS

Institutes and organizations

ATI / TU WIEN Institute of Atomic and Subatomic Physics, Vienna University of Technology

CCFE Culham Centre for Fusion Energy

CIEMAT Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas, Madrid, Spain

CNRS Centre National de la Recherche Scientifique, Paris, France

CREATE Consorzio di Ricerca per l'Energia e le Applicazioni Tecnologiche dell'Elettromagnetismo, Naples, Italy

DRFC/CEA Cadarache

Département de Recherche sur la Fusion Contrôlée/Commissariat à l'Energie Atomique, Cadarache, France

DTU Technical University of Denmark

EFDA European Fusion Development Agreement

EPA/CRPP Ècole Polytechnique Fédérale de Lausanne, Centre de Recherches en Physique des Plasmas, Lausanne, Switzerland

EPS European Physical Society

FZ Jülich Forschungszentrum Jülich, Germany

F4E The European Joint Undertaking for ITER and the Development of Fusion Energy (“Fusion for Energy”)

HAS Hungarian Academy of Sciences, Budapest

IAEA International Atomic Energy Agency

IAP/TU Wien Institute of Applied Physics, Vienna University of Technology

IFPN/IST Instituto de Plasmas e Fusăo Nuclear/Centro de Fusão Nuclear/Instituto Superior Técnico, Lisbon, Portugal

IPP Garching Institut für Plasmaphysik Garching, Germany

IPP.CR Institute of Plasma Physics, Academy of Sciences of the Czech Republic, Prague

ITP-TUG Institut für Theoretische Physik – Computational Physics, Graz University of Technology

JAERI Japan Atomic Energy Research Institute

KINR Kiev Institute for Nuclear Research

KKKÖ Commission for the Coordination of Fusion Research in Austria at ÖAW, Vienna, Austria

MEdC Ministry of Education, Research and Youth, Bucharest, Romania

MESCS Ministry of Education, Science, Culture and Sport, Slovenia

NIFS National Institute for Fusion Science, Gifu, Japan

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ÖAW Austrian Academy of Sciences, Vienna

ÖAW-ESI Erich Schmid Institute of Materials Science at ÖAW, Leoben, Austria

UIBK University of Innsbruck

European networks

ADAS-EU Atomic Data and Analysis Structure for Fusion in Europe

FUSENET European Fusion Education Network

Fusion experiments

AUG ASDEX Upgrade, facility at IPP Garching

COMPASS-D Tokamak at the Institute of Plasma Physics of the Czech Academy of Sciences, Prague

CHS Compact Helical Device, NIFS, Japan

DIII-D Tokamak developed by General Atomics, San Diego

EAST Experimental Advanced Superconducting Tokamak (Hefei, China)

HSX Helically Symmetric Stellarator, University of Wisconsin,Madison,USA

ITER “The way” (under construction at Cadarache, France)

JET Joint European Torus, UKAEA, Culham, UK

JFT-2M Jaeri Fusion Torus – 2M, Tokai-mura, Japan

LHD Large Helical Device, NIFS, Japan

NSTX National Spherical Torus Experiment, Princeton Plasma Physics Laboratory, USA

RFX Reverse Field Pinch experiment, Padova, Italy

TCV Tokamak à Configuration Variable, CRPP, Lausanne, Switzerland

TFTR Tokamak Fusion Test Reactor, Princeton Plasma Physics Laboratory, USA

W7-X Wendelstein 7-X stellarator, IPP, Greifswald, Germany

Scientific and technical abbreviations

AES Auger electron spectroscopy

AMNS data atomic, molecular, nuclear and surface data

BCC metals body-centered cubic metals

BES beam-emission spectroscopy

CPO consistent physical object

CTMC calculations classical trajectory Monte Carlo calculations

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DEA dissociative electron attachment

DED dynamic ergodic divertor

DKES drift kinetic equation solver

DM formalism Deutsch-Märk formalism

ECCD electron cyclotron current drive

ECE electron cyclotron emission

ECRH electron cyclotron resonance heating

EDX energy dispersive X-ray analysis

EEDF electron energy distribution function

EFDC error field correction coils

ELMs edge-localized modes (short, recurrent instabilities of the edge plasma)

ETB external transport barrier

ETS European transport solver

H&CD heating and current drive

HPT high-pressure torsion

ICRF ion cyclotron resonant frequency

ICRH ion cyclotron resonant heating

ITB internal transport barrier

ITER CS ITER central solenoid

ITER TFMC ITER toroidal field model coil

ITM Integrated Tokamak Modelling

KER kinetic energy release

LCFX last closed flux surface

LHCD lower hybrid current drive

LHW lower hybrid waves

MCC Monte Carlo collisions

MHD magneto-hydrodynamics

NBI neutron beam injection

NPA neutral particle analyzer

NRA nuclear reaction analysis

NTM neoclassical tearing mode

NTV neoclassical toroidal viscosity

PDF probability density function

PIC simulation particle-in-cell simulation

PPM parts per million

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PSI data plasma-surface interaction data

PWI Plasma Wall Interaction

PWT plasma wall transition

QCM quartz crystal microbalance

RF heating radio-frequency heating

RFA retarding field analyzer

RMP resonant magnetic perturbation

RRR residual resistance ratio

SANS small-angle neutron scattering

SEM scanning electron microscope

SOL scrape-off layer

SPD severe plastic deformation

TAE toroidicity-induced Alfvén Eigenmodes

TES translational energy spectroscopy

UHV ultra-high vacuum

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AUSTRIAN REPRESENTATIVES IN EUROPEAN COMMITTEES RELEVANT FOR FUSION RESEARCH AND DEVELOPMENT (2013)

Consultative Committee on Fusion (CCE-FU) / Fusion Expert Group

Dr. Daniel Weselka Federal Ministry of Science and Research Mag. Volker Holubetz Federal Ministry of Forestry and Agriculture, Environment and

Water-Economy Univ.Prof.Dr. Friedrich Aumayr Institute of Applied Physics / Vienna University of Technology

EFDA Steering Committee

Univ.Prof.Dr. Friedrich Aumayr Institute of Applied Physics / Vienna University of Technology Dr. Daniel Weselka Federal Ministry of Science and Research

Governing Board of Fusion for Energy

Univ.Prof.Dr. Harald W. Weber Institute of Atomic and Subatomic Physics / Vienna University of Technology

Dr. Daniel Weselka Federal Ministry of Science and Research

F4E Administration and Finance Committee

Mag. Monika Fischer Austrian Academy of Sciences

Public Information Network

Mag. Monika Fischer Austrian Academy of Sciences Mag. Elisabeth Wieninger Austrian Academy of Sciences

Members of expert groups, contact persons

Expert group Contact person Organization

EFDA Task-Force Plasma-Wall Interaction

Univ.Prof.Dr. Friedrich Aumayr Institute of Applied Physics / Vienna University of Technology

EFDA Task-Force Integrated Tokamak Modelling

Dr. David Tskhakaya Institute for Theoretical Physics / University of Innsbruck

JET Administrative Contact Person


Remote Participation Mag. Monika Fischer

Austrian Academy of Sciences

Intellectual Property Rights (IPR)


Industrial Liaison Officer Mag. Maria Ratzinger Austrian Federal Economic Chamber

High-Performance Computers

Dr. David Tskhakaya Institute for Theoretical Physics, University of Innsbruck

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CONTACT INFORMATION

Austrian Academy of Sciences, ÖAW-EURATOM Coordination Office Kegelgasse 27/13, 1030 Wien Tel.: +43-1-51581-2675, 2676

Monika Fischer [email protected] Elisabeth Wieninger [email protected] Friedrich Aumayr [email protected]

Institute for Theoretical Physics, University of Innsbruck Technikerstraße 25, 6020 Innsbruck Tel.: +43-512-507-52206, 52210 Fax: +43-512-507-2919

Siegbert Kuhn [email protected] David Tskhakaya [email protected] Klaus Schöpf [email protected]

Institute of Theoretical and Computational Physics, Graz University of Technology Petersgasse 16, 8010 Graz Tel.: +43-316-873-8182 Fax: +43-316-873-108182

Winfried Kernbichler [email protected] Martin Heyn [email protected]

Institute of Applied Physics, Vienna University of Technology Wiedner Hauptstraße 8-10, 1040 Wien Tel. +43-1-58801-13430 Fax: +43-1-58801-13499

Friedrich Aumayr [email protected]

Institute of Ion Physics and Applied Physics, University of Innsbruck Technikerstraße 25, 6020 Innsbruck Tel.: +43-512-507-52720, 52730, 52660, 52740 Fax: +43-512-507-2922

Alexander Kendl [email protected] Michael Probst [email protected] Paul Scheier [email protected] Roman Schrittwieser [email protected]

Institute of Atomic and Subatomic Physics, Vienna University of Technology Stadionallee 2, 1020 Wien Tel.: +43-1-58801-141552, 142102, 141540, Fax: +43-1-58801-14199

Michael Eisterer [email protected] Helmut Leeb [email protected] Harald W. Weber [email protected] Erich-Schmid Institute of Materials Science, Austrian Academy of Sciences Jahnstr. 12, 8700 Leoben Tel.: +43-3842-804308 Fax: +43-3842-804116

Reinhard Pippan [email protected]

Research Studios Austria Forschungsgesellschaft mbH Leopoldskronstraße 30, 5020 Salzburg Tel.: +43 (0) 662 908585 – 221 Fax: +43-662-908585-299

Markus Biberacher [email protected]

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Meetings

Meeting of the Steering Committee: Austrian Academy of Sciences, 11 June 2013

28th Association Day: Salzburg, 18 October 2013

Austrian Academy of Sciences (ÖAW)

EURATOM European Fusion

Programme EU Commission

DG RTD, Research and Innovation

KKKÖ Commission for the

Coordination of Fusion Research in

Austria at ÖAW (national advisory

body) Chair: P. Steinhauser

Steering Committee

EURATOM ÖAW S. Webster H. Denk A. Iorizzo A. Rebhan M. Pipeleers T.D. Märk

HRU: F. Aumayr Deputy HRU: A. Kendl

M. Eisterer

ÖAW-EURATOM Coordination Office: M. Fischer, E. Wieninger

Scientific Programme in 2013: Coordinated Activities in ITER Physics (2 EFDA Task Agreements)

Power Plant Physic and Technology (3 EFDA Task Agreements) Participation in JET (1 order)

ASSOCIATION EURATOM-ÖAW: MANAGEMENT STRUCTURE IN 2013

EFDA Task Forces and Topical Groups

Back cover: 28th Association Day, Salzburg, 18 October 2013 Photo: Fusion@ÖAW

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