S9-2
European efforts for addressing long pulses and steady-stateissues of magnetically confined plasmas
X. Litaudon1, R. Albanese2, M. Beurskens3, S. Brezinsek4, F. Castejon5, S. Coda6, A.
Dinklage7, A.J.H. Donné8, T. Eich7, G. Falchetto9, G. Federici8, J. Figueiredo1, J. M. García
Regaña8,15, G. Giruzzi9, J. Hobirk7, L. Horton10, S. Jachmich11, E. Joffrin9, D. Kalupin8, K.
Krieger7, J. Lonnroth1,16, P. Martin11, M.L. Mayoral8, H. Meyer3, A. Murari1, I. M. F.
Nunes13, DC. McDonald8, C. Perez von Thun1, H. Reimerdes6, M. Romanelli3, M. Rubel14, E.
Solano1,5, G. Sips10, M. Turnyanskiy8, I. Voitsekhovitch8, H. Weisen6, F. R. Wenninger8, S.
Wiesen41) EUROfusion PMU, Culham Science Centre, Abingdon, Oxon, OX 14 3DB United Kingdom
2) CREATE-ENEA, Universita di Napoli, Naples, Italy
3) CCFE, Culham Science Centre, Abingdon, UK
4) Forschungszentrum Julich, Julich, Germany5) The National Fusion Laboratory, CIEMAT, Madrid, Spain
6) Ecole Polytechnique Federale de Lausanne, CRPP, Lausanne, Switzerland
7) Max-Planck-Institut fur Plasmaphysik, Garching, Germany8) EUROfusion PMU, Garching, Boltzmannstraße 2, D-85748, Garching, Germany9) CEA, IRFM, F-13108 Saint-Paul-lez-Durance, France10) JET Exploitation Unit, Culham Science Centre, Abingdon, Oxon, OX 14 3DB United Kingdom
11) Laboratory for Plasma Physics, ERM/KMS, Brussels, Belgium12) Consorzio RFX, Padova, Italy
13) Institute of Plasmas and Nuclear Fusion, Lisbon, Portugal
14) KTH Royal Institute of Technology, Stockholm, Sweden15) Max-Planck-Insitut für Plasmaphysik, Greifswald, Germany16) Aalto University, P.O. Box 14100, 00076 Aalto, Finlande-mail of corresponding author: xavier.litaudon@euro-fusion.org
Pursuing the operation of magnetically confined fusion plasmas towards steady-stateis one of the main challenging research areas in magnetic confinement fusion. Steady-state
operation needs to integrate both physics and technological issues, on the route to athermonuclear fusion power plant. With this long term perspective, Europe has elaborated a“Roadmap to the realisation of fusion energy” [1]. The European fusion roadmap sets out apragmatic approach to achieve the goal of generating fusion electricity by 2050 with ademonstration fusion power plant (DEMO). The goal-oriented approach of the EU roadmap isset with eight different missions. The recent European progress and prospects for addressing
issues related to plasma operation, heat exhaust and plasma wall interaction of the long pulse
and steady-state magnetically confined plasmas are reviewed in this paper.
The first issue addresses the sustainment and the control of the magnetic configurationand kinetic profiles. Two lines of research are followed in Europe that rely oni)
the optimization of the tokamak configuration by a combination of selfgenerated bootstrap current complemented with non-inductive external current
drive (Mission 1, ‘Plasma regimes of operation’),ii)
the intrinsically steady-state magnetic configurations, with the stellarator(Mission 8, ‘Stellarator’).
Access conditions and confinement studies of high performance and high beta regimes arestudied in JET and European Medium Size Tokamak experiments with metallic walls (Be/WITER-like wall at JET and W wall in ASDEX-Upgrade). Recent confinement studies inmetallic walls devices are reported [2] together with improved confinement regimes obtained
at high beta [3]. In 2015, Wendelstein 7-X (W7-X) will start its first operation [4]. Its fullscientific exploitation under steady-state conditions achieved beyond 2020 should provide thecrucial milestones for the development of the helical-axis advanced stellarator (HELIAS) line.
W7-X is equipped with superconducting coils and steady-state heating even in its first phasethus providing a versatile test-bed for steady-state developments.
The second issue concerns the development of heat-exhaust systems which must becapable of sustaining the transient and continuous large heat and particle fluxes of a future
fusion power plant (Mission 2. Heat-exhaust systems). The baseline strategy for theaccomplishment of Mission 2 consists of reducing the heat load on the divertor targets byradiating a sufficient amount of power from the plasma and by producing and controlling“detached” divertor conditions. Significant progress has been made on ASDEX-Upgrade
where experiments have explored divertor operation at high Psep/R=10MW/m (~2/3 of theITER value) with a metallic environment [5]. The technology issues related to thedevelopment and tests of actively cooled plasma facing components (PFCs) that should
handle continuous power fluxes in the range of ~10MW/m2 are addressed in specific
European linear plasma devices and in the upgrade Tore Supra tokamak, i.e. the WEST
project. In addition, an aggressive programme to develop alternative divertor magnetic
configuration (e.g. super-X, snowflake) is initiated in TCV [6] and MAST-U [7] and liquid
metals PFCs for the divertor are also explored in e.g. FTU, ISTTOK and Magnum-PSI. The
island and actively-cooled high-heat-flux divertor in W7-X comprehensively completes theasset of European exhaust studies particularly addressing 3D effects. The experimental andmodelling effort should give technical and scientific inputs for an assessment of alternative
divertor geometries and provide the required information for the decision on the parameters ofa possible Divertor Tokamak Test.
Finally, on the route towards long pulse operation, one key issue is to develop, within
the optimised divertor configuration, a PFC solution in a fully actively cooled environment
ensuring a satisfactory control of the density, lifetime of the components, material erosion/codeposition, tritium wall inventory and dust production. Europe contributes significantly on
this issue by operating and testing full metallic PFC solutions in ASDEX-Upgrade and JET.
Significant reduction of deuterium retention and dust production are reported with metallicwalls compared to C walls [8, 9]. In 2016, WEST with an actively cooled W divertor will also
contribute actively to these plasma wall interaction aspects in long pulse conditions.
To conclude, the experimental activity is supported by a coherent and integrated
research programme addressing code development, diagnostics and hardware enhancements
as well as theory with first principle modelling (validation on experiments), stellarator
optimization and modelling, integrated modelling for the preparation, analysis of theexperiments, and finally, the extrapolation towards JT-60SA, ITER and reactor conditions
including the modelling of alternative power exhaust solutions for DEMO.
[1] F. Romanelli et al., Fusion Electricity -A roadmap to the realisation of fusion energy,
European Fusion Development Agreement (EFDA) 2012, ISBN 978-3-00-040720-8
http://www.efda.org/efda/activities/the-road-to-fusion-electricity/[2] M. Beurskens, Marc Plasma Phys. Control. Fusion 55 (2013) 124043[3] C. Challis et al in Proc. 25th IAEA FEC St. Petersburg, Russian Federation, EX/9-3[4] A. Dinklage et al in Proc. 25th IAEA FEC St. Petersburg, Russian Federation, FIP/3-1[5] H. Zohm et al in Proc. Proc. 25th IAEA FEC St. Petersburg, Russian Federation, OV/2-2[6] S. Coda et al Proc. 25th IAEA FEC St. Petersburg, Russian Federation, OV/4-2[7] I. Chapman et al Proc. 25th IAEA FEC St. Petersburg, Russian Federation, OV/2-4[8] S. Brezinsek et al 21st International Conference on Plasma Surface Interactions (PSI2014), Kanazawa, Japan. Submitted to J. Nucl. Mater.
[9] R. Neu et al., J. Nucl. Mater. 438 (2013) S34