Annual Report 2013 Annual Annual Report 2013
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Max-Planck-Institut für Plasmaphysik Annual Report 2013 Annual Annual Report 2013 Max-Planck-Institut für Plasmaphysik EURATOM Association Photo: Photo: Bernhard Ludewig One of the final stages of assembly at Wendelstein 7-X: the plasma vessel components Annual Report 2013 Imprint Max-Planck-Institut für Plasmaphysik (IPP) Boltzmannstraße 2, D-85748 Garching bei München phone +49 89 3299-01, [email protected] www.ipp.mpg.de Editorial Team Julia Sieber Andrea Henze Further Information This work was performed under the terms of the agreement between the Max-Planck-Institut für Plasmaphysik (IPP) and the Euro pean Atomic Energy Com mu nity (EURATOM) to conduct joint research in the field of plasma physics. All rights reserved Reproduction – in whole or in part – subject to prior written con sent of IPP and inclusion of the names of IPP and the author. Printing Lerchl Druck, Freising 2013 Copyright by IPP Printed in Germany ISSN 0179-9347 Annual Report 2013 The Max-Planck-Institut für Plasmaphysik is an institute of the Max Planck Gesellschaft, part of the European Fusion Programme (Euratom) and an associate member of the Helmholtz- Gemeinschaft Deutscher Forschungszentren. In Greifswald, the assembly of IPP’s superconducting stellarator Wendelstein 7-X has reached the home stretch. Once the last weld seam on the module connections was closed in June 2013, the focus of the assembly work was on the completion of the in-vessel components, the current leads and the peripheral installations. The often arduous installation of in-vessel components is slowly but steadily progressing, and the final assembly of the last four current lead pairs is nearing completion. Mean - while, space in the torus hall is becoming a scarce and precious commodity, since the remaining steel structures and both ECRH towers are now in place. The preparation for the next big work package, the commissioning of the machine, has also gained considerable momentum; first commissioning works are scheduled for the second quarter of 2014. The very fruitful national and international colla - bo rationscontinue to be an important asset of the project. Karlsruhe Institute of Technology remains an important partner in the development of plasma microwave heating. Forschungszentrum Jülich is developing numerous plasma diagnostic tools and intends to make a significant contribution to the physics programme. The five trim coils for controlling the magnetic field configuration on the plasma Photo: IPP, Stefanie Graul boundary, contributed in kind by the Princeton Plasma Physics Laboratory, have been installed. Work on the ASDEX Upgrade tokamak at IPP’s Garching site continues its strong focus on clarifying fusion plasma physics relating to the operation and scientific exploitation of ITER. A series of expe - ri ments conducted in 2013 showed that the ITER operational point envisaged might not be readily accessible with a metal wall since confinement tends to be degraded relatively to the ITER prediction, and recipes for ELM mitigation, i.e. pellet triggering and RMP suppression, have typically been de - veloped for higher edge safety factor and are not readily transferable. This is in line with findings from JET, where scientists from the ASDEX Upgrade team are contributing significantly to the progress, which encounters similar restrictions when operating with full-metal wall. However, work on ASDEX Upgrade suggests that the margin for ITER reaching its Q=10 goal can be significantly enhanced by drawing benefit from improved confinement at higher normalized plasma pressure and the possibility of ope rating at higher normalized plasma density. On the other hand, studies conducted in He plasmas to mimic the non-nuclear operation of ITER boost confidence that these can serve the goal of com mis - sioning the machine in a relevant operational regime. As preparation for the study of fast-particle physics on ITER, closely related to the goal of dominant self-heating, the set of diagnostics for the fast ion distribution function was further extended on ASDEX Upgrade, and the measurements allow quantitative comparison with theory. For example, slowing- down of fast particles was found to be comparable to neoclassical predictions as long as no MHD activity is present; the latter was shown to lead to significant enhancement of the radial transport of the fast particles as they slow down. An extensive set of reflectometry diagnostics was installed on ASDEX Upgrade in order to enhance the capabilities for turbulence and transport studies, together with EU partners. Core fluctuation mea - sure ments are closely compared with gyro-kinetic GENE simulations to study transitions between different regimes of turbulence. Transport studies at the plasma edge further support the importance of neoclassical theory in determining the radial electric field and current diffusion. As possible ELM trigger, neoclassical tearing modes were identified which couple to ballooning modes to drive them unstable. A finite-ion-temperature model for blob propagation was developed and successfully com- pared with measured blob sizes and radial velocities. Simulations improved in reproducing key obser - va tions related to divertor detachment. The strong radiation from the X-point region as a consequence of nitrogen seeding is reproduced. The code package for simulating impurity migration was advanced and basic atomic data for nitrogen-tungsten surface interaction obtained from laboratory experiments will be used to analyse nitrogen migration studies conducted in 2013 on ASDEX Upgrade and JET. Hydrogen retention in tungsten was shown to depend strongly on the degree of damage. Retention appreciably increases in damaged regions and saturates at intermediate damage levels. Benign be - hav iour of pre-melted tungsten tiles in high-power discharges was found. A steel programme using EUROFER components on ASDEX Upgrade, accompanied by laboratory experiments, was initiated. The ITER-like wall exploitation on JET continued for a few months in 2013, yielding one of its most significant results. Successful operation in general and, in particular, the specific experiment in which operation was successfully demonstrated after deliberate production of a shallow layer of molten tung - sten, together paved the way towards a positive recommendation of the ITER Advisory Committee to begin with a full-tungsten divertor in ITER. This decision was approved by the ITER Council at the end of November and will allow optimal preparation of early ITER operations with a substantial reduction of the investment costs. Efforts by the ITER cooperation project at IPP continued with major contributions to the development of heating systems, diagnostics and plasma control as well as theoretical investigations. The ELISE test facility successfully investigated basic operation parameters and then started operation in caesium, achieving high current densities at relevant parameters. The contributions to the consortium for the development of the ITER ICRF antenna and to the consortium for the ECRH upper launcher continue. For the latter a performance analysis demonstrated crucial operation parameters. Within the Framework Partnership Agreement for the ITER diagnostics pressure gauge work started with detailed project planning and system analysis. The agreement on the development of the ITER bolometer diagnostic was finally awarded to the ITERBolo consortium, headed by IPP. Meanwhile, R&D efforts as part of a nationally funded project have been successfully concluded. For the development of the plasma control system simulation platform for ITER, a prototype of the main components was successfully demonstrated at ITER. Furthermore, IPP finalised a study of the effects of ELMs on ITER performance and demonstrated that tungsten erosion from the target under ITER-controlled ELM conditions pre - sents very little danger to the plasma. Work at our theoretical divisions supports the experimental activities and paves new ways in funda- mental plasma physics. In 2013, a substantial computational effort helped to clarify the “shortfall mystery” in tokamak transport theory. For several years, it has appeared that the best theoretical models available are unable to explain the transport observed in the edge region of L-mode plasmas, triggering a worldwide debate on the applicability of these models. However, the latest, very extensive, computer simulations at IPP now suggest that there is in fact no transport shortfall, and that the ob- servations can indeed be explained by gyrokinetic theory. This is reassuring and creates confidence that extra polations to ITER are reliable. In the field of transport theory, we have also established that some of the most important microinstabilities driving plasma turbulence can be fundamentally dif fe- rent in stellarators to those in tokamaks, and that they can be suppressed by appropriately tailoring the mag netic geometry. On behalf of the Directorate and the Board of Scientific Directors I thank all friends and colleagues for their excellent cooperation and continuous support. Scientific Director Sibylle Günter Content Tokamak Research University Contributions to IPP Programme ASDEX Upgrade . .3 Cooperation with Universities . .113 JET Cooperation . .23 Universität Augsburg AG Experimentelle Plasmaphysik (EPP) . .115 Stellarator Research Universität Bayreuth Lehrstuhl für Theoretische Physik V . .117 Wendelstein 7-X . .29 Technische Universität Berlin Other Activities in Greifswald and Berlin . .59 Plasmaphysik, Plasma-Astrophysik