Highlights 2011

Research news from the division Plasma Edge and Wall

Most Cited Articles in Journal of Nuclear Materials
(21.11.2011)

The review article by J. Roth et al. on “Recent analysis of key plasma wall interactions issues for ITER” with many international co-authors including several from IPP is currently the most cited article published in the last 5 years in the Journal of Nuclear Materials.

Published in the PSI Proceeding of PSI-19 in 2009, the article was until December 5, 2011 cited in 101 articles.

Joachim Roth, E. Tsitrone, A. Loarte, Th. Loarer, G. Counsell, R. Neu, V. Philipps, S. Brezinsek, M. Lehnen, P. Coad, Ch. Grisolia, K. Schmid, K. Krieger, A. Kallenbach, B. Lipschultz, R. Doerner, R. Causey, V. Alimov, W. Shu, O. Ogorodnikova, A. Kirschner, G. Federici, A. Kukushkin and EFDA PWI Task Force, ITER PWI Team, Fusion for Energy, ITPA SOL/DIV

Journal of Nuclear Materials, 390-391 (2009) 1-9:
Recent analysis of key plasma wall interactions issues for ITER

New scaling for divertor peak power loads confirmed at JET and ASDEX Upgrade.
(20.09.2011)

One of the major challenges on the way to a fusion reactor is the power exhaust in the divertor where the plasma interacts with the so called plasma facing components. These components are highly optimized to withstand  peak power loads in the range of 10 - 20 MW/m2. Therefore a reliable extrapolation of the power loads in present experiments to that in future devices is  crucial. A first-order approximation which uses the ratio of the power produced by the fusion reaction and the size of the power exhaust area was not sufficiently understood to be extrapolated to a large future device. In particular understanding was missing about the transport processes determining the radial width of this area.

Joint experiments by the scientific teams at the fusion devices ASDEX Upgrade in Garching and JET in Oxford have now improved the database which can be used to scale to larger devices. These experiments involved dedicated power exhaust studies and made use of state-of-the-art thermographic infra-red systems. The most important property of the resulting scaling is that the power exhaust area increases only linearly with the dimension of the device. Further dependencies were also found on the magnetic field itself and the plasma current, both important parameters for efficient magnetic confinement. These experimental results were compared in close collaboration with the Princeton Plasma Physics Laboratory to a transport model, providing a theoretical basis for the experimental result.

A fusion reactor will need to have a major radius of 6 meters or more to sustain the fusion process and will therefore be about 2 - 4 times larger than the two largest experiments in Europe, ASDEX Upgrade and JET. As a result, the peak power fluxes would exceed a value of 10 - 20 MW/m2 in large reactor-like devices. This finding motivates intensive research of techniques to reduce the peak power flux by additional means like radiative power exhaust or the application of resonant-magnetic perturbations to increase the plasma boundary region and so the power exhaust area. Both topics are priority areas of experimental research in ASDEX Upgrade.

The results have been published in T. Eich et al., Physical Review Letters 107 (2011), 215001.

 

Successful organization “13th International Workshop on Plasma-Facing Materials and Components for Fusion Applications / 1st International Conference on Fusion Energy Materials Science”
(13.05.2011)

One of the most important conferences in the field of plasma-loaded materials for the first wall of fusion devices was held in Rosenheim from 9 – 13 May. The conference, organized by E2M, was at the same time an event of the EU project FEMaS - Fusion Energy Materials Science, which has as a primary goal the integration of new characterization methods  for fusion materials into the international community of fusion materials researchers. The first day of the conference was dedicated to eight tutorial talks, aiming at an overview on plasma-material interaction, both for newcomers to the field, but traditionally also appreciated by old-stagers. The subjects ranged from basic processes of plasma-wall interaction through radiation effects in fusion materials and component test procedures, to the construction of components for the first wall of ITER. And for the first time topics of materials characterization were also a key aspect: modern methods of materials characterization with synchrotron and neutron sources, latest techniques of transmission electron microscopy as well as micro-mechanical test methods and analyzing techniques specially adjusted to first wall material.

With more than 280 participants the conference reached the best turnout ever. In 35 plenary talks current developments in the focal topics of wall materials and components were presented. The subjects ranged from “Diagnostics and Dust”, “First Wall Research at JET”, “Hydrogen Retention” and “Impurity Transport” through “Beryllium as First Wall Material” and “Tungsten under High Heat Loads” to “New Materials Concepts” and “Advanced Characterization Techniques”. In addition to that about 200 posters were presented in Rosenheim. The proceedings of the conference will be published as a special issue of Physica Scripta with more than 80, released papers still in 2011. Due to the continuously increasing numbers of participants at the conference it was renamed. The next “International CONFERENCE on Plasma-facing Materials and Components” will be held at the Forschungszentrum Jülich in spring 2013. From now on Wolfgang Jacob and Christian Linsmeier will be program committee members representing the IPP.