Link do spotkania: https://tiny.pl/96d35

Fast electron dynamics in tokamak plasmas with high-Z impurities
Dr Krzysztof Król
Institute of Nuclear Physics Polish Academy of Sciences, Kraków, Poland

PhD thesis prepared in the framework of IFJ PAN and IRFM CEA collaboration under supervision of Dr hab. Marek Scholz,
Dr hab. Didier Mazon, Dr hab. Yves Peysson and Dr Axel Jardin

In order to avoid the tritium retention issue experienced with carbon walls, the divertor of the International Thermonuclear Experimental Reactor (ITER) will be made of tungsten (W). However, this means that small concentrations of tungsten impurities will be present in the ITER plasma. They are sufficient to significantly affect the operation of the tokamak, sometimes even leading to the termination of the plasma discharge. In particular, a critical issue that needs to be investigated is the effect of high-Z impurities on the dynamics of fast (suprathermal) electrons. This issue arises when considering either the mitigation of a runaway electron beam in a post-disruptive plasma or a suprathermal electron population generated with a current drive method, using, e.g. Lower Hybrid (LH) waves. So far, the main focus has been put on relatively low-Z impurities such as carbon, nitrogen or argon. However, it is now necessary to extend the methods of studying the dynamics of fast electrons to heavier impurities such as krypton, molybdenum or tungsten. Consequently, it is necessary to consider the so-called partial screening effect during the interaction between impurity ions and fast electrons in a plasma. This goal has been achieved by consistently incorporating the partial screening theory into kinetic and non-thermal bremsstrahlung calculations. A particular emphasis is placed on the consequences of high-Z non-fully ionized impurities on LH current drive and the fast electron bremsstrahlung intensity on WEST.

This PhD work has been partially funded by the National Science Centre, Poland (NCN) grant HARMONIA 10 no. 2018/30/M/ST2/00799. I thank the PLGrid project for computational resources on the Prometheus cluster. This work has been carried out within the framework of the EUROfusion Consortium and has received funding from the Euratom research and training programme 2014-2018 and 2019-2020 under grant agreement No 633053. The views and opinions expressed herein do not necessarily reflect those of the European Commission.

The author would like to thank the members of the HARMONIA project: Didier Mazon, Yves Peysson, Marek Scholz, Jakub Bielecki, Axel Jardin, Dominik Dworak and Jędrzej Walkowiak, for the possibility of taking part in the project, help and many inspiring discussions. The author would also like to thank the members of the NZ61 department of IFJ PAN as well as the WEST team.