ELM transient replication using pulsed plasma in Magnum-PSI

Abstract

Plasma-wall interactions are one of the major challenges for the next-generation fusion reactor, ITER. On top of the high steady-state plasma flux, transient events such as Edge-Localized Modes (ELMs) will cause regular transient heating of the surface, and are expected to reduce the lifetime of the divertor and the performance of the plasma. To assess the damage of ELMs on the wall material, a new experimental setup has been developed that can superimpose periodic high density heat and particle fluxes on a steady-state plasma flux by discharging a capacitor bank array through the source of the Magnum-PSI linear plasma device. In this thesis, this setup will be characterized and the response to tungsten targets due to pulsed plasmas on the surface will be presented.The system was shown to dissipate 80% of the stored energy in the plasma, while resembling the pulse duration, approximately 1 ms, and shape as expected for an ELM in ITER. The peak electron temperature and density obtained during a pulse, close to the target, were 6.8 eV and 12x1020m-3, respectively. The peak heat flux on the target surface due to the transient increase of plasma parameters was found to be 180 MWm-2 with corresponding energy flux of 60 kJm-2. Although the peak values are currently lower than the values expected for ITER-like ELMs, it is shown that with higher B-field the required conditions will be met. Through several experiments on tungsten targets, such as monoblocks designed for the ITER divertor, it is shown that the combined transient increase of both particle and heat flux will lead to different effects compared to other ELM replication experiments. The pulsed plasma system could therefore serve in the future as an important facility to test components planned for the ITER design.

Date of Award	31 Jul 2013
Original language	English
Supervisor	Gregory C. De Temmerman (External coach) & Niek Lopes Cardozo (Supervisor 1)