Perspective of analogy between heat loads and impurity production in L-mode discharges with ICRH in WEST

摘要

This study compares experimental observations on plasma surface interactions and heat loads induced by Ion Cyclotron Resonance Heating (ICRH) in WEST medium size tokamak. When powering ICRH, core contamination by metallic impurities systematically results in an increase of the power radiated, often hardening the achievement of long discharges in H-mode at high power. The radiofrequency (RF) sheaths are excited mainly at proximity of ICRF antennas, resulting in an increase of metallic impurity sources. In the presence of RF sheaths, we show that most of the power reaching the wall can become carried by ions. Therefore, both heat loads and material sputtering are the result of ion fluxes on the various plasma facing components, such that some analogy between both phenomena can be made. By combining infrared with spectroscopic measurements, we show experimental evidences from WEST of RF-induced heat fluxes and their correlation with local production of impurity.