HIgh heat flux plasma testing of ITER divertor materials under ELM relevant conditions in QSPA Kh-50

Abstract

Performed studies of plasma-surface interaction include measurements of plasma energy deposited to the material surface and determination of tungsten cracking threshold during repetitive ITER ELM-like plasma exposures in QSPA Kh-50 with plasma pulses of energy density up to 2.5 MJ/m2 and duration of 0.25 ms. The energy threshold for tungsten cracking development is found to be ~0,3 MJ/m2. The Ductile-to-Brittle Transition Temperature (DBTT) is experimentally estimated for ITER relevant tungsten grade. Major crack network (cells size up to 1.3 mm) forms only in cases of initial target temperatures below DBTT. Intergranular micro-cracks network (size of cells corresponds to the grain size) appears under heat loads after melting threshold.