ITER-relevant transient heat loads on tungsten exposed to plasma and beryllium

Tungsten (W) is presently the most attractive plasma facing material for future fusion reactors. Off-normal transient events such as edge localized modes and disruptions are simulated with a pulsed laser system in the PISCES-B facility, providing pulses with 1–10 ms duration with absorbed heat flux factors up to ~90 MJ m−2 s−1/2. This paper characterizes surface morphology changes and damage thresholds under transient heating on W exposed to He plasma or D plasma with and without Be coatings. W is damaged in the form of grain growth, surface roughening, melting and cracking. With a Be coating on the order of μm thick, the laser pulse produces a variety of Be surface changes including Be–W alloying, vaporization of the Be layer, melting and delamination.