Thermal fatigue tests on CVD-W/Cu divertor mock-ups

Tungsten is a promising candidate for plasma-facing materials to cover the surface of the divertor plate in the design of the International Thermonuclear Experimental Reactor (ITER). The Japan Atomic Energy Research Institute (JAERI) has developed divertor mock-ups coated with tungsten using the chemical vapor deposition (CVD) technique. Thermal fatigue and screening tests of ITER-relevant divertor mock-ups carried out in an electron beam gun facility are presented. The two mock-ups consist of a 2 mm thick CVD tungsten layer on heat sinks made of OFHC-Cu and 30 wt.% Cu-infiltrated tungsten, respectively. The cooling channel is equipped with a twisted tape as heat transfer enhancement. Both mock-ups successfully withstood a steady-state deposited heat flux of 5 MW m-2 for 1000 cycles. These experiments show that CVD W-coated divertor mock-ups meet ITER requirements for plasma-facing components. These tests also demonstrate the capability of these mock-ups to withstand a transient deposited heat flux of 22 MW m-2 for 10 s without failure. (orig.)