Electron beam treatment of tungsten mock-ups

To simulate thermal loads in ITER several tungsten (W) water cooled mock-ups were treated by a scanning electron beam (Tsefey-M) at a heat flux up to 1.68 GW m⁻² for a duration of 18 μ s and a frequency about 30 kHz. Surface morphology, chemical composition, structure, and microhardness of formed W layers were analyzed by SEM, EPMA, XRD, OM, and Vickers hardness tester. The irradiation treatment resulted in W melting to a depth of 0.3 mm, increasing sub-surface grain sizes, grain ordering in the metal bulk, deep cracking, and decreasing of microhardness to a depth of 2–4 mm. Installation of the pre-damaged W samples in a tokamak Globus-M divertor did not change practically discharge conditions. (paper)