Synergistic effects of high heat loading and helium irradiation of tungsten

High heat flux experiments using a helium beam have been carried out on powder metallurgy tungsten. The energy of He is 19keV. He beam flux and heat flux at the beam center is 2.0 x 10(21) He/m(2)s and 6.0 MW/m(2), respectively. Beam duration is 3.0-3.9s and interval of beam shot start is 30s. The samples are irradiated up to a fluence of 10(22)-10(24) He/m(2) by the repeated irradiation pulses. In addition to the He beam irradiation, high heat flux experiments using hydrogen and electron beams have also been carried out on the samples. After the irradiation, surface modification by the irradiation has been investigated. Surface modification by helium and hydrogen beams is completely different from results of electron beam heating. In particular, helium beam heating causes remarkably surface modification such as a fine-scale rough surface at a peak temperature above 2400degreesC. (C) 2004 Elsevier B.V. All rights reserved.