Thermal shock tests of carbon materials with high power beam

In tokamak machines, not only present machine but also future tokamak devices, off-normal events, so called plasma disruption, is considered as unavoidable phenomena. During the plasma disruption, plasma energy will deposit onto the surface of plasma facing components (PFC). Erosion induced by the disruption will be considered as primary limitation factor of life time of the PFCs. To evaluate erosion rate during the disruption, high power beam facilities have strongly been required. JAERI constructed an electron beam test facility to simulate the disruption heat load. The facility can produce an intense electron beam at a heat flux of up to 2000 MW/m2 from 1 ms. Many carbon based materials, which have regarded at most promising armor materials, have been tested at the facility at a heat flux range from 300 MW/m2 to 2000 MW/m2. The erosion depth of carbon-fiber-carbon composites (C/C composites) is ∼ 3 times larger than that of numerical prediction. Carbon based B4C-coated and B4C converted materials which have been developed at JAERI have also tested in the facility. The B4C converted C/C composites show high thermal shock resistance. (author)