SPUTTERING CHARACTERISTICS OF B4C-OVERLAID GRAPHITE FOR KEV ENERGY DEUTERIUM ION IRRADIATION

Two types of B4C-overlaid graphite (CFC), conversion and CVD B4C, together with bare CFC (PCC-2S) and/or HP B4C, were investigated with respect to erosion yields for 1 keV D+, D2 /CD4 TDS after 1 keV D+ implantation, and thermal diffusivity/conductivity, in a temperature range from 300 to 1400 K. The erosion yields of both conversion and CVD B4C were found to be much lower than that of the bare CFC (PCC-2S), in both chemical sputtering (600-1100 K) and RES (1200-1400 K) temperature regions. The D2 TDS peak of the conversion B4C was found to be located at nearly 200 K lower temperature than that of the bare CFC (PCC-2S), indicating much lower activation energy for detrapping/recombination of trapped D in the conversion B4C and in the CFC. The CD4 TDS peak of the conversion B4C was found to be much weaker in intensity than that of the bare CFC (PCC-2S), in agreement with the present erosion yield results. Thermal diffusivities and conductivities of both the conversion B4C/PCC-2S and the CVD B4C, were measured to be nearly 1/10 of that of the bare CFC (PCC-2S), and to decrease with increasing temperatures.