Surface morphology and helium retention on tungsten exposed to low energy and high flux helium plasma

Surface modification and helium retention on powder metallurgy tungsten and plasma sprayed tungsten coated CFC exposed by low energy (100 eV) high flux (3.83×10²¹-1.20×10²² m^-2s^-1) helium plasma have been investigated. Fluence is about 10²⁶ He m^-2. It is found that fine surface morphology change occurs by the helium exposure. There is little difference of the surface modification between the powder metallurgy tungsten and the plasma sprayed tungsten. In the case that the surface morphology do not changed, two helium desorption peak appeared. The amount of desorption of helium is larger than that of deuterium from tungsten under the same exposure condition by heating up to 1273 K by TDS. In the case that fine surface morphology change occurs, desorption peak at high temperature newly appears. Surface modification such as blister is not formed on the surface exposed to helium under the same exposure condition which the blister is formed by deuterium exposure.