Carbon Erosion and Dust Formation under Heavy Atomic Hydrogen Irradiation

Experiments on erosion and dust formation on graphite materials have been performed using high power induction plasmas containing high atomic hydrogen flux (∼1024 m-2 s-1 ). Chemical sputtering by atomic hydrogen irradiation with an incident energy below 1 eV eroded the graphite targets significantly, and the sputtering yield was roughly estimated to be 0.002-0.005, which is as high as that obtained by ion beam experiments. The transport of the released hydrocarbon along the gas flow results in carbon dust formation on the eroded graphite target and also on the silicon and graphite targets located at the remote position. The dust structure strongly depends on the target surface temperature, and the graphite dust turns into diamond crystals when the surface temperature rises to 1100 K