Fusion Science and Technology / Volume 41 / Number 3P2 / May 2002 / Pages 919-923
Material Interaction and Permeation / Proceedings of the Sixth International Conference on Tritium Science and Technology Tsukuba, Japan November 12-16, 2001
In view of benefits expected from the employment of membranes for particle control in fusion devices and for separation of hydrogen from its mixtures with hydrocarbons, the behavior of a Pd sample is investigated in a plasma-membrane device with a graphite target. The permeation of hydrogen through a 0.2 mm-thick Pd membrane with clean surfaces was found to be limited by the bulk diffusion. An incident flux of hydrocarbon radicals (approx. 2×1012 cm−2s−1) in hydrogen plasma forms no carbon layer on the Pd surface. Applying of a negative bias to the target gives rise to target sputtering, and to the deposition of carbon onto the membrane surface. The formation of carbon layer results in a decrease of the absorption probabilities of both H2 molecules and H atoms. The effect of the deposition of carbon is found to depend non-monotonically on membrane temperature.