Low-energy tritium ion erosion of graphite

Chemical erosion of pyrolytic graphite was measured over the temperature range 300-950 K, using a mass-analyzed tritium ion beam. The T-2(+) beam was produced by cycling 10 Ci (1 mg) of T-2 gas through the ion source from source getter to pumping getter and back. The T-2(+) beam current was up to 0.66 mu A (similar to 10(18)T(+)/m(2) s) at energies of 502 500 eV/T+. Hydrocarbon formation rates were measured in the residual gas using quadrupole mass spectroscopy. CxTy hydrocarbon formation yields were similar to those obtained for H+ and D+ (0.002-0.1). As with H+ and D+, the T+-induced yields at 200-250 eV/T+ tend to peak at about 700-800 K, with a shift to lower temperature and flatter distributions at lower ion energies. (c) 2004 Elsevier B.V. All rights reserved.