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 T2 gas through the ion source from source getter to pumping getter and back. The T 2 + beam current was up to 0.66 μA (∼1018T+/m2s) at energies of 50–500 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.