Interaction of a sub-eV H0 atom beam with carbon: Methane production and hydrogen retention

Abstract

An UHV-compatible, RF discharge, sub-eV H0 source, capable of delivering an H0 beam of high intensity, very low impurity content and good collimation, has been developed. It has been tested on experiments on CH4 production and hydrogen retention on pyrolytic graphite exposed to H0. Previous results obtained by using the H2 backfill method for the production of H0 (i.e. by contact dissociation of H2 on W), which indicated the existence of temperature-induced activation effects in graphite erosion by sub-eV H0, were confirmed. Additionally, retention experiments indicate the possible existence of two different energies for trapping sub-eV H0 in graphite. With the H0 beam flux density used here ( ~ 5 × 1015 H0/cm2·s) the presence of H2 molecules did not affect either the CH4 production due to H0 atoms, or the retention of H0 atoms.