Isotopic effects in hydrocarbon formation due to low-energy H+/D+ impact on graphite

摘要: Recent developments with gaseous divertors in tokamaks have led to prospects of less energetic ion bombardment (10's eV) material surfaces the divertor region. The present experiments were undertaken objective studying hydrocarbon formation due H+/D+ impact on graphite for energies extending down 10 eV range. Mass spectrometry residual gas was used measure rates as a function pyrolytic temperature (300–1000 K) and energy (10–200 eV/H or D) mass-analysed H3+ D2+ beams (1018 H+(D+)/m2 s) providing unique opportunity also investigate isotopic effects. results indicate that, is reduced, reduction maximum chemical yield (Ym) observed broadening dependence profile leads significant erosion low-energy at room temperature. room-temperature methane total yields display maxima about 50 decrease further reduced. Where kinetic effects are expected affect process, viz., low ( eV)/near Tm, an ratio, YD/YH 1.5–2 measured. Under all other conditions studied, this ratio near unity. Furthermore, it evident that dominating mechanisms (<100 differ from those occurring higher impact.