The relative yields of trace-element-carbide anions from a Cs+-sputtered graphite target and their use for evaluating the long-term ion source memory in AMS

Abstract

Abstract Using a solid graphite sample the relative yields of trace-element-carbide molecular anions, containing between 1 and 8 carbon atoms (MC1−8−), from a Cs+ sputter ion source were surveyed for elements (M) across the periodic table. Except for gaseous and radioactive atoms, all elements are present in the graphite at some trace levels, so this investigation could readily be done using AMS by counting unambiguously a selected Mq+ ion, with charge state q\u202f≥\u202f3, from a MCn− ion beam injected into the accelerator. MC1,2− are found to be the most prolific carbide negative ions for the majority of elements, but Cs is clearly exceptional as CsC4,6,8− are the dominant ones instead. These results are consistent with past observations. Based on the same MC1−8− survey data, the relative elemental abundances in the graphite sample were also assessed. These abundances demonstrated a means for evaluating the basic long-term ion source memory background for any rare atom searches by AMS.