Re-Emission of Ionically Pumped Helium by Helium Ion Bombardment

Abstract

Measurements have been made of the release of ionically pumped helium gas when the metal is bombarded with helium ions. The re‐emitted helium is distinguished from the bombarding helium by the use of a mass spectrometer and by using either He3 as the bombarding atom and He4 as the trapped atom, or vice versa. The data are presented as a function of: (1) the amount of gas initially trapped, (2) the number of bombarding ions, (3) the initial kinetic energy of the trapped atoms, and (4) the kinetic energy of the bombarding ions. Comparison of these data with those obtained using krypton as the bombarding ion is made and indicates quite different behavior in the two cases. A replacement mechanism is more consistent with the data where helium is the bombarding ion. The corresponding data using krypton had been satisfactorily explained by sputtering of the metal target.