High-flux beam source of fast He*(21S) atoms in the 0.2–5 eV energy range

Abstract
A very intense source of metastable helium atoms has been obtained using two helium discharges in series: a high‐pressure arc, which can only produce He*(23S) beams, sustains a low‐pressure arc where the He*(21S) atoms are generated. This double arc source yields total metastable helium fluxes of several 1015 s−1 sr−1. The singlet component reaches about 30%, and the kinetic energy ranges from 0.2 to 5 eV corresponding to velocities from 3000 to 16000 m/s. The velocity distribution can be varied by the pressure and the current in the arcs.