The construction and performance of an electron bombardment ion source designed to produce a beam of lowhyphen;energy (100ndash;400 eV) singly ionized helium (He+) with a significant fraction of ions in the metastable 2S1/2state is described. The source operates in the fringe field of a magnet and injects ions along the field lines into the center of the magnet. He+currents of up to 70 mgr;A with small beam energy spread (3 eV) are obtained. A typical metastable fraction is 0.08percnt; for small He+currents (2ndash;5 mgr;A).
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