Improved low-energy, electron-spin-polarized 4He+ ion source

Recent improvements to a source of electron-spin-polarized 4He+ ions based on an optically pumped, rf-excited helium discharge are described that have resulted in ion polarizations P+ of ∼0.18 at currents of ∼1 nA and in an increase of over an order of magnitude in the quality factor P+2I.