Intense Polarized Electron Beams from Optically Pumped Helium Discharges

Spin conservation in ionizing reactions involving optically oriented $2{}_{}{}^3{}_{}{}^{}S_1^{}{}_{}{}^{}$ metastable helium atoms in a helium discharge has been exploited to produce a continous beam of polarized electrons. A beam polarization of (10 ± 0.5)% is measured, with beam current 0.2 μA. Electrons extracted from the pulsed discharge afterglow have polarization (14 ± 0.7)%. The apparatus is simple and versatile, and should be readily adaptable to atomic and nuclear scattering experiments.