Spin polarizations of positron beams generated using electrostatic and magnetic transportation systems with 68Ge and 22Na sources

Abstract

Spin polarizations of electrostatic positron beams generated using 68Ge and 22Na sources with tungsten moderators were 47 % and 30 %, respectively. A comparable spin polarization (27 %) was obtained with much reduced beam diameter (0.5 mm), when electromagnetic lenses, a 22Na source and a tungsten moderator were used. Replacing the tungsten moderator with a solid neon moderator in this system, the beam flux was significantly enhanced with maintaining the spin polarization. The Doppler broadening of annihilation radiation spectra of polycrystalline Fe measured using the above beams showed clear asymmetry upon field reversal.