Spin polarized low-energy positron source

[摘要] This paper presents an investigation of spin polarization of positrons from a source based on the decay of22Na isotopes. Positrons are moderated by transmission through a tungsten film and electrostatically focussed and transported through a 90 deg deflector to produce a slow positron beam with polarization vector normal to the linear momentum. The polarization of the beam was determined to be about 10% by comparison with polarized electron scattering asymmetries from a thin Fe film on W(110) at 10-10Torr. Low energy electron emission from Fe layer on W(100) surfaces under positron impact is explored. It is shown that the intensity asymmetry of the electron emission as a function of the incident positron energy can be used to estimate the polarization of the positron beam. Also several materials with long mean free paths for spin relaxation are considered as possible moderators with increased polarization of the emergent positrons.

[发布机构] St. Petersburg State Polytechnical University, St. Petersburg; 195251, Russia^1;Centre for Atomic, Molecular and Surface Physics (CAMSP), School of Physics, University of Western Australia, Perth; WA; 6009, Australia^2

[效力级别] 化学

[关键词] Low energy electrons;Mean free path;Polarization vectors;Positron energy;Positron impacts;Positron sources;Slow positron beam;Spin relaxation