已收录 272983 条政策
 政策提纲
  • 暂无提纲
An intense source of spin-polarized electrons based on an optically-pumped flowing helium afterglow
[摘要] The optimization of an optically-pumped, flowing helium afterglow for use as a high-current dc polarized electron source with high electron spin polarization is described. The atomic electron spins of He (2$sp3m Ssb1$) metastable atoms created by a microwave discharge are aligned in the presence of a weak magnetic field by circularly polarized radiation from a recently developed LNA laser. The polarized outer 2s electrons are liberated in spin-conserving Penning ionization reactions with CO$sb2$ and are extracted from the flow tube for polarization analysis. Polarizations approaching 90% were obtained at currents below.1 $mu$A, falling gradually to 70% at 20 $mu$A. Comparisons with other sources, chiefly photoemission from GaAs, suggest that for most applications requiring dc currents less than 50 $mu$A, the flowing afterglow source is superior. Possible future improvements to the present source are also discussed.
[发布日期]  [发布机构] Rice University
[效力级别]  [学科分类] 
[关键词]  [时效性] 
   浏览次数:3      统一登录查看全文      激活码登录查看全文