A high intensity polarized electron source with on-line polarization analysis
Hodge, Lee Allen
Walters, G. King
Master of Arts
This thesis describes the design, construction and operation of an intense source of polarized electrons suitable for application to most proposed scattering experiments. Polarized electrons are produced in a flowing helium afterglow apparatus by chemiionization reactions involving optically pumped helium 2 S metastables. These electrons are electrostatically extracted from the flow tube and formed into a beam. The electron spin polarization is measured by a unique "on-line" Mott scattering polarization analyzer designed and constructed as an integral source component. In this thesis, applications for a polarized electron beam are reviewed and a comparison of the best available sources is made. The operation of the optically pumped flowing helium afterglow source is described in detail and current and polarization performance characteristics are reported: .1 pA at 5% polarization; 1 juA at 45%; 5 juA at 3% and 1 JJA at 2%. Measurements of the beam emittance show it to be very low (2 mrad-cm at 4 eV). Significant advantages of this source are the ease of electron spin reversal or modulation without a change in beam trajectory and the novel "on-line" Mott detector which allows simultaneous polarization analysis and low energy beam use. Several proposed experiments are suggested with a report on progress to date.