Polarized electrons at MIT-Bates

A description of the MIT-Bates polarized electron source will be presented. Improvements to the polarized injector in recent years, including implementation of a multiple gun system, have made delivery of pulsed polarized beams for medium energy experiments routine and trouble-free. The spin orientation from the source is controlled by a Wien filter which has the added benefit of sweeping backstreaming positive ions away from the photocathode surface. The present challenge for the Bates polarized source is an unprecedented set of requirements on the stability and quality of the beam for the SAMPLE parity violation experiment now in progress, including limits on the source lifetime and helicity correlated beam position differences. The current status of the source lifetime is discussed. Recent results in laser beam position differences are presented as is a description of the diagnostics implemented on the laser transport line for fast and accurate measurements of these differences. Finally, we will discuss the plans for using a mode-locked laser system to achieve the higher laser power necessary for the South Hall Ring