An Overview of Electron Polarimeters and AN Intercomparison

Electron beam polarimetry may be described as the technique of separating scattered particles for detection using some physical interaction between the polarization of the electron beam and the total analyzing power of a target. The target is itself polarized in many polarimeter designs. A careful intercomparison of the relative analyzing power of five electron beam polarimeters was performed at the laboratory during a dedicated two day machine development period. A Wienstyle spin manipulator at the injector was used to vary the spin orientation of the electron beam at each polarimeter. A series of measurements as a function of spin orientation provides determination of the relative analyzing power of each polarimeter, and more importantly, quantifies the instrumental systematics that help realize high precision absolute electron polarimetry. In addition, a comparison of the value of the injector spin angle that provides precise longitudinal beam polarization at each experimental hall leads to an independent and potentially high precision absolute measurement (dE/E~10^-4) of the final electron beam energy. Discussion of the experiment will be presented.