Derivation of the Asymmetry Ratio for a Planar Ge(Li) Gamma Ray Polarimeter

The integral expression, which gives the probability of a scattered gamma ray causing a coincidence count between the center and one of the side detectors, is derived using the assumptions of only a Compton scattering in the center detector and a photo-electric reaction in one of the end detectors, the necessity of leaving at least the minimum detectable amount of energy in both detectors, and the fact that only a certain proportion of the gamma rays leave the center detector with just one scattering; secondary scattering has not been included in this calculation. The calculated asymmetry for the incident energy range .42 to 1.36 Mev. agrees well with the experimental result, and compares favorably with those calculated by Metzger and Deutsch for more conventional polarimeter designs.