Polarimetry Study With a CdZnTe Focal Plane Detector

Polarimetry has been recognized as a very important observational parameter for high energy astrophysics (>; 100 keV). For this reason the capability to perform accurate polarimetric measurement of high energy cosmic sources should be included in future space mission proposals. This idea has become very appealing in the perspective of new high energy focusing telescope implementing Laue lenses. In order to optimize the focal plane design of such mission as a Compton scattering gamma-ray polarimeter, a CdZnTe detector prototype has been tested at the ESRF (European Synchrotron Radiation Facility) under a ~ 100% polarized gamma-ray beam. The prototype detector tested is a 5 mm thick CdZnTe array with the anode segmented into 16 × 16 pixels of 2.5×2.5 mm². One of the most important factors that can affect significantly the polarimetric measurements is the direction of the incoming photons from the polarized radiation source with respect to the focal plane of the polarimeter. We have studied and analyzed the polarimetric response of the CdZnTe prototype as a function of the inclination of a polarized beam with respect to the optical axis of the detector from 0° to 10° tilt angle.