Experimental polarimetric study of a hard X-ray energy telescope prototype

Polarimetry in astronomy for the hard X- and soft gamma-ray energy range has not been developed much to date. Indeed no dedicated polarimeters. have ever been launched either in space or as a balloon-borne experiment. We propose A polarimetry project for hard X-ray and soft gamma-ray astrophysics known as the Coded Imager and Polarimeter for High Energy Radiation (CIPHER) telescope. The novel design of this telescope, using a matrix of thick Me microspectrometers as the detection. plane, will allow this type of measurement to be performed for the first time by a dedicated instrument. In order to compare the results already obtained from simulations with experiment, we have constructed a prototype detector of 4 x 4 pixels, to study the. response of this concept of polarimeter to linearly polarized radiation in the 100 keV to 1 MeV energy range. The use of a beamline at the European Synchrotron Radiation Facility (ERSF) allowed us to study double event efficiency and distribution, for beams of nearly 100% linearly polarized radiation in the energy range from 100 keV to MeV. Polarimetric Q factors higher than 0.4 for relative effiencies higher than 20% were observed. The photon beam energy and detector thickness dependencies will be discussed,. comparing these experimental results With those calculated by Monte Carlo simulations.