Monte Carlo evaluation of polarimetric capabilities of a hard X-ray CdTe focal plane

High energy polarimetry in astrophysics is a quite unexplored field, as well as optical solutions for polarimeters. Herein we propose and compare two different CdTe based polarimeter optics for X-ray and γ-ray astrophysics. The first configuration that we propose is a CdTe pixelised detector for multilayer telescope operating between 10 and 100 keV. In this case we are dealing with a 2 to 5 mm thick and small area detector with a very fine spatial resolution: pixel pitch of 0.5 mm, because typically the point spread function is of the order of 2-3 mm (FWHM). The disadvantages of this solution are mainly two: the effect of the multilayer mirror reflection on the incoming photons polarisation state and the limited energy range for Compton scattering in CdTe. The second configuration proposed is a CdTe thick pixelised matrix detector for Laue optics based telescope. In this case, it is required better detection efficient at high energy (from 60 to 400 keV) therefore a CdTe thickness from 3 to 10 mm is required, but for pixel scales of the order of a few mm because the expected point spread function is about 30 mm (FWHM) for photon energies of about 200 keV. Modulation Q factors and minimum detectable polarisation are calculated from Monte Carlo simulation of the two type CdTe focal plane detector for the Crab pulsar, as on axes reference source using the analytical response of the two optics type.