A small 3D CZT payload for hard X-ray polarimetry and spectroscopic imaging

Currently, it is widely recognised that a measurement of the polarization status of cosmic sources high energy emission is a key observational parameter to understand the active production mechanism and its geometry. Therefore, new instrumentation operating in this energy range should be optimized also for this type of measurement. In this framework, we present the concept of a small high-performance imaging spectrometer designed for polarimetry between 100 and 600 keV suitable both for a stratospheric balloon-borne payload, and a small satellite mission. This instrument would be able to perform accurate and reliable measurement of the polarization status of different cosmic ray sources types simultaneously with fine spectroscopic measurements. The detector with 3D spatial resolution is based on a CZT spectrometer in a highly segmented configuration designed to operate as a high performance scattering polarimeter. We report on different configuration based on recent development results and possible improvements currently under study. Furthermore, we describe a possible baseline design of the payload and we present Monte Carlo evaluations of the achievable sensitivity for polarisation as a function of different detector characteristics.