A 3D CZT hard x-ray polarimeter for a balloon borne payload

Abstract

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 spectrometer designed for polarimetry between 100 and 500 keV suitable as a stratospheric balloon-borne payload dedicated to perform an accurate and reliable measurement of the polarization status of the Crab pulsar, i.e. the polarization level and direction. 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 discuss different configuration based on recent development results and possible improvements currently under study. Furthermore we describe a possible baseline design of the payload, which can be also seen as a pathfinder for a high performance focal plane detector in next generation of hard X and soft gamma ray telescopes based on Laue lenses. Finally, we present Monte Carlo evaluations of the achievable sensitivity for polarisation as a function of different detector characteristics.