Geant4 Simulations of Detector Response Matrix for Caliste-SO

Solar Orbiter is M-class mission of the European Space Agency (ESA) scheduled to be lunch in 2017. One of the SO instruments is the Spectrometer Telescope for Imaging X-rays (STIX) which will provide imaging spectroscopy of solar thermal and non-thermal X-ray emissions from 4 to 150 keV. Main building blocks of the STIX are an X-ray window, an imager with 32 subcollimators with set of tungsten grids, and a spectrometer with 32 Caliste-SO X-ray detectors. Caliste-SO is a hybrid component integrating the sensor material – Cadmium Telluride (CdTe) and dedicated front-end electronics for high resolution X-ray spectroscopy. The detector is pixelized so it demands new aproach for calculation the detector response matrix since several effects cannot be calculated analyticaly or measured on the Earth. We decided to model X-rays photon absorption with a use of GEANT4 package. It allows to investigate the response of detectors with great precision which is extremely important for interpretation of future data.