Read-out Electronics for SDD-based Compton detection in astronomical X-ray polarimetry

We present a readout electronics system designed for Compton scattering detection using silicon drift detectors (SDDs). This system represents the first component of a Compton telescope to be integrated into a CubeSat module as part of the ComPol project. The instrument is designed to observe Cygnus X-1, a binary system consisting of a black hole and a blue supergiant star, with the aim of measuring its X-ray spectrum and polarization. Through the detection of Compton events, the system will determine the angle and degree of polarization of the source. The payload consists of a Si-based detector to scatter the X-rays and a scintillating cerium bromide crystal (CeBr3) with silicon photon multiplier (SiPM) matrix for the detection of the scattered photons. The analog readout chain of the first detection system based on SDD matrices consists of charge preamplifiers, an analog pulse processor (ASIC), while a field programmable gate array (FPGA) module handles the digital data flow to the PC. Experimental characterisation of the prototype shows an energy resolution of 151 eV full width at half maximum (FWHM) with a shaping time of 3 μs. This paper presents the prototype boards designed for the final flight module, together with the results of tests performed with the prototype system.