Event preprocessor for the CdZnTe-strip detector on MIRAX

Abstract

ABSTRACT We present the Event Pre Processor (EPP) for the Cadmium-Zinc-Telluride-strip detector of the Hard X-rayImager (HXI) onboard of the MIRAX satellite. The purpose of the EPP is to provide an onboard data reductionand event “ltering by applying a non linear energy gain correction for each detector strip. This data reductionis necessary because of the limited telemetry capacity of the MIRAX satellite. We decided to use hardwireddata processing electronics based on a Field Programmable Gate Array (FPGA) chip designed in VHDL. Thissolution allows us to combine high computation power with low power consumption. We discuss the functionalityand status of the EPP design developed in T¨ ubingen.Keywords: CdZnTe, strip detector, FPGA, data handling , EPP, MIRAX 1. INTRODUCTION: MIRAX SATELLITE The Monitor e Imageador de Raios-X ( MIRAX ) is a satellite mission proposed by a collaboration of teamsfrom INPE (Brazil), CASS/UCSD (USA), IAA T¨ ubingen (Germany), MIT (USA), the University of Warwick(UK), and SRON (Netherlands) as part of the INPE program of scienti“c micro-satellites (1). The scienceobjective of this mission is to provide continuous broadband imaging in 2 200keV of the central 1000 squaredegrees of our galactic plane for approximately 9 months per year. The continuous monitoring from a low Earthequatorial 550km orbit will allow the study of shortlived high energy events such as bursts from accreting neutronstars, including burst oscillations, or ejection events fro m Galactic microquasars, as well as long-term studiesof accreting compact objects, such as monitoring of the soft and hard states of accreting black holes. MIRAXwill be able to continue the scienti“c legacy of the RXTE All Sky Monitor, with a 10 × increased sensitivity,and of CGRO BATSE, with a sensitivity that is expected to be 40 × better. By concentrat ing on the Galacticcenter region, MIRAX will “ll the gap between the infrequent hard X-ray and gamma-ray observations of theGalactic plane by INTEGRAL , and the quasi-random survey of the X-ray sky provided by Swift , and it will bean important precursor to the EXIST mission.The above scienti“c objectives translate into a mission us ing two scienti“c instruments, the Soft X-ray Imager(SXI) for the energy range 2 28keV, and the Hard X-ray Imager (HXI) for the energy range 20 200keV. Bothinstruments will be using coded masks. The angular resolution of the HXI will be 6 and the “eld of view will be45 .8 × 22 .9 (1). For the SXI, it is foreseen to use the ”ight spare of the BeppoSAX Wide Field Camera (2) with