Multi-chip front-end electronics LYRA for X and γ Ray detector for HERMES mission

Abstract

We present the experimental results of the Application Specific Integrated Circuit (ASIC), called LYRA, specifically designed for the High-Energy Rapid Modular Ensemble of Satellites (HERMES) mission concept, a constellation of nano-satellites able to detect and localize high-energy rapid transient events (up to 2.2 MeV) as the Gamma Ray Bursts (GRBs) from the deep space. LYRA has been desied for the detection system composed by a combination of Gadolinium Aluminum Gallium Garnet (GAGG) scintillators for high-energy photons, coupled to a matrix of 120 silicon drift detectors (SDD), used for detecting both scintillation light and low-energy photons. The LYRA ASIC has been conceived with a multi-chip architecture: 120 LYRA Front-End chips (LYRA-FE) are placed in close proximity to the anodes of the SDD matrix for a first processing of the detector signals and trasmit them in current mode to four 32-channel LYRA Back-End chips (LYRA-BE) to complete the elaboration. The requirements that the LYRA ASIC have to fulfill for the HERMES project are challenging: the maximum input energy measured in Silicon must reach 120 keV — corresponding to 2.2 MeV on GAGG — with a linearity error below 1%, the electronic noise must be less then 30 el. r.m.s. and the power consumption less then 1 mW per channel in a system with 120 channels working in parallel. The characterization of LYRA has been carried out on a dedicated test board, coupling one channel of the ASIC with a 25 mm2 SDD. An input full scale range of 5.2 fC and an electronic noise of 22 el. r.m.s. have been measured at -33∘C with a power consumption of 745 µW per channel.