A Scalable Detection and Readout Platform for Large SDD Arrays for the TRISTAN Project

Among several efforts targeting the determination of neutrino mass, the TRISTAN project aims at upgrading the detector of the KATRIN (Karlsruhe Tritium Neutrino) experiment for the search of the Sterile neutrino. Differently from the standard operation of KATRIN, where a high-resolution spectrometer allows the exploration of the endpoint region of the beta spectrum of electrons emitted by Tritium decay with a rate of 1 cps, in sterile neutrino mode the retarding potential is lowered and the count rate can reach 10¹⁰ cps. Such a high rate requires the partition of the detector into about 3500 pixels of 3 mm diameter. Within this framework, we present the design of the detection module, based on a large array of 166 SDDs with integrated JFET. The detection module comprises the detector, low-parasitic interconnection, mechanical and cooling assembly, and the readout electronics. Since the existence of the Sterile neutrino would produce a kink in the continuous spectrum below the ppm level, all possible distortion sources in the detection chain must be carefully identified and minimized. The front-end is represented by a 12-channel charge-sensitive preamplifier ASIC named Ettore. In this work we present the preliminary experimental characterization of the acquisition chain with a readout platform coupling the front-end to an integrated 16-channel analog shaper (SFERA) and FPGA acquisition. Although less performing than the definitive acquisition system, based on digital pulse processing and discarding of charge-sharing and backscattering events, the analog solution allows more flexibility and scalability during the initial development phase of the detection system.