DEVELOPMENT OF A MULTI-CHANNEL ANALOG PULSE PROCESSING AND DATA ACQUISITION SYSTEM FOR THE TRISTAN DETECTOR
The aim of this thesis is the design, development and characterization of the Analog Pulse Processing and Data Acquisition (APP-DAQ) system for the detector readout of the TRISTAN project. Its experimental target is the search of sterile neutrino in the keV-scale, a promising dark matter candidate. To reach this goal, it envisions the operation of 21 detection modules each equipped with a monolithic array of 166-pixel Silicon Drift Detectors exploiting the existing KATRIN (KArlsruhe TRItium Neutrino) apparatus.
Existence of sterile neutrino would manifest as a kink of < 1 ppm in the continuous spectrum of tritium β-decay, proving the presence of a fourth neutrino flavor. The requirements for the 3-year measurement session are a FWHM energy resolution for electrons of 300 eV at 20 keV and a countrate of about 100 kcount/s/pixel.
Within this framework, the APP-DAQ platform Kerberos and its Data Concentrator Athena were developed.
The first is aimed to provide a simple and low-cost multi-channel read-out solution in the early phase of the TRISTAN detector development. It is based on three 16-channel programmable analog pulse processor front-end ASICs (SFERA), three high linearity ADCs, and an FPGA.
The platform is able to acquire data from up to 48 pixels in parallel, providing also different readout and multiplexing strategies. The experimental characterization of the platform has been carried out both in the laboratories of Politecnico di Milano and in the final experiment Monitor Spectrometer, in Karlsruhe (Germany).
Instead, Athena is designed to increase the capabilities of Kerberos, connecting up to 4 of them, reaching the parallel readout of 192 pixels at the same time.
Athena platform acts as global trigger and event builder constructed for the readout of the final 166-pixel detector module for TRISTAN. It is based on a Zynq Ultrascale+ MPSoC, exploiting both the FPGA and microprocessor functions. The installation of Athena in the Monitor Spectrometer is expected by the end of 2021.
The thesis also addresses the characterization of a new ASIC, SFERA-TAC. Based on the SFERA ASIC used in Kerberos, 16 Time-to-Amplitude converters were added. In this way, the analog information of the events energy is completed by a timestamp of each individual event arrival, given by its integrated TACs. The timing of events is necessary for charge sharing and backscattering analysis and reconstruction. The systems hereby presented demonstrate that the use of an analog ASIC-based solution instead of a Digital Pulse Processor, represents a viable and scalable processing system at the price of slightly limited versatility and count rate capability, especially for applications with large numberof channels or more stringent power consumption constraints.
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