Abstract
AbstractGamma radiation detection finds many applications in different fields, including astrophysics, nuclear physics and medical diagnostics. Nowadays large Lanthanum Bromide crystals coupled to Photomultiplier Tubes (PMTs) represent the state of the art for gamma detection modules, in particular for spectroscopic measurements. Nevertheless, there is an interest in substituting photomultiplier tubes with solid state photodetectors like Silicon Photomultipliers (SiPMs), owing to the latter’s significant advantages. These include insensitivity to magnetic fields, low bias voltage, compactness, fast response and mechanical robustness. The aim of this thesis work, which was carried out within the context of the GAMMA project supported by IstitutoNazionale di FisicaNucleare (INFN), is the design, development and experimental characterization of a -ray spectrometer based on large Lanthanum Bromide scintillator crystals coupled with Silicon Photomultipliers. This detector specifications are compliant with nuclear physics experiments with energies ranging from 100 keV to 20 MeV, characterized by state-of-the-art energy resolution and imaging capability, in a compact, modular and robust structure. In order to perform the readout of large scintillator crystals, a matrix of 144 Silicon Photomultipliers was designed using NUV-HD SiPMs from Fondazione Bruno Kessler (FBK). These were chosen due to their high Photon Detection Efficiency in correspondence with the peak emission wavelength of the crystal, the high cell density and low Dark Count Rate.
Highlights
My thesis work entails the design of each element of the instrument (Fig. 7.1). Starting from the SiPM tile and the optimization of the instrument mechanics, through to the development of the electronics boards and custom ASICs
A peculiar feature of the Gain Amplitude Modulated Multichannel ASIC (GAMMA) ASIC is the Active Gain Change mechanism, that profit from a “predictive” analog algorithm to choose the best gain of the amplifier to process the input pulse in order to minimise the contribution of the output noise as depicted by Fig. 7.3
Holder used to avoid DC current integration. This 1 Hz low pass filter with non-linear behaviour is used in feedback to the Gated Integrator filter, in order to drain the DC current from the input stage as depicted by Fig. 7.4
Summary
My thesis work entails the design of each element of the instrument (Fig. 7.1). Starting from the SiPM tile and the optimization of the instrument mechanics, through to the development of the electronics boards and custom ASICs. A peculiar feature of the GAMMA ASIC is the Active Gain Change mechanism, that profit from a “predictive” analog algorithm to choose the best gain of the amplifier to process the input pulse in order to minimise the contribution of the output noise as depicted by Fig. 7.3. Another important feature of the analog filter is the Baseline
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