Laser-Based Scintillator Crystal Emulator for Optical Testing of SiPM Readout Technologies

In most SiPM-based gamma detection technologies, it is important to precisely characterize both the optical sensor’s light response and the interfaced electronics readout performances. Traditional setups, involved in this procedure, are based on radioactive gamma sources, with a-priori known energy spectra, used to perform both an accurate characterization of SiPM non-linearity and a calibration of the acquisition system. However, several disadvantages affect these techniques, such as the low versatility and the need of using also highly energetic radioactive sources, in order to perform a correct calibration procedure. Moreover, high energy range (e.g. up to 20MeV) is very unpractical to explore with radioactive sources or beam tests. A possible alternative consists in a pulsed light source setup, emulating the behavior of different source-crystal couplings and directly interfaced with the optical sensors. Purpose of this work is the development of an electro-optical device, generating light flashes with tunable intensity and duration: the former ranges from few units to hundreds of thousands of photons, the latter can be set in order to be comparable to that of common scintillation events. A further specification consists in the optical power stability over time and temperature: a closed loop control system has been designed, based on a microcontroller performing a real time modulation of the light source driving current.