Amplitude Measurements With SiPM and ASIC (Citiroc 1A) Front-End Electronics

The use of application-specific integrated circuits (ASICs) in nuclear physics instrumentation is drastically increasing because of the possibility of incorporating a large number of acquisition channels in compact devices. In this article, we describe a silicon photomultiplier (SiPM)-based application with Costruzioni Apparecchiature Elettroniche Nucleari (CAEN) front-end readout system based on Citiroc 1A chip from Weeroc. Besides the use of this chip for well-known single photon spectra and event counting, this article exploits the possibility to acquire energy spectra directly from scintillators, paired with SiPM, through peak-and-hold readout. In particular, good energy resolutions have been achieved even with slow scintillators, such as lutetium yttrium silicate (LYSO), caesium iodine [CsI(Tl)], and bismuth germanate (BGO), which have 40, 1000, and 300 ns of light decay time, respectively. These values are of the same order of magnitude of the shaping time of the Citiroc 1A chip (maximum value of 87.5 ns) in the case of LYSO and higher in the case of CsI(Tl) and BGO. Several measurements have been performed using multiple radioactive
$\gamma $
sources, and the resulting energy spectra demonstrate a resolution compatible with that found in the literature, as well as with an alternative acquisition system based on a digitizer that implements an algorithm of charge integration in the FPGA.