Anti-coincidence rejection of SiPM dark pulses for improved detection of low energy radiation
Neutron and gamma detectors of the CSIRO air cargo scanner are based on scintillators readout by photodiodes (PD). The scanner imaging resolution is limited by the scintillator size. It, in turns, is limited by the number of interactions that can be detected by the PD. Silicon photomultipliers (SiPM) could be used in place of PDs to improve the neutron and gamma detector efficiency. It would ultimately improve the scanner performance in terms of speed, cargo size and image quality.
Efficient use of SiPM requires gain stabilisation and dark counts suppression. This work presents a technique to strip the dark counts and the electronic noise off the genuine source-induced spectrum. The method requires the use of a pair of SiPM coupled to the same scintillator. By rejecting the events not detected by both the SiPMs, the background counts were reduced by more than 99%.