A Position Sensitive Detector With Real-Time Gamma/Neutron Discrimination Capability

Abstract

In recent years, the demand for a gamma and neutron camera with real time discrimination capabilities has emerged in nuclear physics and medical imaging fields. Specifically, in the field of hadrontherapy, prompt gamma imaging (PGI), a technique for range verification purposes, is strongly affected by the presence of a large neutron background, which can limit the possibility to perform precise range monitoring, especially in the framework of carbon ion radiation therapy (CIRT). This work focuses on the design and development of a compact camera with gamma/neutron discrimination to perform range verification in hadrontherapy, exploiting the gamma signal while discarding the uncorrelated neutron component. Thanks to its dual imaging capability, neutron images can still be stored and used in other applications. Pulse shape discrimination (PSD) was selected as the method for gamma/neutron discrimination after evaluating several techniques. Among the available options, we selected a Cs2LiYCl6:Ce (CLYC) inorganic scintillator as the optimal choice to perform PSD. The detector, based on a $5\times 5\times 2$ cm CLYC crystal, read out by SiPM tiles and compact electronics, acquires and converts in real time digital PSD coefficients. The use of four 16-channel custom gain amplitude modulation multichannel application-specific integrated circuits (GAMMA ASICs) allows to store the channel’s amplitude information, allowing to retrieve the particle point of interaction in the monolithic crystal and obtaining PSD-resolved images. The system discrimination capability was verified with experimental measurements in the laboratory and beam tests, and a preliminary evaluation of its imaging capability with real-time PSD was successfully conducted.