Year
2012
Abstract
Neutron detectors are used in material control and accountability, homeland security, safeguards and other related applications. Currently He-3 tubes are mainly used for neutron detection. However the diminishing He-3 stock pile and constantly increasing He-3 price stimulated recent advances in research for alternative neutron detection technologies. There is an increasing demand for instruments that could effectively replace He-3 tubes and provide additional information about the gamma radiation without sacrificing the neutron efficiency and neutron-gamma separation. Therefore RMD developed a line of high performance scintillation materials which can be utilized for simultaneous detection of gamma and neutron radiation. For example Cs2LiYCl6:Ce (CLYC) is an excellent material for dual-neutron gamma detection due to its ability to reliably separate gamma and neutron signals based on the shape of the scintillation pulse. Several pulse shape discrimination (PSD) methods for CLYC signals have been developed, including digital, mixed digital-analog and analog. However, the handheld instrumentation imposes restrictions on the size and power consumption of the PSD implementation. In this study we investigated two compact and low power PSD methods – analog and mixed analog-digital. Both methods provide adequate detection performance. Equally important is the size and shape of the scintillation crystal and mainly the type of its optical readout. Utilizing photomultiplier (PMT) as an optical sensor makes the detector bulky and not practical for handheld applications. Therefore in the study we investigated the CLYC coupling to a Multi-Pixel Silicon Photomultiplier (SiPM) since this combination can provide very compact implementation and small instrument form-factor. With the CLYC–SiPM detector we obtained excellent neutron gamma discrimination and low loss of neutron efficiency.