Application of $^{6}{\rm LiI}({\rm Eu})$ Scintillators With Photodiode Readout for Neutron Counting in Mixed Gamma-Neutron Fields

This paper investigates the potential of
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LiI(Eu)/photodiode (PD) detector systems for application as neutron counters in radioisotope identification devices (RIID). Those are exposed to mixed neutron-gamma fields. An effective suppression of signals due to gamma interactions with the scintillator or the PD bulk material is of major importance since neutron alarms in RIID are triggered by a few single neutron counts; any gamma signal not rejected may generate a false neutron alarm. Measurements demonstrated that digital signal processing combined with simultaneous pulse height and pulse shape analysis can provide efficient neutron-gamma discrimination. The results were obtained with a compact, basic detector configuration and sampling rates of only 10 MS/s. Such systems can be realized with state-of-the-art miniaturized electronics.