Feasibility study of an innovative active neutron dosemeter

Abstract

Prototypes of a novel pocket-sized active neutron dosemeter, based on a sensor made from the scintillator material Cs2LiYCl6:Ce (CLYC) coupled to a silicon photomultiplier (SiPM), were exposed to several well-characterised neutron fields produced at the National Physical Laboratory (NPL), UK.6Li-enriched CLYC is extremely interesting as a dosemeter sensor because it can detect not only gamma rays but also thermal and fast neutrons, gammas being distinguishable from neutrons by pulse shape discrimination. Thermal and low energy neutrons are detected by the 6Li(n, α)3H reaction, which gives rise to a well-defined peak in the pulse height spectrum. Fast neutrons typically interact via 35Cl(n, p) or (n, α) reactions, and the kinetic energy of the reaction product gives rise to a pulse height spectrum that relates fairly straightforwardly to the original neutron energy spectrum. Because of this spectrometry capability, such a dosemeter has the potential to retain its accuracy to a much greater extent, compared with conventional devices, when used in radiation fields that differ from the one used for calibration.SiPMs are low-power and compact, allowing the prototype dosemeters produced for testing to fit entirely within a standard existing personal dosemeter housing. Tests were carried out in the low-scatter neutron facility at NPL, with measurements made both on-phantom and free-in-air. The former were done to evaluate the device's performance as a personal dosemeter, and the latter to explore its potential as a very light neutron area survey meter. In this paper the experimental results are presented, performance issues encountered during the trials are discussed, and preferred application scenarios are proposed.