Comparison between CLYC-6 and 3He for thermal neutron detection.

A Cs2LiYCl6:Ce crystal, enriched in 6Li to > 95% (CLYC-6), was investigated for thermal neutron detection: it was characterised in terms of intrinsic efficiency and γ-ray discrimination capability and compared with a 3He counter (partial 3He pressure 2.3 atm). The intrinsic efficiency was determined by irradiating the detectors with thermal neutrons. The γ-ray discrimination capability was evaluated in a mixed neutron/137Cs field. The intrinsic efficiency per unit volume is about a factor of 6.45 larger for CLYC-6 than for the 3He counter. The detectors' performances in the presence of an intense γ-ray background are comparable: up to γ-ray fluence rates of the order of 105 cm-2·s-1, both detectors correctly reject γ-rays. At fluence rates of the order of 106 cm-2·s-1, CLYC-6 starts being affected by count losses due to γ-ray-induced dead time, while the 3He counter starts suffering from pile-up. Above this γ-ray intensity, both detectors are not reliable.