Investigation of CLYC-6 for thermal neutron detection and CLYC-7 for fast neutron spectrometry

Abstract

Highly enriched 6Li and 7Li Cs2LiYCl 6 (CLYC) scintillators were investigated in view of their application as thermal neutron counter (CLYC-6) and as fast neutron spectrometer (CLYC-7) in the recently developed B-RAD radiation survey metre, an instrument designed to work in regions of high magnetic fields, currently equipped with a probe for photon dose rate measurements and γ-spectrometry. Both crystals were irradiated with a 2.5 MeV mono-energetic neutron beam from a Deuterium–Deuterium (D–D) generator and characterised in terms of neutron/γ-ray (n/γ) discrimination capability by the Pulse Shape Discrimination (PSD) method, energy resolution and quenching factor. Both crystals exhibit an excellent n/γ discrimination, quantified by a Figure of Merit higher than 2. The measured thermal energy resolution of CLYC-6 is 6%. The quenching factor for the 6Li(n,t)α thermal neutron reaction is 0.65 and for the 35Cl(n,p)35S reaction is 0.91. The measured neutron detection efficiency per unit volume of CLYC-6 is 60% higher than that of a 3He proportional counter. CLYC-7 was tested as a fast neutron spectrometer below 10 MeV, when irradiated with continuum neutron spectra from Am–Be and 252Cf sources. A proton/α-particle (p/α) discrimination was performed exploiting the PSD technique, without any unfolding procedure. The resulting spectra match the corresponding ISO spectra better than the spectra without the p/α discrimination, especially in the range 3 MeV to 5 MeV. A more sensitive PSD algorithm might help to improve particle discrimination at lower energies, while different reaction channels arise at higher energies preventing a spectrometry analysis.