Analysis and comparison of the Core-to-Valence Luminescence mechanism in a large CLYC crystal under neutron and γ-ray irradiation through optical filtering selection of the scintillation light

$^7$Li enriched Cs$_2$LiYCl$_6$:Ce$^{3+}$ (CLYC) is a promising inorganic scintillator for real-time γ-ray and fast neutron spectrometry. The neutron/γ-ray discrimination is usually accomplished exploiting the different quenching effects of high Linear Energy Transfer (LET) particles on different scintillation mechanisms, usually by means of the time analysis of the pulse shape. In principle, the emission wavelength information could be used to address the same task. However, a systematic study of the correlations between the CLYC decay time, its radio-luminescence spectrum and the LET of the impinging particle has not yet been performed. We therefore investigated the CLYC scintillation process under neutron and γ-ray irradiation, correlating the time response to the scintillation wavelength spectrum using a 1–inch right cylinder > 99% $^7$Li enriched CLYC. We found that the relative intensity of the Core to Valence Luminescence (CVL) is almost constant with photons in the energy range 20–660 keV, i.e. 0.5–5 keV/μm LET, and is only partially quenched by neutrons. Instead, the direct electron-hole capture scintillation mechanism is completely cut under neutron irradiation. The luminescence in between the deep-Ultraviolet and the Near Ultraviolet region (250–350 nm) might be attributed to both the CVL and the host luminescence, also in thick highly Ce$^{3+}$-doped crystals.