Neutron Detection with Isotopically Enriched Boron Carbide Thin Layers Combined with an Oxygen Vacancy-Enriched Sapphire Scintillator

Abstract Isotopically enriched 10B5C neutron absorber layers were combined with α-Al2O3 crystals to achieve scintillation-based neutron detection, utilizing the 10B(n,α)7Li nuclear reaction and ionoluminescence induced by the stopping of secondary charged particles as reaction products. The thin 10B5C layers were deposited by DC magnetron sputtering on Si wafers. The modified near-surface region of α-Al2O3 contained excess oxygen vacancy-related optical centers to enhance the ionoluminescence yield in the scintillator. Neutron absorption and neutron irradiation-induced scintillation measurements were performed with cold neutrons of a 3.4 Å average wavelength. Measured and calculated values agree well for neutron absorption vs the areal density of deposited 10B atoms. The maximum neutron-to-light conversion efficiency was found at ∼20% neutron absorption for a 10B5C layer of 2.5 μm thickness. The measured and calculated relative scintillation yields agree well and show that the maximum neutron detection efficiency is determined by the total amount of ionization energy deposited in Al2O3. The net scintillation light yield is a result of the interplay between neutron absorption in 10B5C and the degree of penetration of the nuclear reaction products into Al2O3. The ionization profiles induced in Al2O3 are confined to the 10B5C/Al2O3 interface; therefore, it is enough to sensitize only a thin surface region of the scintillator to achieve significant enhancement in neutron detection efficiency. This work assigns 10B5C as an effective neutron absorber material for small-scale compact solid state neutron detectors with a wide range of possible applications.