Thermal neutron detection with Ce3+ doped LiCaAlF6 single crystals

Cerium-doped LiCaAlF6 (Ce:LiCAF) crystals have been studied as scintillators in application to thermal neutron detection. Three crystals: high-doping Ce:LiCAF, low-doping Ce:LiCAF with 50% enrichment of 6Li (both 10 mmx10 mmx2 mm, rectangular) and high-doping Ce:LiCAF with 95% enrichment of 6Li (O50.8 mmx2 mm, discus) coupled to Photonis XP5300B PMT, were tested. The response of these crystals to neutrons emitted from a paraffin moderated 238PuBe source has been investigated. Thermal neutron peaks have been found at a Gamma Equivalent Energy (GEE) of ∼2.5 MeV for high-doping Ce:LiCAF (50% 6Li), ∼2 MeV for low-doping Ce:LiCAF (50% 6Li) and ∼1.9 MeV for high-doping Ce:LiCAF (95% 6Li). The light output of Ce:LiCAF was also measured (175-250 phe/MeV from sample to sample). Lithium-6 glass GS20 from Saint Gobain was used as a reference scintillator (O50 mmx2 mm, circle). Relative neutron efficiency, normalized to that of GS20 lithium glass, as well as gamma-neutron intrinsic efficiency for all tested samples was calculated. Intrinsic efficiency on thermal neutron detection for small Ce:LiCAF samples was estimated at about 32-35% of that of GS20 and for large Ce:LiCAF sample as about 82% of that of GS20.