SrBPO5:Eu2+ storage phosphors for wide-range neutron detection

Storage characteristics of SrBPO₅:Eu²⁺ phosphor were investigated in order to apply the phosphor to wide-range neutron detection. To increase thermal and fast neutron detection efficiencies, Li₂B₄O₇ powders and polyethylene powders were added, respectively. The optimization of the phosphor for maximum photostimulated luminescence yields have been performed. The experimental results showed that the maximal fast neutron sensitivity can be obtained without adding any polyethylene powders at neutron energy of 14.8 MeV, where the molar ratio of SrBPO₅:Eu²⁺ phosphor to Li₂B₄O₇ powders was fixed to 1:0.25. These experimental results well agreed with theoretical predictions by Monte Carlo simulation using PHITS code. The energy deposition by slow or intermediate neutrons was mainly due to charged particles as a result of nuclear reaction of ¹⁰B(n,α)⁷Li and ⁶Li(n,α)T. According to relativistic calculation, the energy of alpha particles or ⁷Li particles cannot be uniquely determined in a laboratory system but has a certain distribution even if incident neutron energy is fixed when neutron energy is high. The calculation showed that charged particles produced by nuclear reactions such as ¹⁶O(n,α) in addition to ¹⁶O(n,n)¹⁶O mainly contribute the total energy deposition at neutron energy of 14.8 MeV.