Lithium glass scintillator neutron detector as an improved alternative to the standard ³ he proportional counter

摘要

Lithium glass scintillator made from ⁶Li-enriched substrate is a well known for its neutron detection capability. In spite of neutron interaction, cross section of ⁶Li happens to be lower than that of ³He. However, the neutron detection efficiency could be higher due to higher volume content of ⁶Li nuclear in the solid scintillator vs. gas filled proportional counter. At the same time, as lithium glass is sensitive to gamma and charge particle radiation, non-neutron radiation discrimination is required. Our detector is composed of two equal-size cylindrical Li(Ce) glass scintillators. The first one is high-sensitive to thermal neutrons GS-20 (⁶Li doped), the second one is GS-30 (⁷Li doped) type Scint-Gobain made lithium glass scintillator. Each of scintillators is coupled with R7400U Hamamatsu subminiature photomultiplier tube, and all assembly is fitted into NP100H ³He tube size. ⁶Li absorbs thermal neutrons releasing alpha particles and triton with 4.8 MeV total energy deposit inside the scintillator (equivalent to about ∼1.3 MeV gamma energy depositions). Because ⁷Li isotope does not absorb thermal neutrons, and the physical properties of the two scintillators are virtually identical, the difference between these two scintillators could be used to provide neutron dose rate information. Results of study of neutron detector assembled of two Li(Ce) scintillators and NP100H moderator are presented.