Yuanzineng kexue jishu (Aug 2023)
Study on Performance of 6LiF/ZnS(Ag) Scintillation Screen for Scintillator Neutron Detector in China Spallation Neutron Source
Abstract
The 6LiF/ZnS(Ag) scintillation screen is key component of the scintillation neutron detector, and its performance will directly affect the application of the detector. In order to improve the performance of scintillator neutron detector and screen out a high-performance scintillator screen that meets the requirements of neutron detector for the engineering material diffraction and the energy resolution neutron imagining diffractometer on the China Spallation Neutron Source (CSNS), the No.20 neutron beam line of Chinese Spallation Neutron Source was used to systematically study the neutron detection efficiency and the light yield of different 6LiF/ZnS(Ag) scintillation screen samples with different thicknesses and different mass ratios from Britain’s Applied Scintillation Technologies (AST) manufacture. According to the results of neutron detection efficiency for these samples, the effects of 6LiF/ZnS(Ag) mass fraction ratio, thickness and substrate material type on the thermal neutron detection efficiency of 6LiF/ZnS(Ag) scintillator screen were analyzed by controlling variables. It is found that when the 6LiF∶ZnS(Ag) mass fraction ratio is 1∶2, the thickness is 300 μm, the substrate material type is plastic, and the thermal neutron detection efficiency of the 6LiF/ZnS(Ag) scintillator screen is the highest. Theoretically, increasing the 6Li score or increasing the thickness of the scintillation screen can improve the thermal neutron detection efficiency of the 6LiF/ZnS(Ag) scintillator. According to the charge spectra of the emitted light of these samples, the calibrated photomultiplier tube was used to estimate the output light yield of the samples. The output light yield was compared with the number of scintillation photons generated by the scintillator. It is found that most of the photons generated by the scintillator are self-absorbed by the scintillator. For PMT, the output light yield difference between the sample and the sample is not large. On the basis of giving priority to the thermal neutron detection efficiency of the detector and taking into account the performance of the output light yield, a high-performance scintillation screen was comprehensively selected. The results show that the AST-26139 scintillation sample with 6LiF/ZnS(Ag) mass fraction ratio of 1∶2, plastic substrate and thickness of 300 μm has the highest thermal neutron detection efficiency. The light yield from the surface of this screen is about 4.558×103. The AST-26139 was chosen as the best screen for the scintillation neutron detection. In engineering application, the “oblique incidence” structure for the 6LiF/ZnS(Ag) scintillation screen was designed to further improve the thermal neutron detection efficiency to meet the physical requirements of the scintillator neutron detector.
