Research On Key Technology Of Neutron Detector Based On High-pressure ~4He Gas Scintillator

Accurate measurement of neutron kinetics in fast neutron burst reactor is an important method to understand the dynamics of fast neutron burst reactor.The method of measuring neutron kinetics based on time probability distribution requires detectors to have fast response time,good n-y discrimination performance and appropriate detection efficiency.The traditional Lithium glass scintillator detector,~3He proportional counter,fast neutron fission chamber and new SiC detector have their own limitations,which are not suitable for the neutron measurement in strong gamma environment.Gas scintillators with ~4He as working medium have the advantages of low atomic number,low electron concentration,easy gamma discrimination,high elastic scattering cross section of fast neutrons,fast response time and large output of scintillation light.The development of neutron detectors based on high pressure ~4He gas scintillators is expected to meet the requirements of dynamic kinetics for detectors.At present,no relevant research institute has developed a high-pressure ~4He gas scintillator detector in China and foreign research groups have blocked the technology.Based on the research goal of preparing prototype of high pressure ~4He gas scintillator neutron detector,this paper focuses on four key issues in the process of detector design,processing and testing:physical design of detector,performance test of TPB wavelength conversion layer,preparation process of detector and performance test of detector.In the physical design of the detector,Geant4 program is used to analyze the influence of gas pressure,length and tube on the detector performance.The size parameters and gas pressure of the optimized detector are given according to the actual processing technology.In the of preparation of TPB wavelength-shifting layer,the influence of processing technic and thickness of TPB wavelength-shifting material on emission spectral intensity was studied,and the optimum preparation technology and thickness were given.The variations of TPB luminescence properties after irradiation with alpha particles,gamma rays and neutrons were studied.Finally,the whole process of the detector from design to processing is discussed in detail,the problems encountered in the process are analyzed and the solutions are given.Finally,the prototype of the detector is successfully prepared.By testing the counting rate and waveform of the prototype,the working characteristics of the detector are determined.The time-of-flight spectra of neutrons and gamma are given by using the time-of-flight method,and the differences in waveforms between neutrons and gamma are given.Based on these differences,the n-y discrimination method is established.Through the calculation and experimental research in this paper,we have mastered the physical design method and key preparation technology of high-pressure ~4He gas scintillator neutron detector,and the preparation technology and technology of TPB wavelength-shifting layer,and successfully prepared the prototype of detector.