Research Of N-? Time Correlation Measurement Based On EJ299-33A Plastic Scintillator

With the rapid development of nuclear science and the increasingly mature application fields,the identification and control of fissile materials is becoming more and more important in national security.Time-correlated measurement technology has broad application prospects for nuclear material identification.The main work of this paper is as follows:Firstly,the performance of the new EJ299-33A plastic scintillator detectors was systematically studied through experiments.According to the principle of ray-substance interaction,the energy calibration of the detectors was done.The charge comparison method was used to study the pulse shape discrimination ability of the selected detector.This part work was to verify the performance of the EJ299-33A plastic scintillatordetector for n/?mixed radiation field measurement.Secondly,the time correlation measurement system based on EJ299-33A plastic scintillator detectors was built by analog circuit and digital circuit.The measurement results based on ⁶⁰Co and ²²Na sources show that time resolution of the system is<1 ns.Under the same experimental conditions,the advantages and disadvantages of the two circuits for time-correlated measurement performance were compared.The digital data acquisition system can guarantee the experimental data with different threshold conditions in one experiment under the same experimental conditions.The efficiency is high and the reliability is strong.The energy threshold dependence of time resolution was studied to obtain the detector system response required for the process of time correlation measurement.Finally,the ⁶⁰Co and ²²Na sources used for time resolution calibration were compared and the broadening factors of ²²Na source were discussed,why is not suitable for time resolution calibration.Thirdly,the time correlation measurements of the ²⁵²Cf n/?mixed radiation field were applied by the digital time correlation measurement system,which verified the feasibility of the EJ299-33A time correlation measurement system for the time correlation measurement of nuclear materials.A comparative experiment of Am-Li source and ²⁵²Cf source under shielding conditions was carried out,and the system can effectively identify non-fission materials.Finally,the post-processing program was programmed by MATLAB to realize the decoupling of the time-correlated spectrum,and the time-correlated feature quantity was successfully extracted.Furthermore,the characteristics of different shielding conditions,energy thresholds and distance characteristics under distance conditions are analyzed.Finally,the MCNP simulated the process of EJ299-33A time correlation measurement system detecting the ²⁵²Cf source,and the comparison between the simulated values of the time-correlation components and the experimental values was realized.The fast time resolution characteristics and the accuracy of the eigenvalues of the experimental system were verified.At the same time,in the absence of experimental conditions,the time-correlated feature quantities can be obtained through the MCNP simulation.Through the time-correlation experiment feature extraction,the theoretical calculation of ²⁵²Cf source activity was carried out,and the feasibility of coincident method is explored.