Study Of Particle Discrimination And Spectrum Measurement In Strong β-γ Mixed Field Based On Phoswich

Strongβ-γmixed field,in which bothβfluence rate andγfluence rate are relative strong and the measurement of both rays could interfere each other,is common in workplaces of nuclear facilities.It is necessary to measure spectrum of each ray respectively in radiation monitoring and radiation protection work.In order to obtainβ/γspectrums respectively,the key technique is to discriminate the type of particle depositing energy in the detector.Phoswich detectors are favored with uncomplicated structure and low costs.Utilizing phoswich detectors to discriminateβ/γis one of the most dynamic research areas in radiation monitoring and radiation protection study.Focused on discriminating particle type and obtainingβandγspectrums by a phoswich detector in strongβ-γmixed field,this dissertation carried out a series of research on the optimization design method of detector structure,the algorithm of pulse shape discrimination and the method of obtainin g spectrums.The main work are as follows:（1）The different structure s of phoswich detector s and correspondin g methods for discriminatingβ/γwere studied.To provide research approaches for optimization design of detector structure and particle discrimination method,a Monte Carlo simulation platform,which can calculate the situation of energy deposition and the pulse shape,was constructed.The study results showed that a three-layer-crystal phoswich was the best solution and it has a better performance than a two-layer-crystal one in both discrimination effects and energy measurement ability.Based on the optimization result,the methods of choosing scintillator materials and determining scintillator dimensions were studied.Finally,a design solution of phoswich detector was achieved and the corresponding decision methods were designed as well.（2）A pulse-shape-discrimination algorithm for the phoswich detector was presented.This dissertation presented a pulse-shape-discrimination algorithm named T&A,which was applied for a three-layer-crystal phoswich detector.The design method of T&A algorithm was studied and achieved.By extracting time and amplitude features of pulses,this algorithm calculated 3discrimination parameters,by which 7 kinds of possible energy depos ition situations were determined andβ/γrays were discriminated.Compared to other common-used algorithms,T&A algorithm had an excellent performance in both discrimination effects and computation speed.（3）A phoswich detector prototype was developed based on the above work and the methods for discriminating particle type and obtainβspectrum andγspectrum respectively were implemented on the prototype successfully.By laboratory experiments withβsources(¹⁴C,³⁶Cl and ⁹⁰Sr/^{9 0}Y)andγsources(^{24 1}Am,^{13 7}Cs and ⁶⁰Co),it showed that the phoswich prototype worked well in discriminatingβ/γparticle and obtaining the spectrums of both rays simultaneously by only one-time measurement,which verified the research result of this work.In order to test the pr ototype function,the phoswich detector prototype was applied successfully in a typical mixed radiation field in a real nuclear facility and a proper result of field measurement was obtained.This dissertation work provided technological base for measurement in strongβ/γmixed fields in workplaces of nuclear facilities and a phoswich detector prototype was developed,which provided an engineering mean for promotion in the future.