Research On Performance Of Particle Time-of-flight Detector Based On The Fast-timing Photomultiplier Tube

The high time resolution based on particle time-of-flight detectors is becoming more and more important in the applications of high-energy physics and medical physics.The main factors that limit the time resolution include scintillator,photodetector,and readout circuit.The particle time-of-flight detector uses photomultiplier tubes or photovoltaic detectors as the sensors.However,photomultiplier tubes have poor time resolution and are difficult to apply under strong magnetic field conditions.Photovoltaic detectors are limited by their time resolution,radiation damage,and dark count rate.In order to meet the requirements of high time resolution and adapt to the strong magnetic field environment,this dissertation adopts the fast-timing photomultiplier tube as the sensor of the particle time-of-flight detector.In the dissertation,the time characteristics of the fast-timing photomultiplier tube（FPMT）were studied.This dissertation proposed a design idea of coupling FPMT and scintillator to form a particle time-of-flight detector.In order to achieve the goal of high time resolution of particle time-of-flight detectors and its application in strong magnetic field,the main research contents of this dissertation include:The detection principle and data acquisition method of particle time-of-flight detector were studied in this dissertation.In this dissertation,the luminous characteristics of the scintillator,FPMT detection principle and the readout circuit were studied,respectively.We analyzed the interaction of particles with the scintillator and the propagation process of light in the scintillator.We also analyzed the high-precision time measurement technology in the readout circuit,including timing and time-to-digital conversion technology.Among them,the constant-fraction timing technology can eliminate the influence of amplitude walk.On this basis,the study of waveform digitization technology and its data processing method was carried out,which laid the foundation for the extraction of charge and time information in the test.The structure design and time characteristics of FPMT were studied in this dissertation.We analyzed the trajectory of electrons inside the FPMT.We established the FPMT model and explored the factors affecting its time performance based on the Monte Carlo method and the finite integration technique.On this basis,the structural parameters of the FPMT were optimized.We built an experimental platform and conducted a test study on the designed FPMT samples.By comparing and analyzing the test methods of the time resolution of the FPMT,the waveform digitization and constant-fraction timing test methods were finally used to obtain the time resolution of FPMT.The intrinsic time resolution of the FPMT sample tube can reach 56.64 ps.The performance of the particle time-of-flight detector in strong magnetic field was studied in the dissertation.We analyzed and solved the differential equations of the electrons in the FPMT under a uniform electromagnetic field to obtain the electrons’trajectory.We used the Monte Carlo method and the finite integration technique to analyze the influencing factors of the magnetic field immunity of the FPMT.On this basis,we optimized the structure of the FPMT.We proposed a method to test the magnetic field immunity based on the linear dynamic range of FPMT and built a test platform.The experimental results show that the FPMT has good magnetic field immunity.The magnetic field tolerances of the sample tube in the axial and transverse magnetic fields are 4.6 T and 2.8 T,respectively.In addition,the limit time resolution of FPMT does not depend on the magnetic field strength.The time resolution performance of a particle time-of-flight detector based on the coupling of a FPMT and a scintillator was studied in this dissertation.We studied the characteristics of scintillation light pulses.On this basis,we analyzed the time resolution of the scintillator.We also examined the factors affecting the time resolution of the scintillator.We tested and studied the performance parameters that affect the time resolution of the Gd₃(Al_1-xGa_x)₅O₁₂:Ce（GAGG:Ce）scintillators.We analyzed the coincidence time resolution mechanism of the particle time-of-flight detector.We built a particle time-of-flight detector experimental platform based on FPMTs and 3×3×5 mm³lutetium-based scintillators.We tested the coincidence time resolution is 93.77±0.94 ps.The comparison with the previous measurement results shows that FPMT is suitable for particle time-of-flight detectors.Based on the prior performance parameters of the GAGG:Ce scintillators and the FPMT,we simulated the coincidence time resolution of the particle time-of-flight detector using the Monte Carlo method.We use a 4×4×22mm³ GAGG:Ce scintillator,and the time resolution simulation result is 204.61±2.63 ps.Compared with the existing particle time-of-flight detectors,it verifies the rationality of the particle time-of-flight detector based on a GAGG:Ce scintillator coupled with FPMT for medical equipment.