Co-simulation Of Photoelectron Generation And Control In Image Tube

During the Inertial Confinement Fusion(ICF)reaction,high-energy laser strikes produce high-temperature,high-density plasma,which radiates large amounts of X-rays,and information such as fusion duration and implosion motion images can be obtained by studying the spatio-temporal properties of X-ray radiation.The streak cameras have ultrahigh spatio-temporal and optical intensity resolution,and is one of the main diagnostic devices for X-ray detection in ICF experiments.The photoelectric emission characteristics of Cs I greatly affect or even determine the spatio-temporal resolution and measurement accuracy of streak cameras,so it is necessary to conduct more in-depth and detailed research on Cs I materials to fully understand and grasp their photoelectric emission characteristics and improve the structural matching of photoelectric conversion elements and other detection components.In the structural design of the electro-optical system of the streak camera,the anisotropic focusing streak tube composed of the electric quadrupole lens and the rectangular frame cylindrical lens,can separate the focusing of the time direction and the spatial direction of the image converter tube,thus achieving anisotropic focusing of the electron beam.The existing simulations on streak tubes are all single photoelectric emission characteristics simulations or electro-optical system design simulations,lacking the holistic simulation for streak tubes,which greatly limits the accuracy of the simulation results.The research of this thesis runs through the whole process of photoelectron generation and control.Geant4 and CST are combined with Matlab for the first time to realize the full dynamic simulation of photoelectron generation and control.The specific work is as follows:1.By consulting a large amount of literatures,the working principle of the streak camera is studied in detail,and the material characteristics and structure of the X-ray streak photocathode are analyzed emphatically.The photocathode studied in this thesis is determined to be the transmission type Cs I photocathode,and the tube type of the streak tube to be designed in this thesis is anisotropic focusing streak tube.2.On the basis of fully understanding the theory of photoelectron emission,Geant4 software was used to model and simulate the photoconversion process of Cs I photocathode based on Monte Carlo method.The photoelectron emission characteristics of the photocathode were studied,and the effects of the electric base and substrate film,and the thickness of the Cs I film on the photoelectron emission characteristics of the photocathode were analyzed.The results show that the combined characteristics of the chosen electric base and substrate film materials have a small or even negligible effect on the photoelectric emission characteristics of the photocathode,and the emission characteristics of the secondary electron such as the emission energy,angle,position and time are basically not affected by the thickness of Cs I film.3.With the help of Matlab,the co-simulation of Geant4 and CST is realized,and the photoelectron distribution simulated by Geant4 is directly used as the particle source of the electron optical system model of the streak tube in CST,and the full dynamic simulation of the generation and control of photoelectrons is achieved.A scale imaging anisotropic focusing streak tube with magnification of 2 is designed.