Research On Ultra-broadband Terahertz Gyrotron Electron Optical System Based On Iterative Algorithm

Terahertz science and technology is an important scientific and technological development direction in this century.As an emerging frontier science and technology,the unique physical characteristics and wide range of applications of terahertz(THz)wave make it very valuable in many fields.As a vacuum radiation source that can generate stable high-power terahertz waves,gyrotrons play an increasingly important role in applications such as millimeter-wave communications,microwave weapons,controllable nuclear fusion,and NMR system.The magnetron injection electron gun(MIG)is a key component of the gyrotron,the performance of the gyrotron depends on the electron beam from MIG.Based on the theory of electron optics and electrodynamics,this thesis focuses on the study of a gyrotron electron optical system that can work in an ultra-wide magnetic field range.The specific research contents are as follows:1.The numerical simulation method of high-density electron beam optics,and the physical model of the static magnetic field under the rotationally symmetric cylindrical coordinate system is studied and analyzed.The analytical formulas of the on-axis magnetic field expansion method and the coil magnetic field fitting method are given,and the magnetic field generated by the two sets of static magnetic field methods in space are analyzed.According to the numerical calculation program written by the coil simulation method,the 3D coil model corresponding to any magnetron electronic optical system and its full-space magnetic field solution can be calculated.2.Based on Maxwell's equations and electron motion equations,the basic working principle of the electron-optical system is systematically investigated,and a co-simulation algorithm for ultra-wideband gyrotron electron-optical systems is designed,which can call the particle simulation software by controlling the MATLAB calculation program.The automatic optimization of the MIG structure is realized through the algorithm optimization model.3.Based on the electron gun theory and algorithm optimization model,a singleanode electron gun that can work in the magnetic field range of 6.03 T-9.64 T and a double-anode electron gun that can work in the magnetic field range of 6 T-12 T are designed.And both electron guns can be used for ultra-wideband tunable terahertz gyrotrons.The single-anode electron gun can achieve a continuous change in velocity spread from 2.9% to 6.6%,and the pitch ratio from 1.03 to 1.55 in the working magnetic field of 6.03 T-9.64 T;the double-anode electron gun can achieve a continuous change in velocity spread from 2.6% to 5.3%,and the pitch ratio from 0.92 to 1.32 in the working magnetic field of 6 T-12 T.