Study On The High-Power Relativistic Magnetron

This thesis gives a theretical study on the relativisitic magnetron,and presents the particle simulations of the C-band,S-band,L-band,and P-band relativistic magnetrons.Firstly,we investigate the Hull condition and the Buneman-Hartree condition numerically to obtain the design method for magnetrons.The numerical results show that,(1) the Hull condition curve rises up with increasing the equivalent anode-cathode gap d;(2) the Buneman-Hartree condition curve rises up with increasing the equivalent anode-cathode gap d,and changing cathode radius has more effect on the Buneman-Hartree condition than changing other parameters;(3) for the same mode, the Buneman-Hartree condition curve rises up with increasing the resonance frequency; (4) under the same geometry parameters,the Buneman-Hartree condition curve ofπmode is higher than that of 2πmode.The present thesis also gives theoretical investigations on the relativistic magnetron using the linear fluid model.The dispersion curve is obtained.In order to have a good set of design parameters,this paper analyzes the dispersion relation and determines its operating parameters varying with geometrical structure of the relativistic magnetron. The result shows that the resonance frequency reduces when the radius of the resonance cavity increases or the radius of the cathode increases;while the resonance frequency increases when the radius of the anode increases or the angle of the resonance cavity increases.Secondly,in the computer simulations,based on the theoretical investigations,a relativistic magnetron is designed which operates in the frequency regime of C-band.Its working and output characteristics are investigated using a 3D PIC code,and the results can also prove the correctness of the linear theory.In order to optimize the relativistic magnetron,the parameters of the geometrical structure of the C-band relativistic magnetron,electron beam,magnetic field,and the cathode cap are analyzed using the simulation results.Many useful conclusions are obtained.Through the optimization of the C-band relativistic magnetron,good results are obtained.For an electron beam of 1.04MeV and 20.3kA,a microwave at the output window is generated with peak power of 4.38GW and frequency of 4.37GHz when the magnetic field is about 0.7T.The beam-to-microwave efficiency is about 20.7%.In order to extend the investigation of the relativistic magnetron,this paper also gives the studies on the S-band,L-band and P-band relativistic magnetron respectively through the computer simulation and gives the geometry parameters at each band. Under certain geometry parameters,for an electron beam of 746.9keV and 16.4kA,a microwave at the output window is generated with peak power of 3.59GW and frequency of 3.42GHz at S-band when the magnetic field is about 0.7T.The beam-to-microwave efficiency is about 29.3%.Under certain geometry parameters,for an electron beam of 1.17MeV and 8.9kA,a microwave at the output window is generated with average power of 1.40GW and frequency of 1.70GHz at L-band when the magnetic field is about 0.4T.The beam-to-microwave efficiency is about 13.4%. Under certain geometry parameters,for an electron beam of 856keV and 5.36kA,a microwave at the output window is generated with average power of 1.0GW and frequency of 0.93GHz at P-band when the magnetic field is about 0.45T.The beam-to-microwave efficiency is about 21.6%.There are few reports on the P-band relativistic magnetron in the world.This paper also designs a relativistic magnetron using the computer simulation, which can realize the frequency tuning from C-band to S-band only by changing the working voltage and magnetic field.The geometry parameters and the working parameters are given.Finally,the experimental design is given for the C-band relativisitic magnetron.