Design Of A Double-cusp Electron Gun For Millimeter Wave Gyrotron

Under the promotion of anti-interference high accuracy radar, electroniccountermeasure, directional weapons and so on, the high power coherent radiationsource in millimeter wave range has received a great deal of attention. It is now one ofthe front subjects in microwave vacuum electronics. Gyrotron traveling wave tube(Gyro-TWT) is a kind of fast wave device, which is of high working frequency, largeaverage power capability, broad bandwidth, and considered to be the most perfectpower source for high performance radar and electron countermeasure system.However, Gyro-TWT is hard to match the theoretical prediction due to its sensitivityto the quality of electron beam and the modes oscillation competition problems. Thedouble cusp electron gun is capable of generating large orbit electron beam. The largeorbit electron beam can greatly overcome the sensitivity to electron beam and modesoscillation competition problems for its modes selectivity. In addition, the double cuspelectron gun is capable of generating small orbit electron beam and linear electronbeam. In this dissertation, the double-cusp gun generating large orbit electron beam isgenerally studied. The small orbit electron beam and linear electron beam are alsodiscussed in great detail. The numerical simulation results are obtained with the helpof mature electron trajectory program EGUN and PIC particle simulation programMAGIC. The factors which affect electron beam characters have been simulated andanalyzed.In detail, the basic theory of electronic optics is presented. The physical model ofdouble cusp electron gun is constructed, and the basic theory of double cusp electrongun is analyzed. The mechanism and physical characters of large orbit electron beam,small orbit electron beam, and linear electron beam are discussed. The non-idealmagnetic cusp model is also studied.Based on the numerical simulation programs EGUN and MAGIC, the doublecusp gun used for generating large orbit electron beam is simulated, which is suitablefor Ka band second harmonic gyrotron traveling wave tube. The influences of factors, such as anode voltage, the two magnetic cusp transition lengths and the axial positionsof the two cusps, on the electron beam are modeled and analyzed. By using thesimulated results, the optimized double cusp electron gun for generating large orbitelectron beam is simulated, and the results of beam characters are good.Based on the mechanism of double cusp electron gun, small orbit electron beamand linear electron beam are simulated by using the double cusp electron gundesigned for large orbit electron beam, respectively. The small orbit double-cusp guncan be used in low frequency gyrotrons, while the linear double-cusp gun is oftenused in terahertz band. The factors which affect the electron beam are analyzed.By the simulation of double cusp electron gun for generating large orbit electronbeam, small orbit electron beam and linear electron bam respectively, the gunparameters affecting the electron beam are presented in great detail. It is helpful forthe optimize design for the double cusp electron gun.