Theory Study And Numerical Investigation On Gyroklystron Amplifier

The gyro-device is a new type of microwave tube capable of producinghigh-power millimeter- and submillimeter wave radiation and has emerged as thepremier source of high-power millimeter- and submillimeter waves.As an importantbranch of the gyro-device family,gyroklystrons are microwave amplifiers thatcombine the energy extraction mechanism of the cyclotron resonance maser interactionto an axis-encircling hollow electron beam azimuthally bunch with the multi-cavityconfiguration and ballistic bunching of a klystron.The possible applications ofgyroklystron amplifiers from communications,radar systems,material disposal,to theRF source in next generation linear colliders and plasma heating,span a wide range oftechnologies because of their high peak power,high average power,high efficiency,high gain and opportune bandwidth.Scientists all over the world have done a lot of efforts on the research work todevelop the gyroklystrons because of them being long viewed as a strong candidate forproducing kilowatts of power at millimeter wavelengths.Research on gyroklystrons inthe University of Electronic Science and Technology of China (UESTC) is centered onthe development of a Ka-Band gyroklystron.Fundamental frequency Ka -Bandgyroklystrons have been successfully designed,built and tested at UESTC.The current design is a four cavity (input,prebuncher,buncher,and output)34 GHz TE₀₁ circular mode gyroklystron.This thesis details a systematic theoreticalstudy of the quasi-self-consistent nonlinear theory specially developed for thecalculations of the interaction between electron beam and RF field in gyroklystronswith a series of steplike and gradual transitions,obtained from the relativistic equationswhich describe the motion of electrons and conversation of energy.A simulationsoftware GKER (Gyroklystron emulator) which can be installed and run independentlyin Window system was developed for the calculations of the interaction betweenelectron beam and RF field in gyroklystrons based on the quasi-self-consistent fieldnonlinear theory using the union programming technique.Many numerical simulationsof the electron beam interacting with RF field in gyroklystrons were carried out and investigation was done for design and optimization of gyroklystrons using GKER.Various factors influencing gains and efficiency of the tubes including nonuniformityof the electron beam,physical parameters of gyroklystrons such as the length of drifttubes between cylindrical resonant cavities and electron beam parameters (acceleratingvoltage,beam current,input power,velocity ratio etc.) are discussed.The performancedata of an optimized gyroklystron was presented:An output peak power of 342 kW inmultimode calculation and exhibited gains of 37.56 dB with 43.68% efficiency wasachieved by operating a four cavity Ka band gyroklystron at electron beam voltagesand currents of 65 kV and 12 A respectively.The numerical simulations are beneficialto the actual engineering design consideration and paved the way for furtherimprovement of the high power gyroklystron amplifier to produce optimal results.Theachieved power level for the four-cavity tube in recent experiment was 300 kW at 30%efficiency according to calorimetric measurements.