Optimizing Design Of Electron Optical System For Gyro-travelling Wave Tube And Study Of Laserplasma Interaction

Gyro-travelling wave tube(Gyro-TWT) is the most important microwave amplifier in millimeter microwave band. It can be applied in radar system, communication and industry. Compared with the conventional linear vacuum amplifies, the Gyro-TWT is advantaged in high power, wide band and high gain. The research focuses in stability and high power generation of Gyro-TWT. The stability of the electron beam is affected by beam uniformity, and high power output is limited by capability of collector.This dissertation studied the theory of Gyro-TWT, and designed a Q band high power Gyro-TWT. Chapter 2 demonstrated the electron optics theory and optimizing method based on genetic algorithm. Chapter 3 analyzed the beam trajectory in collector and employed a curved geometry to enhance capability. Chapter 4 introduced the design platform of Gyro-TWT which can design the tube efficiently. Chapter 5 introduced the THz generation using two-color laser ionization in air. Also the genetic algorithm optimizing tool was used in experiment to improve the THz signal.The electron optics theory of MIG was demonstrated. The beam trajectory was simulated by EGUN software. A Q band triode MIG with velocity ratio of 1.09 and axial velocity spread of 1.43% was designed, and the results was verified by the MAGIC. Based on the genetic algorithm, an optimizing method was employed to enhance the beam uniformity whose axial velocity spread decreases to 0.72%. According to the electricmagnetic field mismatch, a curved anode geometry was proposed to reduce the beam velocity spread, and final axial velocity spread reaches 0.39%. By thermal analysis, the heat efficiency of cathode had been greatly enhanced.The design and optimization of collector was demonstrated. The spent electrons were analyzed by the adiabatic compression theory. A curved geometry collector was employed and the spent electrons were collected uniformly in a long axial range. Compared with the conventional geometry collector, the average dissipated power density and maximum dissipated power density were decreased by 16% and 57% respectivelty. The secondary emission electrons were considered. The results showed the influence of secondary electrons can be suppressed by the curved collector. Thermal analysis indicated the temperature has been decreased from 227℃ to 142℃. The curved collector can be operated in a higher power condition than conventional geometry.The work of Gyro-TWT design platform was introduced. By considering the efficiency and performance of Gyro-TWT, a design platform with synergy simulation, design and optimization was developped. The platform can design the MIG, RF structure, collector and input/output system efficiently. Also it can optimize geometry, 6-sigma analysis, export DWG files and record the experimet data. The designed MIG can get electron beam with velocity ratio of 1.1, axial velocity spread of 0.72%. The interaction circuit can obtain 200 k W output power with 70 k V-10 A electron and 500 m W input power. And the collector can efficiently recover 100 k W electron beam in 200 mm distance and maximum dissipated power density lower than 500W/cm2. The platform can enhance the design efficiency and reduce mistakes.The THz generation using two-color laser ionization in the air is demonstrated. Based on Lambda Cubed laser system, the THz signal was observed in the experiment. The method of optimizing the geometry of plasma was used to improve the THz signal amptitude. By empolying genetic algorithm controlling program, the THz signal was enhanced 2.5-4 times in experiment.