140GHz Gyromanagement Theory And Experimental Research

Gyrotron is one of the most potential vacuum devices to achieve high peak power and high average power in millimeter wave band.It has important applications in magnetic confinement fusion plasma heating,directional energy weapons,material processing and so on.At present,gyrotron is developing towards higher single-txibe continuous wave power,higher frequency,better tuning ability,higher efficiency and better continuous operation stability.The purpose of this paper is to explore the technical ways to improve the power of single-tube and tuning ability of gyrotron,and to experimentally explore the factors influencing operation stability in continuous-wave state,focusing on the 140 GHz frequency point to carry out relevant theoretical calculations,simulations and experimental studies.As the basis of all the research work in this paper,a series of desigl programs have been completed based on gyro management theory,including electron gun design program,cavity cooling parameter calculation program,single mode steady state calculation program and multi-lode time domain calculation program,and the verification of single mode steady state calculation program and multi-mode time domain calculation program has been carried out to verify the correctness of the program.Firstly,a series of codes are compiled based on gyrotron theories as the basis of all the research work in the thesis,including electron gun design code,cold-cavity calculation code,single-mode steady-state calculation code and multi-mode time-dependent calculation code.Emphasis is laid on verification of single-mode steady-state calculation code and multi-mode time-dependent calculation code,which indicate the correctness of the codes.Secondly,the TE34,10-mode is selected as the operation mode in the study of higher power gyrotron.To solve the mode competition problem which threatens stable operation of ultra-high order modes and further restricts the output power,the competition state of the gyrotron is systematically analyzed.Two methods of suppressing mode competition are proposed and verified,including magnetic field adjustment method and voltage adjustment method.The single-mode stable operation with output power greater than 1.5MW is realized.The voltage adjustment method can be naturally combined with the rising process of beam voltage,which has better maneuverability.After that,an approach for ultra-wide step tuning of quasi-optical gyrotron is proposed.Different from the idea of seeking multi-mode efficient radiation of dimple wall launchers,the quasi-optical mode conversion system based on Vlasov launcher is adopted in this paper.The basis of mode selection is determined by the transmission conditions of quasi-optical mode conversion system and the coupling radius conditions of the cavity.A tapered wall cavity is used to decrease the Q-factor difference between the lower and higher modes.The single mode parameter optimization and mode competition analysis at each frequency point are carried out,and the broadband step tuning of the high frequency cavity is realized.The cavity,quasi_optical system and output window can support tuning ability of nearly 6 octaves.Because of the mismatch between the electron gun and the cavity at the low end of the magnetic field,the gyrotron can achieve broadband step timing of nearly 3 octaves.Compared with the widest tuning bandwidth of less than 2 octaves of conventional method,the tuning ability of gyrotron has been greatly improved..Finally,the design and experiment of 140 GHz/50 kW gyrotron are carried out,to further verify the design method and codes used on the one hand,and to experimentally explore the influence factors of continuous operation stability on the other hand.Frequency curves,low-power curves and high-power curves are tested,the maximum pulse power of 56 kW is achieved,which are in good agreement with the theoretical results.Nottingham effect is tested and its effect on the emission beam is analyzed.Continuous operation experiments were carried out,the output power was measured to be only 20.3 kW with a duration of 1 minute due to the power capacity limitation of the window,and the efficiency with single-stage depressed collector was 28.3%.The test of current induced by reflux electrons on the electrodes showed that the gyrotron operated stably under this power.