The Study Of Cathode Materials Used In The Field Of High Power Microwave

In the background of the subject of high power microwave, this paper took on the mission of the research on the cathode materials. Cathode material is the key technology of the High Power Microwave system. The development of high power microwave cries for the cathode materials with good performance of long pulse and repetition frequency. Aiming at searching for the cathode materials having the characteristics of high emission current destiny,low plasma expansion velocity,the ability of long pulse and repetition frequency performance, this paper proceeded in the study of cathode materials used in the field of high power microwave.This paper firstly selected velvet,graphite,metal-ceramics,carbon fiber,ferroelectric cathode as the subjects investigated according to the ideal characteriatics of the cathodes, then designed the shapes of the cathodes according to the request of the experimental facilities and the system of high power microwave,including cylindrical cathode,cyclic cathode,flaky cathode. After doing that, the cathodes were prepared by selecting appropriate preparation methods. The experiment established efficient testing system to measure electronic circuit of the electron emission of the cathode materials. We have predominated the central technology of the experiments, then through the contrast experiments among velvet,graphite and ferroelectric cathodes and the study of the experimental waveform and microscopic pattern , we generalized the emission characteristics of the cathodes, incorporated with the material characteriatics of them. At last, the cathodes were studied on the flatform of high power microwave, including the accelerating system of SPARK-04 and TORCH-01, the characteristics of electron emission and microwave outport were studied according to the results of experiments. The conclusions are:(1)The electron emission mechanism of velvet cathode is surface flashover and field enhancement of the tips, its good characteristics are: short starting time,high emission current destiny,easy formation of homogeneous and large areaial electronic beam,low plasma expansion velocity. High disinflation is its disadvantages. The characteristics of microwave outport are: with single experiment, the microwave power and pulse length can reach the best state, as increasing the frequency of the experiment, the performance turns bad quickly.(2)The emission mechanism of graphite cathode is field enhancement induced explosive emitting, its advantages are: low disinflation and long life span; its disadvantages are: high threshold voltage,long starting time,high plasma expansion velocity,non-homogeneous electronic beam. The characteristics of microwave outport are: small microwave power,short pulse length,good repetitiveness,long life span.(3)In the process of electron emission of metal-ceramics cathode, it does not have any microwave output because of non-homogeneous electron emission, but its good characteristics such as low disinflation,long life span,good repetition frequency embody its good potence in the working status of long pulse and repetition frequency.(4)The electron emission mechanism of the carbon fiber cathode synthesizes explosive emission mechanism in the tips and surface flashover mechanism in the side faces. It has many merits in the electron emission performance: short starting time,high emission current destiny,low threshold voltage,low plasma expansion velocity,homogeneous electronic beam,good repeatability,high disinflation,long lifespan.(5)The ferroelectric electron emission follows the plasma assisted electron emission mechanism. Its merits are good repetition frequency,long life span,low disinflation,low request of vacuum environment; its drawbacks are low electron current and long starting time.