| Be subject to the device theory,stabilization,miniaturization and engineering of accelerator,achieving higher output power of single device is quiet difficult,which limit the promotional applications of the high power microwaves.One effective way to solve this problem is based on the power combination of several microwave sources.Because the intense relativistic klystron amplifier(RKA)has the characteristics of high power,high gain and high efficiency,it is one of the best microwave devices used for power combination.However phase jitter will seriously affect the efficiency of the combination,especially for the high power and long pulse case.In order to reduce the phase jitter and improve the stability of RKA,the phase characters mechanism are studied through theory analyze,simulation and experiment research.Based on the space-charge wave physics of RKA,considering the higher-order nonlinearity of beam modulation,and one dimension non-linear theory used to analysis the phase characteristics of RKA is build,Which achieved the computational accuracy of phase effectively under intense current and relativistic.According to this theory,an S-band intense RKA with three cavities and annular electron beams is studied to give its expression of beam modulation and output microwave,and finally with the credible simulation results confirm the theory.Then,the main reasons lead to phase jitter of RKA is found by study the characteristics of electron beams,input microwave and cavities.It's the intense pulse,self-oscillation,beam emission and transmission.Then the self-oscillation caused by the front edge of intense pulse power and the frequency shifting caused by fluctuation of intense pulse power are studied by tropical and simulation,which obtained the relationship among the frequency shifting,phase jitter and characteristics of intense pulse power.At last,the optimization method to improve the stabilization of RKA's phase is presented.Those results will be a theoretical guide to realize the frequency and phase stable of RKA's output microwave.Based on the results of theories and simulation,the phase jitter of S-band intense RKA with annular beams are optimized as follows.(1)By study the electric field on the surface of the cathode,the structure of diode and magnetic field are optimized and a standard of diode assembling is built to improve the quality of beams emission and transformation.(2)By research the reason of self-oscillation excited and adding microwave absorbing material to suppress the self-oscillation.(3)On the condition of output power greater than GW level,the parameters of the cavities are optimized and the fluctuation of phase reduces by 30%At last,an experiment research of S-band intense RKA phase is carried out on the LTD accelerator.In the experiment,the phase jitter caused by the fluctuation of pulse power is reduced.On the condition the peak power is on the GW level,the phase jitter of output microwave is about 18.0 degrees in 100ns pulse width when single RKA work single time and 18.2 degrees when single RKA operate at 25 per second times per 1 second.When double RKAs operate simultaneous,the phase jitter is about 19.8 degrees.Besides,in the experiment of phase control the phase can be adjusted on the accuracy of 6.6 degrees when single RKA and the accuracy are about 12.0 degrees when double RKAs operate.Those results have satisfied the applications of RKA. |
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