Research On Phase Control Of Relativistic Backward Wave Oscillator

The relativistic backward wave oscillator?RBWO?is a kind of high power microwave generation device with high potential,high power and high efficiency.If we can realize the microwave phase control of RBWO output,it is of great value to further expand the application of RBWO,such as power synthesis and so on.In this paper,the theoretical analysis,numerical simulation and experimental research on the RBWO injection phase traction technology are carried out,and the phase control of the GW-level HPM signal generated by the RBWO is realized by using the kW-level injection signal.The method has the advantages of low injection power,continuous phase adjustment and better control precision,and is easy to obtain high power and efficiency.The main research contents and results are as follows:The RLC oscillation equivalent circuit model of the RBWO starting process is established.The microwave generation in RBWO and the response process of the injection signal are described.And the amplitude and phase continuity equation in the process of starting up is given.The analysis shows that the mode competition is the main factor that affects the phase traction effect.The electron beam bunching and energy exchange equation are derived under relativistic conditions.Analysts believe that the power growth rate of microwave is approximately constant when RBWO starts up,and the relationship between the oscillation equation of RBWO oscillation process and the oscillation equation given by RLC oscillation circuit model is established.According to the characteristics of RBWO structure,a microwave coaxial injection scheme is proposed,which has a good isolation between the injection channel and the microwave generation region.A rectangular waveguide TE₁₀ mode to overmoded coaxial waveguide TEM mode converter scheme is given.It solves the technical problems of high efficiency injection and field uniformity.The effects of the input cavity and the pre-modulation cavity on the electron beam modulation are studied.The results show that the best modulation effect can be obtained when the standing wave field is formed between the two cavities.Finally,the design scheme of the whole injection structure is given by numerical simulation,and the design results are obtained at the operating frequency9.3GHz,the field amplitude jitter is less than±1.6%,and the phase jitter is less than±0.6°.2.5-dimensional particle simulation is used to analyze the influence of the parameters such as the extraction chamber,the pre-modulation cavity,the drift of the electron beam,the structure parameters of the diode,the operating voltage and the guiding magnetic field on the working state of the RBWO.This paper presents a method to restrain the model competition by adjusting the reflection characteristics of the reflection and resonant cavity of the slow wave structure,and realizes the suppression of the competition between the 5?/7 mode and the TM₀₂ mode.By numerical simulation,the results show that the output microwave power 3.34GW,frequency 9.31GHz,efficiency of about 43%is obtained when the magnetic field is 3.8Tesla and the diode operating voltage is 860kV.The numerical simulation of the injection phase is carried out,and the criterion of judging the phase traction effect is given.It is considered that the randomness of the synchronization time between the injection signal and the diode voltage signal is the main cause of the phase deviation.The influence of the power,frequency and amplitude of the diode voltage and the variation of the waveform on the phase traction is evaluated.In the numerical simulation,when the frequency difference of the injection signal is less than or equal to 50MHz,the power is greater than 88kW,and the diode voltage fluctuation is less than±10kV,the phase difference between the pulses can be controlled within the range of±15°.The experimental platform is built based on TPG2000 pulse driver.when the diode operating voltage 930kV,current 10.6kA,and the guiding magnetic field 3.57Tesla,the output microwave pulse width of 31ns,power of 3.2GW,efficiency about 32%are obtained.The experimental study of the injection phase traction is carried out.The influence of the injection signal power,frequency and diode voltage on the phase of the RBWO output is compared with that of the numerical simulation.When the injection signal is about 210kW,the experimental result shows that the phase jitter can be controlled within the range of±14°in the range of pulse 20ns,and the phase deviation is less than 13°.Compared with the no injection signal,the starting time of RBWO is reduced by about 8ns,and microwave pulse width is also increased.The results show that the injection signal has a positive effect on the increase of microwave pulse width and energy conversion efficiency of RBWO.