Research On A Novel Millimeter Wave Radial Relativistic Backward Wave Oscillator

In recent years,due to great development of the pulsed power source technology,plasma technology,electric vacuum technology and other disciplines,the research on high power microwave technology which is widely applied in military and civilian aspects,has been greatly promoted.Especially,due to the intrinsic advantage,such as narrow band,high energy density and resolution,strong anti-interference ability,more and more attention has been grabbed to millimeter wave.But the power capacity of the high power microwave source has restricted the development of the device in the millimeter wave band.So,this paper proposes and investigates a novel radial millimeter relativistic backward wave oscillator.The device can work in a relatively low magnetic field to output GW-class microwave with a compact structure when operates in millimeter wave band.The radial slow wave structure is studied systematically and comprehensively in this chapter.The dispersion curve of the radial slow wave structure has been figure out by the electromagnetic simulation software,and the relations between structure parameters and the dispersion curve have been discussed.According to the analysis of electric field distribution in structure,the TM01 mode which shows the characteristic of volume wave is chosen as the working mode of the device.And we discover that the volume wave characteristics of TM01 mode can be optimized by decreasing the spacing between two pieces of the radial slow wave structure,increasing the cavity width and reducing the cavity depth.The longitudinal resonant characteristic of the finite-length radial slow wave structure are studied by the S-parameter method,and the method to increase mode separation in the radial slow wave structure at high frequency band has also been proposed.The advantages of the segmented radial slow wave structure,the reflection cavity and the output cavity are verified by the simulation.Simulation shows that the segmented radial slow wave structure can effectively enhance the beam-wave efficiency of the radial high power microwave oscillator.It is necessary to design a reflector to prevent the microwave leakage to the diode area.The output efficiency can be improved due to the supplement of the output cavity.The working process of the radial device is intuitively and comprehensively showed by 2.5-dimensional particle simulation software.The effects of the gap between the anode and the cathode,the operation parameters and the guiding magnetic field on the working state of the device are investigated.In order to reduce the maximum field strength,the radial slow wave structure is inverted.After optimization of the structure and the parameters,a high power radial millimeter wave backward wave oscillator is obtained.A microwave with output power of 1.47 G and frequency of 36.27 GHz is generated in simulation when the diode voltage is 418 kV and the beam current is about 15.7 kA.The device can work in the low magnetic field of 0.6 T,and the efficiency can reach 22.4% when the maximum electric field intensity is just 800 kV/cm in the cavity.Radial confining magnetic field is proposed at last.In order to obtain a radial magnetic field about 0.6 T,we calculated out the solenoid inductance parameters,number of required capacitor groups and length of the electromagnetism line and the radial device can work normally with the guidance of the magnetic field in the PIC simulation software.