Generation And Transmission Of The Radial Electron Beam

In the process of the development of high power microwave, high power, high frequency, high efficiency and miniaturization has become most of the high power microwave source developing direction. However, with the increase of the microwave frequency, the gradually decreased size of the device will leads to the power feed into the device was limited. Even though increase the voltage or current in the same condition can solve the problem of the decreased feed power,this will cause the difficulty in insulation design. At the same time, beam conversion efficiency will decrease with the weight and power loss of magnetic field system increase for beam density grows. So we have to explore the new type of electron beam structure used in microwave devices to meet the development of high power microwave. Due to radial electron beam has a larger emission cross section, which could reduce the current density while keeping the system compact and higher beam conversion efficiency potential simultaneously at the same input power, and lower the influence of larger beam density on the performance of guiding magnetic field system and microwave system. So the radial electron beam is expected to be used in high power microwave source as a new way. The generation and transmission of the radial beam is the first problem need to be solved in the radial beam high power microwave source, while the research report to this problem is less. On this background, this paper design a kind of coaxial foilless diode and guiding magnetic field system to generate and focusthe radial beam transmission, also the problem related to the beam generation and transmission were studied. The research content mainly includes the following aspects:Firstly, the generation of the radial electron beam was studied. We design a kind of foilless diode to generate the radial electron beam, and then the I-V relation, impedance and beam emitting characteristic of the diode were investigated by simulation with numerical calculation. Further we design the insulator structure of the diode. The asymmetrical distrbuciton of azimuthally magnetic field in diode is analyzed. Combined with single electron motion theory,deflection characteristics of the radial electron beam were studied.Furtherly, the relationship between deflection and diode impedance is investigated.Secondly,the space charge limited current of the radial beam was investigation. We establish the space charge field model of the radial electron beam, by solving the Poisson equation and boundary condition for the radial electron in radial transmission line, the potential, electric field and space charge limited current analytic expression of the beam itself were obtain. Next we numerical analysis the nonlinear equation for beam potential and obtain the space charge limited current under the specific condition. At last the theoretical and numerical analysis results is compared, the reason and law of the influence of radial transmission line and beam parameters on the space charge limited current is analyzed, and the influence of the beam current on the non-uniform distribution of the beam density is given.The transmission of the radial electron beam under immersed focusing system is investigated. The magnetic field distribution between plane coils feed with opposite current direction is studied. Transmission model of radial electron beam under immersed focusing system is established. Based onsingle electron motion theory, the transmission characterization of radial electron beam underimmersed focusing system is theoretical analyzed.Relationship between magnetic field intensity with diode impedance is also investigated.Furtherly, the condition of beam deflection under immersed focusing system can be ignored is derived.Thenthe guiding magnetic field system with spirals planes is designed.The steady beam trajectorywithbeam voltage is 300kV and beam current is 7.3kA is obtained within 100mm in radial direction.Then the effect of axial magnetic field component and the uniformity of magnetic field distribution in initial region are analyzed. In order to increase the beam quality and reduce power consumption of magnetic field,a kind of magnetic field system based on the plane coils and permanent magnet is designed. Steady beam trajectorywithbeam voltage is 300kV and beam current is 7.5kA is obtained within 100mm in radial direction.At last the transmission of the radial electron beam under non-immersed focusing system is investigated. A kind of coaxial foilless diode with focusing electrode is designed. Under the condition of no magnetic field is applied, the relationship between beam defiection with diode impedance is analyzed. Then the transmission characterization of radial electron under non-immersion focusing system is theoretically analyzed and the motion status is given.On this basis, a kind of non-immersed focusing system comprised by coil planes and shield plate is designed, with the beam trajectory is simulated. Then the distribution of the magnetic field generated by the finite length cathode stick current is studied. The error analysis of the double port feed current model in simulation is theoretically analyzed and the influence of cathode stick length on non-immersed focusing is investigatied. At last, the principle theory of radial magnetic field focusing radial electron beam is theoretically analyzed. The focusing performance of ideal static radial electron beam transmission under radial period magnetic field is preliminary analyzed. A kind of radial periodic magnetic field system is designed.For beam parameter of voltage is 200kV and current is 100A,transmission characterizatics of radial beamgenerated by diode under radial periodic permanent magnetic field system are studied by simulation. Effect of magnetic intensity on the beam trajectory is given at the same time.