Research On Relativistic Cerenkov Generator Focused By Coaxial Periodic Permanent Magnet

High power microwave(HPM)technology has a wide range of applications in both civil and military areas.With the development of practical HPM system,research on the compactness and miniaturization of HPM generators has attracted more and more attention.Reducing the guiding magnetic field,and then realizing the permanent magnet packaging of the HPM generator,is an important technical route for the miniaturization of the HPM generation system.However,the volume and mass of the existing permanent magnet systems are still relatively large,which brings some restrictions to the HPM application.In order to further reduce the mass of the guiding magnet of the HPM generator,the HPM generation technology under the focusing of periodic permanent magnet(PPM)is explored and studied in this thesis.The coaxial relativistic Cerenkov generator(CRCG)focused by the cusped coaxial PPM is conducted systematically.Through theoretical calculations and numerical simulations,the influence of the main parameters of the cusped coaxial PPM on the envelope amplitude and oscillation period of the annular intensive relativistic electron beam(IREB)is studied,and the necessary condition for the stable transmission of the annular IREB is given.It reveals the minimum envelope condition and the calculation formula of the beam envelope period for the annual IREB guided by coaxial PPM,which provides theoretical guidance for the magnet design.Based on the requirements of the electron beam quality when the annular IREB is transmitted by PPM,a foilless diode that can produce high-quality annular IREB is proposed.The introduction of a focusing electrode effectively suppresses the radial diffusion of the IREB and realizes the diode's effective operation under low magnetic field.Using the method of etching graphite cathode by laser,the cathode emission threshold is reduced,and the cathode emission uniformity under low magnetic field is improved.A new magnetic circuit configuration of the integrated cusped coaxial PPM,with a magnet embedded in the focusing electrode and a coaxial magnet in the transmission area,is proposed.Based on the research results of the beam transmission,the design of magnetic circuit is achieved.After overcoming many engineering and technical problems,the coaxial PPM system with a weight of 45 kg is successfully developed.Subsequently,based on the developed magnet,the transmission experiment of the annular IREB focused by coaxial PPM is carried out,and the effective transmission of annular IERB is realized.Based on the cusped coaxial PPM magnetic field,the technical scheme of the large overmode CRCG was proposed.Through simulation optimization,under the measured magnetic field of the developed magnet,an output power of 450 MW in Ku band is obtained in the PIC simulation.Afterwards,the experiment of HPM generation is carried out.For the first time at home and abroad,the HPM generation under cusped coaxial PPM is realized in the experiment.The microwave with an output power of 160 MW at 14.08 GHz is achieved,and the pulse width could reach 20 ns.Technical feasibility of HPM generation under PPM is systematically verified.