Optimal Design On Mixing Focusing System For High Power Radial Electronic Beam

High efficiency,high power and miniaturization have become the trends of most high power microwave sources these days.Owing to the large emission section of the radial electron beam,the space-charge effect and beam current density are low when the input current is same.So lower intense guiding magnetic field can be used to obtain higher beam-wave conversion efficiency.And the power and weigh of excitation system generating guiding magnetic field can be reduced,which contributes to the miniaturization and high efficiency of the microwave source.The design of radial electron beam focusing system is one of the key problems in developing high power microwave source.However,there is relatively few researches about design of radial electron beam focusing system now.In this thesis the high power radial electron beam mixing focusing system has been studied based on permanent magnet and spiral coil on the basis of the existing research.The main work of the thesis are:Firstly,the theoretical radial electron beam mixing focusing system is introduced.And radial electron beam space charge field distribution,the principle of immersed focusing for radial beam,the principle of immersed focusing for radial beam influenced by the axial magnetic field,and the principle of pulsed magnetic field generated by spiral are concluded.Secondly,the magnetic field distribution of the high power radial electron beam mixing focusing system is optimized.The stabilized transmission beam trajectories of a 400kV?30kA radial beam under different immersed focusing magnetic fields are studied through simulation,and the radial magnetic field is optimized according to the law of the radial electron beam pulsation.The magnetic field distributions of a pair of coils with opposite current and a pair of axially magnetized permanent magnets are studied.A kind of radial beam focusing system based on permanent magnet and spiral coils are designed.The simulation results show that the axial component of the magnetic field of the mixing focusing system increases the beam fluctuation of the electron beam and reduces the beam width of the electron beam.The 400kV?30kA radial beam can transmit with a small fluctuation under the magnetic field generated by the designed focusing system.Finally,the spiral coil of the mixing focusing system is designed.The influence of coil winding mode on the focusing system power supply system is analyzed.The results show that the radial beam can transmit with a small fluctuation under the magnetic field generated by the designed focusing system.Besides,compared to single-winding spiral coils circuit,the proposed double-winding spiral coils circuit posses shorter pulse current front and more narrow pulse current width,and lower required capacitance,which is more conducive to the miniaturization of system.The effects of the coil frequency of the coil excitation current,the wall thickness of the anode wall and the radial transmission line on the magnetic field of the coil pulse are studied by simulation.On this basis,the two-wire coiled coil in the mixing focusing system is designed synthetically.When the coil is at the maximum current which is 1.099 ms,the guiding magnetic field ensuring the stabilized transmission of the electron beam is generated.Since the pulse time of the designed magnetic field of the coil is in the order of microsecond,and the time at which the coaxial non-foil diode generates and transmits the electron beam is in the order of nanosecond,the coil-guided magnetic field can be regarded as a stable magnetic field,and can ensure the electron beam transmit stably in the designed magnetic field system during the stable transmission of radial electron beam.