Research On Breakdown Phenomenon Of High Power Microwave Window

The RF breakdown of the high power microwave window is the factor that greatly influences the microwave source and the entire vacuum system.The RF breakdown of the high power microwave window is often excited by the multipactor effect on the surface of the window.Therefore,it is of great practical significances and research values to carry out the study on the multipactor effect of high power microwave window.In this paper,the multipactor effect in the circular waveguide window is studied,the key factors influencing the multipactor are analyzed,and the suppression action of the resonant magnetic field on the multipactor effect of the pill-box window is analyzed.?1?A model for multipactor in a circular waveguide window on the surface of the window under the action of the TE₁₁ mode is established,and the Monte Carlo algorithm is used to track the electron trajectory.Theoretical analysis and simulation results show that the longitudinal velocity of electrons along the z-axis is the main reason for maintaining the multipactor effect on the surface of the window.The research was found that the multipactor effect is influenced by the window radius,field frequency,polarization mode and reflected wave.Either increasing the radius of the window disk or reducing the field frequency aggravated the multipactor effect.Moreover,the waveguide window transmitting the circularly polarized TE₁₁ mode led to a more severe multipactor than that in the linearly polarized TE₁₁ mode using the same parameters.The effect of the reflected wave was also proved to deteriorate the multipactor effect in a circular waveguide window.By simulating these influencing factors one by one,when changing these influencing factors to increase the power capacity of the energy output window,the effect of multipactor needs to be fully considered.?2?A model for multipactor inside the pill-box window is established,and the study on suppressing the multipactor effect is carried out by resonant magnetic field.The motion equations of electrons under the action of an external DC magnetic field in three directions are deduced,and the electrons cloud avalanche is observed,which were found that the multipactor cannot be suppressed on the surface of the window when the resonant magnetic field was used in three directions.To analyze the conclusion,the effect of external DC magnetic field on suppressing the multipactor under the action of the orthogonal field mixed mode(TE₁₁+TM11)is studied.The susceptibility diagrams of x and y direction are fitted,respectively.As the simulated results show,if the resonant magnetic field is perpendicular to the tangential electric field and the normal electric field,respectively,when the normal electric field lags behind the tangential electric field by ?/2,as Ezf increases,the area of multipactor moves in the negative direction of the y-axis and the area of the multipactor region also shrinks.When the normal electric field leads the tangential electric field by ?/2,there will be two susceptibility diagrams,and one of the strong susceptibility diagrams will have a narrow area and increases with the increase of the orthogonal electric fields.When the resonant magnetic field is parallel to the tangential electric field,the increase of Ez/f suppresses the multipactor,and the increase of Ey/f aggravates the multipactor.