Calculation of Axial Magnetic Field for Combined-periodic Permanent Magnet Focusing System

keywords:combined-periodic  periodic permanent magnet  calculation of the axial magnetic field  traveling wave tube

Abstract:Aiming at the requirements of high beam current density and low-ripple electron beam focusing for high power and high frequency vacuum electronic devices, a high peak-value and high-harmonic adjustable combined-periodic permanent magnet focusing system is designed, theoretically modeled and computed. The structure introduces a new pole piece to form a combined period to adjust the high harmonics of the magnetic field to improve the stability of high current density electron beam. In order to optimize the high harmonics of the magnetic field, in order to optimize the high harmonics of the magnetic field and further expand the stability region of the magnetic field parameter, the influence of the magnetic field strength at the pole is considered, and a theoretical model is established on the basis of the idealized theoretical model. By analyzing the influence of each parameter of the focusing structure on the different harmonics respectively and comparing the results of the calculations with those of the CST software, the calculation error at the peak of the magnetic field of the theoretical model is reduced from 8. 08% to 3. 91%, and the average error is reduced from 1. 30% to 1. 04%, which provides a good basis for the rapid design of the composite-cycle permanent magnet focusing system rapid design provides a method.