Theoretical research on the annular intensive relativistic electron motion focused by coaxial cusped periodic permanent magnetic field

摘要

This paper theoretically investigates the motion characteristics of an annular intensive relativistic electron beam (IREB) in a coaxial, smooth waveguide under a cusped periodic permanent magnetic (CPPM) field. The motion of the electron beam clearly exhibits a periodic oscillation in a CPPM. For the effective transmission of an IREB, the structural parameters of the CPPM must be chosen carefully. Based on theoretical analysis, stability conditions are suggested. The influence of the magnetic field phase, strength, and period on the oscillation amplitude of the beam envelope is analyzed, and the criteria for minimal oscillation amplitude are proposed accordingly. Notably, the theoretical formula, used to predict the oscillation period of the beam envelope, is proposed and verified by single-particle and particle-in-cell simulation results.