Analysis of electron dynamics and two mechanisms in a coaxial magnetic wiggler

Abstract

The electron dynamics in a coaxial magnetic wiggler are analyzed numerically and studied in particle-in-cell (PIC) simulation. Electrons wiggle in angular direction to coherently generate a TE01 mode, and the results are consistent with each other. The trajectory of the electron in 3-D space and the effects on the trajectories of the initial phases of wiggler magnetic fields are researched, which helps to choose appropriate initial phases to control the trajectory of the electron. An oscillator of FEL with a coaxial magnetic wiggler based on a quasi cavity is designed for efficiently generating the TE01 mode with the high saturation power and high efficiency. The advantages of the quasi cavity structure are analyzed and the parameter-selection rules are investigated. Based on the electron dynamics, the process of electron bunching in the self amplified spontaneous emission (SASE) and the Seeded mechanisms are studied. The Seeded mechanism could accelerate electron bunching greatly and reduce the saturation time than the SASE by half.