Abstract

Both theoretical and experimental investigations have indicated that the spread of the electron beam (e-beam) limits the operating wavelength, gain, and efficiency of the free-electron lasers and masers. Recently, several authors proposed methods of e-beam conditioning.^1-3 Here we present a novel method of conditioning the e-beam by using a tapered, reversed axial guide magnetic field. The results of nonlinear 3-D simulation have confirmed our proposal. In the simulation we consider a solid e-beam having radius Rb = 0.25 cm, energy Eb = 750 keV, and current Ib = 300 A in a cylindrical waveguide with radius Rw = 0.51 cm, where an axial guide field Bz and 3-D wiggler with amplitude Bw and period lw = 3.18 cm govern the electrons and 5000 electrons with the initial state of Gaussian random distribution are tested.

© 1994 IEEE