Profile of a Relativistic Electron Beam Propagated through a Linear Wiggler and an Axial Guide Field

The density and parallel temperature of an electron beam passing through a magnetic guide field and a linear wiggler are determined as functions of distance from the anode. Starting with a given beam emittance and phase-space distribution at the anode, single-particle orbits are employed to propagate the beam along the drift tube. Finite-gyro-orbit effects induce substantial modulation in density. Additionally, the evolution of an initial spread in the parallel speed of the electrons is sensitively dependent on the wiggler strength and contributes to further density fluctuation. The beam's parallel temperature, a critical factor in determining laser efficiency and gain, is found to increase significantly when the wiggler strength is raised.