Effect of the Electron‐Beam Self‐Fields on Gain in an Optical Wiggler Pumped Free‐Electron Laser

Abstract

The effects of self fields on gain for a free-electron lasers (FELs) with electromagnetic-wave wiggler and an axial guide magnetic field is presented. The relativistic equation of motion for a single electron for all relevant fields, including wiggler, self-fields and axial guide magnetic field has been solved. Two classes of possible single-particle trajectories in this configuration are found. Result of the numerical calculation shown that the relativistic part of group I (group II) orbits decreases (increases) monotonically with the axial field. The gain equations for the FEL configuration by adding the effect of self-fields have been derived. The numerical calculation has been employed to analysis the gain induced by the effects of the self-fields. It is shown that, for group I orbits the gain decreases in the presence of self-fields and the gain decrement increases with increasing axial guide magnetic field, while for group II orbits the self-fields enhances the gain. The gain decrement and enhancement are due to diamagnetic and paramagnetic effects of the self-magnetic field, respectively. The comparison of the gain for electromagnetic-wave wiggler with the gain in helical wiggler has been done.

Nonlinear simulation of TM mode free electron laser in rectangular waveguide with ion-channel

“…Free electron laser (FEL) devices can operate as a broadband high power microwave (HPM) source in which the kinetic energy of bunched electrons are converted to the energy of a co-propagating wave in the presence of a wiggler [1,2]. Essentially, the mechanism of the wiggler could be based on electrostatic, magnetostatic or electromagnetic periodic fields and have varieties of configurations [3][4][5][6][7][8][9][10] which have been widely studied theoretically and experimentally. Among them, planar wigglers are especially easy to construct and the arrangement of implied magnets determines the polarization of radiated power [11,12].…”

Interaction of a relativistic dense electron beam with a laser wiggler in a vacuum: self-field effects on the electron orbits and free-electron laser gain

“…Although a great deal of attention has been focused on the laser-pumped FEL configuration in recent years, most treatments heretofore have neglected the influence of the equilibrium self-fields of the electron beam, especially in the FELs with a linearly polarized laser wiggler (Bacci et al, 2006;Mehdian et al, 2008;Sprangle et al, 2009;Olumi et al, 2011;Hasanbeigi et al, 2010;Jafari et al, 2014;Hedayati et al, 2015;Amri & Mohsenpour, 2016). It is known that space-charge effects are important in Raman FELs which operate at high electron density and low (relativistic) energy.…”