Self-fields in a free-electron laser with electromagnetic-wave wiggler and ion-channel guiding

Abstract

A theory of self-fields in a free-electron laser with electromagnetic-wave wiggler and ion-channel guiding is presented. The equations of motion for an electron have been analyzed. This equation together with its numerical solutions shows that the first part of group I and II trajectories is unstable. The effects of self-fields on the gain for groups I and II orbits have also been investigated by deriving the gain formula and numerical calculation. A gain decrement is found due to the effects of self-fields for group I orbits, and the gain enhancement for group II orbits. The gain decrement (enhancement) arises from diamagnetic (paramagnetic) generated by the self-fields. The gain decrement (enhancement) increases by increasing the beam density.

Self-field effects on small-signal gain in two-stage free-electron lasers

“…Employing the method used by Mehdian et al [19], i.e., z(t) = cβ t+c t 0 t 0β z (t )dt dt , we can write…”

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

“…The nonlinear formulation for the analysis of self-field effects in FELs for both planar and helical wiggler configurations described by Freund et al [5]. The self-field can either enhance or reduce the external pump field, depending on the latter's phase velocity and strength of the longitudinal guide magnetic field [6,7]. Some theoretical studies of the electron orbits in the electromagnetic-wave wiggler have been carried out [8][9][10][11][12].…”

Kinetic description of a wiggler-pumped ion-channel free-electron laser by applying the Einstein coefficient technique

“…A uniform axial magnetic field is often employed to collimate the relativistic electron beam in the transverse direction. Another advantage of the ion-channel guiding is that the effect of the ion channel would also be to increase both the gain and efficiency of the interaction (Jha and Kumar 1996;Mahdian and Raghavi 2006;Mahdian et al 2008;Hasanbeigi et al 2011;Su and Tang 2011;Sadegzadeh et al 2012); it also permits beam currents higher than the vacuum limit. The use of the ionchannel guiding as an effective method for enhanced focusing of an intense electron beam in a single-pass FEL was offered by Takayama and Hiramatsu years ago to improve the system performance (Takayama and Hiramatsu 1988).…”

“…The use of the ion-channel guiding approximately solves the transverse beam breakage instability due to an intense electron beam (Jha and Kumar 1998). Another advantage of the ion-channel guiding is that the effect of the ion channel would also be to increase both the gain and efficiency of the interaction (Jha and Kumar 1996;Mahdian and Raghavi 2006;Mahdian et al 2008;Hasanbeigi et al 2011;Su and Tang 2011;Sadegzadeh et al 2012); it also permits beam currents higher than the vacuum limit. The presence of an ion channel as an electron-beam guiding device is a cost-effective alternative to the axial guide magnetic field.…”