Theory of harmonic radiation using a singleelectron source model
Abstract
Significant progress was recently made toward the understanding of the various mechanisms that generate harmonic radiation in planepolarized free electron lasers. Within the context of a single frequency coherentspontaneous emission model, a distributed transverse source function for a single electron was derived. This source is multiply peaked, with the number of peaks being equal to the harmonic number. The peaks and nulls in the radiation source are analogous to the radiation peaks seen in the spontaneous radiation pattern of a single electron. When the distributed source function is averaged over transverse space, the simplified 1D results are recovered. The distributed source function model predicts the generation of even harmonic radiation with oddsymmetry in the electron wiggle plane (for electrons traveling along the wiggler axis) and odd harmonic radiation patterns with even transverse symmetry. A method for modeling the multipole nature of the harmonic radiation on a discrete grid is described. When the transverse electron beam distribution is slowly varying, all the harmonics can be adequately modeled with multipoles having only a few peaks. This model was incorporated into the 3D FEL simulation code FELEX. Simulations of the Los Alamos and Stanford FEL oscillators were performed. How the harmonic transverse spatial electric field profiles change for different operating conditions is examined.
 Publication:

Presented at the 11th International Free Electron Laser Conference
 Pub Date:
 1989
 Bibcode:
 1989ifel.confT....S
 Keywords:

 Electron Sources;
 Free Electron Lasers;
 Harmonic Generations;
 Harmonic Radiation;
 Mathematical Models;
 Computer Programs;
 Computerized Simulation;
 Electron Beams;
 Spatial Distribution;
 Wave Equations;
 Wiggler Magnets;
 Lasers and Masers