GENERALIZED DERIVATION OF FREE-ELECTRON-LASER HARMONIC RADIATION FROM PLANE-POLARIZED WIGGLERS

Radiation at the harmonic frequencies in free-electron lasers is affected by several factors including misalignment of the electron beam and wiggler axes, and transverse gradients of the electron beam and wiggler field. These processes manifest themselves as changes in the harmonic power and transverse intensity profile. A transverse source function for the monochromatic radiation from a single electron in a plane-polarized wiggler magnetic field is derived that addresses these various effects. The resultant source is a composite of multiply peaked sources distributed over the local transverse wiggle range of each electron where the nth source has n peaks. For transverse-electron-beam density distributions that are slowly varying, an excellent description of the harmonic radiation can be obtained by including only the first few sources. Transverse averages of the distributed sources are taken to make comparisons with previous one-dimensional theories where they exist. © 1990 The American Physical Society.