HARMONICS IN FEL WITH PLANE POLARIZED WIGGLER AND AXIAL-GUIDE FIELD

Spontaneous and coherent emission of radiation in a FEL with planar wi ggler and axial magnetic fields is investigated. The eccentricities of the resulting electron trajectory and spontaneous emission are seen t o be different. On interaction with e.m. radiation electron orbits giv e rise to elliptically polarised coherent emission at principal and ha rmonic frequencies. Beam amplifications at higher harmonics peak at lo wer axial field strengths. The peak gains are significantly larger tha n the gain obtained at the next lower frequency in the absence of axia l magnetic fields.