Analysis of the electron dynamics in a Raman free electron laser with reversed axial guide magnetic field

Numerical simulations of the electron dynamics in a combined helical wiggler and reversed guide field arrangement, currently being under investigation at the MIT Plasma Fusion Center, are presented. The paper focuses on the unexpected breakdown of the FEL amplifier performance for a specific value of the reversed guide field, corresponding to the positive value at magnetoresonance. As an outgrowth, the theoretical possibility of higher harmonics generation in the presence of a reversed guide field is highlighted.