A SLOW-WAVE FREE-ELECTRON LASER IN A LONGITUDINAL WIGGLER FIELD

Linearized Vlasov-Maxwell equations are solved to obtain the growth ra te of free electron laser instability from tenuous relativistic electr on beam propagating in a partially dielectric loaded waveguide immerse d in combined axial and longitudinal wiggler magnetic fields. The inst ability appears via cyclotron resonance interactions for wave perturba tions very close to w - kV(z) - w(c) = nk0V(Z), where n is the general harmonic number. For n = 0, the gain is similar to a slow wave cyclot ron amplifier. For n greater-than-or-equal-to 1, the growth rate is su bstantially larger than the standard slow wave free electron laser sch eme utilizing a transverse wiggler field.