Axial magnetic field effects on the operation of a millimeter-wave free electron laser

A new experimental configuration has been assembled to study Raman free electron laser operation at millimeter wavelengths. Initial experiments have been conducted with the device operating as a superradiant amplifier to study the effects of the axial magnetic guide field on the electron dynamics and beam-wave interaction in the wiggler. Preliminary measurements indicate the production of substantial power at approximately 3.5 mm, a wavelength consistent with a coupling of the pump shifted, slow-space-charge wave with the fundamental waveguide mode. The parametric dependence of power thresholds and wavelength on pump and guide magnetic fields are shown to be in agreement with theory.