R. Drori et al., FREE-ELECTRON MASER OSCILLATOR EXPERIMENT IN THE UHF REGIME, Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment, 358(1-3), 1995, pp. 151-154
A nonrelativistic electron beam (<4 keV) travels in this experiment in
a non-dispersive waveguide along a planar undulator and an axial magn
etic fields. The electron beam has a Gaussian pulse shape with a 1 ms
pulse width. Two distinct radiation bursts are observed during the ele
ctron energy sweep. Each burst contains a different range of microwave
frequencies. One burst corresponds to the FEM interaction, at similar
to 0.8 GHz. The other burst corresponds to the cyclotron resonance in
teraction, at similar to 5 GHz. This experiment demonstrates an FEM op
eration in an extremely long wavelength (37.5 cm) in the UHF regime..