A Ka-band CHI-wiggler free-electron maser: experimental results

Due to the nature of the Coaxial Hybrid Iron wiggler, a resonance between the transverse wiggler and cyclotron motions of the beam exists which can enhance the Free-Electron Maser interaction. The difference in behavior on either side of this resonance is presented. Amplification with a bandwidth on the order of a few percent was achieved. In spite of beam propagation problems, the gain was about 5 dB for operation below gyroresonance, and 7 dB above it, when wideband grazing intersection operation was achieved. A gain as high as 13.5 dB was obtained for cutting intersection between the beam line and the TE01 dispersion curve.