Planar Orotron Experiments in the Millimeter Wavelength Band

摘要

The planar orotron is a device which is capable of producing moderate to high power levels of millimeter and submillimeter wavelength radiation. The resonator is a slow-wave structure consisting of a rectangular metal grating which is opposed by a planar conducting boundary. The device operates in the surface harmonic mode: Electrons interact with axially traveling waves which evanesce above the grating surface, and the amplified radiation leaves the resonator in parallel with the beam. Operation in both the forward and the backward mode is possible. The resonator cavity is designed to enhance longitudinal reflections,and thereby enhance the output power and efficiency. The output frequency and tuning range are determined by the grating parameters. Experiments performed in the backward mode have produced radiation from 30 to 110 GHz at power levels ranging from 100 W to 2 kW. The efficiencies vary from 1 to 7 percent. The measured frequencies are closely predicted by a theory which is also presented in this manuscript. Start currents are as low as 50 mA, and agree with calculated values in the cold-beam single-particle limit. The gratings may be scaled to operate at higher frequencies, and techniques for doing so are presented and discussed. Reprints. (jhd)