Physical Limitations and Design Criteria for a Solid-State Gyrotron.

Scaling of conventional microwave sources to operate in the near millimeter wave 100-1000 GHz portion of the electromagnetic spectrum is difficult and often impossible. Severe fabrication and heat dissipation problems are common. In the microwave tube area, workers at the Naval Research Laboratory and elsewhere have shown that the severity of these problems can be considerably reduced by employing the electromagnetically large gyrotron configuration, and kilowatts of continuous power have been generated at millimeter wavelengths. In this report we investigate the possibility of applying similar design principles to the development of solid-state gyrotron. In this report we review the physical mechanism that gives rise to oscillations and present the underlying mathematics. Numerous nonideal factors are considered namely, a finite electron mean-free-path, injection of electrons which are not monoenergetic, metallic and dielectric ohmic losses in the resonant cavity, and presence of a finite electric field in the interaction region. Use of a reverse-biased Schottky tunnel barrier for electron injection is analyzed in detail and is found to be a promising structure for producing sufficient current to sustain oscillations. Calculations are based on InSb parameters, as this material appears best for this application because of its long mean-free path. The main conclusions of this study are that a with available materials it is unlikely that oscillations can be sustained and b with three- to five-fold increase in the mean-free-path, oscillations appear possible, albeit at a very high frequency approx. 1000 GHz. Author