On the frequency scaling of coaxial gyroklystrons

In this paper, we present scaling arguments for coaxial gyroklystron systems in order to assess their ultimate peak power capabilities as a function of output frequency. After reviewing the tradeoff equations for magnetron injection guns as they relate to frequency scaling, we present an analysis of the scaling properties and limitations of coaxial gyroklystron circuits. We then present concrete designs of both electron guns and microwave circuits to demonstrate the validity of the scaling arguments. The examples are derived from high-energy physics applications, where amplifiers with peak powers in excess of 100 MW are envisioned to be required in the millimeter wave range of frequencies. Concrete designs of coaxial systems predicted to produce about 100 MW in Ku-Band, Ka-Band, and W-Band are presented and compared. We demonstrate that there are a number of potential limitations to high-frequency operation.