Analytical and simulation studies of frequency doubling gyroklystron amplifiers

Abstract

newline The continuous push for higher frequency and higher power microwave sources has created a critical need for advanced vacuum electron devices capable of delivering stable and efficient amplification in the millimeter and submillimeter wave frequency ranges. Conventional microwave tubes face limitations due to miniaturization constraints at these frequencies, while solid-state and quantum-optical devices are restricted by low output power and efficiency. In this context, gyroklystron amplifiers have emerged as promising candidates owing to their capability to exploit fast-wave cyclotron resonance mechanisms, enabling the generation of high output power while operating at moderate magnetic field strengths. newlineHowever, conventional gyroklystron development at higher frequencies encounters significant challenges, primarily higher magnetic field requirements and limited availability of suitable high-power drivers. Operation at higher cyclotron harmonics presents a potential solution to reduce magnetic field requirements, but drastically diminishes efficiency and output power due to weakened beam-wave interaction. To overcome these critical limitations, this research investigates frequency-multiplying gyroklystrons as an innovative approach that facilitates successive frequency multiplication across stages, significantly enhancing electron bunching efficiency that typically deteriorates at higher harmonics. newlineThe research presented in this thesis focuses on the development and performance optimization of frequency-doubling gyroklystron amplifiers. Unlike conventional harmonic devices, frequency-doubling configurations utilize fundamental mode operation in the input cavity and second harmonic mode operation in the output cavity. This configuration not only reduces the higher magnetic field requirements but also allows the use of larger interaction structures, accommodating broader beam diameters and enhancing power handling capabilities. These devices are particularly attractive due to their ability to operate