Current status towards the development of a submillimeter-wave reflex klystron

Summary form only given. The reflex klystron is a promising candidate for use as a source of submillimeter-wave power at the milliwatt level. Such sources are required to fulfill the requirements for small-footprint, cost-effective and efficient fundamental sources for medical imaging and remote sensing applications at terahertz frequencies. Dimensional constraints associated with traditional manufacturing techniques, material issues and the performance requirements placed upon electron sources have impeded the development of such devices for use at extended frequencies. Here, we describe the current status towards the development of such a device through the application of a number of novel techniques. Firstly, an accurate and repeatable process for the fabrication of micrometric-scale re-entrant cavity designs is described. Results of scattering-parameter measurement and subsequent cavity parameter extraction are given, demonstrating the suitability of this technique for the production of resonant cavities for use in extended-frequency reflex klystron designs at submillimetre-wave frequencies. Secondly, preliminary results describing the performance of high-density, un-gated field emitter array structures are provided. These indicate that the achievable current densities are such that these devices are applicable for use in a number of novel high-frequency vacuum microelectronic designs, including the extended frequency reflex klystron discussed herein. Finally, we describe the construction and testing of a complete reflex klystron unit for operation at millimetre and submillimetre wave frequencies. We provide details of the vacuum system layout, cathode run-in process and cavity loading/tuning. Latest results and future work are also discussed.