Development of Ku-band frequency-doubling coaxial gyroklystrons for accelerator applications

Summary form only given. At the University of Maryland, we have been exploring the possibility of using gyroklystrons to drive advanced linear colliders above X-band. We have designed and tested a high-gain four-cavity frequency-doubling system to enable us to use a phase-stable TWT driver. We have also designed an output waveguide system which transforms the power from the output waveguide and equally divides it into two standard WR62 rectangular waveguides. The scheme involves a rippled wall converter to convert the TE₀₂ mode to the TE₀₁ mode, then a custom converter to produce the TE₂₀ mode in the rectangular guide, followed by linear tapers and a standard bifurcation. We hope to use this transport system to energize and test Ku-band accelerator structures. In this paper, we present the experimental results of our four-cavity frequency doubling coaxial gyroklystron. The beam voltage and current are 460 kV and 540 A, respectively, and the applied magnetic field is about 5 kG. The expected interaction efficiency and gain at our design point are 34% and 61 dB, respectively. We also present design and test results for a number of other subsystems. We compare the theoretical calculations with the cold test results for each of the components used in the output waveguide system and present amplitude and phase balance measurements for the two output rectangular waveguides. Finally, we describe efforts to improve beam quality via modifications in emitter design and manufacturing.