Abstract
We present results of calculations of the radiation from a helically cut waveguide launcher, a so-called Vlasov launcher, which is commonly used either internal or external to a gyrotron for purposes of mode conversion. A gyrotron internal mode converter consists of such a launcher that radiates the waveguide mode as a nearly Gaussian beam in free space followed by a set of mirrors to focus and direct the radiation. The radiation from the launcher is first calculated using a geometric optics representation of the waveguide mode. Then the radiation is calculated in the quasi-optical limit, including diffraction. These analytic results are compared to a rigorous calculation using the computer code SURF3D, which uses an electric field integral equation (EFIE) approach. Good agreement is obtained between the quasi-optical theory and the SURF3D calculation. The present results provide new insights into the accuracy of the quasi-optical theory and may be useful for the design and improvement of Vlasov-type mode converters.
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Acknowledgements
The authors would like to thank J. Neilson for providing the SURF3D code, S. T. Han and Y. Hidaka for help with paper preparation. This research is supported by the U. S. Department of Energy, Office of Fusion Energy Sciences, and also by the National Institutes of Health (NIH) / National Institute for Biomedical Imaging and Bioengineering (NIBIB) (contracts EB001965 and EB004866).
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Choi, E.M., Shapiro, M.A., Sirigiri, J.R. et al. Calculation of Radiation from a Helically Cut Waveguide for a Gyrotron Mode Converter in the Quasi-Optical Approximation. J Infrared Milli Terahz Waves 30, 8–25 (2009). https://doi.org/10.1007/s10762-008-9418-x
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DOI: https://doi.org/10.1007/s10762-008-9418-x