Over-sized round waveguide with a diameter about Ø33.0 mm excited in the TE01 mode has been widely adopted for microwave transmission and coupling to the ECR (Electron Cyclotron Resonance) plasma with the superconducting ECR ion sources operating at 24 or 28 GHz, such as SECRAL and VENUS. In order to study the impact of different microwave modes on ECRH (Electron Cyclotron Resonance Heating) efficiency and especially the production of highly charged ions, a set of compact and efficient TE01-HE11 mode conversion and coupling system applicable to 24 GHz SECRAL whose overall length is 330 mm has been designed, fabricated and tested. Good agreements between off-line tests and calculation results have been achieved, which indicates the TE01-HE11 converter meets the application design. The detailed results of the optimized coupling system will be presented in the paper.
Abstract-A novel basis function, called as the Modified Phase Extracted (MPE) basis function, has been proposed to analyze threedimensional scattering problems for electrically large, thin dielectriccoated targets. The MPE basis function, which can be defined on large (e.g., a wavelength or more) curvilinear geometrical elements, is developed for quadrilateral cells. Consequently, combining with the thin dielectric sheet (TDS) approximation, the MPE basis function solves the scattering problem accurately with fewer unknowns than the solutions based on the conventional basis functions. In order to improve the accuracy of the solution solving the problem which has thicker dielectric coatings, some modifications about the TDS approximation model are made. Numerical examples demonstrate that the validity of the proposed approach in solving the scattering from electrically large, thin coated objects.
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