Quasi-optical system for converting gyrotron output into Gaussian beam

Summary form only given. High purity mode operation output ensures effective conversion of output radiation into the Gaussian beam. We have developed a new gyrotron, Gyrotron FU VA, which has a carefully designed resonant cavity in collaboration with the Max-Planck Institute for Plasma Physics and the Institute for High Power Pulse and Microwave Technology at the Research Center (FZK) Karlsruhe. In order to avoid conversion of the cavity mode to spurious modes, the cavity has an optimized design with nonlinear up-tapers and a rounded iris at the output. The resonance calculation using a scattering matrix formalism (SM-code) was performed taking into account the complete gyrotron geometry including the pumping sections (slots) and the window. The radiation patterns are measured by two-dimensionally (x-y plane) moving pyro-electric detector array over the gyrotron window. The measurement demonstrates that Gyrotron FU V can produce outputs of high purity mode for several operation modes. The patterns for these modes agree well with the intensity profiles calculated. This demonstrates that Gyrotron FU VA can produce outputs of high purity mode. Such a feature is favorable for converting a gyrotron output into a Gaussian beam. We have constructed a quasi-optical system intended to convert the radiation of the Gyrotron FU VA into bi-Gaussian beams. The system consists of two components, namely a quasi-optical antenna and an ellipsoidal mirror. The former converts the gyrotron radiation of TE/sub 0n/ and TE/sub 1n/ operating modes into linearly-polarized beams and the latter produces the required far-field pattern. The measurements of the final beam structure have demonstrated that the system developed produces bi-Gaussian beams from the outputs of TE/sub 03/ and TE/sub 13/ operating modes.