Advanced design of quasi-optical launchers using a surface integral formulation

Summary form only given, as follows. The current generation of high power gyrotrons operate in high-order whispering gallery modes. Prior to extraction of the RF power from the gyrotron, a quasi-optical launcher and focusing mirrors are used to convert the power to a Gaussian quasi-optical mode. The current method uses a combination of internal mode converter and step-cut launcher. The efficiency of conversion is currently between 90-95%, meaning that a substantial amount of power is lost inside the gyrotron. The current suite of computational design tools typically achieve less than 90% conversion of cavity power to a usable Gaussian mode. Calabazas Creek Research, Inc. is funded by the U.S. Department of Energy to develop an exact analysis of the converter/launcher system using a surface integral formulation of Maxwell's equations. A forward-backward method and spectral acceleration are used to reduce the computational requirements. Applying these techniques will result in a design code that can run on engineering workstations of modest cost. In addition to eliminating design uncertainties due to analysis approximations, this technique will allow for arbitrary deformations in the converter and launcher surface. Such flexibility would allow engineers to explore alternative designs for achieving higher efficiency. The presentation will describe details of the formulation and comparison to experimental measurements.