Quasi-Optical High Purity HE₁₁-Mode Exciter for Oversized Corrugated Waveguide Transmission

Abstract

Oversized corrugated waveguide transmissions are used to transmit high power millimeter wave for electron cyclotron heating in ITER. The HE₁₁ mode purity of the waveguide components is a critical issue not only in the high power operation but also in the low power operation to evaluate the components. Conventional single Gaussian beam system causes edge diffraction and excites higher order modes at the waveguide aperture. A proposed HE₁₁-mode exciter uses beam interference between two Gaussian beams interference and serves the high purity HE₁₁ mode without the edge diffraction. The HE₁₁-mode exciter consists of a scalar feed horn antenna, quasi-optical mirrors and a beam splitter (combiner). Phase matched mirrors correct the Gaussian-like beam excited from the horn antenna to pure Gaussian beam. Authors report the experimental study of the exciter.