Design and Development of Transmission Line Components at 42GHz for ECRH Applications

Abstract

The gyrotron system is developed by multi-institution for efficient plasma heating at 42±0.2GHz with 200kW/3sec. The output mode of the developed gyrotron is unpolarized TE03 mode. For high power millimeter wave applications, this unpolarized mode must be converted into polarized mode. In order to achieve this, the gyrotron requires external transmission line systems to convert unpolarized mode (TE03) to polarized mode (HE11). The HE11 mode has a distribution of electric field identical to that of an ideal Gaussian mode (polarized mode). The preferred mode for high power transmission is the polarized mode. This transmission is through corrugated waveguide, which attains low insertion loss than any other mode and waveguide. For this conversion, a transmission line system carrying high microwave power has been developed. The components of transmission line system are: mode converters, up tapers, Miter bend, Corrugated Waveguide. The conversion sequence for this transmission line system starts from: up tapers, mode converters (TE03-TE02, TE02-TE01, TE01-TM11, and TM11-HE11), miter bends (TE01 and HE11) and HE11 corrugated waveguide. newlineFor low power testing of the transmission line, components mode transducer has been developed. In this thesis, a novel design approach is proposed for and#9633;TE10 (rectangular) to and#9675;TE01 (circular) mode transducer for electron cyclotron resonance heating (ECRH) applications. The design consists of two parts: first part has a rectangular waveguide, which transforms and#9633;TE10 to and#9633;TE20 mode, and in the second part, conversion of and#9633;TE20 into and#9675;TE01 mode has been attained. The electric field pattern, mode conversion newlineefficiency and the operating principle of the individual parts are discussed, optimized, and analyzed. The novelty of this integrated design lies in the fact that it has merits of sidewall and inline coupling. Simulation study and optimization of the individual sections of the proposed mode converter were carried out using Computer Simulation Technology (CST) and Microwave Studio Software (MWS