Study On Quasi-Optical System For Plasma Radiometer

Quasi-optical systems operate from millimetre and sub-millimetre wave to Terahertz range. They have been widely applied for communication, target detection, guidance, remote sensing, radio astronomy, contactless metal detection and plasma diagnostics. These applications have many advantages over microwave and infrared systems. Quasi-optical technology uses open architecture of optical components and overcomes many demerits of traditional metal waveguide, such as high loss, low power capacity and difficulty for manufacturing. Quasi-optical technology also takes beam coupling and diffraction into account. Therefore, it is an integrated approach of optical theory and electromagnetic calculation.Firstly, the basic theory of Quasi-optic system, Gaussian beam propagation, transformation, truncation and matching are presented in the thesis. It also gives a review on the design method for Quasi-optical systems, focusing on the Gaussian beam coupling to feed elements and design principles of ellipsoidal reflector. Then the design of a Quasi-optical system for the plasma electron cyclotron emission radiometer installed on EAST is presented. The system operates from 100 to 170 GHz and is composed of an ellipsoidal reflector, a planar plate and a circular corrugated waveguide. This system is designed to focus a Gaussian beam at the plasma center to the corrugated waveguide. The Quasi-optical system is simulated by SiMatrix developed by EM Theory and Application International Research Laboratory of BUPT and is verified by commercial software GRASP. SiMatrix based on DGBA is faster than the commercial software GRASP based on Physical Optics. The simulation results of the two softwares both indicate that the designed system satisfies the required specifications.This thesis adopts several analysis methods and simulation softwares to build a Quasi-optical system for plasma radiometer. This system has many advantages, such as broad bandwidth, low loss and high resolution, which are important for plasma electron temperature distribution measurement and related physical research in the Tokamak.