Microwave Imaging Reflectometry For The Measurement Of Turbulent Fluctuations In Tokamaks

Author : Xing Hu
Publisher :
ISBN 13 : 9780355149487
Total Pages : pages
Book Rating : 4.1/5 (494 download)

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Download or read book Design and Implementation of a Microwave Imaging Reflectometer (MIR) for the EAST Tokamak written by Xing Hu and published by . This book was released on 2017 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Nuclear fusion is one of the promising ways to generate renewable energy to solve the current energy crisis. However, controlled nuclear fusion with net power gain has not yet been achieved due to the instabilities inside the fusion plasmas. In order to control and eliminate these instabilities, diagnostic tools have been developed to understand the physics. Most of the characteristic frequencies of fusion plasmas fall within the millimeter wave region of the electromagnetic spectrum, which makes microwave imaging systems excellent tools for visualizing the particle activities inside fusion plasmas. There are two types of microwave imaging diagnostic systems developed at the Plasma Diagnostic Group at UC Davis: one is the electron cyclotron emission imaging (ECEI) system, which measures the ECE radiation from the plasma to determine electron temperature fluctuation and the other is the microwave imaging reflectometer (MIR), which injects multi-frequency probing beams into the plasma and measures the reflected beams from different cutoff surfaces to determine the electron density fluctuation. In this dissertation, the hardware setup of both ECEI and MIR systems is discussed. Characterization of the ECEI system for the HL-2A tokamak at Chengdu, China, and the MIR system for the DIII-D tokamak at La Jolla, USA, are given as an introduction to the laboratory testing methods of these microwave imaging systems. The topic of particular emphasis in this dissertation is the development of the latest generation MIR system for the EAST tokamak at Hefei, China. This system consists of 8 radial channels separated by different probing frequencies ranging from 75 to 103 GHz, and 12 vertically separated receiving channels, providing 96 imaging pixels inside the fusion plasma. As an important protection to the receiver system, development of the frequency selective surface based notch filter is discussed. The improved notch filter resonating at 140 GHz for the EAST MIR system has reduced the pass band insertion loss by half while maintaining over 30 dB rejection at the stop band. The implementation of embedded microcontrollers and RF components with serial peripheral interface (SPI) enables the system to be remotely controlled over the Ethernet. Technology advancements for future MIR systems including the CMOS based transmitter on chip and the digital beam forming technology are briefly discussed at the end of this dissertation.