Design and Development of Microwave Interferometer and Reflectometer Systems for Plasma Diagnostics in Tokamak

Abstract

The microwave interferometry and reflectometry have been extensively used to measure electron density and its fluctuations in various tokamaks. The tokamak has become the leading research tool in the world-wide effort to develop valuable electrical power based on controlled thermonuclear fusion. This is the most successful scheme for confining plasma magnetically. newlineThe present work aims to design and development of microwave interferometer and microwave reflectometer systems for plasma diagnostics in tokamak. A 100 GHz microwave interferometer with seven-channel is designed, established and used for the measurement of the radial profile of the electron density (and#119899;and#119890;) of plasma in AdityaTokamak. The resolution of measurement of the density is and#119899;and#119890;=2.0 ×1011and#119888;and#119898;and#8722;3.The time resolutions and spatial are 10 and#956;s and 7 cm and, respectively. The line-averaged measurements of plasma density in Aditya Tokamak from seven channels are carried out. The radial profile of the plasma density is obtained by using Abel inversion. The density measured by this interferometer is well matched with the measurement of the Thomson scattering diagnostics. newlineA 3mm wave interferometer was designed and developed to measure the plasma density online with the central chord of the Aditya Tokamak. A real-time processing method for fringe signals with a hardware logic up/down-counting circuit that converts fringes to phase shift in units of and#120587; radians was developed. The microwave circuit of the central chord of a homodyne interferometer system is modified to make a quadrature circuit by using phase shifters and magic tees. This is used to produce the sine/cosine fringe signals. These outputs are converted into pulses and passed to wired logic up/down fringe counter. Digital synchronous logic circuit is implemented in a CPLD, followed by DAC and scaler, which produce a voltage proportional to increase or decrease in plasma density in real time. Initially, fringe counter is tested with function generator and then with a prototype quadrature