The Theoretical Research Of Impedance Matching Network In Ion Cyclotron Resonance Heating

Ion cyclotron resonance heating(ICRH) is the most important auxiliary heating for present-day tokamaks and future fusion reactors. When the ICRH wave interaction with plasma,the antenna resistance variation with the change in the plasma parameters such as ELM and L-H mode plasma transition, which lead the antenna resistance not to match the characteristic impedance of RF transmission line any more. So the power of RF wave reflects rapid from antenna,for transfer the ICRH wave energy to antenna and then coupled to plasma more effectively, the antenna system must have a quick impedance matching network. so the theoretical research of impedance matching network has great significance for the current controlled magnetic fusion experimental and the achievement of high performance steady state operation on fusion reactors.To begin with this paper,Adopting the transmission line theory, the paper analyzes the ion cyclotron resonance heating(ICRH)antenna system’s impedance matching, which obtains matching through a conjugate-T loop with a single stub tuner. The relationship between the impedance matching effect and adjustable transmission line length was numerical simulated. The results show that optimum adjustable transmission line length can make the antenna system obtain good matching and improve matching speed when other experimental conditions are same, which lets the RF power transmit to antenna more effectively and reach good impedance matching state of ICRH system. And then, adopting the transmission line theory, analyzes the innovative ICRF heating system equipped with the the innovative twin stub using a frequency feedback control has been designed to reduce the reflected RF power.The relationship between reflection coefficient and antenna loading before and after frequency modulation was numerical simulated, the results show that :the the innovative twin stub tuner with frequency modulation can better reduce the reflection coefficient of antenna transmission system, let the RF power transmit to antenna more effectively.