| Summary: | BackgroundThe ion source is one of the key components of the neutral beam injection system. Radio frequency (RF) ion source has the advantages of long life time, easy maintenance and long pules operation, which make it the main alternative source for the neutral beam ion source in the future.PurposeThis study aims to analyze equivalent impedance characteristics of a high power RF ion source driver with emphasis on the impedance matching network and effective tuning of matching network to achieve high-power and stable plasma discharge.MethodsFirst of all, the analytical model was established on the basis of transformer model. The plasma conductivity was obtained by estimating the ohmic heating frequency and stochastic heating frequency in the plasma. Then, the equivalent impedance of the plasma was coupled to the excitation coils with the transformer model, and the equivalent impedance of the driver was obtained. Finally, parameters of the single drive RF ion source of negative ion based neutral beam injection (NNBI) system of Comprehensive Research Facility For Fusion Technology (CRAFT) were taken as example to calculate variation of equivalent impedance of actuator with plasma electron density by MATLAB code.Results & ConclusionsComputation results show that the analytical model proposed in this study can be used to quickly and accurately calculate the electron temperature in the driver under different gas pressures, and the equivalent impedance under different gas pressures and electron densities, which provides a reference for the reasonable design and tuning of impedance matching network.
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