Investigation of Developed Liquid Stub Tuner for the Antenna Impedance Matching for High-Power RF Plasma Experiments

A 1-5/8" liquid stub tuner (LST) with effective impedance matching for ion cyclotron RF signal transmission is presented. The main objective is to maximize the power transmission from RF source to antenna for Steady-State Superconducting and Aditya Tokamaks. The design and characterization of an LST for varying susceptance from 10 to 100 MHz are described here. The difference in the dielectric constants of air and liquid makes the wavelengths different in these two mediums. This difference in wavelengths of RF waves is utilized for changing the impedance of LST. The LST's experimental susceptance is confirmed by CST simulation and MATLAB analysis. The single-stub matching mechanism is implemented using the validated approach. The theoretical research indicates the LST's mechanical benefits over traditional ones. Instead of finger contact-based sliding mechanics, the LST uses liquid height movement. It avoids sparks from high-current finger connections in traditional air dielectric stub tuners' moving plungers. This idea for impedance matching overcomes the constraints of traditional stub tuners where spark gets developed between moving plunger and coaxial conductors.