Design and Fabrication of Birdcage Resonators for Low-pressure Plasma Excitation

This paper presents a design, analysis and optimization of birdcage resonators employed in a novel radiofrequency plasma source. Three resonators were simulated and fabricated. The resonators differ in their design and in the different materials of used dielectric - polyimide and polytetrafluorethylene (PTFE). The resonance frequency of fabricated samples possesses a maximal error of 2.2% compared to the simulated values. The performance in plasma excitation is related to the electrical parameters, while the best performing resonator (PTFE-based) exhibits the maximum real impedance of 644.3 ohm at the resonance frequency and the 799.5 V/m electric field strength. This resonator shows the best power efficiency in a plasma ignition experiment. The resonator ignited the discharge at ca. 1 Pa of ambient air atmosphere with only 0.34 W of input radiofrequency power.