Electrical features of radio-frequency atmospheric pressure helium discharge with and without dielectric electrodes

A comparative study of radio-frequency atmospheric pressure glow discharge (rf APGD) generated in helium with and without dielectric electrodes to investigate the effect of electrodes insulation on electrical features of APGD is presented. In the α mode, both the rf APGDs remain volumetric, stable and uniform. In the γ mode, the APGD without dielectric electrodes shrinks into a constricted plasma column whereas APGD with dielectric electrodes remains stable and retains the same volume without plasma constriction even at higher densities of discharge current. A comparison of electrical features of both rf APGDs in normal and abnormal glow discharge regimes is presented. In both APGDs with and without dielectric electrodes, impedance measurements have been performed and compared with equivalent circuit models. The measured impedance data is found to be in good agreement with simulated data. (paper)