Comparison of electron temperature in DC glow discharge and AC glow discharge plasma

Abstract

Knowing electron temperature and electron density is important for any plasma related applications. In this research, the electron temperature and electron density of argon plasma generated by low frequency AC power supply and a high voltage DC power supply were investigated. The measurements were compared, both experimentally and theoretically. For the experiment, a long glass cylindrical tube was used as a chamber where the electrodes were placed at 37.5 cm apart. A high voltage function generator power supply was operated at various frequencies and it was also used for DC operation. The electron temperatures were measured by Optical Emission Spectroscopy (OES) technique for different operating pressures of 0.1 mbar, 0.6 mbar and 1.1 mbar. For the simulation, both plasma theory and finite element method were used to simulate dynamics of the plasma in the cylindrical setup. From the experiment, the range of breakdown voltage was found to be between 0.80 to 2.3 kV. The length of DC glow discharge dark regions of the plasma decreases due to increasing in both operating pressure and voltage. AC glow discharge shows positive charge and negative charge swing. From the DC discharge, the maximum value of electron temperature was found to be 0.810 eV and the minimum value was 0.610 eV under the operating pressure 0.1 and 0.6 mbar respectively. From AC glow discharge plasma, the maximum electron temperature was 0.907 eV and the minimum was 0.540 eV under operating pressure 0.1 and 1.1 mbar respectively. Collision loss between ions and electrons causes this variation in the results.