Narrow Results

Spectroscopic and Langmuir probe measurements are presented to characterize the argon glow discharge plasma generated by a cost-effective 50 Hz AC power source. Optical emission spectra (400–700 nm) are recorded for different gas flow rates and filling pressures at constant power level. The plasma parameters (electron temperature and density) are deduced from the relative intensities of Ar-I and Ar-II lines. The variation in the intensity ratio of the selected emission lines, electron temperature and density is studied as a function of gas flow rate and filling pressure. Slight increase in the intensity ratio I₂(426.62 nm)/I₁(404.44 nm) of the emission lines is observed whereas the electron temperature and density are found to decrease with increase in gas flow rate and filling pressure.

The thermal plasma conditions under a practical use could be affected by the insertion of a solid, cold probe severely. In this study, we calculated flowing thermal plasmas with two different sizes of a Langmuir probe into an argon free burning arc system and investigated the thermal and flow disturbances caused by the metallic probe. From the results, the severe disturbance of a large part of the thermal plasma, especially the axial velocity field, by the inserted probe has been found. Therefore, it might be a practical solution to use a Langmuir probe which has sufficiently small diameter for avoiding such a severe disturbance.