Spectral and Electrical Characteristics of a Stabilized DC Arc Seeded With Potassium

A systematic investigation of spectral and voltage-current (U-I) characteristics of a DC arc plasma was performed. The vertical, argon and wall stabilized DC arc plasma was seeded by an easily ionizable element (EIE), potassium, in a wide range of concentrations. It was found that different arc currents and potassium contents in the plasma have considerable influence on the plasma properties. A lower potassium content (< 10 g/l of KCl in solution) introduced into the arc at lower currents (<6A) causes an increase in arc voltage and a change in the arc spectrum (intensity of lines), while at higher arc currents (>6A) it causes no change in the electrical characteristics, but a further change in the intensity of the arc spectrum. Higher potassium concentrations, >20 g/l of KCl, increase the arc voltage at higher currents (>6A). There is a critical quantity of potassium in the plasma which suppresses high energy processes (ionization, excitation…) for a fixed arc current, while spectral composition and lateral distribution of the residual emitted spectra become essentially changed. Amounts of potassium above critical do not cause further changes in the plasma spectral composition nor in the I-U characteristic, except in the spectral line intensities.