Observations of the glow-to-arc transition between thoriated tungsten electrodes with a parallel RC circuit

Abstract

Using a simple discharge circuit, we have investigated effects of the circuit parameters on glow-to-arc transition behaviour. A direct current power source is used with a capacitor and resistors. Plasma is generated between thoriated tungsten electrodes at atmospheric pressure in argon. Current and voltage are recorded while capturing plasma images.A variation of the charge on the capacitor causes a fluctuation in discharge current. Due to the current fluctuation, the electric power dissipated between the electrodes increases during a temporary glow phase and decreases during a temporary arc phase. The cathode tip has been heated in the glow mode and a glow-to-arc transition occurs finally. The current fluctuation can be reduced by increasing the resistance. The temporary arc and glow durations are affected by the time constant of the circuit.