Voltage fluctuations in low-current atmospheric arcs

Large amplitude fluctuations in the arc potential in the initial phase of an arc have been examined for a low‐current resistive break arc at atmospheric pressure. These fluctuations were accompanied by an increase in the emitted intensity of the light coming from Pd I, ${\mathrm{N}}_2^{+}$ , and ${\mathrm{N}}_2^{*}$ , and a leveling of the light from Pd II, suggesting that the initial metallic vapor arc maintains itself by ionizing the surrounding gas. As the gap increases, the arc characteristically enters a second phase in which the discharge is maintained in the gaseous environment.