Investigation of Cathodic Arc Plume in an Atmospheric Pressure Environment Using Stark Broadening

The plume of a cathodic arc operated in atmospheric pressure gas is examined using an intensified camera and a spectrograph. A 0.2-J pulse arc is shown to generate a glowing jet 10 mm in extent. Images recorded in the first microseconds after ignition show that the jet has a smaller core ≈2 mm in length. A spatially resolved Stark broadening measurement is performed along the jet core. The measured electron density is 1-2 x 10²⁰ m^-3. A model for the cathodic arc plasma-gas interaction is presented. The obtained equilibrium between the forward and reverse charge exchange processes is suggested as enabling the extended jet core.