Electrostatic probe measurements in the outer region of a low pressure arc

The plasma density and electron temperature of the plasma generated in a pu lsed low-pressure are operated with Ar gas filling at p = 2 and 10 mbar hav e been determined employing a spherical Langmuir probe located in the outer region of the are channel. A theoretical model has been used for the inter pretation of the probe signals, which predicts the plasma structure resulti ng from the interaction of the metallic ions generated at the cathode spots with the neutral gas. Both collisionless and high-pressure (diffusive) the ories have been employed to infer time-averaged plasma parameters from the probe signals. A reasonable agreement is found between the determined plasm a density, electron temperature and ion flux attenuation with the correspon ding values predicted by the theoretical model.