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

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