Laser scattering and current transport in an argon arc plasma

Finkelnburg and Maecker (1956) have assumed that in electric arcs with considerable axial concentration gradients these gradients could provide such a strong driving force for the electric current that there is little need for the presence of an electric field with a substantial intensity. The considered conditions could exist in high-performance arc lamps or in arc-welding processes. The present investigation has the objective to study the mechanism of current transport in such free-burning arcs, taking into account tests with an arc in argon under atmospheric pressure. The generalized Ohm's law is used for the description of current transport phenomena. A laser diagnostic approach is used for the determination of temperature and density at approximately 100 points within the plasma. The scattered radiation from a dye laser provides information regarding the temperature and the electron density. It is found that the processes sustaining the electric current are partly related to a diffusion of the charged particles in connection with axial temperature and concentration gradients.