Electrical characterization of atmospheric pressure arc plasmas

The properties of atmospheric pressure arcs are investigated by means of electric exploration of plasma column and anode region. For the electrostatic probe technique, where the level of collisionality distorts the characteristic curve, data interpretation is difficult because no comprehensive underlying theory exists for the non-homogeneous electric arcs used in industry. Results are presented from an extended study of Langmuir probes applied to short, point-plane arcs. A multi-wire apparatus, operating for arc currents in the range 50-200 A is described and ion current densities and temperature maps are shown. The reduction of the probe determined temperature with respect to emission spectroscopy values is discussed and the cooling is ascribed to ion-electron recombination within the perturbation region formed around the probe. This region is investigated by means of emission spectroscopy and the extension found agrees both with numerical estimations and fast speed camera photographs. Diamond Like Carbon (DLC) partially coated wires can address data inversion problems and the role of arc flow directionality on charge capture and preliminary observations are shown. Charge capture and anode fall structure can be investigated using a split-anode technique. A prototype of a modified apparatus is described and preliminary results on the collected current are given.Received: 20 August 2003PACS: 52. Physics of plasmas and electric discharges - 52.80.Mg Arcs; sparks; lightning; atmospheric electricity - 52.70.-m Plasma diagnostic techniques and instrumentation