Distribution of plasma parameters in a nitrogen transferred DC arc

• Published in: Journal of physics. D, Applied physics Vol. 28; no. 2; pp. 344 - 352
• Main Authors: Megy, S, Baronnet, J -M, Ershov-Parlov, E A
• Format: Journal Article
• Language: English
• Published: Bristol IOP Publishing 14.02.1995; Institute of Physics
• Subjects: Arcs, sparks, lightning; Electric discharges; Exact sciences and technology; Ions; Nitrogen; Physics; Physics of gases, plasmas and electric discharges; Physics of plasmas and electric discharges; Q1; Spectroscopy; Gases; Spatial distribution; Electron temperature; Atmospheric pressure; Nitrogen molecules; Direct current; Gas flow; Electron density; Experimental study; Electric arcs
• ISSN: 0022-3727; 1361-6463
• DOI: 10.1088/0022-3727/28/2/018

Spatial distributions of plasma temperature and electron density have been measured in a transferred direct current arc running at atmospheric pressure in 500 scc s super(-1) nitrogen gas flow. The measurements were made at 100-250 A current for two arc lengths of 100 and 200 mm. Optical spectroscopy techniques have been used to determine the plasma parameters using local emissivities of atomic and ion spectral lines, as well as continuum radiation. In the arc positive column the parameters agree well, that is the plasma state is close to local thermodynamic equilibrium. Near the cathode some variation has been observed in the measured data, showing a possible deviation from the equilibrium state: emissivities of atomic and ion lines give very different results. The phenomenon can be explained, if one supposes that the plasma ionization composition does not correspond with an equilibrium model of the plasma in this spatial region, with the electron density being higher than would follow from the Saha equation for pure nitrogen plasmas. This is supported by our measurement data of the plasma electron density.