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Cathode erosion in inert gases: The importance of electrode contamination

Abstract

Experimental results are presented for electrode erosion on copper electrodes in magnetically rotated arcs in argon and helium. Measurements were also made of the arc voltage and velocity. The effects due to the contamination of the electrode surface by either a native contaminant layer (copper oxide and carbon traces) or the continuous injection of very small amounts of various diatomic gases (nitrogen, oxygen, chlorine, and carbon monoxide) into the inert plasma gases were determined. The erosion rates for pure argon were significantly higher than those for pure helium (13.5 μg/C for argon and 1 μg/C for helium) and with both gases, very high arc velocities were measured initially (>60 m/s for argon and >160 m/s for helium) when a natural contaminant layer was still present on the cathode. The removal of this layer resulted in lower velocities (2m/s for argon and 20m/s for helium) and higher erosion rates. The removal of the layer was much faster with argon, due possibly to higher electrode surface current densities for argon arcs.

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Szente, R.N., Munz, R.J. & Drouet, M.G. Cathode erosion in inert gases: The importance of electrode contamination. Plasma Chem Plasma Process 9, 121–132 (1989). https://doi.org/10.1007/BF01015830

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  • DOI: https://doi.org/10.1007/BF01015830

Key Words

  • Electrode erosion
  • plasma torches
  • magnetic rotation
  • contamination