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Publication
Detailed numerical simulation of cathode spots in vacuum arcs: Interplay of different mechanisms and ejection of droplets
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Advisor(s)
Abstract(s)
A model of cathode spots in high-current vacuum arcs is developed with account of all the poten tially relevant mechanisms: the bombardment of the cathode surface by ions coming from a pre existing plasma cloud; vaporization of the cathode material in the spot, its ionization, and the inter action of the produced plasma with the cathode; the Joule heat generation in the cathode body;
melting of the cathode material and motion of the melt under the effect of the plasma pressure and
the Lorentz force and related phenomena. After the spot has been ignited by the action of the cloud
(which takes a few nanoseconds), the metal in the spot is melted and accelerated toward the periph ery of the spot, with the main driving force being the pressure due to incident ions. Electron emis sion cooling and convective heat transfer are dominant mechanisms of cooling in the spot, limiting
the maximum temperature of the cathode to approximately 4700–4800 K. A crater is formed on the
cathode surface in this way. After the plasma cloud has been extinguished, a liquid-metal jet is
formed and a droplet is ejected. No explosions have been observed. The modeling results conform
to estimates of different mechanisms of cathode erosion derived from the experimental data on the
net and ion erosion of copper cathodes.
Description
Keywords
Vacuum arcs Cathode spots Numerical simulation Ejection of droplets . Faculdade de Ciências Exatas e da Engenharia
Citation
Kaufmann, H. T. C., Cunha, M. D., Benilov, M. S., Hartmann, W., & Wenzel, N. (2017). Detailed numerical simulation of cathode spots in vacuum arcs: Interplay of different mechanisms and ejection of droplets. Journal of Applied Physics, 122(16), 163303. DOI: 10.1063/1.4995368
Publisher
American Institute of Physics