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SYPT: Symposium Applications and New Trends of Plasmatechnology – An Overview

SYPT 2: Application and New Trends of Plasmatechnology - Part II

SYPT 2.4: Hauptvortrag

Donnerstag, 8. März 2018, 15:30–16:00, M 00.910

Progress in Understanding Arc-Electrode Interaction — •Jürgen Mentel — Ruhr-University Bochum, Electrical Engineering and Plasma Technology, 44780 Bochum, Germany

Within the last years a model of a microscopically thin boundary layer covering the cathode surface was developed managing the current transfer between arc plasma and cathode. An extremely high local electrical power input into the layer effects that the local power- and current-transfer from the arc plasma to the cathode surface are only determined by the local electrode surface temperature and the global cathode fall so that the solution of the cathodic power balance is decoupled from the bulk plasma. For a given arc current generally several solutions are found: always a diffuse mode and mostly several spot modes of arc attachment. The properties of the diffuse mode and of low voltage spot mode are confirmed by measurements at tungsten electrodes. The arc attachment at anodes is determined by the mass flow in front of it and on the anode temperature. In front of cold anodes an electric field reversal and arc constriction occurs, which may need being stabilized by a mass flow. In front of hot, electron emitting anodes the field reversal disappears and the arc attachment becomes diffuse and stable.