Aachen PK 2003 – wissenschaftliches Programm

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P: Plasmaphysik

P 4: Poster I

P 4.47: Poster

Montag, 17. März 2003, 17:45–19:15, Foyer

Investigation of the spot and diffuse mode of the cathodic arc attachment — •Oliver Langenscheidt, Lars Dabringhausen, Marco Redwitz, Stefan Lichtenberg, and Jürgen Mentel — Ruhr University Bochum, Fundamentals of Electrical Engineering Group, Universitätsstr. 150, 44780 Bochum, Germany

For the investigation of high intensity discharge (HID-)lamp electrodes measuring methods were developed and applied to a special model lamp for DC and AC arc discharges in argon or xenon. This work is focussed on the different modes of arc attachments on pure or doped cylindrical tungsten electrodes.

Three different modes of arc attachment were observed during cathodical operation the diffuse, spot and super spot mode. The formation of these modes depends on the electrode material and diameter, arc current and gas pressure (xenon/argon). In addition to the diameter of the attachment zone the current density is the main difference between the three modes. High speed photography as well as electric, pyrometric and spectroscopic measuring methods are used to characterize the modes.

We present first results for the region of existence for the spot and diffuse mode combined with electric and pyrometric measurements of the cathode fall. By time and spatial resolved spectroscopic measurements combined with high speed photography of the near electrode tip region the transition between the diffuse and spot mode during cathodic operation phase is characterized for DC as well as for AC arc currents.

Granted by the BMBF (Project Ref.-No 13N7763.)