Greifswald 2009 – wissenschaftliches Programm

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P: Fachverband Plasmaphysik

P 8: Niedertemperaturplasmen

P 8.11: Vortrag

Dienstag, 31. März 2009, 16:20–16:35, INP-Staffelgeschoß

Dynamics of Cathode Spot Plasma Parameters in Spark and Arc Stages of Vacuum Discharge — •Ralf Methling¹, Dirk Uhrlandt¹, Alexander Batrakov², Sergey Popov², Elena Pryadko², and Klaus-Dieter Weltmann¹ — ¹INP Greifswald, Felix-Hausdorff-Str. 2, D-17489 Greifswald — ²Institute of High-Current Electronics SB RAS, Tomsk, Russia

Modern notations do not foresee principle differences in cathode spot mechanisms in the breakdown stage as compared with steady burning arc. The cathode spots generate similar craters regardless of discharge burning time under the condition of cold cathode. The spot plasma has rather stable parameters while gradual changes in the plasma parameters can convincingly be explained in terms of cathode heating effects. However, invariability of spot mechanisms is not the feature of initial period of spot burning since the moment of gap breakdown.

Recently, we observed a surprising behaviour of cathode spot plasma characteristics within the first microsecond of discharge burning. Though ion energies per charge ratios are the same for all charge states at the long-burning arc discharge, there is a dependency of the ratios on charge states in the starting phase. The similar transition is seen in spot light radiation using high-speed time resolved spectroscopy. Higher ion charge state lines start to emit first, being followed by lowers charge state lines. Finally, atomic lines appeared after the delay as long as half microsecond. The latter fact correlates with exactly the same delay of resonant absorption by spot plasma at atomic lines.