Abstract
The decay of plasma following the forced extinction (similar, equals 1 μs) of a 200 A DC vacuum arc with copper electrodes has been studied by an electrical probing technique. For times between 1 and 12 μs after current zero a constant current was injected into the decaying plasma and the time-dependent voltage across the resulting dynamic ion sheath at the negative electrode was measured. A model of the dynamic sheath is in good agreement with the measurements. The plasma density in the region of the negative electrode is about 4×1018 m−3 at 1 μs after current zero and falls to about 2×1017 m−3 after 12 μs.
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