Unipolar Arcs

Nedospasov, A. V.; Петров, В. Г.; Zykova, N.M.

doi:10.1109/tps.1985.4316414

Cited by 11 publications

(2 citation statements)

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“…When the plasma of a pulsed electrodeless microwave discharge [2] or a pulsed dc discharge [3] interacts with a metal surface, it can give rise to microscale discharges-local plasma objects with characteristic dimensions from a few fractions of a micrometer to several hundred micrometers. In the literature devoted to the interaction of a hot plasma with the chamber walls of magnetic fusion devices, the origin of such microscale discharges is usually attributed to the development of unipolar arcs [4]. In studies of high-current vacuum switches, microscale plasma objects arising at the cathode of an arc discharge are generally referred to as cathode spots [5].…”

Section: Introductionmentioning

confidence: 99%

10.1007/s11452-008-2007-3

2010

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Excitation of microplasma discharges in the interaction of a plasma flow with a metal surface partially covered with a dielectric film is investigated experimentally and theoretically. A new phenomenon-the excitation of microplasma discharges at the boundary between the free metal surface and the area covered with the film-is discovered. Microplasma discharges at the edge of the dielectric film are initiated by a strong electric field that arises between the free metal surface and the outer surface of the film in the interaction with the plasma flow. This field gives rise to surface breakdowns at the film edge, followed by the development of primary microplasma discharges. In turn, the dense plasma of primary microplasma discharges causes secondary microplasma discharges, which also arise at the edge of the dielectric film after the external plasma flow has already terminated. Microplasma discharges gradually evaporate the dielectric film, and the surface cleaned of the film acquires a microrelief due to the local melting and subsequent fast cooling of the metal at the sites of microplasma discharges.

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Section: Introductionmentioning

confidence: 99%

10.1007/s11452-008-2007-3

2010

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“…This will initiate a high probability for the reignition of subsequent arcs at the same locations. It is well known that high power plasmas in contact with extended surfaces can initiate unipolar arcs having a return current path ending at the same surface [3,4]. It is also known that it is very difficult to tum a current in a strongly magnetized plasma, like the edge of a tokamak, back to the surface.…”

Section: Discussionmentioning

confidence: 99%

Arcing through a thick B/sub 4/C layer

Laux

Schneider

Hantzsche

et al.

20th International Symposium on Discharges and Electrical Insulation in Vacuum

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I 3 Abstract -The traces of strong erosion found on solid components covered with thick (0.1 7") B,C-layers facing the edge of a fusion plasma are identified as relicts of arcing. Spots of light observed on the suflace seem to exist during the whole liftime of the fusion plasma ( 4 . 3 s ) and stay motionless despite the strong external magnetic field (B=2.3T). The related big craters are single cylindrical holes reaching through the B,C-layer down to the Cu-substrate. In subsequent discharges the re-ignition of a new arc ai the location of an old crater was found to be very probable. The interesting peculiarities of ignition and burning of arcs on BIC-layers have been confirmed in laboratory experiments (B=0.4T) revealing that the arc current has remarkably IOW noise. Theoretical investigations show that a thermal runaway does not exist because of the rise of the conductivity of the semiconducting B,C with temperature. Long living arcs inzuence strongly the stability of the imbedding fusion plasma and the final erosion of the substrate material at the bottom of the crater holes reduces the suitability of B C as coverage material.

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Unipolar Arcs. Experimental and Theoretical Study

Beilis

2020

Plasma and Spot Phenomena in Electrical Arcs

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Unipolar Arcs

Cited by 11 publications

References 11 publications

10.1007/s11452-008-2007-3

10.1007/s11452-008-2007-3

Arcing through a thick B/sub 4/C layer

Unipolar Arcs. Experimental and Theoretical Study

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