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Physics of spotless mode of current transfer to cathodes of metal vapor arcs
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Orientador(es)
Resumo(s)
A fresh attempt is made to clarify the physics of the
diffuse, or spotless, mode of current transfer that may occur on
cathodes of vacuum arcs if the average cathode surface temper ature is high enough, about 2000 K. It is shown that in the case
of chromium cathode the usual mechanism of current transfer
to arc cathodes cannot sustain current densities of the order of
105–106 A · m−2 observed in the experiment, the reason being
that the electrical power deposited into electron gas in the near cathode space-charge sheath is insufficient. It is hypothesized that
the electrical power is supplied to the electron gas primarily in
the bulk plasma, rather than in the sheath, and a high level of
electron energy in the vicinity of the sheath edge is sustained
by electron heat conduction from the bulk plasma. Estimates of
the current of ions diffusing to the sheath edge from the quasi neutral plasma gave values comparable with the experimental
current density, which supports the above hypothesis. On the
contrary, the spotless attachment of vacuum arcs to gadolinium
cathodes may be interpreted as a manifestation of the usual
mechanism of current transfer to arc cathodes. Results given
for gadolinium cathodes by a model of near-cathode layers in
vacuum arcs conform to available experimental information.
Descrição
Palavras-chave
Arc discharges Electrodes Vacuum arcs . Faculdade de Ciências Exatas e da Engenharia
Contexto Educativo
Citação
Benilov, M. S., & Benilova, L. G. (2015). Physics of spotless mode of current transfer to cathodes of metal vapor arcs. IEEE Transactions on Plasma Science, 43(8), 2247-2252.
Editora
Institute of Electrical and Electronics Engineers