Current-free double layers in helicon sources

Yu Jeng Su, Ker-Chung Shaing

Research output: Contribution to journalArticle

Abstract

A model for the formation of a stationary current-free double layer in collisionless plasmas expanding in a magnetic nozzle is presented. The model consists of the dynamics of cold ions, isothermal hot electrons and fere-isothermal, i.e. almost isothermal, cold electrons. It can determine the position and amplitude of the double layer including the jump in cold electron temperature across the layer. The magnitude of the jump is consistent with experimental observations. Plasmas are accelerated mainly by the magnetic nozzle and the contribution from the double layer is small. The important effects of the ion charge state Z on the flow speed at the nozzle throat and at the exit are also discussed. It is found that the Mach number at the magnetic nozzle throat is √Z which can be tested in experiments. The exit velocity also scales as √Z. To increase the thrust power, the ion charge state Z could be an important parameter.

Original languageEnglish
Article number055008
JournalPlasma Sources Science and Technology
Volume20
Issue number5
DOIs
Publication statusPublished - 2011 Oct 1

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magnetic nozzles
ion charge
throats
collisionless plasmas
hot electrons
Mach number
thrust
nozzles
electron energy
ions
electrons

All Science Journal Classification (ASJC) codes

  • Condensed Matter Physics

Cite this

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abstract = "A model for the formation of a stationary current-free double layer in collisionless plasmas expanding in a magnetic nozzle is presented. The model consists of the dynamics of cold ions, isothermal hot electrons and fere-isothermal, i.e. almost isothermal, cold electrons. It can determine the position and amplitude of the double layer including the jump in cold electron temperature across the layer. The magnitude of the jump is consistent with experimental observations. Plasmas are accelerated mainly by the magnetic nozzle and the contribution from the double layer is small. The important effects of the ion charge state Z on the flow speed at the nozzle throat and at the exit are also discussed. It is found that the Mach number at the magnetic nozzle throat is √Z which can be tested in experiments. The exit velocity also scales as √Z. To increase the thrust power, the ion charge state Z could be an important parameter.",
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Current-free double layers in helicon sources. / Su, Yu Jeng; Shaing, Ker-Chung.

In: Plasma Sources Science and Technology, Vol. 20, No. 5, 055008, 01.10.2011.

Research output: Contribution to journalArticle

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