Sheath parameters for non-Debye plasmas

Simulations and arc damage

I. V. Morozov, G. E. Norman, Z. Insepov, J. Norem

Research output: Contribution to journalArticle

9 Citations (Scopus)

Abstract

This paper describes the surface environment of the dense plasma arcs that damage rf accelerators, tokamaks, and other high gradient structures. We simulate the dense, nonideal plasma sheath near a metallic surface using molecular dynamics (MD) to evaluate sheaths in the non-Debye region for high density, low temperature plasmas. We use direct two-component MD simulations where the interactions between all electrons and ions are computed explicitly. We find that the non-Debye sheath can be extrapolated from the Debye sheath parameters with small corrections. We find that these parameters are roughly consistent with previous particle-in-cell code estimates, pointing to densities in the range 1024-1025m -3. The high surface fields implied by these results could produce field emission that would short the sheath and cause an instability in the time evolution of the arc, and this mechanism could limit the maximum density and surface field in the arc. These results also provide a way of understanding how the properties of the arc depend on the properties (sublimation energy, for example) of the metal. Using these results, and equating surface tension and plasma pressure, it is possible to infer a range of plasma densities and sheath potentials from scanning electron microscope images of arc damage. We find that the high density plasma these results imply and the level of plasma pressure they would produce is consistent with arc damage on a scale 100 nm or less, in examples where the liquid metal would cool before this structure would be lost. We find that the submicron component of arc damage, the burn voltage, and fluctuations in the visible light production of arcs may be the most direct indicators of the parameters of the dense plasma arc, and the most useful diagnostics of the mechanisms limiting gradients in accelerators.

Original languageEnglish
Article number053501
JournalPhysical Review Special Topics - Accelerators and Beams
Volume15
Issue number5
DOIs
Publication statusPublished - May 3 2012
Externally publishedYes

Fingerprint

sheaths
arcs
damage
dense plasmas
simulation
plasma sheaths
plasma pressure
plasma jets
plasma density
accelerators
molecular dynamics
gradients
cold plasmas
liquid metals
sublimation
field emission
interfacial tension
electron microscopes
scanning
causes

ASJC Scopus subject areas

  • Physics and Astronomy (miscellaneous)
  • Surfaces and Interfaces
  • Nuclear and High Energy Physics

Cite this

Sheath parameters for non-Debye plasmas : Simulations and arc damage. / Morozov, I. V.; Norman, G. E.; Insepov, Z.; Norem, J.

In: Physical Review Special Topics - Accelerators and Beams, Vol. 15, No. 5, 053501, 03.05.2012.

Research output: Contribution to journalArticle

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