Macroparticle separation and plasma collimation in positively biased ducts in filtered vacuum arc deposition systems

I. I. Beilis*, M. Keidar, R. L. Boxman, S. Goldsmith

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

Abstract

The objective of the present work was to determine the influence of positive bias on plasma and macroparticle (MP) flow in curved magnetized plasma ducts. The plasma bulk and sheath regions were analyzed. In the plasma bulk, the current density and electrical field component normal to the wall were obtained and used as boundary conditions for the near wall sheath region. In the sheath, a nonstationary model for MP charging and motion was developed. The solution of the hydrodynamic equations in the plasma when a positive bias is applied to the wall result in a radial electrical current. The electric field in the plasma bulk is generated by the separation between the magnetically confined electrons, and the ions, which are thrown outwards by the centrifugal force. The field increases with increasing positive bias. It was shown that MPs traveling in the sheath accumulate a charge which depends on the potential distribution, in contrast to MP charging in the quasineutral plasma where the charge depends on plasma density and electron temperature. MP trapping in the near-wall sheath was found. MPs may move in the sheath region along the wall by a repetitive process of electrostatic attraction to the wall, mechanical reflection and neutralization, followed by MP charging and attraction, etc. For example, titanium MPs with a radius less than 0.4 μm and with a velocity component normal to the wall of about 20 m/s are trapped if the sheath potential drop exceeds 20 V. It was obtained that the MP transmission fraction through filter decreases by more than few orders of magnitude due to the trapping effect when a bias potential of + 100 V is applied between the wall and the plasma.

Original languageEnglish
Pages (from-to)1358-1365
Number of pages8
JournalJournal of Applied Physics
Volume85
Issue number3
DOIs
StatePublished - Feb 1999

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