Numerical analysis of electronegative plasma in the extraction region of negative hydrogen ion sources

S. Kuppel, D. Matsushita, Akiyoshi Hatayama, M. Bacal

Research output: Contribution to journalArticle

32 Citations (Scopus)

Abstract

This numerical study focuses on the physical mechanisms involved in the extraction of volume-produced H? ions from a steady state laboratory negative hydrogen ion source with one opening in the plasma electrode (PE) on which a dc-bias voltage is applied. A weak magnetic field is applied in the source plasma transversely to the extracted beam. The goal is to highlight the combined effects of the weak magnetic field and the PE bias voltage (upon the extraction process of H? ions and electrons). To do so, we focus on the behavior of electrons and volume-produced negative ions within a two-dimensional model using the particle-in-cell method. No collision processes are taken into account, except for electron diffusion across the magnetic field using a simple random-walk model at each time step of the simulation. The results show first that applying the magnetic field (without PE bias) enhances H? ion extraction, while it drastically decreases the extracted electron current. Secondly, the extracted H? ion current has a maximum when the PE bias is equal to the plasma potential, while the extracted electron current is significantly reduced by applying the PE bias. The underlying mechanism leading to the above results is the gradual opening by the PE bias of the equipotential lines towards the parts of the extraction region facing the PE. The shape of these lines is due originally to the electron trapping by the magnetic field.

Original languageEnglish
Article number013305
JournalJournal of Applied Physics
Volume109
Issue number1
DOIs
Publication statusPublished - 2011 Jan 1

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plasma electrodes
hydrogen ions
negative ions
ion sources
numerical analysis
magnetic fields
electrons
ion extraction
equipotentials
electron diffusion
plasma potentials
electric potential
two dimensional models
random walk
ion currents
ions
trapping
collisions
cells

ASJC Scopus subject areas

  • Physics and Astronomy(all)

Cite this

Numerical analysis of electronegative plasma in the extraction region of negative hydrogen ion sources. / Kuppel, S.; Matsushita, D.; Hatayama, Akiyoshi; Bacal, M.

In: Journal of Applied Physics, Vol. 109, No. 1, 013305, 01.01.2011.

Research output: Contribution to journalArticle

Kuppel, S. ; Matsushita, D. ; Hatayama, Akiyoshi ; Bacal, M. / Numerical analysis of electronegative plasma in the extraction region of negative hydrogen ion sources. In: Journal of Applied Physics. 2011 ; Vol. 109, No. 1.
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