Effect of basic physical parameters to control plasma meniscus and beam halo formation in negative ion sources

K. Miyamoto, S. Okuda, S. Nishioka, A. Hatayama

Research output: Contribution to journalArticle

17 Citations (Scopus)

Abstract

Our previous study shows that the curvature of the plasma meniscus causes the beam halo in the negative ion sources: the negative ions extracted from the periphery of the meniscus are over-focused in the extractor due to the electrostatic lens effect, and consequently become the beam halo. In this article, the detail physics of the plasma meniscus and beam halo formation is investigated with two-dimensional particle-in-cell simulation. It is shown that the basic physical parameters such as the H- extraction voltage and the effective electron confinement time significantly affect the formation of the plasma meniscus and the resultant beam halo since the penetration of electric field for negative ion extraction depends on these physical parameters. Especially, the electron confinement time depends on the characteristic time of electron escape along the magnetic field as well as the characteristic time of electron diffusion across the magnetic field. The plasma meniscus penetrates deeply into the source plasma region when the effective electron confinement time is short. In this case, the curvature of the plasma meniscus becomes large, and consequently the fraction of the beam halo increases.

Original languageEnglish
Article number103302
JournalJournal of Applied Physics
Volume114
Issue number10
DOIs
Publication statusPublished - 2013 Sep 14

ASJC Scopus subject areas

  • Physics and Astronomy(all)

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