A constricted plasma source for negative ions

ORAL

Abstract

A constricted plasma source is described which is characterized by a dense plasma close to the anode while the plasma expands outwards in a low pressure region (0.6 Pa) because of differential pressure between the cylindrical hollow cathode through which the gas is injected. Detail characterization of plasma parameters namely electron density (n$_{e})$, positive ion density (n$_{+})$ and plasma potential (V$_{p})$ by hairpin, ion flux and floating emissive probes, respectively, reveals the presence of negative ions adjacent to the anode fall region of the expanding plasma when a mixture of Ar/O$_{2}$ was used as compared with the pure electropositive Ar gas. A linear increase of negative ion density (10$^{16}$ m$^{-3})$ with modest operating powers (400 W) as achieved at low working pressure makes this source highly promising for cesium free negative ion sources.

*This project is funded by EURATOM Association DCU Fusion grant FU07-CT-2007-00052.

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Authors

  • M.A. Mujawar

    • National Centre For Plasma Science and Technology, Dublin City University, Ireland
    • NCPST, Dublin City University, Dublin 9, Ireland

  • S.K. Karkari

    • Dublin City University, Ireland and Institute for Plasma Research, India
    • National Centre for Plasma Science and Technology, Dublin City University, Ireland and Institute for Plasma Research, Bhat, Gandhinagar, India
    • NCPST, Dublin City University, Dublin 9, Ireland \& Institute for Plasma Research, Bhat, Gandhinagar, Gujarat, India, 382428
    • National Centre For Plasma Science and Technology, Dublin City University, Ireland and Institute For Plasma Research, Bhat, Ghandhinagar, India

  • Miles Turner

    • Dublin City University
    • Dublin City University, Ireland
    • National Centre For Plasma Science and Technology, Dublin City University, Ireland
    • NCPST, Dublin City University, Dublin 9, Ireland
    • NCPST, School of Physical Sciences, DCU
    • NCPST, DCU