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The ellipticity criteria for the partial differential equations of axisymmetric single-fluid and Hall magnetohydrodynamic (MHD) equilibria with flow and pressure anisotropy are investigated. The MHD s...
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Confinement of pure electron plasmas in the Columbia Non-neutral Torus

Phys. Plasmas 14, 062503 (2007); doi:10.1063/1.2745814

Published 19 June 2007

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John W. Berkery, Thomas Sunn Pedersen, Jason P. Kremer, Quinn R. Marksteiner, Remi G. Lefrancois, Michael S. Hahn, and Paul W. Brenner
Department of Applied Physics and Applied Mathematics, Columbia University, New York, New York 10027
The Columbia Non-neutral Torus (CNT) [T. S. Pedersen, J. P. Kremer, R. G. Lefrancois, Q. Marksteiner, N. Pomphrey, W. Reiersen, F. Dahlgreen, and X. Sarasola, Fusion Sci. Technol. 50, 372 (2006)] is a stellarator used to study non-neutral plasmas confined on magnetic surfaces. A detailed experimental study of confinement of pure electron plasmas in CNT is described here. Electrons are introduced into the magnetic surfaces by placing a biased thermionic emitter on the magnetic axis. As reported previously, the insulated rods holding this and other emitter filaments contribute to the radial transport by charging up negatively and creating E×B convective transport cells. A model for the rod-driven transport is presented and compared to the measured transport rates under a number of different conditions, finding good agreement. Neutrals also drive transport, and by varying the neutral pressure in the experiment, the effects of rod-driven and neutral-driven transport are separated. The neutral-driven electron loss rate scales linearly with neutral pressure. The neutral driven transport, presumably caused by electron-neutral collisions, is much greater than theoretical estimates for neoclassical diffusion in a classical stellarator with strong radial electric fields. In fact the confinement time is on the order of the electron-neutral collision time. Ion accumulation, electron attachment, and other effects are considered, but do not explain the observed transport rates. ©2007 American Institute of Physics
History: Received 29 March 2007; accepted 8 May 2007; published 19 June 2007
Permalink: http://link.aip.org/link/?PHPAEN/14/062503/1
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KEYWORDS and PACS

Keywords
PACS
  • 52.55.Hc
    Stellarators, torsatrons, heliacs, bumpy tori, and other toroidal confinement devices
  • 52.27.Jt
    Nonneutral plasmas
  • 52.25.Fi
    Plasma transport properties
  • 52.25.Ya
    Neutrals in plasma
  • 52.20.Fs
    Electron collisions in plasma
  • 52.20.Hv
    Atomic, molecular, ion, and heavy-particle collisions in plasma
  • YEAR: 2007

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ISSN:
1070-664X (print)   1089-7674 (online)
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