[Table of Contents]

Plasma and Fusion Research

Volume 3, S1022 (2008)

Regular Articles

Dynamics of Electron-Rich Plasmas in the CNT Stellarator
Thomas S. PEDERSEN, John W. BERKERY, Allen H. BOOZER, Paul W. BRENNER, Benoit Durand de GEVIGNEY, Michael S. HAHN, Quinn R. MARKSTEINER and Haruhiko HIMURA1)
Columbia University, New York, NY 10027, USA
1)
Kyoto Institute of Technology, Matsugasaki, Kyoto 606-8585, Japan
(Received 28 November 2007 / Accepted 5 February 2008 / Published 1 August 2008)

Abstract

Pure electron plasmas and electron plasmas with a finite ion fraction have been studied in the Columbia Nonneutral Torus (CNT) since the end of 2004. Results from the first three years of operation are summarized. Stable, small Debye length pure electron plasmas are routinely created, and have confinement times up to 20 msec. The confinement is limited by radial transport caused by internal rods, as well as electron-neutral collisions. The neutral driven transport rate is indicative of poor particle orbits in CNT, despite the strong radial electric field. Numerical simulations shed light on this issue, demonstrating the detrimental effects of variations in the electrostatic potential on a magnetic surface. With the installation of a magnetic surface conforming electrostatic boundary and the transition to external diagnostics, significantly longer confinement times should be possible. Also presented are observations of sudden confinement jumps that have a hysteretic behavior, and observations of an ion driven instability.

Keywords

stellarator, non-neutral plasmas, neoclassical confinement, magnetic surfaces

DOI: 10.1585/pfr.3.S1022

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This paper may be cited as follows:

Thomas S. PEDERSEN, John W. BERKERY, Allen H. BOOZER, Paul W. BRENNER, Benoit Durand de GEVIGNEY, Michael S. HAHN, Quinn R. MARKSTEINER and Haruhiko HIMURA, Plasma Fusion Res. 3, S1022 (2008).