Abstract Details

Challenges and achievements in Confinement of Toroidal Electron Plasmas

Author: Sambaran Pahari
Submitted: 2005-12-20 04:04:55

Co-authors: R. Ganesh

Contact Info:
Institute for Plasma Research
Bhat Village,
Gandhinagar, Gujarat   382428

Abstract Text:
Magnetised pure electron-plasmas are now routinely confined
for hours in cylindrical geometries such as Penning-Malmberg traps.
Confinement of electron plasmas in toroidal geometries have however
been plagued by the same single-particle drifts, which affect the
toroidal neutral plasmas. Only recently, in large aspect-ratio traps, confinement times have been improved by several orders of magnitude on application of external radial electric fields (E_{ext}). In the absence of E_{ext}, confinement continues to pose an open challenge.

In the absence of E_{ext}, a simple yet innovative way to improve the confinement of toroidal electron plasmas may be to increase the
toroidicity, thereby generating forces intrinsically. In a series of experiments, this idea has been demonstrated in a
SMall Aspect-Ratio Toroidal electron-plasma EXperiment, SMARTEX
(R/a ~ 1.6). Parallels may therfore be drawn with spherical tokamaks which have low aspect-ratio and result in better confinement of neutral plasmas. Toroidal traps, in particular low aspect-ratio ones, however present a host of other challenges. For example, charge measurements and interpretation of capacitive probe diagnostics are marred by severe complexities.

This paper discusses our efforts and achievements in
developing this trap and the accompanying diagnostics. The confinement properties are presented.With improved confinement, toroidal electron plasmas may well turn out to be excellent test-beds to study diverse physical phenomena, such as, study of coherent structures in compressible fluids. Ongoing investigations in SMARTEX in this area and other emerging prospects will also be discussed.

Characterization: E10


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