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Strong, nonaxisymmetric flows driven in a dipole-confined plasma

Author: M W Worstell
Requested Type: Poster Only
Submitted: 2006-12-18 22:04:37

Co-authors: B.A. Grierson, S. Stattel, M.E. Mauel

Contact Info:
Columbia University
500 West 120th Street
New York, NY   10027
USA

Abstract Text:
Previous studies using the Collisionless Terella Experiment
(CTX) have shown plasma dynamics to be dominated by
interchange mixing. Since the geometry of the dipole magnetic
field has no shear, interchange turbulence and interchange
transport becomes two-dimensional. The usually complicated
study of plasma turbulence and transport becomes less so in
dipole geometry, provided plasma dynamics is appropriately
described with field-line averaged quantities. In this
presentation, strong, nonaxisymmetric plasma flows are induced
by application of electrostatic bias via a negatively biased
(-1000 ~V) large diameter probe inserted at various radii in
order to charge a central flux-tube and drive nonaxisymmteric
cross-field currents. Static biasing as well as triggered
biasing have been investigated. Limited positive bias
experiments have been conducted. Very strong plasma flows can
be induced, and these allow systematic study of nonlinear
effects such as electrostatic structure coupling.
Additionally, we observe a dramatic decrease in low-frequency
turbulent fluctuations when the strength of the
nonaxisymmetric bias exceeds a threshold. Mode number
switching has been observed during discharges. Additional
bias probes are being constructed to investigate this
phenomenon further.

Characterization: A2,A3

Comments:
Please place with other dipole posters.