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icc11posterannotated-1.pdf2011-08-26 10:45:40Willliam Young

Magnetic Structure of the Maryland Centrifugal Experiment

Author: Willliam C Young
Requested Type: Consider for Invited
Submitted: 2011-06-10 16:04:05

Co-authors: C. A. Romero-Talamás, R. Reid, R. F. Ellis , A. B. Hassam

Contact Info:
University of Maryland
ERF, Bldg 223
College Park, MD   20742
USA

Abstract Text:
Magnetic Structure of the Maryland Centrifugal Experiment

William C. Young, C. A. Romero-Talamás, R. Reid, R. F. Ellis , A. B. Hassam

The Maryland Centrifugal Experiment (MCX) plasma confinement concept combines a magnetic mirror geometry with a radial electric field generated by a biased, internal, axial electrode. The resulting ExB force drives a rotation with velocity shear that includes a centrifugal force component along the field lines, yielding an axial confinement that counteracts end losses along the open field lines.

To understand magnetic evolution in MCX and with the aim of improving confinement, several arrangements of magnetic loops are used to measure axial and azimuthal profiles of magnetic fields generated by the MCX plasma. Recently added internal magnetic probes, locally make 3-axis magnetic measurements on a microsecond timescale for the duration of the plasma discharge. Typical plasma duration in MCX is 5 milliseconds. The results of these measurements will be shown to provide insight into the coarse structure and evolution of currents within the MCX plasma. Additionally, the internal probes are complemented by loops external to the vacuum vessel that measure the averaged axial and local radial magnetic field, on a millisecond timescale limited only by the time response of the vacuum vessel. Along with average density measurements from an interferometer system, these axial profiles obtained from the internal and external magnetic field measurements allow for peak rotation velocity, peak temperature, and a 2D density profile to be solved for from ideal MHD equilibrium theory. The MHD equilibrium is obtained via a numeric, perturbative solution of the full Grad-Shafranov equation including supersonic rotation for timescales of ~1ms. There is remarkable agreement between the results of this solution from the measured magnetic fields and the rotation velocities measured from multichord impurity Doppler spectroscopy. This comparison demonstrates the signature and efficacy of centrifugal confinement, a central goal of MCX. Research is ongoing of the impact of shorter timescale evolution of the magnetic field on the plasma confinement using the internal magnetic probes and other MCX diagnostics.

Work supported by the U.S. Department of Energy. We thank R. C. Elton for discussions of spectroscopic techniques.

Characterization: A1,D1

Comments:
Please group with other MCX presentations.

University of Washington

Workshop on Innovation in Fusion Science (ICC2011) and
US-Japan Workshop on Compact Torus Plasma
August 16-19, 2011
Seattle, Washington

ICC 2011