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icc07_gangadhara.pdf2007-02-15 14:24:54Sanjay Gangadhara

Generation and confinement of hot thermal ions through the manipulation of magnetic reconnection

Author: Sanjay Gangadhara
Requested Type: Consider for Invited
Submitted: 2006-12-18 12:44:50

Co-authors: B.E. Chapman, D. Craig, D.A. Ennis, D.J. Den Hartog, G. Fiksel, S.C. Prager

Contact Info:
University of Wisconsin, Madison & Center for Magn
1150 University Avenue
Madison, WI   53706

Abstract Text:
Intensification and subsequent reduction of magnetic reconnection has allowed for the production and capture of large ion temperatures in the Madison Symmetric Torus (MST) reversed field pinch. Strong ion heating is generated during discrete reconnection events (“sawtooth crashes”), with majority ion temperatures exceeding 1 keV and impurity ion temperatures reaching 3 keV. Impurity ion temperature profile measurements obtained using charge exchange recombination spectroscopy show that significant ion heating occurs at all radii during a sawtooth crash, with the temperature rising over a period of ~ 100 μs, roughly the reconnection time scale. The heating is largest at high toroidal plasma current (0.5 MA) with strong toroidal magnetic field reversal. Following this heating, inductive auxiliary current drive is applied to modify the plasma current profile. This suppresses reconnection and produces improved particle and energy confinement, allowing sustainment of the impurity and majority ion temperatures at values greater than 1 keV. The ion energy confinement time increases by a factor of ~ 10 during the current drive period, as estimated from ion power balance including convective and charge exchange losses. Coincident with this improvement in ion energy confinement is an improvement in electron energy confinement, as previously reported. Placing the new results in the context of past work, MST has now demonstrated favorable confinement of thermal ions and thermal electrons (with Ti and Te both exceeding 1 keV), energetic runaway electrons (with energies up to 100 keV), and beam-injected fast ions (with energies up to 20 keV). Work supported by U.S.D.O.E. and N.S.F.

Characterization: A5,E3

My first priority for characterization is E3, followed by A5.

University of Maryland

Innovative Confinement Concepts Workshop
February 12-14, 2007
College Park, Maryland

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