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Tearing Mode Correlated Temperature Fluctuations As Equilibrium Diagnostic

Author: Eli B. Parke
Requested Type: Consider for Invited
Submitted: 2014-06-01 12:27:03

Co-authors: D. J. Den Hartog, J. K. Anderson, Curtis Johnson

Contact Info:
University of Wisconsin - Madison
1150 University Ave
Madison, WI   53706
USA

Abstract Text:
The high repetition rate Thomson scattering system on the Madison Symmetric Torus (MST), in combination with advanced Bayesian statistical methods, allows determination of tearing mode correlated temperature fluctuations as small as a few percent of the equilibrium temperature. From the characteristic phase flip observed in temperature fluctuation structures, the tearing mode rational surfaces can be inferred. These rational surface measurements provide a strong constraint for equilibrium reconstruction. Recent experiments in neutral beam heated, non-reversed plasmas indicate an inward shift of the n=6 rational surface of approximately 1.1 cm relative to non-beam heated plasmas. The measured shift of the mode rational surface allows diagnosis of current redistribution and safety factor modification due to the fast ion population. Reconstructed profiles are consistent with increased on-axis current density observed via FIR polarimetry. Additionally, from the phase of correlated temperature fluctuations, the product <pebr> of pressure and radial magnetic perturbations can be determined. This term leads to radial transport of field-aligned current, which contributes to the mean parallel EMF needed to balance Ohm's law (also known as the kinetic dynamo). Previous measurements of density fluctuation driven current transport suggest that the kinetic dynamo plays a role in the RFP dynamo process. The first measurements of temperature fluctuation driven current transport are presented, indicating that both terms are needed for a complete picture of the kinetic dynamo.

This work supported by the U.S. Department of Energy

Characterization: 4.0

Comments:

Workshop on Exploratory Topics in Plasma and Fusion Research (EPR) and US-Japan Compact Torus (CT) Workshop
August 5-8, 2014
Madison, Wisconsin

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