Runaway electron plateau current profile reconstruction using synchrotron emission imaging in DIII-D
ORAL
Abstract
Current profile reconstructions are obtained for the first time in high current (≅500 kA) post-disruption runaway electron (RE) beam plasmas plateaus in DIII-D.
A reliable current profile is critical for the study of RE instabilities behind deconfinement and final loss dynamics to minimize post-disruption wall damage
for safe operation of reactor-scale tokamaks. A novel method of analyzing synchrotron emission (SE) imaging is presented here, enabling an accurate spatial
localization of the MHD modes which form in RE plateaus at high Ip: both a locked, steady edge (2/1) mode and episodic, fast growing/crashing central (1/1) mode. The current profile is reconstructed using the observed radii of (m/n) = (2/1) and (1/1) modes, allowing localization of the safety factor q = 2 and q = 1 surfaces. Current profiles estimated using SE agree with line-integrated Ar-II line polarization measurements and are compared with predictions by two codes: a Fokker-Planck code (DREAM) and a kinetic test particle code (IonBalance), both
giving good agreement. The reconstructed current profile is peaked on the magnetic axis, it is not hollow as the SE profile might suggest.
A reliable current profile is critical for the study of RE instabilities behind deconfinement and final loss dynamics to minimize post-disruption wall damage
for safe operation of reactor-scale tokamaks. A novel method of analyzing synchrotron emission (SE) imaging is presented here, enabling an accurate spatial
localization of the MHD modes which form in RE plateaus at high Ip: both a locked, steady edge (2/1) mode and episodic, fast growing/crashing central (1/1) mode. The current profile is reconstructed using the observed radii of (m/n) = (2/1) and (1/1) modes, allowing localization of the safety factor q = 2 and q = 1 surfaces. Current profiles estimated using SE agree with line-integrated Ar-II line polarization measurements and are compared with predictions by two codes: a Fokker-Planck code (DREAM) and a kinetic test particle code (IonBalance), both
giving good agreement. The reconstructed current profile is peaked on the magnetic axis, it is not hollow as the SE profile might suggest.
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Presenters
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Claudio Marini
University of California, San Diego
Authors
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Claudio Marini
University of California, San Diego
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Eric M Hollmann
University of California, San Diego
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Shawn W Tang
University of California,
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Jeffery Herfindal
Oak Ridge National Laboratory
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Daisuke Shiraki
Oak Ridge National Laboratory
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Robert Wilcox
ORNL
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Diego Del-Castillo-Negrete
Oak Ridge National Lab, Oak Ridge National Laboratory
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minglei yang
Oak Ridge National Laboratory
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Nicolas Eidietis
General Atomics, GA
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Mathias Hoppe
Department of Electrical Engineering, KTH Royal Institute of Technology, Stockholm, Sweden, KTH Royal Institute of Technology