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Title: Plasma response measurements of non-axisymmetric magnetic perturbations on DIII-D via soft x-ray imaging

Abstract

Recent observations on DIII-D have advanced the understanding of plasma response to applied resonant magnetic perturbations (RMPs) in both H-mode and L-mode plasmas. Three distinct 3D features localized in minor radius are imaged via filtered soft x-ray emission: (i) the formation of lobes extending from the unperturbed separatrix in the X-point region at the plasma boundary, (ii) helical kink-like perturbations in the steep-gradient region inside the separatrix, and (iii) amplified islands in the core of a low-rotation L-mode plasma. In this study, these measurements are used to test and to validate plasma response models, which are crucial for providing predictive capability of edge-localized mode control. In particular, vacuum and two-fluid resistive magnetohydrodynamic(MHD) responses are tested in the regions of these measurements. At the plasma boundary in H-mode discharges with n = 3 RMPs applied, measurements compare well to vacuum-field calculations that predict lobe structures. Yet in the steep-gradient region, measurements agree better with calculations from the linear resistive two-fluid MHD code, M3D-C1. Relative to the vacuum fields, the resistive two-fluid MHD calculations show a reduction in the pitch-resonant components of the normal magnetic field (screening), and amplification of non-resonant components associated with ideal kink modes. However, the calculations still over-predictmore » the amplitude of the measuredperturbation by a factor of 4. In a slowly rotating L-mode plasma with n = 1 RMPs, core islands are observed amplified from vacuum predictions. Finally, these results indicate that while the vacuum approach describes measurements in the edge region well, it is important to include effects of extended MHD in the pedestal and deeper in the plasma core.« less

Authors:
 [1];  [1];  [1];  [2];  [3];  [3];  [1];  [1];  [2]
  1. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
  2. Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States)
  3. General Atomics, San Diego, CA (United States)
Publication Date:
Research Org.:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Sponsoring Org.:
USDOE Office of Science (SC)
OSTI Identifier:
1265266
Alternate Identifier(s):
OSTI ID: 1226640
Grant/Contract Number:  
AC05-00OR22725; AC02-09CH11466; FC02-04ER54698
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Physics of Plasmas
Additional Journal Information:
Journal Volume: 21; Journal Issue: 12; Journal ID: ISSN 1070-664X
Publisher:
American Institute of Physics (AIP)
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY

Citation Formats

Shafer, Morgan W., Unterberg, Ezekial A., Wingen, Andreas, Battaglia, D. J., Evans, T. E., Ferraro, N. M., Harris, Jeffrey H., Hillis, Donald Lee, and Nazikian, R. Plasma response measurements of non-axisymmetric magnetic perturbations on DIII-D via soft x-ray imaging. United States: N. p., 2014. Web. doi:10.1063/1.4905129.
Shafer, Morgan W., Unterberg, Ezekial A., Wingen, Andreas, Battaglia, D. J., Evans, T. E., Ferraro, N. M., Harris, Jeffrey H., Hillis, Donald Lee, & Nazikian, R. Plasma response measurements of non-axisymmetric magnetic perturbations on DIII-D via soft x-ray imaging. United States. doi:10.1063/1.4905129.
Shafer, Morgan W., Unterberg, Ezekial A., Wingen, Andreas, Battaglia, D. J., Evans, T. E., Ferraro, N. M., Harris, Jeffrey H., Hillis, Donald Lee, and Nazikian, R. Mon . "Plasma response measurements of non-axisymmetric magnetic perturbations on DIII-D via soft x-ray imaging". United States. doi:10.1063/1.4905129. https://www.osti.gov/servlets/purl/1265266.
@article{osti_1265266,
title = {Plasma response measurements of non-axisymmetric magnetic perturbations on DIII-D via soft x-ray imaging},
author = {Shafer, Morgan W. and Unterberg, Ezekial A. and Wingen, Andreas and Battaglia, D. J. and Evans, T. E. and Ferraro, N. M. and Harris, Jeffrey H. and Hillis, Donald Lee and Nazikian, R.},
abstractNote = {Recent observations on DIII-D have advanced the understanding of plasma response to applied resonant magnetic perturbations (RMPs) in both H-mode and L-mode plasmas. Three distinct 3D features localized in minor radius are imaged via filtered soft x-ray emission: (i) the formation of lobes extending from the unperturbed separatrix in the X-point region at the plasma boundary, (ii) helical kink-like perturbations in the steep-gradient region inside the separatrix, and (iii) amplified islands in the core of a low-rotation L-mode plasma. In this study, these measurements are used to test and to validate plasma response models, which are crucial for providing predictive capability of edge-localized mode control. In particular, vacuum and two-fluid resistive magnetohydrodynamic(MHD) responses are tested in the regions of these measurements. At the plasma boundary in H-mode discharges with n = 3 RMPs applied, measurements compare well to vacuum-field calculations that predict lobe structures. Yet in the steep-gradient region, measurements agree better with calculations from the linear resistive two-fluid MHD code, M3D-C1. Relative to the vacuum fields, the resistive two-fluid MHD calculations show a reduction in the pitch-resonant components of the normal magnetic field (screening), and amplification of non-resonant components associated with ideal kink modes. However, the calculations still over-predict the amplitude of the measuredperturbation by a factor of 4. In a slowly rotating L-mode plasma with n = 1 RMPs, core islands are observed amplified from vacuum predictions. Finally, these results indicate that while the vacuum approach describes measurements in the edge region well, it is important to include effects of extended MHD in the pedestal and deeper in the plasma core.},
doi = {10.1063/1.4905129},
journal = {Physics of Plasmas},
issn = {1070-664X},
number = 12,
volume = 21,
place = {United States},
year = {2014},
month = {12}
}

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