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Title: Turbulence, transport, and zonal flows in the Madison symmetric torus reversed-field pinch

Abstract

The robustness and the effect of zonal flows in trapped electron mode (TEM) turbulence and Ion Temperature Gradient (ITG) turbulence in the reversed-field pinch (RFP) are investigated here from numerical solutions of the gyrokinetic equations with and without magnetic external perturbations introduced to model tearing modes. For simulations without external magnetic field perturbations, zonal flows produce a much larger reduction of transport for the density-gradient-driven TEM turbulence than they do for the ITG turbulence. Zonal flows are studied in detail to understand the nature of their strong excitation in the RFP and to gain insight into the key differences between the TEM- and ITG-driven regimes. The zonal flow residuals are significantly larger in the RFP than in tokamak geometry due to the low safety factor. Collisionality is seen to play a significant role in the TEM zonal flow regulation through the different responses of the linear growth rate and the size of the Dimits shift to collisionality, while affecting the ITG only minimally. A secondary instability analysis reveals that the TEM turbulence drives zonal flows at a rate that is twice that of the ITG turbulence. In addition to interfering with zonal flows, the magnetic perturbations are found to obviatemore » an energy scaling relation for fast particles.« less

Authors:
ORCiD logo [1];  [1];  [1];  [2]
  1. Univ. of Wisconsin, Madison, WI (United States). Dept. of Physics
  2. Jakob-Brucker-Gymnasium, Kaufbeuren (Germany); Max Planck Inst. for Plasma Physics, Garching (Germany)
Publication Date:
Research Org.:
Univ. of Wisconsin, Madison, WI (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Fusion Energy Sciences (FES); National Science Foundation (NSF)
OSTI Identifier:
1523258
Alternate Identifier(s):
OSTI ID: 1414036
Grant/Contract Number:  
FG02-85ER53212; TG-PHY130027
Resource Type:
Accepted Manuscript
Journal Name:
Physics of Plasmas
Additional Journal Information:
Journal Volume: 24; 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

Williams, Z. R., Pueschel, M. J., Terry, P. W., and Hauff, T. Turbulence, transport, and zonal flows in the Madison symmetric torus reversed-field pinch. United States: N. p., 2017. Web. doi:10.1063/1.5000252.
Williams, Z. R., Pueschel, M. J., Terry, P. W., & Hauff, T. Turbulence, transport, and zonal flows in the Madison symmetric torus reversed-field pinch. United States. doi:10.1063/1.5000252.
Williams, Z. R., Pueschel, M. J., Terry, P. W., and Hauff, T. Tue . "Turbulence, transport, and zonal flows in the Madison symmetric torus reversed-field pinch". United States. doi:10.1063/1.5000252. https://www.osti.gov/servlets/purl/1523258.
@article{osti_1523258,
title = {Turbulence, transport, and zonal flows in the Madison symmetric torus reversed-field pinch},
author = {Williams, Z. R. and Pueschel, M. J. and Terry, P. W. and Hauff, T.},
abstractNote = {The robustness and the effect of zonal flows in trapped electron mode (TEM) turbulence and Ion Temperature Gradient (ITG) turbulence in the reversed-field pinch (RFP) are investigated here from numerical solutions of the gyrokinetic equations with and without magnetic external perturbations introduced to model tearing modes. For simulations without external magnetic field perturbations, zonal flows produce a much larger reduction of transport for the density-gradient-driven TEM turbulence than they do for the ITG turbulence. Zonal flows are studied in detail to understand the nature of their strong excitation in the RFP and to gain insight into the key differences between the TEM- and ITG-driven regimes. The zonal flow residuals are significantly larger in the RFP than in tokamak geometry due to the low safety factor. Collisionality is seen to play a significant role in the TEM zonal flow regulation through the different responses of the linear growth rate and the size of the Dimits shift to collisionality, while affecting the ITG only minimally. A secondary instability analysis reveals that the TEM turbulence drives zonal flows at a rate that is twice that of the ITG turbulence. In addition to interfering with zonal flows, the magnetic perturbations are found to obviate an energy scaling relation for fast particles.},
doi = {10.1063/1.5000252},
journal = {Physics of Plasmas},
number = 12,
volume = 24,
place = {United States},
year = {2017},
month = {12}
}

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Cited by: 4 works
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Figures / Tables:

FIG. 1 FIG. 1: Linear instability analysis for the low-n, 200 kA PPCD. In (a), growth rates are strongest in the ky ∼ 0.1–1 range. In (b), dominant frequencies are in the electron diamagnetic direction, with positive branches arising from the ubiquitous TEM. In (c), gradient scans at kyρs = 0.5 andmore » r/a = 0.7905 are shown, with experimental values circled. The three solid-line curves correspond to variation of the density gradient (triangles), ion temperature gradient (diamonds), and electron temperature gradient (squares) with other gradients held fixed. The density gradient drive is the strongest for nominal parameters. Dashed lines correspond to a separate, ion-direction unstable mode branch.« less

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