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

Authors:
ORCiD logo [1];  [1];  [1];  [2]
  1. Department of Physics, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
  2. Jakob-Brucker-Gymnasium, 87600 Kaufbeuren, Germany, Max-Planck-Institut für Plasmaphysik, 85748 Garching, Germany
Publication Date:
Sponsoring Org.:
USDOE
OSTI Identifier:
1414036
Grant/Contract Number:
FG02-85ER-53212
Resource Type:
Journal Article: Publisher's Accepted Manuscript
Journal Name:
Physics of Plasmas
Additional Journal Information:
Journal Volume: 24; Journal Issue: 12; Related Information: CHORUS Timestamp: 2017-12-19 10:50:43; Journal ID: ISSN 1070-664X
Publisher:
American Institute of Physics
Country of Publication:
United States
Language:
English

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. 2017. "Turbulence, transport, and zonal flows in the Madison symmetric torus reversed-field pinch". United States. doi:10.1063/1.5000252.
@article{osti_1414036,
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 = {},
doi = {10.1063/1.5000252},
journal = {Physics of Plasmas},
number = 12,
volume = 24,
place = {United States},
year = 2017,
month =
}

Journal Article:
Free Publicly Available Full Text
This content will become publicly available on December 19, 2018
Publisher's Accepted Manuscript

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  • The first localized measurements of tearing mode flows in the core of a hot plasma are presented using nonperturbing measurements of the impurity ion flow. Emission from charge exchange recombination is collected by a novel high optical throughput duo spectrometer providing localized ({+-}1 cm) measurements of C{sup +6} impurity ion velocities resolved to <500 m/s with high bandwidth (100 kHz). Poloidal tearing mode flows in the Madison Symmetric Torus reversed-field pinch are observed to be localized to the mode resonant surface with a radial extent much broader than predicted by linear magnetohydrodynamic (MHD) theory but comparable to the magnetic islandmore » width. The relative poloidal flow amplitudes among the dominant core modes do not reflect the proportions of the magnetic amplitudes. The largest correlated flows are associated with modes having smaller magnetic amplitudes resonant near the midradius. The MHD dynamo due to these flows on the magnetic axis is measured to be adequate to balance the mean Ohm's law during reduced tearing activity and is significant but does not exclude other dynamo mechanisms from contributing during a surge in reconnection activity.« less
  • A recent study investigating the role of electron density fluctuations in particle transport has been conducted on the Madison Symmetric Torus reversed field pinch. Four diagnostics enabled this experiment: a high-speed multichord far-infrared laser interferometer, a multichord H array, a 64- position magnetic coil array, and a Doppler spectrometer that measured impurity ion flow fluctuations. Correlation analysis is used to elucidate the relationship among density, magnetic and impurity ion flow fluctuations. We observe that the electron density fluctuations are highly coherent with magnetic fluctuations resulting from core-resonant resistive tearing modes. Moreover, the fluctuation-induced particle transport, obtained from the correlation betweenmore » electron density and flow fluctuationism indicates that the core-resonant tearing modes do not drive significant particle transport in the plasma edge. We will address these four primary diagnostics, details of the analysis techniques and principals from this study.« less
  • Measurements of edge turbulence and the associated transport are ongoing in the Madison Symmetric Torus (MST) reversed-field pinch (Fusion Technol. {bold 19}, 131 (1991)) using magnetic and electrostatic probes. Magnetic fluctuations are dominated by {ital m}=1 and {ital n} {similar to}2{ital R}/{ital a}, tearing modes. Particle losses induced by magnetic field fluctuations have been found to be ambipolar ({l angle}{ital {tilde J}}{sub {parallel}} {ital {tilde B}}{sub {ital r}}{r angle}/{ital B}{sub 0}=0). Electrostatic fluctuations are broadband and turbulent, with mode widths {Delta}{ital m}{similar to}3--7 and {Delta}{ital n}{similar to}70--150. Particle, parallel current, and energy transport arising from coherent motion with the fluctuatingmore » {bold {tilde E}}{times}{bold B} drift have been measured. Particle transport via this channel is comparable to the total particle loss from MST. Energy transport (from {l angle}{ital {tilde P}{tilde E}}{sub {phi}} {r angle}/{ital B}{sub 0}) due to electrostatic fluctuations is relatively small, and parallel current transport (from {l angle}{ital {tilde J}}{sub {parallel}} {ital {tilde E}}{sub {phi}}{r angle}/{ital B}{sub 0}) may be small as well.« less
  • In this paper measurements of momentum and current transport caused by current driven tearing instability are reported. The measurements are done in the Madison Symmetric Torus reversed-field pinch [R. N. Dexter, D. W. Kerst, T. W. Lovell, S. C. Prager, and J. C. Sprott, Fusion Technol. 19, 131 (1991)] in a regime with repetitive bursts of tearing instability causing magnetic field reconnection. It is established that the plasma parallel momentum profile flattens during these reconnection events: The flow decreases in the core and increases at the edge. The momentum relaxation phenomenon is similar in nature to the well established relaxationmore » of the parallel electrical current and could be a general feature of self-organized systems. The measured fluctuation-induced Maxwell and Reynolds stresses, which govern the dynamics of plasma flow, are large and almost balance each other such that their difference is approximately equal to the rate of change of plasma momentum. The Hall dynamo, which is directly related to the Maxwell stress, drives the parallel current profile relaxation at resonant surfaces at the reconnection events. These results qualitatively agree with analytical calculations and numerical simulations. It is plausible that current-driven instabilities can be responsible for momentum transport in other laboratory and astrophysical plasmas.« less
  • The first period of physics operation of the Madison Symmetric Torus (MST) reversed field pinch ({ital Plasma} {ital Physics} {ital and} {ital Controlled} {ital Nuclear} {ital Fusion} {ital Research} 1988 (IAEA, Vienna, 1989), Vol 2, p. 757) has produced information on sawtooth oscillations, edge magnetic and electrostatic fluctuations, and equilibrium parameters at large plasma size. Sawtooth oscillations are prevalent at all values of pinch parameter and might constitute discrete dynamo events. Both electrostatic and magnetic fluctuations are of sufficient magnitude to be relevant to transport in the reversed field pinch. In the plasmas studied to date (up to a plasmamore » current of 0.5 MA) the poloidal beta value is about 10% or greater.« less