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Title: Evidence for drift waves in the turbulence of reversed field pinch plasmas

A detailed characterization of the high-frequency range of the fluctuation spectrum in reversed field pinch plasmas is presented, revealing a variety of new features distinct from global tearing modes and the cascade that they are thought to drive. The anisotropic broadband spectrum of the fluctuating electric field is measured. The power in the fluctuating kinetic energy (1/2) m(i)n(i)(V) over tilde (2)((E) over tilde xB0), previously measured to be smaller than the magnetic energy in the tearing-mode-unstable frequency range, becomes greater than and diverges from the magnetic energy above 60-80 kHz. The lack of equipartition at high frequencies coincides with the measured signatures of the independent fluctuation activity broadly consistent with the drift-wave fluctuations. Statistical coherence measurements reveal the mode activity that is compressive with a large amplitude in the vicinity of strong density gradients and with a phase speed comparable to the electron drift speed. There is a distinct high-frequency correlation between the fluctuations of density and the parallel magnetic field. Elevated coherences associated with this fluctuation feature return more quickly after a sawtooth event than the corresponding coherences associated with tearing activity.
Authors:
 [1] ;  [2] ;  [2] ;  [2]
  1. Univ. of Wisconsin, Madison, WI (United States); Center for Magnetic Self-Organization in Lab. and Astrophysical Plasmas, Madiscon, WI (United States); Washington Univ., Chestertown, MD (United States)
  2. Univ. of Wisconsin, Madison, WI (United States); Center for Magnetic Self-Organization in Lab. and Astrophysical Plasmas, Madiscon, WI (United States)
Publication Date:
Grant/Contract Number:
FC02-05ER54814
Type:
Accepted Manuscript
Journal Name:
Physics of Plasmas
Additional Journal Information:
Journal Volume: 24; Journal Issue: 2; Journal ID: ISSN 1070-664X
Publisher:
American Institute of Physics (AIP)
Research Org:
Univ. of Wisconsin, Madison, WI (United States)
Sponsoring Org:
USDOE Office of Science (SC)
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY
OSTI Identifier:
1465672
Alternate Identifier(s):
OSTI ID: 1349356

Thuecks, D. J., Almagri, A. F., Sarff, J. S., and Terry, P. W.. Evidence for drift waves in the turbulence of reversed field pinch plasmas. United States: N. p., Web. doi:10.1063/1.4976838.
Thuecks, D. J., Almagri, A. F., Sarff, J. S., & Terry, P. W.. Evidence for drift waves in the turbulence of reversed field pinch plasmas. United States. doi:10.1063/1.4976838.
Thuecks, D. J., Almagri, A. F., Sarff, J. S., and Terry, P. W.. 2017. "Evidence for drift waves in the turbulence of reversed field pinch plasmas". United States. doi:10.1063/1.4976838. https://www.osti.gov/servlets/purl/1465672.
@article{osti_1465672,
title = {Evidence for drift waves in the turbulence of reversed field pinch plasmas},
author = {Thuecks, D. J. and Almagri, A. F. and Sarff, J. S. and Terry, P. W.},
abstractNote = {A detailed characterization of the high-frequency range of the fluctuation spectrum in reversed field pinch plasmas is presented, revealing a variety of new features distinct from global tearing modes and the cascade that they are thought to drive. The anisotropic broadband spectrum of the fluctuating electric field is measured. The power in the fluctuating kinetic energy (1/2) m(i)n(i)(V) over tilde (2)((E) over tilde xB0), previously measured to be smaller than the magnetic energy in the tearing-mode-unstable frequency range, becomes greater than and diverges from the magnetic energy above 60-80 kHz. The lack of equipartition at high frequencies coincides with the measured signatures of the independent fluctuation activity broadly consistent with the drift-wave fluctuations. Statistical coherence measurements reveal the mode activity that is compressive with a large amplitude in the vicinity of strong density gradients and with a phase speed comparable to the electron drift speed. There is a distinct high-frequency correlation between the fluctuations of density and the parallel magnetic field. Elevated coherences associated with this fluctuation feature return more quickly after a sawtooth event than the corresponding coherences associated with tearing activity.},
doi = {10.1063/1.4976838},
journal = {Physics of Plasmas},
number = 2,
volume = 24,
place = {United States},
year = {2017},
month = {2}
}