Observation of trapped-electron-mode microturbulence in reversed field pinch plasmas
Abstract
Density fluctuations in the large-density-gradient region of improved confinement Madison Symmetric Torus reversed field pinch (RFP) plasmas exhibit multiple features that are characteristic of the trapped-electron mode (TEM). Core transport in conventional RFP plasmas is governed by magnetic stochasticity stemming from multiple long-wavelength tearing modes. Using inductive current profile control, these tearing modes are reduced, and global confinement is increased to that expected for comparable tokamak plasmas. Under these conditions, new short-wavelength fluctuations distinct from global tearing modes appear in the spectrum at a frequency of f ~ 50 kHz, which have normalized perpendicular wave numbers k⊥ρs≲0.2 and propagate in the electron diamagnetic drift direction. They exhibit a critical-gradient threshold, and the fluctuation amplitude increases with the local electron density gradient. These characteristics are consistent with predictions from gyrokinetic analysis using the Gene code, including increased TEM turbulence and transport from the interaction of remnant tearing magnetic fluctuations and zonal flow.
- Authors:
-
[1];
[1];
[1];
- Univ. of Wisconsin, Madison, WI (United States). Dept. of Physics
- Univ. of California, Los Angeles, CA (United States). Dept. of Physics and Astronomy
- Publication Date:
- Research Org.:
- Univ. of Wisconsin, Madison, WI (United States); Univ. of California, Los Angeles, CA (United States)
- Sponsoring Org.:
- USDOE Office of Science (SC), Fusion Energy Sciences (FES)
- OSTI Identifier:
- 1524582
- Alternate Identifier(s):
- OSTI ID: 1415156
- Grant/Contract Number:
- FC02-05ER54814; FG02-01ER54615
- Resource Type:
- Accepted Manuscript
- Journal Name:
- Physics of Plasmas
- Additional Journal Information:
- Journal Volume: 25; Journal Issue: 1; 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
Duff, J. R., Williams, Z. R., Brower, D. L., Chapman, B. E., Ding, W. X., Pueschel, M. J., Sarff, J. S., and Terry, P. W. Observation of trapped-electron-mode microturbulence in reversed field pinch plasmas. United States: N. p., 2018.
Web. doi:10.1063/1.5010198.
Duff, J. R., Williams, Z. R., Brower, D. L., Chapman, B. E., Ding, W. X., Pueschel, M. J., Sarff, J. S., & Terry, P. W. Observation of trapped-electron-mode microturbulence in reversed field pinch plasmas. United States. https://doi.org/10.1063/1.5010198
Duff, J. R., Williams, Z. R., Brower, D. L., Chapman, B. E., Ding, W. X., Pueschel, M. J., Sarff, J. S., and Terry, P. W. Sat .
"Observation of trapped-electron-mode microturbulence in reversed field pinch plasmas". United States. https://doi.org/10.1063/1.5010198. https://www.osti.gov/servlets/purl/1524582.
@article{osti_1524582,
title = {Observation of trapped-electron-mode microturbulence in reversed field pinch plasmas},
author = {Duff, J. R. and Williams, Z. R. and Brower, D. L. and Chapman, B. E. and Ding, W. X. and Pueschel, M. J. and Sarff, J. S. and Terry, P. W.},
abstractNote = {Density fluctuations in the large-density-gradient region of improved confinement Madison Symmetric Torus reversed field pinch (RFP) plasmas exhibit multiple features that are characteristic of the trapped-electron mode (TEM). Core transport in conventional RFP plasmas is governed by magnetic stochasticity stemming from multiple long-wavelength tearing modes. Using inductive current profile control, these tearing modes are reduced, and global confinement is increased to that expected for comparable tokamak plasmas. Under these conditions, new short-wavelength fluctuations distinct from global tearing modes appear in the spectrum at a frequency of f ~ 50 kHz, which have normalized perpendicular wave numbers k⊥ρs≲0.2 and propagate in the electron diamagnetic drift direction. They exhibit a critical-gradient threshold, and the fluctuation amplitude increases with the local electron density gradient. These characteristics are consistent with predictions from gyrokinetic analysis using the Gene code, including increased TEM turbulence and transport from the interaction of remnant tearing magnetic fluctuations and zonal flow.},
doi = {10.1063/1.5010198},
journal = {Physics of Plasmas},
number = 1,
volume = 25,
place = {United States},
year = {Sat Dec 29 00:00:00 EST 2018},
month = {Sat Dec 29 00:00:00 EST 2018}
}
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Cited by: 9 works
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Figures / Tables:
FIG. 1: Frequency power spectra for line-integrated electron density fluctuations in tearing-dominated (black) and improved-confinement (red) plasma conditions at impact parameter $x$ = 0.43 m. The tearing-dominated spectrum is averaged over $t$ = 10–11 ms, and the improved-confinement spectrum is averaged over $t$ = 20–21 ms with respect to Fig.more »
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