Evidence and modeling of turbulence bifurcation in L-mode confinement transitions on Alcator C-Mod
Abstract
Analysis and modeling of rotation reversal hysteresis experiments show that a single turbulent bifurcation is responsible for the Linear to Saturated Ohmic Confinement (LOC/SOC) transition and concomitant intrinsic rotation reversal on Alcator C-Mod. Plasmas on either side of the reversal exhibit different toroidal rotation profiles and therefore different turbulence characteristics despite the profiles of density and temperature, which are indistinguishable within measurement uncertainty. Elements of this bifurcation are also shown to persist for auxiliary heated L-modes. The deactivation of subdominant (in the linear growth rate and contribution to heat transport) ion temperature gradient and trapped electron mode instabilities is identified as the only possible change in turbulence within a reduced quasilinear transport model across the reversal, which is consistent with the measured profiles and inferred heat and particle fluxes. Experimental constraints on a possible change from strong to weak turbulence, outside the description of the quasilinear model, are also discussed. These results indicate an explanation for the LOC/SOC transition that provides a mechanism for the hysteresis through the dynamics of subdominant modes and changes in their relative populations and does not involve a change in the most linearly unstable ion-scale drift-wave instability.
- Authors:
-
- Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
- University of California San Diego, San Diego, California 92093, USA
- Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
- Publication Date:
- Research Org.:
- Univ. of California, San Diego, CA (United States); Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States)
- Sponsoring Org.:
- USDOE Office of Science (SC), Fusion Energy Sciences (FES)
- Contributing Org.:
- Alcator C-Mod Team
- OSTI Identifier:
- 1618845
- Alternate Identifier(s):
- OSTI ID: 1618588
- Grant/Contract Number:
- FG02-04ER54738; SC0014264; FC02-99ER54512
- Resource Type:
- Accepted Manuscript
- Journal Name:
- Physics of Plasmas
- Additional Journal Information:
- Journal Volume: 27; Journal Issue: 5; 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; hysteresis; modeling; turbulence; turbulent bifurcation; Alcator C-Mod; plasma; plasma physics; ion temperature gradient; instabilities
Citation Formats
Cao, N. M., Rice, J. E., Diamond, P. H., White, A. E., Chilenski, M. A., Ennever, P. C., Hughes, J. W., Irby, J., Reinke, M. L., and Rodriguez-Fernandez, P. Evidence and modeling of turbulence bifurcation in L-mode confinement transitions on Alcator C-Mod. United States: N. p., 2020.
Web. doi:10.1063/1.5144444.
Cao, N. M., Rice, J. E., Diamond, P. H., White, A. E., Chilenski, M. A., Ennever, P. C., Hughes, J. W., Irby, J., Reinke, M. L., & Rodriguez-Fernandez, P. Evidence and modeling of turbulence bifurcation in L-mode confinement transitions on Alcator C-Mod. United States. doi:https://doi.org/10.1063/1.5144444
Cao, N. M., Rice, J. E., Diamond, P. H., White, A. E., Chilenski, M. A., Ennever, P. C., Hughes, J. W., Irby, J., Reinke, M. L., and Rodriguez-Fernandez, P. Thu .
"Evidence and modeling of turbulence bifurcation in L-mode confinement transitions on Alcator C-Mod". United States. doi:https://doi.org/10.1063/1.5144444. https://www.osti.gov/servlets/purl/1618845.
@article{osti_1618845,
title = {Evidence and modeling of turbulence bifurcation in L-mode confinement transitions on Alcator C-Mod},
author = {Cao, N. M. and Rice, J. E. and Diamond, P. H. and White, A. E. and Chilenski, M. A. and Ennever, P. C. and Hughes, J. W. and Irby, J. and Reinke, M. L. and Rodriguez-Fernandez, P.},
abstractNote = {Analysis and modeling of rotation reversal hysteresis experiments show that a single turbulent bifurcation is responsible for the Linear to Saturated Ohmic Confinement (LOC/SOC) transition and concomitant intrinsic rotation reversal on Alcator C-Mod. Plasmas on either side of the reversal exhibit different toroidal rotation profiles and therefore different turbulence characteristics despite the profiles of density and temperature, which are indistinguishable within measurement uncertainty. Elements of this bifurcation are also shown to persist for auxiliary heated L-modes. The deactivation of subdominant (in the linear growth rate and contribution to heat transport) ion temperature gradient and trapped electron mode instabilities is identified as the only possible change in turbulence within a reduced quasilinear transport model across the reversal, which is consistent with the measured profiles and inferred heat and particle fluxes. Experimental constraints on a possible change from strong to weak turbulence, outside the description of the quasilinear model, are also discussed. These results indicate an explanation for the LOC/SOC transition that provides a mechanism for the hysteresis through the dynamics of subdominant modes and changes in their relative populations and does not involve a change in the most linearly unstable ion-scale drift-wave instability.},
doi = {10.1063/1.5144444},
journal = {Physics of Plasmas},
number = 5,
volume = 27,
place = {United States},
year = {2020},
month = {5}
}
Web of Science
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