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Title: Intrinsic torque reversals induced by magnetic shear effects on the turbulence spectrum in tokamak plasmas

Abstract

We report that intrinsic torque, which can be generated by turbulent stresses, can induce toroidal rotation in a tokamak plasma at rest without direct momentum injection. Reversals in intrinsic torque have been inferred from the observation of toroidal velocity changes in recent lower hybrid current drive (LHCD) experiments. Here we focus on understanding the cause of LHCD-induced intrinsic torque reversal using gyrokinetic simulations and theoretical analyses. A new mechanism for the intrinsic torque reversal linked to magnetic shear (sˆ) effects on the turbulence spectrum is identified. This reversal is a consequence of the ballooning structure at weak sˆ . Based on realistic profiles from the Alcator C-Mod LHCD experiments, simulations demonstrate that the intrinsic torque reverses for weak sˆ discharges and that the value of sˆ crit is consistent with the experimental results sˆ exp crit [Rice et al., Phys. Rev. Lett. 111, 125003 (2013)]. In conclusion, the consideration of this intrinsic torque feature in our work is important for the understanding of rotation profile generation at weak and its consequent impact on macro-instability stabilization and micro-turbulence reduction, which is crucial for ITER. It is also relevant to internal transport barrier formation at negative or weakly positive sˆ .

Authors:
 [1];  [2];  [3];  [1];  [2];  [4];  [5]
  1. Univ. of California, San Diego, CA (United States). Center for Energy Research, Department of Mechanical and Aerospace Engineering, Center for Momentum Transport and Flow Organization, and Center for Astrophysics and Science
  2. Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States)
  3. Univ. of California, San Diego, CA (United States). Center for Momentum Transport and Flow Organization and Center for Astrophysics and Space Science
  4. Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States). Plasma Science and Fusion Center
  5. Plasma Science and Fusion Center, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
Publication Date:
Research Org.:
Univ. of California, San Diego, CA (United States); Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
1253129
DOE Contract Number:  
AC02-09CH11466; FG02-OER54871
Resource Type:
Journal Article
Journal Name:
Physics of Plasmas
Additional Journal Information:
Journal Volume: 22; 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; ALCATOR DEVICE; BALLOONING INSTABILITY; ITER TOKAMAK; LOWER HYBRID CURRENT DRIVE; PLASMA; ROTATING PLASMA; SHEAR; SIMULATION; SPECTRA; STABILIZATION; STRESSES; TORQUE; TURBULENCE

Citation Formats

Lu, Z. X., Wang, W. X., Diamond, P. H., Tynan, G., Ethier, S., Gao, C., and Rice, J. Intrinsic torque reversals induced by magnetic shear effects on the turbulence spectrum in tokamak plasmas. United States: N. p., 2015. Web. doi:10.1063/1.4919395.
Lu, Z. X., Wang, W. X., Diamond, P. H., Tynan, G., Ethier, S., Gao, C., & Rice, J. Intrinsic torque reversals induced by magnetic shear effects on the turbulence spectrum in tokamak plasmas. United States. doi:10.1063/1.4919395.
Lu, Z. X., Wang, W. X., Diamond, P. H., Tynan, G., Ethier, S., Gao, C., and Rice, J. Mon . "Intrinsic torque reversals induced by magnetic shear effects on the turbulence spectrum in tokamak plasmas". United States. doi:10.1063/1.4919395.
@article{osti_1253129,
title = {Intrinsic torque reversals induced by magnetic shear effects on the turbulence spectrum in tokamak plasmas},
author = {Lu, Z. X. and Wang, W. X. and Diamond, P. H. and Tynan, G. and Ethier, S. and Gao, C. and Rice, J.},
abstractNote = {We report that intrinsic torque, which can be generated by turbulent stresses, can induce toroidal rotation in a tokamak plasma at rest without direct momentum injection. Reversals in intrinsic torque have been inferred from the observation of toroidal velocity changes in recent lower hybrid current drive (LHCD) experiments. Here we focus on understanding the cause of LHCD-induced intrinsic torque reversal using gyrokinetic simulations and theoretical analyses. A new mechanism for the intrinsic torque reversal linked to magnetic shear (sˆ) effects on the turbulence spectrum is identified. This reversal is a consequence of the ballooning structure at weak sˆ . Based on realistic profiles from the Alcator C-Mod LHCD experiments, simulations demonstrate that the intrinsic torque reverses for weak sˆ discharges and that the value of sˆ crit is consistent with the experimental results sˆ expcrit [Rice et al., Phys. Rev. Lett. 111, 125003 (2013)]. In conclusion, the consideration of this intrinsic torque feature in our work is important for the understanding of rotation profile generation at weak and its consequent impact on macro-instability stabilization and micro-turbulence reduction, which is crucial for ITER. It is also relevant to internal transport barrier formation at negative or weakly positive sˆ .},
doi = {10.1063/1.4919395},
journal = {Physics of Plasmas},
issn = {1070-664X},
number = 5,
volume = 22,
place = {United States},
year = {2015},
month = {5}
}