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Title: Tearing mode dynamics and locking in the presence of external magnetic perturbations

Journal Article · · Physics of Plasmas
DOI:https://doi.org/10.1063/1.4953438· OSTI ID:1471533

In normal operation, Madison Symmetric Torus (MST) [R. N. Dexter et al., Fusion Technol. 19, 131 (1991)] reversed-field pinch plasmas exhibit several rotating tearing modes (TMs). Application of a resonant magnetic perturbation (RMP) results in braking of mode rotation and, if the perturbation amplitude is sufficiently high, in a wall-locked state. The coils that produce the magnetic perturbation in MST give rise to RMPs with several toroidal harmonics. As a result, simultaneous deceleration of all modes is observed. In this paper, the measured TM dynamics is shown to be in qualitative agreement with a magnetohydrodynamical model of the RMP interaction with the TM [R. Fitzpatrick, Nucl. Fusion 33, 1049 (1993)] adapted to MST. To correctly model the TM dynamics, the electromagnetic torque acting on several TMs is included. Quantitative agreement of the TM slowing-down time was obtained for a kinematic viscosity in the order of ν k i n 10 20 m2/s. Analysis of discharges with different plasma densities shows an increase of the locking threshold with increasing density. Modeling results show good agreement with the experimental trend, assuming a density-independent kinematic viscosity. Finally, comparison of the viscosity estimates in this paper to those made previously with other techniques in MST plasmas suggests the possibility that the RMP technique may allow for estimates of the viscosity over a broad range of plasmas in MST and other devices.

Research Organization:
Univ. of Wisconsin, Madison, WI (United States)
Sponsoring Organization:
USDOE Office of Science (SC), Fusion Energy Sciences (FES)
Grant/Contract Number:
FC02-05ER54814
OSTI ID:
1471533
Alternate ID(s):
OSTI ID: 1256537
Journal Information:
Physics of Plasmas, Vol. 23, Issue 6; ISSN 1070-664X
Publisher:
American Institute of Physics (AIP)Copyright Statement
Country of Publication:
United States
Language:
English
Citation Metrics:
Cited by: 3 works
Citation information provided by
Web of Science

References (56)

Mitigation of type-I ELMs with n = 2 fields on JET with ITER-like wall journal June 2013
Field error instabilities in JET journal January 1994
Effect of resonant magnetic perturbations on COMPASS-C tokamak discharges journal December 1992
Bifurcated states of a rotating tokamak plasma in the presence of a static error-field journal September 1998
Error field assessment from driven rotation of stable external kinks at EXTRAP-T2R reversed field pinch journal March 2013
Nonlinear tearing mode interactions and mode locking in reversed‐field pinches journal December 1996
Nonlinear growth of the tearing mode journal January 1973
Strong E × B Flow Shear and Reduced Fluctuations in a Reversed-Field Pinch journal March 1998
The interaction between plasma rotation, stochastic fields and tearing mode excitation by external perturbation fields journal January 2008
Mode locking phenomena observed near the stability boundary of the ideal interchange mode of LHD journal September 2012
Plasma Angular-Momentum Loss by MHD Mode Locking journal April 1990
Tearing mode velocity braking due to resonant magnetic perturbations journal September 2012
Locked modes in DIII-D and a method for prevention of the low density mode journal May 1991
Interaction of an external rotating magnetic field with the tearing mode in a plasma surrounded by a resistive wall journal July 2001
RMP ELM suppression in DIII-D plasmas with ITER similar shapes and collisionalities journal January 2008
Hydromagnetic stability of a diffuse linear pinch journal June 1960
Reduced Edge Instability and Improved Confinement in the MST Reversed-Field Pinch journal October 2001
Effect of a resistive vacuum vessel on dynamo mode rotation in reversed field pinches journal October 1999
Nonlinear dynamo mode dynamics in reversed field pinches journal September 2000
Effects of multiple resistive shells and transient electromagnetic torque on the dynamics of mode locking in reversed field pinch plasmas journal November 2002
Neoclassical tearing modes and their control journal May 2006
Error field detection in DIII-D by magnetic steering of locked modes journal February 2014
Measurements of the toroidal torque balance of error field penetration locked modes journal January 2015
Locking of multiple resonant mode structures in the reversed-field pinch journal August 1998
Tearing modes transition from slow to fast rotation branch in the presence of magnetic feedback journal October 2014
Control of tearing modes in toroidal fusion experiments using “designer” error fields journal June 2001
Non-resonant magnetic braking on JET and TEXTOR journal July 2012
Control of 3D equilibria with resonant magnetic perturbations in MST journal September 2015
Statistical analysis of disruptions in JET journal April 2009
Nonlinear magnetohydrodynamics simulation using high-order finite elements journal March 2004
Hysteresis in the tearing mode locking/unlocking due to resonant magnetic perturbations in EXTRAP T2R journal September 2015
Influence of externally applied magnetic perturbations on neoclassical tearing modes at ASDEX Upgrade journal December 2014
Active control of type-I edge localized modes with n = 1 and n = 2 fields on JET journal January 2010
Momentum Transport from Nonlinear Mode Coupling of Magnetic Fluctuations journal October 2000
Locked mode thresholds on the MAST spherical tokamak journal August 2007
Effect of externally applied resonant magnetic perturbations on resistive tearing modes journal July 2012
Observation of tearing mode deceleration and locking due to eddy currents induced in a conducting shell journal May 2004
Advanced techniques for neoclassical tearing mode control in DIII-D journal October 2009
First charge exchange recombination spectroscopy and motional Stark effect results from the Madison Symmetric Torus reversed field pinch journal January 2001
Braking due to non-resonant magnetic perturbations and comparison with neoclassical toroidal viscosity torque in EXTRAP T2R journal September 2015
Control of 3D edge radiation structure with resonant magnetic perturbation fields applied to the stochastic layer and stabilization of radiative divertor plasma in LHD journal September 2013
Avoidance of tearing modes wall-locking in a reversed field pinch with active feedback coils journal December 2008
Resonant magnetic perturbation effect on tearing mode dynamics journal February 2010
The tearing mode locking–unlocking mechanism to an external resonant field in EXTRAP T2R journal August 2014
Error field mode studies on JET, COMPASS-D and DIII-D, and implications for ITER journal November 1999
Magnetohydrodynamic-activity-induced toroidal momentum dissipation in collisionless regimes in tokamaks journal May 2003
The interaction of resonant magnetic perturbations with rotating plasmas journal March 1991
Interaction of tearing modes with external structures in cylindrical geometry (plasma) journal July 1993
Mode locking in tokamaks journal December 1990
Improved evolution equations for magnetic island chains in toroidal pinch plasmas subject to externally applied resonant magnetic perturbations journal October 2001
Feedback control of resistive wall modes in reversed field pinches journal August 2002
Semi-implicit magnetohydrodynamic calculations journal June 1987
Momentum transport and flow damping in the reversed-field pinch plasma journal November 1998
Rotation in a reversed field pinch with active feedback stabilization of resistive wall modes journal August 2006
Suppression of Large Edge-Localized Modes in High-Confinement DIII-D Plasmas with a Stochastic Magnetic Boundary journal June 2004
Active MHD control at high currents in RFX-mod journal July 2007