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Title: Avoidance of tearing mode locking with electro-magnetic torque introduced by feedback-based mode rotation control in DIII-D and RFX-mod

Journal Article · · Nuclear Fusion
 [1];  [2];  [3];  [3];  [4];  [5];  [3];  [2];  [2];  [2];  [3];  [2];  [2];  [2];  [6];  [4]
  1. Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States)
  2. Consorzio RFX, Padova (Italy)
  3. General Atomics, San Diego, CA (United States)
  4. Columbia Univ., New York, NY (United States)
  5. FAR-TECH, Inc., San Diego, CA (United States)
  6. Columbia Univ., New York, NY (United States); Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
+ Show Author Affiliations

Disruptions caused by tearing modes (TMs) are considered to be one of the most critical roadblocks to achieving reliable, steady-state operation of tokamak fusion reactors. Here we have demonstrated a promising scheme to avoid mode locking by utilizing the electro-magnetic (EM) torque produced with 3D coils that are available in many tokamaks. In this scheme, the EM torque is delivered to the modes by a toroidal phase shift between the externally applied field and the excited TM fields, compensating for the mode momentum loss through the interaction with the resistive wall and uncorrected error fields. Fine control of torque balance is provided by a feedback scheme. We have explored this approach in two widely different devices and plasma conditions: DIII-D and RFX-mod operated in tokamak mode. In DIII-D, the plasma target was high β N in a non-circular divertor tokamak. Here β N is defined as β N = β/(I p /aB t) (%Tm/MA), where β, I p, a, B t are the total stored plasma pressure normalized by the magnetic pressure, plasma current, plasma minor radius and toroidal magnetic field at the plasma center, respectively. The RFX-mod plasma was ohmically-heated with ultra-low safety factor in a circular limiter discharge with active feedback coils outside the thick resistive shell. The DIII-D and RFX-mod experiments showed remarkable consistency with theoretical predictions of torque balance. The application to ignition-oriented devices such as the International Thermonuclear Experimental Reactor (ITER) would expand the horizon of its operational regime. The internal 3D coil set currently under consideration for edge localized mode suppression in ITER would be well suited for this purpose.

Research Organization:
Princeton Plasma Physics Laboratory (PPPL), Princeton, NJ (United States); General Atomics, San Diego, CA (United States)
Sponsoring Organization:
USDOE Office of Science (SC), Fusion Energy Sciences (FES)
Contributing Organization:
The DIII-D and RFX-mod Teams
Grant/Contract Number:
AC02-09CH11466; SC0008520; FG02-08ER85195; FG02-04ER54761; FC02-04ER54698; AC05-00OR22725
OSTI ID:
1338619
Alternate ID(s):
OSTI ID: 1333514; OSTI ID: 1372089
Journal Information:
Nuclear Fusion, Vol. 57, Issue 1; ISSN 0029-5515
Publisher:
IOP ScienceCopyright Statement
Country of Publication:
United States
Language:
English
Citation Metrics:
Cited by: 18 works
Citation information provided by
Web of Science

References (22)

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An active feedback recovery technique from disruption events induced by m = 2, n = 1 tearing modes in ohmically heated tokamak plasmas journal March 2015
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Comprehensive control of resistive wall modes in DIII-D advanced tokamak plasmas journal October 2009
Normal mode approach to modelling of feedback stabilization of the resistive wall mode journal May 2003
The spectral basis of optimal error field correction on DIII-D journal April 2014
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Cited By (6)

Intrinsic flow and tearing mode rotation in the RFP during improved confinement journal July 2019
Relationship between locked modes and thermal quenches in DIII-D journal March 2018
Plasma response to rotating resonant magnetic perturbations with a locked mode in the J-TEXT tokamak journal January 2019
Progress in disruption prevention for ITER journal June 2019
A new stabilizing regime of tearing mode entrainment in the presence of a static error field journal September 2019
Feedforward and feedback control of locked mode phase and rotation in DIII-D with application to modulated ECCD experiments journal February 2018

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Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
tokamak
toroidal confinement experiment
MHD stability
neo-classical tearing mode