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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

Abstract

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 dischargemore » 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.« less

Authors:
 [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)
Publication Date:
Research Org.:
Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States); General Atomics, San Diego, CA (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Fusion Energy Sciences (FES)
Contributing Org.:
The DIII-D and RFX-mod Teams
OSTI Identifier:
1338619
Alternate Identifier(s):
OSTI ID: 1333514; OSTI ID: 1372089
Grant/Contract Number:  
AC02-09CH11466; SC0008520; FG02-08ER85195; FG02-04ER54761; FC02-04ER54698; AC05-00OR22725
Resource Type:
Accepted Manuscript
Journal Name:
Nuclear Fusion
Additional Journal Information:
Journal Volume: 57; Journal Issue: 1; Journal ID: ISSN 0029-5515
Publisher:
IOP Science
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; tokamak; toroidal confinement experiment; MHD stability; neo-classical tearing mode

Citation Formats

Okabayashi, M., Zanca, P., Strait, E. J., Garofalo, A. M., Hanson, J. M., In, Y., La Haye, R. J., Marrelli, L., Martin, P., Paccagnella, R., Paz-Soldan, C., Piovesan, P., Piron, C., Piron, L., Shiraki, D., and Volpe, F. A.. Avoidance of tearing mode locking with electro-magnetic torque introduced by feedback-based mode rotation control in DIII-D and RFX-mod. United States: N. p., 2016. Web. https://doi.org/10.1088/1741-4326/57/1/016035.
Okabayashi, M., Zanca, P., Strait, E. J., Garofalo, A. M., Hanson, J. M., In, Y., La Haye, R. J., Marrelli, L., Martin, P., Paccagnella, R., Paz-Soldan, C., Piovesan, P., Piron, C., Piron, L., Shiraki, D., & Volpe, F. A.. Avoidance of tearing mode locking with electro-magnetic torque introduced by feedback-based mode rotation control in DIII-D and RFX-mod. United States. https://doi.org/10.1088/1741-4326/57/1/016035
Okabayashi, M., Zanca, P., Strait, E. J., Garofalo, A. M., Hanson, J. M., In, Y., La Haye, R. J., Marrelli, L., Martin, P., Paccagnella, R., Paz-Soldan, C., Piovesan, P., Piron, C., Piron, L., Shiraki, D., and Volpe, F. A.. Fri . "Avoidance of tearing mode locking with electro-magnetic torque introduced by feedback-based mode rotation control in DIII-D and RFX-mod". United States. https://doi.org/10.1088/1741-4326/57/1/016035. https://www.osti.gov/servlets/purl/1338619.
@article{osti_1338619,
title = {Avoidance of tearing mode locking with electro-magnetic torque introduced by feedback-based mode rotation control in DIII-D and RFX-mod},
author = {Okabayashi, M. and Zanca, P. and Strait, E. J. and Garofalo, A. M. and Hanson, J. M. and In, Y. and La Haye, R. J. and Marrelli, L. and Martin, P. and Paccagnella, R. and Paz-Soldan, C. and Piovesan, P. and Piron, C. and Piron, L. and Shiraki, D. and Volpe, F. A.},
abstractNote = {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.},
doi = {10.1088/1741-4326/57/1/016035},
journal = {Nuclear Fusion},
number = 1,
volume = 57,
place = {United States},
year = {2016},
month = {11}
}

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    Works referencing / citing this record:

    Intrinsic flow and tearing mode rotation in the RFP during improved confinement
    journal, July 2019

    • Craig, D.; Tan, E. H.; Schott, B.
    • Physics of Plasmas, Vol. 26, Issue 7
    • DOI: 10.1063/1.5095620

    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