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Title: Fast and pervasive heat transport induced by multiple locked modes in DIII-D

Abstract

This work presents the impact that multiple island chains co-existent across a tokamak plasma profile have on the heat transport and final temperature of that plasma. Numerical studies using the TM1 code show that error fields (EFs) with multiple poloidal components accelerate the core field penetration compared to pure m/n = 2/1 EF penetration (here m and n are the poloidal and toroidal mode numbers respectively). After field penetration, locked magnetic islands of m=n = 2/1, 3/1 and 4/1 atten the temperature at the corresponding rational surfaces. The co-existence of these islands significantly enhances the plasma heat transport throughout a wide swath of plasma from the core 2/1 rational surface to plasma edge. The electron temperature T e profile from 2/1 to 4/1 rational surfaces can be nearly attened even if there is no island overlap, and the temperature inside each island is determined by the boundary temperature at the outboard separatrix of the island. The resulting central T e decreases by more than 50%, in good agreement with experimental observations and much lower than modeling with only a single 2/1 locked island. Further comparisons of the T e profile between numerical modeling and DIII-D experiment indicates that the observedmore » reduction in the edge temperature requires edge island overlap and stochasticity. Numerical scans reveal the T e profile decreases further when large EF amplitudes create larger islands, wider edge stochastic regions and secondary island structures. Scans of the relative phase between EF harmonics reveal that the 3/1 island width is most sensitive to the island phase and the central T e changes with the 3/1 island width. These results indicate that the coexistence of multiple LMs in tokamak plasmas deteriorate thermal confinement more than the sum of their isolated impacts would and that this may be responsible for the fast thermal quench observed prior to major disruptions.« less

Authors:
 [1];  [2];  [3];  [1];  [4];  [1]
  1. Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States)
  2. General Atomics, San Diego, CA (United States)
  3. Max-Plank-Inst. fur Plasmaphysik, Garching (Germany)
  4. Princeton Univ., NJ (United States). Mechanical and Aerospace Engineering
Publication Date:
Research Org.:
General Atomics, San Diego, CA (United States)
Sponsoring Org.:
USDOE Office of Nuclear Energy (NE)
OSTI Identifier:
1468767
Grant/Contract Number:  
FC02-04ER54698
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Nuclear Fusion
Additional Journal Information:
Journal Volume: 59; 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; multiple locked modes; heat transport; disruption; thermal quench; error field

Citation Formats

Hu, Q., Du, X., Yu, Q., Logan, N. C., Kolemen, E., and Nazikian, R.. Fast and pervasive heat transport induced by multiple locked modes in DIII-D. United States: N. p., 2018. Web. doi:10.1088/1741-4326/aaeb57.
Hu, Q., Du, X., Yu, Q., Logan, N. C., Kolemen, E., & Nazikian, R.. Fast and pervasive heat transport induced by multiple locked modes in DIII-D. United States. doi:10.1088/1741-4326/aaeb57.
Hu, Q., Du, X., Yu, Q., Logan, N. C., Kolemen, E., and Nazikian, R.. Mon . "Fast and pervasive heat transport induced by multiple locked modes in DIII-D". United States. doi:10.1088/1741-4326/aaeb57.
@article{osti_1468767,
title = {Fast and pervasive heat transport induced by multiple locked modes in DIII-D},
author = {Hu, Q. and Du, X. and Yu, Q. and Logan, N. C. and Kolemen, E. and Nazikian, R.},
abstractNote = {This work presents the impact that multiple island chains co-existent across a tokamak plasma profile have on the heat transport and final temperature of that plasma. Numerical studies using the TM1 code show that error fields (EFs) with multiple poloidal components accelerate the core field penetration compared to pure m/n = 2/1 EF penetration (here m and n are the poloidal and toroidal mode numbers respectively). After field penetration, locked magnetic islands of m=n = 2/1, 3/1 and 4/1 atten the temperature at the corresponding rational surfaces. The co-existence of these islands significantly enhances the plasma heat transport throughout a wide swath of plasma from the core 2/1 rational surface to plasma edge. The electron temperature Te profile from 2/1 to 4/1 rational surfaces can be nearly attened even if there is no island overlap, and the temperature inside each island is determined by the boundary temperature at the outboard separatrix of the island. The resulting central Te decreases by more than 50%, in good agreement with experimental observations and much lower than modeling with only a single 2/1 locked island. Further comparisons of the Te profile between numerical modeling and DIII-D experiment indicates that the observed reduction in the edge temperature requires edge island overlap and stochasticity. Numerical scans reveal the Te profile decreases further when large EF amplitudes create larger islands, wider edge stochastic regions and secondary island structures. Scans of the relative phase between EF harmonics reveal that the 3/1 island width is most sensitive to the island phase and the central Te changes with the 3/1 island width. These results indicate that the coexistence of multiple LMs in tokamak plasmas deteriorate thermal confinement more than the sum of their isolated impacts would and that this may be responsible for the fast thermal quench observed prior to major disruptions.},
doi = {10.1088/1741-4326/aaeb57},
journal = {Nuclear Fusion},
issn = {0029-5515},
number = 1,
volume = 59,
place = {United States},
year = {2018},
month = {11}
}

Journal Article:
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