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Title: A new explanation of the sawtooth phenomena in tokamaks

Abstract

The ubiquitous sawtooth phenomena in tokamaks are so named because the central temperature rises slowly and falls rapidly, similar to the blades of a saw. First discovered in 1974, it has so far eluded a theoretical explanation that is widely accepted and consistent with experimental observations. We propose here a new theory for the sawtooth phenomena in auxiliary heated tokamaks, which is motivated by our recent understanding of “magnetic flux pumping.” In this theory, the role of the (m, n) = (1, 1) mode is to generate a dynamo voltage, which keeps the central safety factor, q0, just above 1.0 with low central magnetic shear. When central heating is present, the temperature on axis will increase until at some point, and the configuration abruptly becomes unstable to ideal MHD interchange modes with equal poloidal and toroidal mode numbers, m = n > 1. It is these higher order modes and the localized magnetic stochasticity they produce that cause the sudden crash of the temperature profile, not magnetic reconnection. In conclusion, long time 3D MHD simulations demonstrate these phenomena, which appear to be consistent with many experimental observations.

Authors:
ORCiD logo [1]; ORCiD logo [2]; ORCiD logo [1]
  1. Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States)
  2. Dutch Inst. for Fundamental Energy Research, Eindhoven (The Netherlands)
Publication Date:
Research Org.:
Princeton Plasma Physics Laboratory (PPPL), Princeton, NJ (United States)
Sponsoring Org.:
USDOE Office of Science (SC)
OSTI Identifier:
1606331
Alternate Identifier(s):
OSTI ID: 1606066
Grant/Contract Number:  
AC02-09CH11466; AC02-05CH11231; WP19-20-ERG-DIFFR/Krebs
Resource Type:
Accepted Manuscript
Journal Name:
Physics of Plasmas
Additional Journal Information:
Journal Volume: 27; Journal Issue: 3; 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

Citation Formats

Jardin, S. C., Krebs, I., and Ferraro, N. A new explanation of the sawtooth phenomena in tokamaks. United States: N. p., 2020. Web. doi:10.1063/1.5140968.
Jardin, S. C., Krebs, I., & Ferraro, N. A new explanation of the sawtooth phenomena in tokamaks. United States. https://doi.org/10.1063/1.5140968
Jardin, S. C., Krebs, I., and Ferraro, N. Tue . "A new explanation of the sawtooth phenomena in tokamaks". United States. https://doi.org/10.1063/1.5140968. https://www.osti.gov/servlets/purl/1606331.
@article{osti_1606331,
title = {A new explanation of the sawtooth phenomena in tokamaks},
author = {Jardin, S. C. and Krebs, I. and Ferraro, N.},
abstractNote = {The ubiquitous sawtooth phenomena in tokamaks are so named because the central temperature rises slowly and falls rapidly, similar to the blades of a saw. First discovered in 1974, it has so far eluded a theoretical explanation that is widely accepted and consistent with experimental observations. We propose here a new theory for the sawtooth phenomena in auxiliary heated tokamaks, which is motivated by our recent understanding of “magnetic flux pumping.” In this theory, the role of the (m, n) = (1, 1) mode is to generate a dynamo voltage, which keeps the central safety factor, q0, just above 1.0 with low central magnetic shear. When central heating is present, the temperature on axis will increase until at some point, and the configuration abruptly becomes unstable to ideal MHD interchange modes with equal poloidal and toroidal mode numbers, m = n > 1. It is these higher order modes and the localized magnetic stochasticity they produce that cause the sudden crash of the temperature profile, not magnetic reconnection. In conclusion, long time 3D MHD simulations demonstrate these phenomena, which appear to be consistent with many experimental observations.},
doi = {10.1063/1.5140968},
journal = {Physics of Plasmas},
number = 3,
volume = 27,
place = {United States},
year = {Tue Mar 24 00:00:00 EDT 2020},
month = {Tue Mar 24 00:00:00 EDT 2020}
}

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Cited by: 22 works
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