A new explanation of the sawtooth phenomena in tokamaks

Jardin, S. C.; Krebs, I.; Ferraro, N.

doi:10.1063/1.5140968

Title: A new explanation of the sawtooth phenomena in tokamaks

Journal Article · Tue Mar 24 00:00:00 EDT 2020 · Physics of Plasmas

DOI:https://doi.org/10.1063/1.5140968· OSTI ID:1606331

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Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States)
Dutch Inst. for Fundamental Energy Research, Eindhoven (The Netherlands)

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.

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Research Organization:: Princeton Plasma Physics Laboratory (PPPL), Princeton, NJ (United States)

Sponsoring Organization:: USDOE Office of Science (SC)

Grant/Contract Number:: AC02-09CH11466; AC02-05CH11231; WP19-20-ERG-DIFFR/Krebs

OSTI ID:: 1606331

Alternate ID(s):: OSTI ID: 1606066

Journal Information:: Physics of Plasmas, Vol. 27, Issue 3; ISSN 1070-664X

Publisher:: American Institute of Physics (AIP)Copyright Statement

Country of Publication:: United States

Language:: English

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Cited by: 22 works

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