A new explanation of the sawtooth phenomena in tokamaks

TitleA new explanation of the sawtooth phenomena in tokamaks
Publication TypeJournal Article
Year of Publication2020
AuthorsS.C Jardin, I. Krebs, N.M Ferraro
JournalPhysics of Plasmas
Volume27
Issue3
Pagination032509
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, q(0), 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. Long time 3D MHD simulations demonstrate these phenomena, which appear to be consistent with many experimental observations.

DOI10.1063/1.5140968
Division

FP

Department

IMT

PID

fbd3c1487d138d21c1fdfe6423719556

Alternate TitlePhys. Plasmas

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