Testing a model for triggering sawtooth oscillations in tokamaks

Journal Article · Sat Jul 15 04:00:00 EDT 2006 · Physics of Plasmas

DOI:https://doi.org/10.1063/1.2218329· OSTI ID:20860128

Bateman, Glenn; Nguyen, Canh N; Kritz, Arnold H; Porcelli, Franco ^[1]

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1. Department of Physics, Lehigh University, 16 Memorial Drive East, Bethlehem, Pennsylvania 18015 (United States)

Simulations of JET and TFTR discharges with the BALDUR integrated modeling code are used to test a sawtooth model that consists of sawtooth triggering mechanisms [Porcelli et al., Plasma Phys. Contolled Fusion 38, 2163 (1996)] together with a modified version of the Kadomtsev sawtooth reconnection model [Kadomtsev, Sov. J. Plasma Phys. 1, 389 (1975)]. In simulations of 12 TFTR low confinement (L-mode) and 5 JET high confinement (H-mode) discharges, sawtooth triggering conditions are examined in order to determine which physical mechanisms are responsible for the crashes. It is found that most sawtooth crashes in the simulations are triggered by the m=1 resistive internal kink instability in plasmas that are in the semicollisional regime. However, in some discharges, some of the sawtooth crashes are triggered as a consequence of the driving force for the internal kink instability overcoming the fast ion stabilization. In rare instances, a sawtooth crash is triggered when the driving force for the internal kink instability overcomes the stabilization produced by the diamagnetic rotation of thermal ions. Generally, the median sawtooth period is found to increase as the magnetic reconnection fraction is increased. Optimal agreement with experimental data for the discharges considered is obtained with a magnetic reconnection fraction of approximately 37% although there is considerable scatter in the sawtooth periods observed in each discharge, both in the experimental data and in the simulations.

• OSTI ID: 20860128
• Journal Information: Physics of Plasmas, Journal Name: Physics of Plasmas Journal Issue: 7 Vol. 13; ISSN PHPAEN; ISSN 1070-664X
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
H-MODE PLASMA CONFINEMENT
IONS
JET TOKAMAK
KINK INSTABILITY
L-MODE PLASMA CONFINEMENT
MAGNETIC RECONNECTION
MAGNETOHYDRODYNAMICS
PLASMA
PLASMA DIAMAGNETISM
PLASMA SIMULATION
PLASMA WAVES
RADIATION TRANSPORT
ROTATION
SAWTOOTH OSCILLATIONS
STABILIZATION
TFTR TOKAMAK