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Title: Multi-Device Scaling of Neoclassical Tearing Mode Onset with Beta

Multi-Device Scaling of Neoclassical Tearing Mode Onset with Beta The islands from tearing modes driven unstable and sustained by helically perturbed neo-classical bootstrap current at high beta often provide the practical limit to long-pulse, high confinement tokamak operation [1,2]. The discharges studied are ELMy H-mode single-null divertor (SND) at q{sub 95} {approx}> 3. Periodic sawteeth with m/n = 1/1 and 2/2 are observed to induce m/n = 3/2 neoclassical tearing modes (NTMs) in the tokamaks Asdex-Upgrade [3], DIII-D [4] and JET [5]; confinement can drop by up to 30%, constituting a ''soft'' beta limit. Data for the onset of these modes was obtained by slowly raising beta on a time scale longer than the sawteeth period and observing the beta value at onset. Comparison of the measured critical beta to a model for the critical beta is made in terms of dimensionless parameters. This modeling is then used for extrapolation/prediction to a reactor-grade tokamak.
Authors: ; ; ; ;
Publication Date:
OSTI Identifier:766699
Report Number(s):GA-A23138
TRN: US0109257
DOE Contract Number:AC03-99ER54463
Resource Type:Conference
Data Type:
Resource Relation:Conference: 26th European Physical Society Conference on Controlled Fusion and Plasma Physics, Maastricht (NL), 06/14/1999--06/18/1999; Other Information: PBD: 1 Jul 1999
Research Org:General Atomics, San Diego, CA (US)
Sponsoring Org:US Department of Energy (US)
Country of Publication:United States
Language:English
Subject: 70 PLASMA PHYSICS AND FUSION TECHNOLOGY; BOOTSTRAP CURRENT; H-MODE PLASMA CONFINEMENT; DIVERTORS; DOUBLET-3 DEVICE; TEARING INSTABILITY; HIGH-BETA PLASMA; SAWTOOTH OSCILLATIONS; MATHEMATICAL MODELS