Nonlinear coupling of tearing fluctuations in the Madison Symmetric Torus

Conference · Sun Nov 01 00:00:00 EST 1992

OSTI ID:6706724

Sarff, J S; Almagri, A F; Cekic, M; Den Hartog, D J; Fiksel, G; Hokin, S A; Ji, H; Prager, S C; Shen, W; Stoneking, M R ^[1]; Assadi, S ^[2]; Sidikman, K L ^[3]

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1. Wisconsin Univ., Madison, WI (United States)
2. Fermi National Accelerator Lab., Batavia, IL (United States)
3. Oak Ridge National Lab., TN (United States)

Three-wave, nonlinear, tearing mode coupling has been measured in the Madison Symmetric Torus (MST) reversed-field pinch (RFP) [Fusion Technol. 19, 131 (1991)] using bispectral analysis of edge magnetic fluctuations resolved in k-space. The strength of nonlinear three-wave interactions satisfying the sum rules m[sub 1] + m[sub 2] = m[sub 3] and n[sub 1] + n[sub 2] = n[sub 3] is measured by the bicoherency. In the RFP, m=l, n[approximately]2R/a (6 for MST) internally resonant modes are linearly unstable and grow to large amplitude. Large values of bicoherency occur for two m=l modes coupled to an m=2 mode and the coupling of intermediate toroidal modes, e.g., n=6 and 7 coupled to n=13. These experimental bispectral features agree with predicted bispectral features derived from MHD computation. However, in the experiment, enhanced coupling occurs in the crash'' phase of a sawtooth oscillation concomitant with a broadened mode spectrum suggesting the onset of a nonlinear cascade.

• Research Organization: Wisconsin Univ., Madison, WI (United States)
• Sponsoring Organization: USDOE; USDOE, Washington, DC (United States)
• DOE Contract Number: FG02-85ER53198
• OSTI ID: 6706724
• Report Number(s): DOE/ER/53198-211; CONF-921103-9; ON: DE93010131
• Resource Relation: Conference: Meeting of the Division of Plasma Physics of the American Physical Society, Seattle, WA (United States), 16-20 Nov 1992
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
REVERSE-FIELD PINCH
TEARING INSTABILITY
MAGNETIC FIELD CONFIGURATIONS
MAGNETOHYDRODYNAMICS
MATHEMATICAL MODELS
NONLINEAR PROBLEMS
FLUID MECHANICS
HYDRODYNAMICS
INSTABILITY
MECHANICS
PINCH EFFECT
PLASMA INSTABILITY
PLASMA MACROINSTABILITIES
700370* - Plasma Fluid & MHD Properties- (1992-)