Array magnetics modal analysis for the DIII-D tokamak based on localized time-series modelling

Journal Article · Mon Jul 14 00:00:00 EDT 2014 · Plasma Physics and Controlled Fusion

DOI:https://doi.org/10.1088/0741-3335/56/9/095012· OSTI ID:1356334

Olofsson, K. Erik J. ^[1]; Hanson, Jeremy M. ^[1]; Shiraki, Daisuke ^[1]; Volpe, Francesco A. ^[1]; Humphreys, David A. ^[2]; La Haye, Robert J. ^[2]; Lanctot, Matthew J. ^[2]; Strait, Edward J. ^[2]; Welander, Anders S. ^[2]; Kolemen, Egemen ^[3]; Okabayashi, Michio ^[3]

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1. Columbia Univ., New York, NY (United States)
2. General Atomics, San Diego, CA (United States)
3. Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States)

Here, time-series analysis of magnetics data in tokamaks is typically done using block-based fast Fourier transform methods. This work presents the development and deployment of a new set of algorithms for magnetic probe array analysis. The method is based on an estimation technique known as stochastic subspace identification (SSI). Compared with the standard coherence approach or the direct singular value decomposition approach, the new technique exhibits several beneficial properties. For example, the SSI method does not require that frequencies are orthogonal with respect to the timeframe used in the analysis. Frequencies are obtained directly as parameters of localized time-series models. The parameters are extracted by solving small-scale eigenvalue problems. Applications include maximum-likelihood regularized eigenmode pattern estimation, detection of neoclassical tearing modes, including locked mode precursors, and automatic clustering of modes, and magnetics-pattern characterization of sawtooth pre- and postcursors, edge harmonic oscillations and fishbones.

• Research Organization: General Atomics, San Diego, CA (United States)
• Sponsoring Organization: USDOE Office of Nuclear Energy (NE)
• Grant/Contract Number: FC02-04ER54698
• OSTI ID: 1356334
• Journal Information: Plasma Physics and Controlled Fusion, Vol. 56, Issue 9; ISSN 0741-3335
• Publisher: IOP Science
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
inference methods
magnetohydrodynamics
microinstabilities