Reduction of magnetic confinement fusion data for data mining applications

Abstract

We develop a practical, structured analysis of multi-channel time series measurements where the main interest lies in the coherent temporal fluctuations and spatial structures and their time dependence. The current approach to most large scale plasma experiments, tokamak and stellarators alike, is the quest for the experimental data taken under optimal conditions for each study. These data are then analysed in detail and sometimes distributed in a reference database such as the tokamak profile database of the ITER 1D Modelling Working Group. While these results are important for our understanding of future fusion devices, they do not provide easy means to support the evidence based on statistical ensembles. The raw data which are not accessible to simple search queries, are usually kept in large data repositories. At H-1, we routinely log the global experimental parameters in a summary database which is stored in a easily accessible database. In order to facilitate statistical analysis and the search for a wide class of magnetic phenomena, we developed a data processing procedure that reduces the raw signal of an array of Mirnov coils at the H-1 into a series of feature descriptors in time-frequency space which are stored in an SQL-accessible database, which can be used together with the summary database. References R. S. Anderssen, F. De Hoog, and M. Hegland, A stable finite difference ansatz for higher order differentiation of non-exact data, Bull. Austral. Math. Soc. 58 (1998), 223--232. S. Beucher, The watershed transformation applied to image segmentation, Conference on Signal and Image Processing in Microscopy and Microanalysis, September 1991, pp. 299--314. T. Dudok de Witt, Enhancement of multichannel data in plasma physics by biorthogonal decomposition, Plasma Physics and Controlled Fusion 37 (1995), no. 2, 117--135, http://stacks.iop.org/0741-3335/37/117. G. H. Golub and C. F. Van Loan, Matrix computations, third ed., Johns Hopkins Studies in the Mathematical Sciences, Johns Hopkins University Press, Baltimore, MD, 1996. MR1417720 (97g:65006) J. H. Harris, M. G. Shats, B. D. Blackwell, W. M. Solomon, D. G. Pretty, S. M. Collis, J. Howard, H. Xia, C. A. Michael, and H. Punzmann, Fluctuations and stability of plasmas in the H-1NF heliac, Nucl. Fusion 44 (2004), 279, doi:10.1088/0029-5515/44/2/008. T. Hastie, R. Tibshirani, and J. H. Friedman, The elements of statistical learning, Springer, August 2001. M. Hegland and R. S. Anderssen, Resolution enhancement of spectra using differentiation, Inverse Problems 21 (2005), no. 3, 915--934, http://stacks.iop.org/0266-5611/21/915. C. Nardone, Multichannel fluctuation data analysis by the singular value decomposition method. Application to MHD modes in JET, Plasma Physics and Controlled Fusion 34 (1992), no. 9, 1447--1465, http://stacks.iop.org/0741-3335/34/1447. A. Rosenfeld and J. L. Pfaltz, Sequential operations in digital picture processing, J. Assoc. Comp. Mach. 13 (1966), 471--494, doi:10.1145/321356.321357. J. Serra, Image analysis and mathematical morphology, Academic Press, Inc., Orlando, FL, USA, 1983. O. Skylar and W. Huber, Image analysis for microscopy screens: Image analysis and processing with EBIimage, R. News 6 (2006), no. 5, 1215, http://CRAN.R-project.org/doc/Rnews/Rnews_2006-5.pdf. R. Stening, T. Reztsova, D. Ivers, J. Turner, and D. Winch, Morning quiet-time ionospheric current reversal at mid to high latitudes, Annales Geophysicae 23 (2005), 385, http://adsabs.harvard.edu/abs/2005AnGeo..23..385S. "The ITER 1D Modelling Working Group", D. Boucher, J. W. Connor, W. A. Houlberg, M. F. Turner, G. Bracco, A. Chudnovskiy, J. G. Cordey, M. J. Greenwald, G. T. Hoang, G. M. D. Hogeweij, S. M. Kaye, J. E. Kinsey, D. R. Mikkelsen, J. Ongena, D. R. Schissel, H. Shirai, J. Stober, P. M. Stubberfield, R. E. Waltz, and J. Weiland, The international multi-tokamak profile database, Nuclear Fusion 40 (2000), no. 12, 1955--1981, http://stacks.iop.org/0029-5515/40/1955. S. Whitehouse, Magick with images, Linux J. (1998), 7, http://www.linuxjournal.com/article/2707.