Singular Value Decomposition Analysis of Multichannel Electron Cyclotron Emission Signals of Tokamak Plasma

Singular value decomposition (SVD) was applied to multichannel signals obtained by an electron cyclotron emission diagnostic system in the JT-60U tokamak. As a result, on grating polychromator signals, the equilibrium and perturbative terms of electron temperature profile were successfully separated, and the structure of a magnetic island produced by the tearing mode was revealed. By neglecting the components of small singular values, the noise component of the signals was removed to improve the signal-to-noise ratio while conserving well the pulse-like waveforms. The usefulness of the SVD-based spectral analysis is shown by a typical set of signal waveforms.