On Limitations of the Spectrogram in the Representation of the Amplitude of Nonstationary Fusion Plasma Signals

The spectrogram capability to track the amplitude of signal components is discussed. A study using theoretical signal models shows that significant discrepancies may exist between the evolutions of the amplitude of a nonstationary signal component and of the magnitude of the corresponding spectrogram. To illustrate the practical consequences of this spectrogram shortcoming, the growth of magnetohydrodynamic (MHD) modes observed in the JET tokamak is addressed.
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EFDC060102 604.57 Kb