| Article ID | Journal | Published Year | Pages | File Type |
|---|---|---|---|---|
| 271363 | Fusion Engineering and Design | 2013 | 6 Pages |
•Choi–Williams distribution yields excellent time–frequency resolution for discrete signal.•CWD method provides clear time–frequency pictures of EAST and HT-7 fast MHD events.•CWD method has advantages to wavelets transform scalogram and the short-time Fourier transform spectrogram.•We discuss about how to choose the windows and free parameter of CWD method.
The Choi–Williams distribution is applied to the time–frequency analysis of signals describing rapid magneto-hydro-dynamic (MHD) modes and events in tokamak plasmas. A comparison is made with Soft X-ray (SXR) signals as well as Mirnov signal that shows the advantages of the Choi–Williams distribution over both continuous wavelets transform scalogram and the short-time Fourier transform spectrogram. Examples of MHD activities in HT-7 and EAST tokamak are shown, namely the onset of coupling tearing modes, high frequency precursors of sawtooth, and low frequency MHD instabilities in edge localized mode (ELM) free in H mode discharge.
