(a) EFIT reconstruction of MAST discharge 21856 (filled contours) vs CENTORI simulation equilibrium flux surfaces (black lines). (b) Midplane density profile from Thomson scattering measurements (open circles) and CENTORI simulation (solid curve, (c) Midplane Thomson scattering electron temperature profile (open circles), simulation Te (red curve), and Ti (blue curve).
Snaphsot at t = 2.58 ms of (a) potential, normalised to flux surface average electron temperature, showing dominantly m = 0 structure, and (b) density fluctuation, normalised to the flux surface average over 1 ms, showing mainly m = 1 up/down mode, but with significant deviation due to shaping.
(a) Time evolution of density fluctuations with radius along for the first 2 ms of simulation (b) Series of snapshots of density fluctuation at intervals showing envelope and outward phase propagation (c) Root-mean-square of density fluctuations for t = 2–5 ms at different poloidal coordinates.
Power spectra of experimental and simulated potential fluctuations , normalized to the standard deviation of the fluctuations over the time period, on the outboard midplane 4 cm inside the last closed flux surface.
(a) Radial (outward) phase velocity of peaks in density fluctuation, (b) normalized radial wavenumber , where .
Density fluctuation power for (a) , (b) , (c) , and (d) . Black line shows the sound speed transit frequency , the magenta dashed line is the predicted local GAM frequency from Eq. (1) .
Simulation vs predicted GAM frequency for main and secondary plateaux. Linear fit: gradient = 0.88 ± 0.12, , together with MAST discharge 21856 GAM peak.
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