Camera view inside the DIII-D vacuum vessel showing a typical field of view relative to the full plasma cross section. 40 cm refers to the vertical distance at the wall.
Cross power and coherence between the camera signal (from a region near the midplane surface) and magnetic Mirnov signal (mapped to the same time base as the camera frame rate) for shot 133 454. The 2/1 TM frequency decreases due to mode coupling to the wall, which drags on the mode and slows the rotation.
The line-integrated (a) Fourier amplitude, (b) phase, and (c) a mode snapshot obtained by Fourier filtering each pixel’s time series at the 2/1 mode frequency . (d)–(f) show Fourier images obtained by filtering at the harmonic frequency , showing the structure of the harmonic. Overlaid are contours of the square root of normalized toroidal flux mapped to the point of tangency for each pixel’s sightline, with ranging from 0.1 to 1.0 in equal increments.
(a) The perturbed poloidal magnetic field due to a 2/1 island detected with a Mirnov coil for shot 131 364. (b) Normalized and poloidal beta decrease throughout mode evolution. [(c)–(e)] Images of show the line-integrated perturbed bremsstrahlung emission normalized to the raw signal near the magnetic axis. The times of the images correspond to the dashed lines in (a) and (b).
Midplane profile of the line-integrated amplitude and phase obtained by Fourier filtering at the mode frequency. At the island center, the fluctuation amplitude has a local minimum and the phase is inverted.
Island widths determined from camera measurements compared with the expected scaling from Ref. 22, shown as a dashed line.
(a) Model of island-induced perturbation of bremsstrahlung emission in a poloidal plane (no line integration). [(b)–(g)] Comparison of synthetic camera images to real camera data, where the synthetic camera images are obtained from the model shown in (a). The synthetic camera images [(b)–(d)] show a larger area than the experimental data [(e)–(g)].
Magnetic and kinetic energy of toroidal mode numbers during the growth of the 2/1 seed island simulated using NIMROD.
Poincare plot of magnetic field lines from the saturated state of the NIMROD simulation showing the dominant 2/1 island and other nonlinearly generated island structures.
Synthetic camera applied to NIMROD simulations showing line-integrated images of perturbations from (a) density, (b) electron temperature, and (c) perturbed bremsstrahlung emission. (d) Camera data of which should be compared to image (c).
(a) The electron temperature measured at a location near on the inboard midplane with the vertical lines marking the times of the images. (b) Snapshots of the 15 kHz component of the perturbed visible light during a sawtooth crash; all images have the same normalization, where is the raw signal near the magnetic axis at the crash onset.
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