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Modeling fast-ion transport during toroidal Alfvén eigenmode avalanches in National Spherical Torus Experiment
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View: Figures


Image of FIG. 1.
FIG. 1.

(a) Spectrogram of Mirnov coil [black-1, red-2, green-3, blue-4, cyan-5, magenta-6]. (b) Voltage for neutral beam sources “A,” “B,” and “C.” (c) Neutron rate (black) and total injected beam power (red). (d) Plasma current.

Image of FIG. 2.
FIG. 2.

(a) Electron density profile. (b) Electron (red) and ion (black) temperature profiles. (c) Rotation profile at 0.285 s for shot shown in Fig. 1.

Image of FIG. 3.
FIG. 3.

Cross section of NSTX showing locations of soft x-ray camera chords (red and blue), range of reflectometer array measurements (green bar), and toroidal arrays of Mirnov coils (black squares). Blue and red arcs are tangency radii for soft x-ray chords. Solid black curve is poloidal projection of limiter surfaces.

Image of FIG. 4.
FIG. 4.

(a) Spectrogram of magnetic fluctuations showing sequence of avalanche events; colors indicate toroidal mode numbers [black-1, red-2, green-3, blue-4, cyan-5, magenta-6]. (b) Neutron rate showing drops of at avalanches.

Image of FIG. 5.
FIG. 5.

(a) Spectrogram of 50 GHz interferometer. (b) rms fluctuation level from 30 to 200 kHz of 50 GHz (red), 42 GHz (blue), and 30 GHz (green) reflectometers. (c) rms fluctuation level from 30 to 200 kHz for Mirnov coil (black) and 50 GHz reflectometer (red).

Image of FIG. 6.
FIG. 6.

(a) Local soft x-ray emissivity (solid lines) and chord integrated (dashed lines) profiles. (b) Chord integrated soft x-ray fluctuations for mode (red-upper camera, blue-lower camera).

Image of FIG. 7.
FIG. 7.

Polarization measurement of edge magnetic fluctuations. (a) Relative phase of toroidal Mirnov coil array (blue squares), Mirnov coil oriented to measure toroidal fluctuations (red circle). (b) Amplitudes of magnetic fluctuations. (c) Lissajous figure showing polarization of magnetic fluctuations.

Image of FIG. 8.
FIG. 8.

Energy spectrum of fast ions from tangentially viewing NPA and neutron rate showing drops of at avalanches.

Image of FIG. 9.
FIG. 9.

TRANSP simulation of neutron rate (in red) assuming He prefill, injection of deuterium neutral beams and recycling of 13% D, and 87% He compared to measured rate (black).

Image of FIG. 10.
FIG. 10.

Ion distribution function at on the outboard midplane as calculated in TRANSP.

Image of FIG. 11.
FIG. 11.

q-profiles from LRDFIT equilibrium reconstructions at time of initial TAE activity, 0.25 s (blue), at time of avalanche being analyzed, 0.285 s (green), and comparison of q-profiles for shots 124 780 (red) and 124 781 (black).

Image of FIG. 12.
FIG. 12.

Continuum as calculated with NOVA for the modes. Also shown, on right, are representative eigenmode solutions. Solutions found in Boozer coordinates (blue), equal arc coordinates (red), and higher resolution equal arc coordinates (black).

Image of FIG. 13.
FIG. 13.

Three “degenerate” eigenmodes of the equal arcs solutions shown in Fig. 11.

Image of FIG. 14.
FIG. 14.

(a) Spectrogram showing TAE activity. (b) Evolution of q(0) and deduced from equilibrium reconstruction and (c) neutron rate.

Image of FIG. 15.
FIG. 15.

Variations in the core q-profile for the NOVA simulations shown in Fig. 13.

Image of FIG. 16.
FIG. 16.

Continuum corresponding to the four q-profile variations shown in Fig. 12. The corresponding eigenmodes for each q-profile are shown to the right (labeled by the frequency in kilohertz).

Image of FIG. 17.
FIG. 17.

TAE gap corrected for sheared rotation. Eigenmodes are shown to the right; the numbers indicate the frequency in kilohertz.

Image of FIG. 18.
FIG. 18.

Simulated density profiles at peak and minimum for mode at half of the peak amplitude: blue—density perturbation from displacement, red—density perturbation from displacement and compression, scaled up by 2.

Image of FIG. 19.
FIG. 19.

Comparison of reflectometer data with NOVA eigenmode structures for four modes: (a) 85.2 kHz with no Doppler corrections, (b) 69.4 kHz with no Doppler corrections, (c) 115.2 kHz with Doppler corrections, and (d) 108.8 kHz with Doppler correction.

Image of FIG. 20.
FIG. 20.

Pitch of magnetic fluctuations relative to equilibrium field; black–NOVA and red-experiment.

Image of FIG. 21.
FIG. 21.

Best NOVA eigenmode fits for the and modes.

Image of FIG. 22.
FIG. 22.

The percent of fast ions lost vs normalized mode amplitudes (red), losses with only mode (blue).

Image of FIG. 23.
FIG. 23.

The four bars indicate percentages of fast-ion losses in the indicated energy ranges.


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752b84549af89a08dbdd7fdb8b9568b5 journal.articlezxybnytfddd
Scitation: Modeling fast-ion transport during toroidal Alfvén eigenmode avalanches in National Spherical Torus Experiment