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Energetic ion transport by microturbulence is insignificant in tokamaksa)
a)Paper JI2 5, Bull. Am. Phys. Soc. , 151 (2012).
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View: Figures


Image of FIG. 1.
FIG. 1.

Time evolution of plasma parameters from shot 145183 indicating the regions of energetic ion transport mechanisms and the presence of off-axis NBI. (a) Line-averaged density, (b) central electron temperature, (c) plasma current, (d) neutron rate, and (e) neutral beam power.

Image of FIG. 2.
FIG. 2.

Magnetic equilibrium from shot 145183 at  = 1585 ms. Color contour represents the birth pitch of off-axis injected neutral beam particles.

Image of FIG. 3.
FIG. 3.

Phase space weighting of the FIDA chord at  = 1.97 m in shot 145183.

Image of FIG. 4.
FIG. 4.

Magnetic equilibrium from shot 142358 at  = 1525 ms showing typical positions of the FIDA (vertical black lines), BES (green rectangle), CECE/reflectometer (blue ovals), and DBS (red ovals) views.

Image of FIG. 5.
FIG. 5.

Beam ion distributions calculated by NUBEAM with varying number of ions followed: (a) 10, (b) 10, and (c) 10.

Image of FIG. 6.
FIG. 6.

Plasma profiles from shot 145183 indicating the individual measurements along with best-fit splines (solid lines) and statistical uncertainty range (dashed lines). Profiles are shown for (a) electron density, (b) electron and ion temperature, and (c) toroidal rotation.

Image of FIG. 7.
FIG. 7.

Spectra of electron temperature fluctuations in shot 145183.

Image of FIG. 8.
FIG. 8.

Values of energetic ion anomalous diffusivity, , as calculated by the DEP code for (a) passing and (b) trapped ions, and by the analytic Pueschel expressions for (c) passing and (d) trapped ions.

Image of FIG. 9.
FIG. 9.

(a) FIDA spectrum from shot 145183 during the MHD-quiescent period. The experimental spectrum (black trace) is shown with a representative error bar. The classical spectrum (red dashed trace) and the boundaries of the FIDA density integration region are indicated. The inset plot is the experimental data on a semi-log scale to highlight the energetic ion tail (linear portion of plot parallel to dotted blue line). (b) FIDA density as measured (+-symbols) and as expected from classical and turbulent transport models (lines).

Image of FIG. 10.
FIG. 10.

FIDA brightness profile from the main ion system during off-axis beam injection in shot 145183. The ×-symbols represent the absolutely measured brightness, while the ○-symbols represent the measured data after being scaled to produce the best-fit to the simulated profile (represented by the dashed line).

Image of FIG. 11.
FIG. 11.

Time evolution of plasma parameters from the matched shot pairs of 142358 and 142380 and 142371 and 142381. Displayed parameters are: (a) plasma current, (b) , (c) central -value, (d) line-averaged electron density, (e) central density, (f) neutral beam power, (g) electron cyclotron heating power, (h) central electron temperature, (i) central ion temperature, and (j) central toroidal rotation velocity.

Image of FIG. 12.
FIG. 12.

Radial profiles from the MHD-quiescent period of the on-axis NBI shots. Profiles include: (a) electron temperature, (b) ion temperature, (c) electron density, and (d) toroidal rotation.

Image of FIG. 13.
FIG. 13.

Profiles of turbulent fluctuation levels measured in the low and high paired plasmas. (a) Long wavelength density fluctuations measured with BES. (b) Long wavelength electron temperature fluctuations measured with CECE show a factor of two increase between these cases.

Image of FIG. 14.
FIG. 14.

Cross-phase angle between density and temperature fluctuations in the (a) higher and (b) lower cases. GYRO calculated values are given by the green dashed-dotted trace, while the experimental values are indicated by the dark lines (the lighter lines represent frequencies for which the coherency between the signals is too low to resolve the cross-phase angle).

Image of FIG. 15.
FIG. 15.

Real frequency of the most unstable mode as calculated by TGLF for . Positive frequencies correspond to electron modes, and negative frequencies correspond to ion modes.

Image of FIG. 16.
FIG. 16.

FIDA density profiles from the higher cases for (a) an early time during which Alfvén eigenmodes are present, and (b) during the MHD-quiescent period. The red dashed lines represent the classically expected FIDA density as computed by the synthetic diagnostic FIDASIM. The uncertainty ribbon about the simulation trace represents a 25% range.

Image of FIG. 17.
FIG. 17.

FIDA density (×-symbols) and growth rate of the most unstable mode (dashed trace) for the DIII-D on-axis NBI case.

Image of FIG. 18.
FIG. 18.

Values of calculated using the Pueschel formulation for the lower case of shot 142371.

Image of FIG. 19.
FIG. 19.

Comparison between classically expected ( ) and Pueschel model [ from Eqs. (2) and (3) ] profiles of (a) energetic ion density and (b) beam-driven current for the lower case during on-axis injection.

Image of FIG. 20.
FIG. 20.

(a) FIDA spectra from the lower on-axis NBI case with vertical dashed bars representing the energetic ion tail region across . (b) FIDA density as measured (⋄-symbols) and as modeled by the classical (dashed trace) or Pueschel formulation (solid trace).

Image of FIG. 21.
FIG. 21.

Radial profiles of FIDA spectra fitting. (a) Quality of the scaled fit in terms of . (b) Value of the scale factor (applied to the experimentally measured data) corresponding to the best fit. (c) Experimentally measured spectra compared to the best-fit model results for and 0.57.

Image of FIG. 22.
FIG. 22.

(a) Autopower spectrum of line-averaged electron density fluctuations from shot 142371 indicating the presence of coherent modes through . The MHD-quiescent period is enclosed by the dashed rectangle. (b) Plasma stored energy from the paired shots (142371 and 142381) along with the TRANSP-calculated results from the Classical and Pueschel models.

Image of FIG. 23.
FIG. 23.

Minimum value of as a function of for FIDA density profile fitting across the range of shots studied.

Image of FIG. 24.
FIG. 24.

Difference in the beam ion distribution, , between the  Pueschel case and the classical case in shot 145183. The contour labeled “FIDA Signal Region” represents the approximate boundary of the 0.08% contribution range of the FIDA phase space weighting shown in Fig. 3 .


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752b84549af89a08dbdd7fdb8b9568b5 journal.articlezxybnytfddd
Scitation: Energetic ion transport by microturbulence is insignificant in tokamaksa)