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Measurements of the cross-phase angle between density and electron temperature fluctuations and comparison with gyrokinetic simulationsa)
a)Paper KI3 1, Bull. Am. Phys. Soc. 54, 137 (2009).
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10.1063/1.3323084
/content/aip/journal/pop/17/5/10.1063/1.3323084
http://aip.metastore.ingenta.com/content/aip/journal/pop/17/5/10.1063/1.3323084

Figures

Image of FIG. 1.
FIG. 1.

The wave number spectrum of at calculated from nonlinear GYRO simulations shows the decrease in cross phase as is increased by 50%. Values of at plotted vs percent change in . Linear GYRO runs (blue circles) and nonlinear GYRO runs (red diamonds) show good agreement both for the magnitude of the cross-phase angle and the trend with increasing .

Image of FIG. 2.
FIG. 2.

Diagram of coupled CECE and reflectometer diagnostics at DIII-D. The inset shows profiles of plasma frequencies with example values of and where CECE and reflectometer radial measurement locations will overlap.

Image of FIG. 3.
FIG. 3.

Example of measured correlated long wavelength and in a plasma with only Ohmic heating and ECH (no beams) at DIII-D (133 626, , ). (a) The power spectrum of density fluctuations measured with the scattered power signal from the reflectometer, (b) the power spectrum of electron temperature fluctuations measured with CECE using a two-channel correlation technique, (c) the coherency spectrum of density and electron temperature fluctuations, and (d) the cross-phase angle spectrum between density and electron temperature fluctuations.

Image of FIG. 4.
FIG. 4.

Measured plasma profiles comparing reference shots with NBI only (black) and a shot with NBI and ECH (red-grey), corresponding to a “Base” case and “High ” case, respectively. Data from 138 038 (red-grey) and 138 040 (black), are shown.

Image of FIG. 5.
FIG. 5.

Changes in linear stability of the ITG mode and TEM calculated using TGLF comparing reference shots 138 040 and 138 038 corresponding to a “Base” case (black) and “High ” case (red-grey), respectively. Results at in 138 038 (red-grey) and 138 040 (black) at are shown.

Image of FIG. 6.
FIG. 6.

Changes in transport as calculated using ONETWO comparing a “Base” case (black) and a “High ” case (red-grey). Experimental profiles from reference shots 138 038 and 138 040 at were used as input to ONETWO. Dashed lines indicate a one-sigma standard deviation resulting from random uncertainties in the input profiles.

Image of FIG. 7.
FIG. 7.

The measured coherency, , and cross-phase angle, , comparing “Base” cases (black) and “High ” cases (red-grey) are shown at three radial locations. At and 0.65 smaller cross-phase angles are measured in the High Case. At there is no change in cross-phase angle outside experimental error bars. Horizontal dashed lines on the coherency plot indicates a statistical noise limit, error bars on the cross-phase angle are the one-sigma standard deviations, and a horizontal line at is plotted for reference.

Image of FIG. 8.
FIG. 8.

The “Base” case (black) and the “High-” case (red-grey) cross-phase angles measured at three radial locations. The plotted values are the average cross-phase angle in the frequency range , the errors bars are the one-sigma standard deviation on the frequency averaged cross-phase angle.

Image of FIG. 9.
FIG. 9.

The measured changes in long wavelength electron temperature and density fluctuation levels measured with CECE and BES, respectively. The electron temperature fluctuation level is obtained by integrating the CECE cross-power spectrum between and long-wavelength density fluctuation level is obtained by integrating the BES cross-power spectrum between . Error bars represent the experimental uncertainty in the measurements.

Image of FIG. 10.
FIG. 10.

Comparison of experimental results at to postexperimental simulation results using the local parameters from 138 038, as input. (a) The GYRO unfiltered (black-solid), synthetic diagnostic (blue-dashed), and experimental (red-grey) cross-power spectra have been normalized to compare the spectral shape. (b) The GYRO unfiltered (black-solid), synthetic diagnostic (blue-dashed), and experimental cross-phase angles (red-grey) are compared. The one-sigma standard deviations are plotted as error bars at each frequency in (a) and (b). Note that the experimental phase angle is meaningfully compared with the simulations only where it is resolved (frequencies where the coherency is high), between . Outside this frequency range the measured is in the noise.

Image of FIG. 11.
FIG. 11.

The sample volumes for the synthetic CECE and reflectometer signals are separated by and the radial separation, , is scanned. The cross-phase angle is shown in (a) and the coherency is shown (b).

Image of FIG. 12.
FIG. 12.

The sample volumes for the synthetic CECE and reflectometer signals are separated by and the vertical separation, , is scanned. The cross-phase angle is shown in (a) and the coherency is shown in (b).

Tables

Generic image for table
Table I.

Local parameters at midradius used in two pre-experiment GYRO simulations. The “Base” case parameters are from DIII-D discharge 128 913, , . For the “High ” case the input electron temperature to GYRO has been increased 50%.

Generic image for table
Table II.

Results from the pre-experiment set of local, nonlinear GYRO simulations comparing transport and turbulence at for the “Base” and “High ” cases. Statistical errors are 1% for turbulence levels and 2%–3% for transport levels.

Generic image for table
Table III.

Local parameters at from reference discharges 138 040 and 138 038 at , corresponding to an experimental “Base” case and “High ” case, respectively. These are used as inputs for the postexperiment GYRO simulations.

Generic image for table
Table IV.

Postexperiment GYRO simulations from 138 038, , . Turbulence amplitudes and cross phase are compared with synthetic diagnostic results.

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2010-03-12
2014-04-17
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752b84549af89a08dbdd7fdb8b9568b5 journal.articlezxybnytfddd
Scitation: Measurements of the cross-phase angle between density and electron temperature fluctuations and comparison with gyrokinetic simulationsa)
http://aip.metastore.ingenta.com/content/aip/journal/pop/17/5/10.1063/1.3323084
10.1063/1.3323084
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