2D properties of core turbulence on DIII-D and comparison to gyrokinetic simulations

M. W. Shafer; R. J. Fonck; G. R. McKee; C. Holland; A. E. White; D. J. Schlossberg

doi:10.1063/1.3691965

2D properties of core turbulence on DIII-D and comparison to gyrokinetic simulations

M. W. Shafer, R. J. Fonck, G. R. McKee, C. Holland, A. E. White, D. J. Schlossberg

Advanced Tokamak Physics

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Abstract

Quantitative 2D characteristics of localized density fluctuations are presented over the range of 0. 3 r / a 0. 9 in L-mode plasmas on DIII-D [J. L. Luxon, Nucl. Fusion 42, 614 (2002)]. Broadband density fluctuations increase in amplitude from n / n 0. 5 % in the deep core to n / n ∼ 2. 5 % near the outer region. The observed Doppler-shift due to the E B velocity matches well with the measured turbulence group and phase velocities (in toroidally rotating neutral beam heated plasmas). Turbulence decorrelation rates are found to be ∼200 kHz at the edge and to decrease toward the core (0. 45 r / a 0. 9) where they approach the E B shearing rate (∼50 kHz). Radial and poloidal correlation lengths are found to scale with the ion gyroradius and exhibit an asymmetric poloidally elongated eddy structure. The ensemble-averaged turbulent eddy structure changes its tilt with respect to the radial-poloidal coordinates in the core, consistent with an E B shear mechanism. The 2D spatial correlation and wavenumber spectra [S (k r, k )] are presented and compared to nonlinear flux-tube GYRO simulations at two radii, r / a = 0. 5 and r / a = 0. 75, showing reasonable overall agreement, but the GYRO spectrum exhibits a peak at finite k r for r / a = 0. 75 that is not observed experimentally; E B shear may cause this discrepancy.

Original language	English
Article number	032504
Journal	Physics of Plasmas
Volume	19
Issue number	3
DOIs	https://doi.org/10.1063/1.3691965
State	Published - Mar 2012

Funding

The authors thank K. Burrell, R. Waltz, and J. Candy for useful discussions, and the DIII-D program for its support of this collaborative research program. This work supported in part by the U.S. Department of Energy under DE-FG02-08ER54999, DE-FG02-89ER53296, DE-FG02-07ER54917, DE-AC05-06OR23100, and DE-FC02-04ER54698.

Funders	Funder number
U.S. Department of Energy	DE-FG02-08ER54999, DE-FC02-04ER54698, DE-FG02-07ER54917, DE-FG02-89ER53296, DE-AC05-06OR23100

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title = "2D properties of core turbulence on DIII-D and comparison to gyrokinetic simulations",

abstract = "Quantitative 2D characteristics of localized density fluctuations are presented over the range of 0. 3 r / a 0. 9 in L-mode plasmas on DIII-D [J. L. Luxon, Nucl. Fusion 42, 614 (2002)]. Broadband density fluctuations increase in amplitude from n / n 0. 5 % in the deep core to n / n ∼ 2. 5 % near the outer region. The observed Doppler-shift due to the E B velocity matches well with the measured turbulence group and phase velocities (in toroidally rotating neutral beam heated plasmas). Turbulence decorrelation rates are found to be ∼200 kHz at the edge and to decrease toward the core (0. 45 r / a 0. 9) where they approach the E B shearing rate (∼50 kHz). Radial and poloidal correlation lengths are found to scale with the ion gyroradius and exhibit an asymmetric poloidally elongated eddy structure. The ensemble-averaged turbulent eddy structure changes its tilt with respect to the radial-poloidal coordinates in the core, consistent with an E B shear mechanism. The 2D spatial correlation and wavenumber spectra [S (k r, k )] are presented and compared to nonlinear flux-tube GYRO simulations at two radii, r / a = 0. 5 and r / a = 0. 75, showing reasonable overall agreement, but the GYRO spectrum exhibits a peak at finite k r for r / a = 0. 75 that is not observed experimentally; E B shear may cause this discrepancy.",

author = "Shafer, {M. W.} and Fonck, {R. J.} and McKee, {G. R.} and C. Holland and White, {A. E.} and Schlossberg, {D. J.}",

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T1 - 2D properties of core turbulence on DIII-D and comparison to gyrokinetic simulations

AU - Shafer, M. W.

AU - Fonck, R. J.

AU - McKee, G. R.

AU - Holland, C.

AU - White, A. E.

AU - Schlossberg, D. J.

PY - 2012/3

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N2 - Quantitative 2D characteristics of localized density fluctuations are presented over the range of 0. 3 r / a 0. 9 in L-mode plasmas on DIII-D [J. L. Luxon, Nucl. Fusion 42, 614 (2002)]. Broadband density fluctuations increase in amplitude from n / n 0. 5 % in the deep core to n / n ∼ 2. 5 % near the outer region. The observed Doppler-shift due to the E B velocity matches well with the measured turbulence group and phase velocities (in toroidally rotating neutral beam heated plasmas). Turbulence decorrelation rates are found to be ∼200 kHz at the edge and to decrease toward the core (0. 45 r / a 0. 9) where they approach the E B shearing rate (∼50 kHz). Radial and poloidal correlation lengths are found to scale with the ion gyroradius and exhibit an asymmetric poloidally elongated eddy structure. The ensemble-averaged turbulent eddy structure changes its tilt with respect to the radial-poloidal coordinates in the core, consistent with an E B shear mechanism. The 2D spatial correlation and wavenumber spectra [S (k r, k )] are presented and compared to nonlinear flux-tube GYRO simulations at two radii, r / a = 0. 5 and r / a = 0. 75, showing reasonable overall agreement, but the GYRO spectrum exhibits a peak at finite k r for r / a = 0. 75 that is not observed experimentally; E B shear may cause this discrepancy.

AB - Quantitative 2D characteristics of localized density fluctuations are presented over the range of 0. 3 r / a 0. 9 in L-mode plasmas on DIII-D [J. L. Luxon, Nucl. Fusion 42, 614 (2002)]. Broadband density fluctuations increase in amplitude from n / n 0. 5 % in the deep core to n / n ∼ 2. 5 % near the outer region. The observed Doppler-shift due to the E B velocity matches well with the measured turbulence group and phase velocities (in toroidally rotating neutral beam heated plasmas). Turbulence decorrelation rates are found to be ∼200 kHz at the edge and to decrease toward the core (0. 45 r / a 0. 9) where they approach the E B shearing rate (∼50 kHz). Radial and poloidal correlation lengths are found to scale with the ion gyroradius and exhibit an asymmetric poloidally elongated eddy structure. The ensemble-averaged turbulent eddy structure changes its tilt with respect to the radial-poloidal coordinates in the core, consistent with an E B shear mechanism. The 2D spatial correlation and wavenumber spectra [S (k r, k )] are presented and compared to nonlinear flux-tube GYRO simulations at two radii, r / a = 0. 5 and r / a = 0. 75, showing reasonable overall agreement, but the GYRO spectrum exhibits a peak at finite k r for r / a = 0. 75 that is not observed experimentally; E B shear may cause this discrepancy.

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2D properties of core turbulence on DIII-D and comparison to gyrokinetic simulations

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