Implementation and application of two synthetic diagnostics for validating simulations of core tokamak turbulence

C. Holland; A. E. White; G. R. McKee; M. W. Shafer; J. Candy; R. E. Waltz; L. Schmitz; G. R. Tynan

doi:10.1063/1.3085792

Implementation and application of two synthetic diagnostics for validating simulations of core tokamak turbulence

C. Holland, A. E. White, G. R. McKee, M. W. Shafer, J. Candy, R. E. Waltz, L. Schmitz, G. R. Tynan

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Abstract

The deployment of multiple high-resolution, spatially localized fluctuation diagnostics on the DIII-D tokamak [J. L. Luxon, Nucl. Fusion 42, 614 (2002)] opens the door to a new level of core turbulence model validation. Toward this end, the implementation of synthetic diagnostics that model physical beam emission spectroscopy and correlation electron cyclotron emission diagnostics is presented. Initial results from their applications to local gyrokinetic simulations of two locations in a DIII-D L -mode discharge performed with the GYRO code [J. Candy and R. E. Waltz, J. Comput. Phys. 186, 545 (2003)] are also discussed. At normalized toroidal flux ρ =0.5, we find very good agreement between experiment and simulation in both the energy flows and fluctuation levels measured by both diagnostics. However, at ρ =0.75, GYRO underpredicts the observed energy flows by roughly a factor of 7, with rms fluctuation levels underpredicted by a factor of 3. Interestingly, at both locations we find good agreement in the shapes of the radial and vertical density correlation functions and in the shapes of the frequency power spectra. At both locations, the attenuation of the GYRO-predicted fluctuations due to the spatial averaging imposed by the diagnostics' spot sizes is significant, and its incorporation via the use of synthetic diagnostics is shown to be essential for quantitative comparisons such as these.

Original language	English
Article number	052301
Journal	Physics of Plasmas
Volume	16
Issue number	5
DOIs	https://doi.org/10.1063/1.3085792
State	Published - 2009
Externally published	Yes

Funding

The authors would like to thank T. L. Rhodes, W. A. Peebles, E. J. Doyle, R. Prater, J. DeBoo, K. H. Burrell, P. H. Diamond, J. E. Kinsey, G. M. Staebler, D. R. Mikkelsen, R. V. Bravenec, and R. V. Budny for many useful discussions. This work was supported by the U.S. Department of Energy under Grant Nos. DE-FG02-07ER54917, DE-FG03-95ER54309, DE-FG02-89ER53296, and DE-FG03-01ER54615 and GA Subcontract No. NS53250. A.E.W.’s research was performed under appointment to the Fusion Energy Sciences Fellowship Program administered by Oak Ridge Institute for Science and Education under a contract between the U.S. Department of Energy and the Oak Ridge Associated Universities. This research used resources of the National Center for Computational Sciences at Oak Ridge National Laboratory, which is supported by the Office of Science of the Department of Energy under Contract No. DE-AC05-00OR22725, and the National Energy Research Scientific Computing Center, which is supported by the Office of Science of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231.

Funders	Funder number
National Energy Research Scientific Computing Center
Office of Science of the Department of Energy	DE-AC05-00OR22725
U.S. Department of Energy
Office of Science
Fusion Energy Sciences
Oak Ridge Associated Universities
Oak Ridge Institute for Science and Education

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abstract = "The deployment of multiple high-resolution, spatially localized fluctuation diagnostics on the DIII-D tokamak [J. L. Luxon, Nucl. Fusion 42, 614 (2002)] opens the door to a new level of core turbulence model validation. Toward this end, the implementation of synthetic diagnostics that model physical beam emission spectroscopy and correlation electron cyclotron emission diagnostics is presented. Initial results from their applications to local gyrokinetic simulations of two locations in a DIII-D L -mode discharge performed with the GYRO code [J. Candy and R. E. Waltz, J. Comput. Phys. 186, 545 (2003)] are also discussed. At normalized toroidal flux ρ =0.5, we find very good agreement between experiment and simulation in both the energy flows and fluctuation levels measured by both diagnostics. However, at ρ =0.75, GYRO underpredicts the observed energy flows by roughly a factor of 7, with rms fluctuation levels underpredicted by a factor of 3. Interestingly, at both locations we find good agreement in the shapes of the radial and vertical density correlation functions and in the shapes of the frequency power spectra. At both locations, the attenuation of the GYRO-predicted fluctuations due to the spatial averaging imposed by the diagnostics' spot sizes is significant, and its incorporation via the use of synthetic diagnostics is shown to be essential for quantitative comparisons such as these.",

author = "C. Holland and White, {A. E.} and McKee, {G. R.} and Shafer, {M. W.} and J. Candy and Waltz, {R. E.} and L. Schmitz and Tynan, {G. R.}",

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Implementation and application of two synthetic diagnostics for validating simulations of core tokamak turbulence

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