Title: Validation of gyrokinetic simulations with measurements of electron temperature fluctuations and density-temperature phase angles on ASDEX Upgrade

Abstract

Measurements of turbulent electron temperature fluctuation amplitudes, $$δT_e⊥/T_e$$, frequency spectra, and radial correlation lengths, $$L_r(T_{e⊥}$$), have been performed at ASDEX Upgrade using a newly upgraded Correlation ECE diagnostic in the range of scales $$k_⊥<1.4 cm^{-1}, k_r < 3.5 cm^{-1} (k_⊥ρ_s < 0.28$$ and $$k_rρ_s < 0.7$$). The phase angle between turbulent temperature and density fluctuations, α_nT, has also been measured by using an ECE radiometer coupled to a reflectometer along the same line of sight. These quantities are used simultaneously to constrain a set of ion-scale non-linear gyrokinetic turbulence simulations of the outer core (ρ_tor = 0.75) of a low density, electron heated L-mode plasma, performed using the gyrokinetic simulation code, GENE. The ion and electron temperature gradients were scanned within uncertainties. It is found that gyrokinetic simulations are able to match simultaneously the electron and ion heat flux at this radius within the experimental uncertainties. The simulations were performed based on a reference discharge for which $$δT_{e⊥}/T_e$$ measurements were available, and $$L_r(T_{e⊥}$$) and α_nT were then predicted using synthetic diagnostics prior to measurements in a repeat discharge. While temperature fluctuation amplitudes are overestimated by >50% for all simulations within the sensitivity scans performed, good quantitative agreement is found for $$L_r(T_{e⊥}$$) and α_nT. Finally, a validation metric is used to quantify the level of agreement of individual simulations with experimental measurements, and the best agreement is found close to the experimental gradient values.

Authors:

Freethy, S. J.  ^[1];

• Search DOE PAGES for author "Freethy, S. J."
• Search DOE PAGES for ORCID "0000-0003-4535-565X"

Görler, T.  ^[2];

• Search DOE PAGES for author "Görler, T."
• Search DOE PAGES for ORCID "0000-0002-0851-6699"

Creely, A. J.  ^[3];

• Search DOE PAGES for author "Creely, A. J."
• Search DOE PAGES for ORCID "0000-0002-4464-150X"

Conway, G. D. ^[2]; Denk, S. S.  ^[4];

• Search DOE PAGES for author "Denk, S. S."
• Search DOE PAGES for ORCID "0000-0003-4364-9363"

Happel, T. ^[2]; Koenen, C.  ^[5];

• Search DOE PAGES for author "Koenen, C."
• Search DOE PAGES for ORCID "0000-0002-4848-4898"

Hennequin, P. ^[6]; White, A. E. ^[3]

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+ Show Author Affiliations

1. Max Plank Inst. for Plasma Physics, Garching (Germany); Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States). Plasma Science and Fusion Center
2. Max Plank Inst. for Plasma Physics, Garching (Germany)
3. Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States). Plasma Science and Fusion Center
4. Max Plank Inst. for Plasma Physics, Garching (Germany); Technische Univ. München, Garching (Germany). Physik-Dept.
5. Technische Univ. München, München (Germany). Lehrstuhl für Hochfrequenztechnik
6. Ecole Polytechnique, Palaiseau (France). Lab. de Physique des Plasmas

Publication Date:

Fri Mar 16 00:00:00 EDT 2018

Research Org.:

Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States)

Sponsoring Org.:

USDOE Office of Science (SC)

Contributing Org.:

ASDEX Upgrade Team

OSTI Identifier:

1540164

Alternate Identifier(s):

OSTI ID: 1426527

Grant/Contract Number:  

SC0006419; SC0017381

Resource Type:

Accepted Manuscript

Journal Name:

Physics of Plasmas

Additional Journal Information:

Journal Volume: 25; Journal Issue: 5; Journal ID: ISSN 1070-664X

Publisher:

American Institute of Physics (AIP)

Country of Publication:

United States

Language:

English

Subject:

70 PLASMA PHYSICS AND FUSION TECHNOLOGY; physics