Electron temperature critical gradient and transport stiffness in DIII-D

Smith, Sterling P.; Petty, Clinton C.; White, Anne E.; Holland, Christopher; Bravenec, Ronald; Austin, Max E.; Zeng, Lei; Meneghini, Orso

doi:10.1088/0029-5515/55/8/083011

Electron temperature critical gradient and transport stiffness in DIII-D

Journal Article · Mon Jul 06 00:00:00 EDT 2015 · Nuclear Fusion

DOI:https://doi.org/10.1088/0029-5515/55/8/083011· OSTI ID:1345509

Smith, Sterling P. ^[1]; Petty, Clinton C. ^[2]; White, Anne E. ^[3]; Holland, Christopher ^[4]; Bravenec, Ronald ^[5]; Austin, Max E. ^[6]; Zeng, Lei ^[7]; Meneghini, Orso ^[2]

General Atomics, San Diego, CA (United States); General Atomics
General Atomics, San Diego, CA (United States)
Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States)
Univ. of California, San Diego, CA (United States)
Fourth State Research, Austin, TX (United States)
Univ. of Texas, Austin, TX (United States)
Univ. of California, Los Angeles, CA (United States)

The electron energy flux has been probed as a function of electron temperature gradient on the DIII-D tokamak, in a continuing effort to validate turbulent transport models. In the scan of gradient, a critical electron temperature gradient has been found in the electron heat fluxes and stiffness at various radii in L-mode plasmas. The TGLF reduced turbulent transport model [G.M. Staebler et al, Phys. Plasmas 14, 055909 (2007)] and full gyrokinetic GYRO model [J. Candy and R.E. Waltz, J. Comput. Phys. 186, 545 (2003)] recover the general trend of increasing electron energy flux with increasing electron temperature gradient scale length, but they do not predict the absolute level of transport at all radii and gradients. Comparing the experimental observations of incremental (heat pulse) diffusivity and stiffness to the models’ reveals that TGLF reproduces the trends in increasing diffusivity and stiffness with increasing electron temperature gradient scale length with a critical gradient behavior. Furthermore, the critical gradient of TGLF is found to have a dependence on q₉₅, contrary to the independence of the experimental critical gradient from q₉₅.

View Accepted Manuscript (DOE)

Research Organization:: General Atomics, San Diego, CA (United States)

Sponsoring Organization:: USDOE Advanced Research Projects Agency - Energy (ARPA-E)

Grant/Contract Number:: FC02-04ER54698; FC02-99ER54512; FG02-08ER54984; FG03-97ER54415

OSTI ID:: 1345509

Alternate ID(s):: OSTI ID: 1238892

Journal Information:: Nuclear Fusion, Journal Name: Nuclear Fusion Journal Issue: 8 Vol. 55; ISSN 0029-5515

Publisher:: IOP ScienceCopyright Statement

Country of Publication:: United States

Language:: English

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