Speaker
Mr
Christopher Holland
(USA)
Description
A series of carefully designed validation experiments have been conducted on DIII-D to rigorously test gyrofluid and gyrokinetic predictions of transport and turbulence stiffness in both the ion and electron channels. In the first experiment, the ratio of the volume-averaged electron temperature profile to its value at rho=0.84 was found to be essentially invariant with increased heating over a factor of 3 variation in neutral beam injection (NBI) heating in H-mode plasmas with constant pedestal conditions, while a small increase was observed in the ion temperature ratio. The TGLF [1] transport model reproduces the profile measurements and trends with increased NBI heating, providing significant additional support for the fidelity of TGLF in H-modes. Building off these global studies, experiments that quantified local electron stiffness by varying the deposition of electron cyclotron heating (ECH) about a specified reference radius were performed. Applying this technique to L-mode plasmas with no other external heating, a critical inverse temperature gradient scale length a/L_Te,crit = 2.0±0.3 (1/L_Te = −nabla T_e/T_e, a=0.6 m) has been identified for the first time in DIII-D. Both TGLF and nonlinear GYRO [2] simulations predict similar levels of near-zero turbulence and transport at or below the experimental critical gradient and experimentally relevant levels above it, and a similar transition is observed in linear growth rate calculations. However, both codes also underpredict the power balance calculations of the electron and ion heat fluxes Q_e and Q_i, and increases to both a/L_Te and a/L_Ti larger than experimental uncertainties are needed to match the power balance results. These results build upon previous validation studies [3] of electron transport at DIII-D, for which new gyrokinetic modeling results will be reported.
[1] G.M. Staebler, et al., Phys. Plasmas 14 (2007) 055909.
[2] J. Candy and R.E. Waltz, Phys. Rev. Lett. 91 (2003) 45001.
[3] J.C. DeBoo et al., Phys. Plasmas 17 (2010) 056105.
Work supported by the US DOE under DE-FG02-07ER54917, DE-FG02-06ER54871, DE-FC02-04ER54698, DE-FC02-99ER54512, DE-FG02-08ER54984, DE-FG02-89ER53296 and DE-FG02-08ER54999.
Country or International Organization of Primary Author
USA
Primary author
Mr
Christopher Holland
(USA)
Co-authors
Ms
Anne E. White
(Massachusetts Institute of Technology)
Dr
C. Craig Petty
(General Atomics)
Dr
Edward J. Doyle
(University of California Los Angeles)
Dr
Gary M. Staebler
(General Atomics)
Dr
George R. McKee
(University of Wisconsin-Madison)
Dr
Guiding Wang
(University of California Los Angeles)
Dr
James C. DeBoo
(General Atomics)
Dr
Jeffrey Candy
(General Atomics)
Dr
Jon C. Hillesheim
(University of California Los Angeles)
Dr
Jon E. Kinsey
(General Atomics)
Dr
Keith H. Burrell
(General Atomics)
Dr
Lei Zeng
(University of California Los Angeles)
Dr
Lothar Schmitz
(University of California Los Angeles)
Dr
Philip B. Snyder
(General Atomics)
Dr
Ronald E. Waltz
(General Atomics)
Dr
Sterling P. Smith
(General Atomics)
Dr
Terry L. Rhodes
(University of California Los Angeles)
Ms
Zheng Yan
(University of Wisconsin-Madison)
