Poloidally and radially resolved parallel D{sup +} velocity measurements in the DIII-D boundary and comparison to neoclassical computations
- University of California-San Diego, La Jolla, California 92093 (United States)
- General Atomics, P.O. Box 85608, San Diego, California 92186-5608 (United States)
- Princeton Plasma Physics Laboratory, Princeton, New Jersey 08543-0451 (United States)
- Sandia National Laboratories, Albuquerque, New Mexico 87185 (United States)
- Lawrence Livermore National Laboratory, Livermore, California 94551 (United States)
- Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831 (United States)
First measurements of the D{sup +} parallel velocity, V{sub ||}{sup D+}, in L-mode discharges in the DIII-D [J. L. Luxon, Nucl. Fusion 42, 614 (2002)] tokamak boundary region at two poloidal locations, {theta}{approx}0 deg. and {theta}{approx}255 deg., made using Mach probes, feature a peak with velocities of up to 80 km/s at the midplane last closed flux surface (LCFS), as high as ten times the charge exchange recombination C{sup 6+} toroidal velocity, V{sub {phi}}{sup C6+}, in the same location. The V{sub ||}{sup D+} profiles are very asymmetric poloidally, by a factor of 8-10, and feature a local peak at the midplane. This peak, 1-2 cm wide, is located at or just inside the LCFS, and it suggests a large source of momentum in that location. This momentum source is quantified at {approx}0.31 N m by using a simple momentum transport model. This is the most accurate measurement of the effects of so called 'intrinsic' edge momentum source to date. The V{sub ||}{sup D+} measurements are quantitatively consistent with a purely neoclassical computational modeling of V{sub ||}{sup D+} by the code NEO[E. A. Belli and J. Candy, Plasma Phys. Controlled Fusion 50, 095010 (2008)], using V{sub {phi}}{sup C6+} as input, for {rho}{approx}0.7-0.95 at the two poloidal locations, where V{sub ||}{sup D+} measurements exist. The midplane NEO-calculated V{sub ||}{sup D+} grows larger than V{sub ||}{sup C6+} in the steeper edge gradient region and trends to agreement with the probe-measured V{sub ||}{sup D+} data near {rho}{approx}1, where the local V{sub ||}{sup D+} velocity peak exists. The measurements and computations were made in OH and L-mode discharges on an upper single null, with ion {nabla}B{sub T} drift away from the divertor. The rotating layer finding is similar in auxiliary heated discharges with and without external momentum input, except that at higher density the edge velocity weakens.
- OSTI ID:
- 21537296
- Journal Information:
- Physics of Plasmas, Vol. 18, Issue 3; Other Information: DOI: 10.1063/1.3559492; (c) 2011 American Institute of Physics; ISSN 1070-664X
- Country of Publication:
- United States
- Language:
- English
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