TITLE

Poloidally and radially resolved parallel D+ velocity measurements in the DIII-D boundary and comparison to neoclassical computations

AUTHOR(S)
Boedo, J. A.; Belli, E. A.; Hollmann, E.; Solomon, W. M.; Rudakov, D. L.; Watkins, J. G.; Prater, R.; Candy, J.; Groebner, R. J.; Burrell, K. H.; deGrassie, J. S.; Lasnier, C. J.; Leonard, A. W.; Moyer, R. A.; Porter, G. D.; Brooks, N. H.; Muller, S.; Tynan, G.; Unterberg, E. A.
PUB. DATE
March 2011
SOURCE
Physics of Plasmas;Mar2011, Vol. 18 Issue 3, p032510
SOURCE TYPE
Academic Journal
DOC. TYPE
Article
ABSTRACT
First measurements of the D+ parallel velocity, V∥D+, in L-mode discharges in the DIII-D [J. L. Luxon, Nucl. Fusion 42, 614 (2002)] tokamak boundary region at two poloidal locations, θ∼0° and θ∼255°, 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 C6+ toroidal velocity, V[lowercase_phi_synonym]C6+, in the same location. The V∥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 ∼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∥D+ measurements are quantitatively consistent with a purely neoclassical computational modeling of V∥D+ by the code NEO [E. A. Belli and J. Candy, Plasma Phys. Controlled Fusion 50, 095010 (2008)], using V[lowercase_phi_synonym]C6+ as input, for ρ∼0.7-0.95 at the two poloidal locations, where V∥D+ measurements exist. The midplane NEO-calculated V∥D+ grows larger than V∥C6+ in the steeper edge gradient region and trends to agreement with the probe-measured V∥D+ data near ρ∼1, where the local V∥D+ velocity peak exists. The measurements and computations were made in OH and L-mode discharges on an upper single null, with ion ∇BT 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.
ACCESSION #
59744110

 

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