Modeling Fast Ion Transport in TAE Avalanches in NSTX
Authors: E.D. Fredrickson, N.A. Crocker, R.E. Bell, D. Darrow, N.N. Gorelenkov, G. Kramer, S. Kubota, F.M. Levinton, D. Liu, S.S. Medley, M. Podesta, K. Tritz, R.B. White
Abstract:
Experiments on the National Spherical Torus Experiment [M. Ono, et al., Nucl. Fusion 40 (2000) 557 ] have found strong bursts of Toroidal Alfven Eigenmode (TAE) activity correlated with abrupt drops in the neutron rate. A fairly complete data set offers the opportunity to benchmark the NOVA [C. Z. Cheng, Phys. Reports 211, 1-51 (1992)] and ORBIT [R. B. White and M. S. Chance, Phys. Fluids 27, 2455 (1984)] codes in the low aspect ratio tokamak (ST) geometry. The internal structure of TAE were modeled with NOVA and good agreement is found with measurements made with an array of five fixed-frequency reflectometers. The fast-ion transport resulting from these bursts of multiple TAE were then modeled with the ORBIT code. The simulations are reasonably consistent with the observed drop in neutron rate. While these results represent our best attempts to find agreement, we believe that further refinements in both the simulation of the TAE structure and in the modeling of the fast ion transport are needed. Benchmarking stability codes against present experiments is an important step in developing the predictive capability needed to plan future experiments.
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Submitted to: Physics of Plasmas (August 2009)
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Download PPPL-4433 (pdf 2.0 MB 24 pp)
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