Sherwood 2015

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Towards Simulations with Self-Consistent SOL Density Evolution when RF Antennas are Powered

Author: David N. Smithe
Requested Type: Poster Only
Submitted: 2015-01-19 14:05:24

Co-authors: T. G. Jenkins, D. A. D’Ippolito, J. R. Myra

Contact Info:
Tech-X Corporation
5621 Arapahoe Ave.
Boulder, CO   80303

Abstract Text:
Recent numerical simulations of the dispersion and wave propagation characteristics of slow waves in front of ICRF antennas [1] have shown that a sufficiently low density plasma in the scrape-off-layer in front of the antenna can permit a thin propagation layer bounded by a lower hybrid resonance and a cutoff. The resonance, in particular, would allow such a layer to accommodate an energy build-up and become a power loss mechanism, with many qualitative similarities to the NSTX parasitic power losses [2], including a normal propagation requirement, and similar layer thickness and placement relative to the Faraday screens. However, the density required for such to occur is lower, by about a factor of three, than what is experimentally observed, when the antennas are not powered. When the antennas are powered, several effects may work to deplete the SOL density, though a limited understanding of the range of possible density variation makes it difficult to determine whether it could lower to a point which would permit a resonant layer. We are preparing an effort to self-consistently model SOL density behavior, when the antennas are powered, taking into account ponderomotive density expulsion [3] and looking at approaches to treating sheath-driven convective cells, which are also thought to contribute to poloidal asymmetry of the density [4,5]. We will give an overview of our modeling plans, and invite commentary and discussion regarding ways to accurately treat this difficult modeling problem.

1. T. G. Jenkins and D. N. Smithe, USBPO eNews, 11/30/2014.
2. J.C. Hosea et al., AIP Conf. Proceedings 1187 (2009) 105.
3. J. R. Myra et. al., Nucl. Fusion 46, S455 (2006).
4. D. A. D’Ippolito et al., Physics of Fluids B: Plasma Physics 5 (1993) 3603.
5. M. Bécoulet et al., Phys. Plasmas 9, 2619 (2002).


March 16-18, 2015
The Courant Institute, New York University