Abstract Details
Abstracts
Author: Gregorio Luigi Trevisan
Requested Type: Poster
Submitted: 2017-03-17 13:38:32
Co-authors: A. Wingen, L.L. Lao, T.E. Evans, H.Y. Guo, B.C. Lyons, S. Munaretto, D.M. Orlov, C. Paz-Soldan, E.J. Strait, W. Wu
Contact Info:
Oak Ridge Associated Universities
100 ORAU Way
Oak Ridge, Tennessee 37830
United States
Abstract Text:
Plasma-material interaction is a critical aspect in tokamak magnetic fusion devices. The Small Angle Slot (SAS) upper divertor was recently installed in DIII-D to investigate divertor detachment physics [HY Guo et al, NF 57, 2017]. The SAS combines a small angle and a closed slot structure to enhance the build-up of neutral density near the strike point, thus favoring detachment and reducing the overall heat flux in the divertor area. SOLPS modeling shows that the strike-point angle plays a crucial role in the detachment physics [CF Sang et al, to appear in NF, 2017]. Two similar codes – the TRIP3D magnetic field-line tracing code [TE Evans et al, PoP 9, 2002] and the MAFOT divertor footprint analyzer [A Wingen et al, NF 49, 2009] – have been exploited to investigate the topology of the strike point and the nearby scrape-off layer due to 3D perturbation magnetic fields in “vacuum” computations, i.e., without including the 3D magnetic plasma response. By providing insight into the topology to which the plasma will respond, “vacuum” computations represent the first step toward the solution of the full 3D problem. In DIII-D, 3D fields are typically either error fields produced by the toroidal field TF-coil (currently buswork, in the future ripple and shifts, too) and the poloidal field-shaping F-coils (tilts and shifts), or perturbation fields applied by the external control C- or the internal I-coils. The 3D fields then lead to complex 3D topological structures including magnetic lobes, magnetic islands, and magnetic stochastization. Results of the TRIP3D and MAFOT analyses indicate that, for typical TF‑, F-, and I-coils currents, the magnetic lobes remain confined within the SAS and that the toroidal modulation of the strike point position on the SAS is only slightly affected. Future studies will take into account the 3D magnetic plasma response, as well.
Work supported by US DOE under DE-FG02-95ER54309, DE‑FC02‑04ER54698, and DE-AC05-00OR22725.
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