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Axisymmetric Vertical-Displacement Event Modeling with NIMROD*

Author: C. R. Sovinec
Requested Type: Poster Only
Submitted: 2015-01-19 15:01:58

Co-authors: K. J. Bunkers

Contact Info:
University of Wisconsin-Madison
1500 Engineering Dr.
Madison, WI   53706-1
USA

Abstract Text:
Disruption of tokamak discharges involving vertical displacement is known to exert large forces and heat loads on solid structures that surround the plasma. With disruptions being among the highest priorities for ITER [Hender, et al., NF 47, S128, for example] and for tokamak fusion development, addressing questions of current path and plasma evolution with a variety of approaches is warranted. Computations require attention to boundary conditions and the region outside the separatrix [Zakharov, PoP 15, 062507; Strauss, PoP 21, 032506]. While large-scale motion of the entire plasma torus is most readily described using a moving reference frame, Eulerian computation is also suitable. The NIMROD code [Sovinec, et al., JCP 195, 335] provides an established platform for Eulerian-frame computations of plasma evolution during VDEs. Growth rates of external-kink and resistive-wall modes and the threshold for vertical instability have been verified with NIMROD [Bunkers and Sovinec, BAPS 59, no. 15, BP8.00016; Becerra, et al., BAPS 59, no. 15 BP8.00047], and nonlinear vertical displacement and kink have been demonstrated.

Recent progress on applying NIMROD to VDE studies is summarized in this presentation. Initializing diverted, vertically elongated equilibria with the NIMEQ code [Howell and Sovinec, CPC 185, 1415] is now possible with revisions that distinguish the closed-flux region from the private-flux region. Parallel communication across resistive-wall interfaces in NIMROD speeds our time-dependent computations for VDE and other non-ideal wall studies. Development allowing flow normal to bounding surfaces at the ExB drift speed, using the resistive electric field in the wall, permits our initial comparisons of no-slip and absorbing conditions.

*Work supported by the U.S. Dept. of Energy, award number DE-FG02-06ER54850.

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