April 15-17

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Abstracts

Author: Nate M Ferraro
Requested Type: Pre-Selected Invited
Submitted: 2019-02-22 10:03:58

Co-authors: B.C. Lyons, C.C. Kim, Y.Q. Liu, S.C. Jardin

Contact Info:
PPPL
100 Stellarator Rd
Princeton, NJ   08543-0
USA

Abstract Text:
Considerable progress has been made recently in developing our capability to model disruptions in tokamaks. Here we describe the application of a new model in the M3D-C1 extended-magnetohydrodynamic code for simulating tokamak disruptions. This model includes separate equations for ion and electron temperature evolution, and separately tracks the densities of each of the charge states of an impurity species. This type of model, which has not been used in previous simulations of disruptions, is necessary for accurately describing dynamics that are faster than the ion-electron equilibration or ion charge state equilibration timescales, which can be on the order of ten milliseconds or longer at parameters typical of a fusion plasma. Simulations of a fast thermal and current quench that are initiated by the introduction of large quantities of impurity ions are presented. It is demonstrated that, even for well-mixed impurities, the cooling of the plasma leads to the contraction of the current channel and associated magnetohydrodynamic instabilities that lead to rapid cooling of the plasma. This indicates that impurity injection may need to be highly localized near the magnetic axis in order to maintain macroscopic stability of the plasma during disruption mitigation.

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