April 4-6

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approvedsherwoodposter22.pdf2022-04-01 16:00:34Valerie Izzo


Author: Valerie Izzo
Requested Type: Poster
Submitted: 2022-02-25 10:48:39


Contact Info:
Fiat Lux
3550 General Atomics Ct
San Diego, California   92093
United States

Abstract Text:
In DIII-D natural disruptions, such as those caused by locked-modes, a large increase in electron density and a significant spike in radiated power are seen, from which a significant influx of carbon from the divertor and deuterium from the first wall can be inferred [1]. This influx is as important to the thermal-quench (TQ) phase of the disruption as the presence of large islands or stochasticity in the edge which initiated the event. The NIMROD code is used to perform MHD simulations in which the magnetic configuration is initialized with 3/1, 5/2, and 2/1 tearing-like perturbations, producing an initially stochastic edge adjacent to a large 2/1 island. The growth-phase (and corresponding relevant physics) of these islands is neglected, but, a source of carbon localized near the outer divertor strike point is added to explore the relative importance of various effects as the TQ is triggered. Without the carbon source, the edge stochastic region eventually overlaps with the 2/1 island and triggers an inward cascade of flux-surface destruction, but the inclusion of the carbon initiates this process much earlier, as carbon radiation causes the cold-front to extend into the q=2 island earlier. Following on these numerical experiments will be attempts to match more closely parameters from specific natural disruptions on DIII-D and then to combine mitigation models with natural disruption scenarios.

[1] E.M. Hollmann, et al., J. Nucl. Mater. 390-391 (2009) 597.

*Supported by DOE under Award Number DE-FG02-95ER54309