April 4-6

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Author: Brendan C. Lyons
Requested Type: Poster
Submitted: 2022-03-04 19:24:18

Co-authors: J. McClenaghan (GA), C.C. Kim (SLS2), S.C. Jardin (PPPL), N.M. Ferraro (PPPL), N.W. Eidietis (GA), L.L. Lao (GA), N. Hawkes (CCFE), G. Szepesi (CCFE), and JET contributors

Contact Info:
General Atomics
PO Box 85608
San Diego, California   92186-5
United States

Abstract Text:
Future tokamaks will require robust disruption mitigation to prevent machine damage. The leading-candidate for this is shattered-pellet injection (SPI), which is being tested experimentally on several tokamaks and will be used on ITER. Verified, predictive models are needed to project the performance of these systems on future devices. We present an overview of disruption-mitigation modeling performed with M3D-C1, a 3D, nonlinear, extended magnetohydrodynamics code. M3D-C1 has been coupled to a coronal non-equilibrium model for impurity ionization, recombination, and radiation along with a state-of-the-art model for pellet ablation. A 3D benchmark between M3D-C1 & NIMROD for an injected pellet in DIII-D has been improved due to a number of code enhancements and increased resolution. The codes agree on the peak radiated power as well as time scales for thermal quench, current quench, & onset of macroscopic MHD instability. Understanding of remaining discrepancies, including the effect of boundary conditions, will be considered. The agreement found gives confidence in the ability of both codes to perform high-fidelity, predictive modeling for ITER and other future devices. M3D-C1 modeling has also been performed for realistic SPI plumes based on JET experiments. Pure-neon & neon-deuterium pellets are considered, which vary in speed & shatter distribution due to the differing composition. Simulations with the velocities swapped show that at low speeds, the quench dynamics are similar for the two compositions, while at high speeds, the mixed pellet travels further into the plasma before complete thermal quench. These results show the competition of time scales between the traversal of the pellet and outside-in radiative collapse.

Work supported by US DOE grants DE-SC0018109, DE-SC0020299, DE-FC02-04ER54698, & DE-FG02-95ER54309, the ITER Organization under Contract # IO/19/CT/4300002130, and is contributing to the ITER-Organization Disruption-Mitigation Task Force.