April 4-6

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approvedstrauss_sherwood22.pdf2022-04-03 12:58:41Henry Strauss


Author: Henry Strauss
Requested Type: Consider for Invited
Submitted: 2022-03-04 03:48:48

Co-authors: B.C. Lyons

Contact Info:
HRS Fusion
2 Januson Ct
West Orange, NJ   07052
United States

Abstract Text:
Fast disruptions occur in JET, DIII-D and other present experiments. The
thermal quench (TQ) occurs in about 1ms.
Many disruptions in JET and DIII-D are of the locked mode type.
The plasma toroidal rotation slows and locks. Tearing modes produce stochastic parallel thermal transport in the edge region, which along with impurity influx, cools the edge.
This precursor stage might last 100ms. It is followed by an MHD instability, which causes the thermal quench (TQ). This has been identified in JET as a resistive wall tearing mode (RWTM) [1], by comparing theory and M3D simulations with experimental data. The TQ time is the inverse of the RWTM growth rate. RWTMs grow to a much larger amplitude than tearing modes (TM). Simulations are in progress with M3DC1 and M3D of locked mode disruptions in DIII-D [2]. If the TQ can be identified with a RWTM, it is important because the RWTM in ITER will be much slower [3]. The RWTM growth rate depends on the resistive wall time, which is 50 times longer in ITER than in JET and DIII-D.
The analytic linear dispersion relation of the RWTM includes tearing modes (TM),
and a new (neo) resistive wall mode (NRWM). These modes branch from the TM no wall limit, while the usual RWM branches from the ideal no wall limit.
TMs cause the disruption precursor, and a RWTM may cause the TQ.
The NRWM might be unstable before the TMs are destabilized, a subject requiring
further investigation.

[1] H. Strauss and JET Contributors, Phys. Plasmas 28, 032501 (2021)
[2] R. Sweeney et al, Nucl. Fusion 58, 056022 (2018)
[3] H. Strauss, Phys. Plasmas 28, 072507 (2021)