Resistive Wall Tearing Mode Disruptions*

Recent  simulations of  JET [1], ITER [2], DIII-D [3]

and Madison Symmetric Torus (MST) [4]  found the thermal quench (TQ)

in disruptions  was 

caused by resistive wall tearing modes (RWTM).

In JET and DIII-D, with resistive wall time of 5ms,

the TQ time was found in simulations  to be 1.5 ms and 2.5  ms respectively,  in agreement

with experiment.

In ITER, with resistive wall time 250ms, simulations predict a TQ time of

about 100 ms. In MST

 disruptions are not observed within the

the experimental shot time of 50ms.

Recent simulations and theory [4]  found  a TQ time of about 200 ms.

A model is presented of locked mode disruption precursors.

Impurity radiation and tearing mode island overlap cool the

edge and cause the current to contract.  Model sequences of equilibria

with current contraction are analyzed for linear stability [5]. Current contraction

is found to destabilize RWTMs, while too much contraction stabilizes them.

This is consistent with DIII-D data, in which there is a minimum rational surface in which there is a minimum rational surface

radius for disruptions [4].

Active stabilization of RWTMs by feedback is under investigation with theory

and simulations. Results will be presented.

[1] H. Strauss and JET Contributors,

Phys. Plasmas 28, 032501 (2021) 

[2] H. Strauss, 

 Phys. Plasmas 28 072507 (2021) 

[3]  H. Strauss, B. C. Lyons, M. Knolker,

Phys. Plasmas 29  112508 (2022).

[4]  H. R. Strauss, B. E. Chapman, N. C. Hurst,

PPCF 65  084002 (2023).

[5]  H. R. Strauss, arXiv (2023).