Speaker
Description
The cause of the thermal quench (TQ) in tokamak disruptions has not been well understood.
Recent work identified the TQ in JET locked mode disruptions with
a resistive wall tearing mode (RWTM) [1].
New research finds a similar instability in DIII-D locked mode shot 154576 [2]. The instability is studied with simulations, theory, and comparison to experimental data. Linear theory and simulations show the mode is stable for an ideal wall, and unstable with a resistive wall.
Its growth rate $\gamma$ scales asymptotically as the resistive wall
time $\tau_{wall}$ to a negative fractional power,
$\gamma \propto \tau_{wall}^\alpha,$ which varies between $-4/9 \ge \alpha \ge -1.$
The scaling depends on the tearing stability parameter $\Delta',$ with and without an ideal wall.
The growth rate increases as the edge safety factor approaches $q = 2.$
The growth time is consistent with the experimental thermal quench time.
Nonlinear simulations show that the mode grows to large amplitude, causing a thermal quench.
These results could be important for ITER [3], greatly mitigating the effects of disruptions.
The ITER thermal quench time could be
much slower, because the wall resistive penetration time is
50 times longer than in JET and DIII-D.
[1] H. Strauss and JET Contributors,
Effect of Resistive Wall on Thermal Quench in JET Disruptions,
Phys. Plasmas 28, 032501 (2021)
[2] R. Sweeney, W. Choi, M. Austin, et al.
Relationship between locked modes and thermal quenches in DIII-D, Nucl. Fusion 58, 056022 (2018)
[3] H. Strauss, Thermal quench in ITER disruptions,
Phys. Plasmas 28 072507 (2021)
| Speaker's title | Mr |
|---|---|
| Speaker's email address | hank@hrsfusion.com |
| Speaker's Affiliation | HRS Fusion, West Orange |
| Member State or IGO | United States of America |
