Abstract Details
| status: | file name: | submitted: | by: |
|---|---|---|---|
| approved | aps24g5.pdf | 2025-02-25 06:48:49 | Henry Strauss |
Abstracts
Author: Henry Strauss
Requested Type: Consider for Invited
Submitted: 2025-02-18 04:13:11
Co-authors:
Contact Info:
HRS Fusion
2 Januson Ct
West Orange, NJ 07052
United States
Abstract Text:
Many tokamak disruptions are caused by resistive wall tearing modes (RWTM).
There are two main criteria for RWTM disruptions. The most important
is that the q = 2 radius is sufficiently close to the resistive wall surrounding the plasma. This was found in a database of DIII-D locked mode disruptions [1]. The criterion is r_2 > 0.75 a, where r_2 is the q = 2 rational surface radius and a is
the plasma radius. This allows the (2,1) tearing mode to grow to large amplitude [2], producing a complete thermal quench. It also causes the mode to interact with the wall.
If feedback is applied at the wall, major disruptions can be prevented.
A second criterion found in the database [1] is that the current profile is sufficiently peaked, which
can be a consequence of edge cooling. This can be expressed in terms of internal inductance and edge q.
The RWTM criteria are confirmed in experimental data, simulations and theory [2]. It was demonstrated in simulations that feedback allows only minor disruptions.
At high beta, it is well known that resistive wall modes (RWM) can be feedback stabilized. It is demonstrated that RWTM disruptions can occur at high beta, and can also be feedback stabilized. This was observed in NSTX experiments [3] and simulated [2] in modified NSTX equilibria.
The r_2 > .75 condition requires wall radius r_w = 1.2, as in DIII-D, NSTX, and other experiments. For other wall radii the criterion is r_2 > 0.625 r_w. In the limit r_2 = a,
r_w < 1.5 a. For larger wall radius the mode is a no wall tearing mode, which can not be stabilized by feedback.
These results could potentially eliminate most tokamak major disruptions, greatly enhancing the
prospects of magnetic fusion.
[1] R. Sweeney, W. Choi, R. J. La Haye, et al,
Nucl. Fusion 57 0160192 (2017).
[2] H. R. Strauss,
arXiv2411.13256 (2024), submitted to Phys. Plasmas (2025).
[3] S. A. Sabbagh, S.P. Gerhardt, J.E. Menard, et al,
Nucl. Fusion 5
Characterization: 1.0
Comments: