Prevention of tokamak disruptions with feedback
ORAL
Abstract
Many tokamak disruptions are caused by resistive wall tearing modes (RWTM). There are two main criteria for disruptions in a DIII-D locked mode database [1],
which are also resistive wall tearing mode (RWTM) instability criteria. The rational surface of a (2,1) tearing mode (TM) must be
close enough to the resistive wall surrounding the plasma to interact with it. This implies possible feedback stabilization.
The second criterion is a minimum value of internal inductance. The current must be sufficiently peaked. This can be
caused by radiative edge cooling, turbulence, UFOs, and other precursors. This also a RWTM criterion.
The edge cooling suppresses edge bootstrap current and prevents neoclassical TMs (NTM), which aredisruption precursors.
RWTMs are also found at high beta, eg. in NSTX [2] and KSTARs. Feedback control of resistive wall modes (RWMs) includes RWTMs as a by-product.
RWTMs can grow to much larger amplitude than ideal wall TMs, and cause a complete thermal quench.
Analytic theory and numerical modeling [3] demonstrate the two RWTM criteria. Numerical simulations are presented of feedback control in MST and NSTX.
[1] R. Sweeney et al, Nucl. Fusion 57 0160192 (2017)
[2] S. A. Sabbagh et al, Nucl. Fusion 50 025020 (2010).
[3] H. R. Strauss, Phys. Plasmas 32 032505 (2025)
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which are also resistive wall tearing mode (RWTM) instability criteria. The rational surface of a (2,1) tearing mode (TM) must be
close enough to the resistive wall surrounding the plasma to interact with it. This implies possible feedback stabilization.
The second criterion is a minimum value of internal inductance. The current must be sufficiently peaked. This can be
caused by radiative edge cooling, turbulence, UFOs, and other precursors. This also a RWTM criterion.
The edge cooling suppresses edge bootstrap current and prevents neoclassical TMs (NTM), which aredisruption precursors.
RWTMs are also found at high beta, eg. in NSTX [2] and KSTARs. Feedback control of resistive wall modes (RWMs) includes RWTMs as a by-product.
RWTMs can grow to much larger amplitude than ideal wall TMs, and cause a complete thermal quench.
Analytic theory and numerical modeling [3] demonstrate the two RWTM criteria. Numerical simulations are presented of feedback control in MST and NSTX.
[1] R. Sweeney et al, Nucl. Fusion 57 0160192 (2017)
[2] S. A. Sabbagh et al, Nucl. Fusion 50 025020 (2010).
[3] H. R. Strauss, Phys. Plasmas 32 032505 (2025)
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Publication: [1] R. Sweeney et al, Nucl. Fusion 57 0160192 (2017)<br><br>[2] S. A. Sabbagh et al, Nucl. Fusion 50 025020 (2010).<br><br>[3] H. R. Strauss, Phys. Plasmas 32 032505 (2025)
Presenters
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Henry R Strauss
HRS Fusion
Authors
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Henry R Strauss
HRS Fusion