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Rotation and kinetic modifications of the tokamak ideal-wall pressure limit
J E Menard1, Z Wang1, Y Liu2
1Princeton Plasma Physics Laboratory, Princeton University, Princeton, New Jersey 08543, USA.
Physical Review Letters
|January 3, 2015
Summary
High toroidal rotation and energetic ions can destabilize tokamak ideal wall modes. Drift-kinetic effects can counteract this, improving agreement between theory and experiments on the NSTX spherical torus.
Area of Science:
- Plasma physics
- Fusion energy research
- Magnetohydrodynamics
Background:
- Tokamak devices are crucial for fusion energy research.
- Ideal wall modes can limit plasma confinement in tokamaks.
- Understanding stability limits is essential for reactor design.
Purpose of the Study:
- To investigate the impact of toroidal rotation, energetic ions, and drift-kinetic effects on tokamak ideal wall mode stability.
- To compare theoretical predictions with experimental data for the first time.
- To explore new insights into tearing mode triggering.
Main Methods:
- Theoretical analysis incorporating toroidal rotation, energetic ions, and drift-kinetic effects.
- Experimental validation using the National Spherical Torus Experiment (NSTX) device.
- Investigation in a unique parameter regime of high toroidal rotation and kinetic pressure.
Main Results:
- High toroidal rotation, primarily via angular velocity shear, acts as a destabilizing mechanism.
- Non-Maxwellian fast ions can also destabilize ideal wall modes.
- Drift-kinetic damping shows potential to offset destabilization from rotation and fast ions.
- Inclusion of these effects significantly improves agreement between measured and predicted stability characteristics.
Conclusions:
- Toroidal rotation, energetic ions, and drift-kinetic effects are critical factors influencing tokamak ideal wall mode stability.
- The NSTX spherical torus provides a unique platform for studying these effects.
- Improved theoretical models enhance the prediction of plasma stability and may offer insights into tearing mode triggering.
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