Motivation

Motivation

• Motivation

• The relationship between plasma rotation and RWM stability in NSTX is more complex than simple models suggest, and kinetic theory has the potential to explain it.

• Outline

• The MISK code is used to calculate RWM stability.
• Kinetic theory matches NSTX experimental results of instability at moderate rotation.
• Kinetic theory can match the evolution of a shot.
• DIII-D results suggest the importance of hot ions.

Written by Bo Hu, University of Rochester

• Written by Bo Hu, University of Rochester

• Hu, Betti, PRL, 2004 and Hu, Betti, and Manickam, POP, 2005

• Uses a perturbative calculation, with marginal stability eigenfunction from the PEST code.

• Calculation of δWK includes the effects of:

• Trapped Ions
• Trapped Electrons
• Circulating Ions
• Alfven Layers
• Hot Ions

Density and temperature profiles are self-similarly scaled while keeping β constant (ie, n*2 and T/2 or n/2 and T*2).

• Density and temperature profiles are self-similarly scaled while keeping β constant (ie, n*2 and T/2 or n/2 and T*2).
• We find a low rotation “critical” threshold.
• However, there is also a band of marginally stable moderate rotation, and it is here that the experiment goes unstable.

Examining the evolution of a shot

• Examining the evolution of a shot

• For NSTX shot 121083, β and ωφ are relatively constant leading up the the RWM collapse.
• Calculation of the RWM kinetic growth rate for multiple equilibria shows a turn towards instability just before the RWM.