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Author: Michael R Halfmoon
Requested Type: Poster
Submitted: 2016-02-15 04:59:37

Co-authors: D.P. Brennan

Contact Info:
University of Tulsa
39A Linden Lane
Princeton, NJ   08540
United States

Abstract Text:
Previous analysis of toroidal confinement experiments has shown that energetic ions interact with and affect MHD mode stability, which has been extensively modeled and simulated for ideal MHD instabilities and resistive wall modes [1,2]. In addition, the 2/1 tearing mode was found to be damped or stabilized by energetic ions, with the most significant effects on the slow growing resistive mode [2]. This study focuses on the mode-particle interactions between energetic particles and pressure-driven, slow growing tearing modes which have been shown to be driven unstable in experiments as pressure increases [3]. Using a reduced analytic description of a high aspect ratio tokamak equilibrium, we add in the effects of high energy particles as a scalar modification to the perturbed pressure. Our equilibrium model consists of a cylinder with step function current and pressure profiles, with an imposed approximation to magnetic curvature which is necessary to model particle dynamics. Using this configuration, we find the importance of global magnetic shear (s = 1/q dq/dr) on the pressure gradient and the particle precession drift frequency. We find that for s > 0 at the radial position of the pressure jump, particles contribute a stabilizing effect to the 2/1 tearing mode. However, we find that for s <= 0, particles drive mode development similar to the effect seen in [3]. Future work will take in to consideration the effects of coupling between a nonresonant 1/1 mode and resonant 2/1 tearing with particle effects.

1. B. Hu, and R. Betti, "Resistive wall mode in collisionless quasistationary plasmas." Physical Review Letters 93.10 (2004): 105002.
2. R. Takahashi et al, "Kinetic effects of energetic particles on resistive MHD stability." Physical Review Letters 102.13 (2009): 135001.
3. Brennan, D. P., C. C. Kim, and R. J. La Haye. "Energetic particle effects on n= 1 resistive MHD instabilities in a DIII-D hybrid discharge." Nuclear Fusion 52.3 (2012): 033004.