Plasma and Fusion Research

Volume 7, 2403081 (2012)

Regular Articles

Nonlinear Simulation of Energetic Particle Modes in High-Beta Tokamak Plasma

Andreas BIERWAGE, Nobuyuki AIBA, Yasushi TODO¹⁾, Wenjun DENG²⁾, Masao ISHIKAWA, Go MATSUNAGA, Kouji SHINOHARA and Masatoshi YAGI

: Japan Atomic Energy Agency, Naka 311-0193, Japan
1): National Institute for Fusion Science, Toki 509-5292, Japan
2): University of California, Irvine CA 92697, USA

(Received 2 December 2011 / Accepted 1 May 2012 / Published 26 July 2012)

Abstract

The effect of bulk pressure on the nonlinear dynamics of energetic particle modes (EPM) in a neutral-beam-driven JT-60U discharge is examined through nonlinear hybrid (MHD + particle) simulations with realistic values of the plasma beta and in realistic flux surface geometry. In the scenario studied, the linear EPM growth rate is 20% higher in the finite-beta compared to the zero-beta case, but compressibility stabilizes the mode by roughly the same amount. In the finite-beta case, the nonlinear frequency shift and the radial spreading/propagation of the mode are affected by the beta-induced gap in the shear Alfvén continuum. Although the evolution of the modes is affected by bulk pressure, compressibility and geometry, the overall energetic ion transport during the first few 100 Alfvén times following the saturation of the EPM is comparable in all cases studied.

Keywords

high beta tokamak, shear Alfvén wave, energetic particle mode, nonlinear simulation, transport

DOI: 10.1585/pfr.7.2403081

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This paper may be cited as follows:

Andreas BIERWAGE, Nobuyuki AIBA, Yasushi TODO, Wenjun DENG, Masao ISHIKAWA, Go MATSUNAGA, Kouji SHINOHARA and Masatoshi YAGI, Plasma Fusion Res. 7, 2403081 (2012).