The effects of sheared toroidal rotation on stability limits in tokamak plasmas

Abstract

Sheared toroidal rotation is found to increase the ideal external kink stability limit, thought to be the ultimate performance limit in fusion tokamaks. However, at rotation speeds approaching a significant fraction of the Alfvén speed, the toroidal rotation shear drives a Kelvin-Helmholtz-like global plasma instability. Optimizing the rotation profile to maximize the pressure before encountering external kink modes, but simultaneously avoiding flow-driven instabilities, can lead to a window of stability that might be attractive for operating future high-performance fusion devices such as a spherical tokamak component test facility.

Effects of parallel sound wave damping and drift kinetic damping on the resistive wall mode stability with various plasma rotation profiles

“…This is a very important research area in terms of rotational stabilization of MHD instabilities in fusion plasmas (Chu 1998; Bierwage, Yu & Günter 2007; Chapman et al. 2011, 2012; Wahlberg, Graves & Chapman 2013).…”

“…The reason for choosing these three rotation profiles is that they have different shear amplitudes and signs at rational surfaces q = 2, 3. This is a very important research area in terms of rotational stabilization of MHD instabilities in fusion plasmas (Chu 1998;Bierwage, Yu & Günter 2007;Chapman et al 2011Wahlberg, Graves & Chapman 2013).…”

Steady-state tokamak research: Core physics

“…Moreover, the eigenvalue analysis may fail to identify the most unstable solution when the time evolution of this solution is no longer expðtÞ. MHD stability codes treating toroidal flow have been developed during the 1990s including MARS by Chu et al (1999) and more recently MINERVA by Aiba et al (2011) and CASTOR-FLOW by Chapman et al (2011). If we can assume ¼ expðtÞ, the eigenvalue ¼ þ in!…”

Energy-Casimir, dynamically accessible, and Lagrangian stability of extended magnetohydrodynamic equilibria

“…Also there are many studies proposing that plasma sheared rotation variously affects the stability properties of Tokamak equilibria in several cases, either inducing stabilization or destabilization (e.g. [5][6][7][8][9]), with the main destabilizing mechanism being the Kelvin-Helmholtz instability [10]. * dkaltsas@cc.uoi.gr † gthroum@uoi.gr ‡ morrison@physics.utexas.edu Furthermore, many astrophysical phenomena, such as the development of turbulence in various stages of the solar wind and in magnetized accretion disks, are consequences of flow-driven instabilities such as the Kelvin-Helmholtz instability (e.g.…”