Intrinsic momentum transport in up-down asymmetric tokamaks

Abstract

Recent work demonstrated that breaking the up-down symmetry of tokamak flux surfaces removes a constraint that limits intrinsic momentum transport, and hence toroidal rotation, to be small. We show, through MHD analysis, that ellipticity is most effective at introducing up-down asymmetry throughout the plasma. We detail an extension to GS2, a local $\delta f$ gyrokinetic code that self-consistently calculates momentum transport, to permit up-down asymmetric configurations. Tokamaks with tilted elliptical poloidal cross-sections were simulated to determine nonlinear momentum transport. The results, which are consistent with experiment in magnitude, suggest that a toroidal velocity gradient, $(\partial u_{\zeta i}/\partial \rho )/v_{thi}$, of 5% of the temperature gradient, $(\partial T_i/\partial \rho )/T_i$, is sustainable. Here $v_{thi}$ is the ion thermal speed, $u_{\zeta i}$ is the ion toroidal mean flow, $\rho$ is the minor radial coordinate normalized to the tokamak minor radius, and $T_i$ is the ion temperature. Since other intrinsic momentum transport mechanisms scale poorly to larger machines, these results indicate that up-down asymmetry is the most feasible method to generate the current experimentally-measured rotation levels in reactor-sized devices.

References in corpus (4)

• Toroidal momentum transport in a tokamak caused by symmetry breaking parallel derivatives
• Turbulent momentum pinch of diamagnetic flows in a tokamak
• The Zero Turbulence Manifold in Fusion Plasmas
• Conditions for up-down asymmetry in the core of tokamak equilibria

Cited by in corpus (14)

• Intrinsic rotation in tokamaks: theory
• Three-Dimensional Inhomogeneity of Electron-Temperature-Gradient Turbulence in the Edge of Tokamak Plasmas
• Equivalence of two different approaches to global $\delta f$ gyrokinetic simulations
• Optimized up-down asymmetry to drive fast intrinsic rotation in tokamaks
• Conditions for up-down asymmetry in the core of tokamak equilibria
• Radial penetration of flux surface shaping in tokamaks
• Local up-down asymmetrically shaped equilibrium model for tokamak plasmas
• Poloidal tilting symmetry of high order tokamak flux surface shaping in gyrokinetics
• Intrinsic rotation driven by turbulent acceleration
• Turbulent momentum transport due to the beating between different tokamak flux surface shaping effects
• Scaling of up-down asymmetric turbulent momentum flux with poloidal shaping mode number in tokamaks
• Up-down asymmetric tokamaks
• Effect of the Shafranov shift and the gradient of $\beta$ on intrinsic momentum transport in up-down asymmetric tokamaks
• Quasilinear gyrokinetic theory: A derivation of QuaLiKiz