Linear gyrokinetic stability of a high $\beta$ non-inductive spherical tokamak

Abstract

Spherical tokamaks (STs) have been shown to possess properties desirable for a fusion power plant such as achieving high plasma ? and having increased vertical stability. To understand the confinement properties that might be expected in the conceptual design for a high $\beta$ ST fusion reactor, a 1GW ST plasma equilibrium was analysed using local linear gyrokinetics to determine the type of micro-instabilities that arise. Kinetic ballooning modes (KBMs) and micro-tearing modes (MTMs) are found to be the dominant instabilities. The parametric dependence of these linear modes was determined and from the insights gained, the equilibrium was tuned to find a regime marginally stable to all micro-instabilities at ${\theta }_0$ = 0:0. This work identifies the most important micro-instabilities expected to generate turbulent transport in high $\beta$ STs. The impact of such modes must be faithfully captured in first principles based reduced models of anomalous transport that are needed for predictive simulations.

43 pages, 67 figures, 4 tables

References in corpus (4)

• Extended electron tails in electrostatic microinstabilities and the nonadiabatic response of passing electrons
• The Zero Turbulence Manifold in Fusion Plasmas
• The physics of a small-scale tearing mode in collisionless slab plasmas
• Subcritical Turbulence in the Mega Ampere Spherical Tokamak

Cited by in corpus (10)

• Flat-top plasma operational space of the STEP power plant
• Electromagnetic gyrokinetic instabilities in STEP
• Kinetic-Ballooning-Limited Pedestals in Spherical Tokamak Plasmas
• On electromagnetic turbulence and transport in STEP
• Electromagnetic instabilities and plasma turbulence driven by electron-temperature gradient
• Nonlinear microtearing modes in MAST and their stochastic layer formation
• New linear stability parameter to describe low-$\beta$ electromagnetic microinstabilities driven by passing electrons in axisymmetric toroidal geometry
• Microstability of $\beta \sim 1$ tokamak equilibria
• Microtearing turbulence saturation via electron temperature flattening at low-order rational surfaces
• Scale invariance and critical balance in electrostatic drift-kinetic turbulence