Ion-temperature-gradient stability near the magnetic axis of quasisymmetric stellarators
arXiv:2102.12390 · doi:10.1088/1361-6587/abfdd4
Abstract
The stability of the ion-temperature gradient mode in quasisymmetric stellarators is assessed. This is performed using a set of analytical estimates together with linear gyrokinetic simulations. The peak growth rates, their corresponding real frequencies and wave-vectors are identified. A comparison is made between a first-order near-axis expansion model and eleven realistic designs obtained using numerical optimization methods. It is found that while the near-axis expansion is able to replicate the growth rates, real frequencies and perpendicular wave-vector at the inner core (both using simplified dispersion relations and first-principle gyrokinetic simulations), it leads to an overestimation of the growth rate at larger radii. An approximate analytic solution of the ITG dispersion relation for the non-resonant limit suggests growth rates could be systematically higher in quasi-axisymmetric (QA) configurations compared to quasi-helically (QH) symmetric ones. However except for very close to the axis, linear gyrokinetic simulations do not show systematic differences between QA and QH configurations.
References in corpus (4)
- Near-Axis Expansion of Stellarator Equilibrium at Arbitrary Order in the Distance to the Axis
- Construction of Quasisymmetric Stellarators Using a Direct Coordinate Approach
- The Use of Near-Axis Magnetic Fields for Stellarator Turbulence Simulations
- Optimized quasisymmetric stellarators are consistent with the Garren-Boozer construction
Cited by in corpus (5)
- Critical gradient turbulence optimization toward a compact stellarator reactor concept
- Coarse-grained gyrokinetics for the critical ion temperature gradient in stellarators
- Calculating the linear critical gradient for the ion-temperature-gradient mode in magnetically confined plasmas
- Collisionless zonal-flow dynamics in quasisymmetric stellarators
- Energetic Particle Tracing in Optimized Quasisymmetric Stellarator Equilibria