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.

评估了准对称仿星器中离子温度梯度模式的稳定性。这是使用一组分析估计值以及线性陀螺动力学模拟来执行的。峰值增长率、它们相应的实际频率和波矢量被识别。将一阶近轴膨胀模型与使用数值优化方法获得的 11 个实际设计进行了比较。发现虽然近轴膨胀能够复制内核处的增长率、真实频率和垂直波矢（均使用简化的色散关系和第一性原理陀螺动力学模拟），但它导致高估了较大半径处的增长率。非共振极限的 ITG 色散关系的近似解析解表明，与准螺旋 (QH) 对称配置相比，准轴对称 (QA) 配置中的增长率可以系统地更高。然而，除了非常接近轴外，线性陀螺动力学模拟并未显示 QA 和 QH 配置之间的系统差异。