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The stability of the ion-temperature gradient mode in quasisymmetricstellarators is assessed. This is performed using a set of analytical estimatestogether with linear gyrokinetic simulations. The peak growth rates, theircorresponding real frequencies and wave-vectors are identified. A comparison ismade between a first-order near-axis expansion model and eleven realisticdesigns obtained using numerical optimization methods. It is found that whilethe near-axis expansion is able to replicate the growth rates, real frequenciesand perpendicular wave-vector at the inner core (both using simplifieddispersion relations and first-principle gyrokinetic simulations), it leads toan overestimation of the growth rate at larger radii. An approximate analyticsolution of the ITG dispersion relation for the non-resonant limit suggestsgrowth rates could be systematically higher in quasi-axisymmetric (QA)configurations compared to quasi-helically (QH) symmetric ones. However exceptfor very close to the axis, linear gyrokinetic simulations do not showsystematic differences between QA and QH configurations.

Ion-temperature-gradient stability near the magnetic axis of quasisymmetric stellarators