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arXiv · 2502.04459

Turbulence-Generated Stepped Safety Factor Profiles in Tokamaks with Low Magnetic Shear

Arnas Volčokas·Justin Ball·Giovanni Di Giannatale·Stephan Brunner
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Abstract

Nonlinear local and global gyrokinetic simulations of tokamak plasmas demonstrate that turbulence-generated currents flatten the safety factor profile near low-order rational surfaces when magnetic shear is low, even when the plasma $\beta$ is small. A large set of flux tube simulations with different safety factor profiles (e.g. linear and non-linear safety factor profiles) and global simulations with reversed magnetic shear profiles show that such stepped safety factor profiles dramatically reduce the heat transport and are a robust phenomenon. This mechanism may play a key role in the triggering of internal transport barriers (ITBs) and more generally reveal novel strategies for improving confinement in devices with low magnetic shear.

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Arnas Volčokas, Justin Ball, Giovanni Di Giannatale, Stephan Brunner. 2025-02-06. Turbulence-Generated Stepped Safety Factor Profiles in Tokamaks with Low Magnetic Shear. https://arxiv.org/abs/2502.04459

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