Hybridizing Tokamaks:Advances Toward Compact Stellarator-Tokamak Experiments

The compact stellarator-tokamak hybrid offers a promising path toward stable, steady-state fusion devices [1, 2, 3, 4]. These configurations can be developed analytically [5] or through stellarator optimization techniques [6] applied to tokamaks, introducing three-dimensional (3D) magnetic perturbations that preserve favorable neoclassical properties via quasi-axisymmetry [7]. The 3D shaping enables additional rotational transform generated by external coils, which has been shown in prior experiments to suppress disruptions [8]. This added transform also reduces the required plasma current, supporting steady-state operation. We present recent progress in both upgrading existing tokamaks and designing new stellarator-tokamak hybrid experiments. While retrofitting existing machines poses challenges—including spatial constraints and stringent current limitations—we demonstrate practical solutions addressing these issues and outline the progress achieved toward realizing viable hybrid configurations.



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