Modeling the vertical stability of negative triangularity reactors

While negative triangularity (NT) plasmas can operate with the high confinement properties of H-mode without edge localized modes, larger Shafranov shifts and more elongated inner flux surfaces make them more susceptible to the n=0 vertical instability. A new equilibrium solver named “TokaMaker” is validated via comparison to DIII-D NT experimental data and used to verify the dependence of instability growth rates on key NT plasma parameters, including beta and internal inductance. Geometric properties such as plasma elongation and distance from the vacuum vessel are also varied to study the effect on stability. A workflow is developed to generate arbitrary reactors and coil sets using the MANTA NT tokamak [1] design concept as a baseline and a scan of reactor shapes is performed. This study provides comprehensive coverage of the NT reactor space and reveals the stabilizing effect of non-conformal walls, identifying the ideal operating regimes for NT fusion plasmas and introducing key considerations for reactor design.

[1] USBPO Presentation, March 2023 https://burningplasma.org/resources/ref/Web_Seminars/MANTA_video1914962414.mp4