Predictive scaling of the NT pedestal width and height

Establish a predictive scaling for the pedestal width and height in negative triangularity tokamak plasmas based on first-principle models to enable reliable design and optimization of negative triangularity fusion pilot plants.

Background

Across the DIII-D negative triangularity dataset, the edge pedestal does not generally align with the first stability limit for infinite-n ballooning modes, indicating additional gradient-limiting physics beyond ideal ballooning. Comparisons with the EPED1 model show that NT pedestals exhibit reduced poloidal beta and an approximately linear relationship with pedestal width, differing from the standard sqrt scaling expected in positive triangularity H-mode pedestals.

The paper highlights that NT pedestal structure varies widely (from narrow, shear-dominated layers near the separatrix to broader regions extending inward), and that existing H-mode-based predictive models (e.g., EPED1) may not accurately capture NT pedestal behavior. A first-principle-based predictive scaling is therefore needed to inform NT-relevant scenario development and pilot plant design.