Kinetic-Ballooning-Bifurcation in Tokamak Pedestals Across Shaping and Aspect-Ratio

• DOI: 10.48550/arxiv.2312.05216
• Publication Date: 2024-03-01
• Authors: J. F. Parisi; A. O. Nelson; R. Gaur; S. M. Kaye; F. I. Parra; J. W. Berkery; K. Barada; C. Clauser; A. J. Creely; A. Diallo; W. Guttenfelder; J. W. Hughes; L. A. Kogan; A. Kleiner; A. Q. Kuang; M. Lampert; T. Macwan; J. E. Menard; M. A. Miller
• Keywords: Plasma Physics (physics.plasm-ph); 0103 physical sciences; FOS: Physical sciences; 01 natural sciences; Physics - Plasma Physics

We use a new gyrokinetic threshold model to predict a bifurcation in tokamak pedestal width-height scalings that depends strongly on plasma shaping and aspect-ratio. The bifurcation arises from the first and second stability properties of kinetic-ballooning-modes that yields wide and narrow pedestal branches, expanding the space of accessible pedestal widths and heights. The wide branch offers potential for edge-localized-mode-free pedestals with high core pressure. For negative triangularity, low-aspect-ratio configurations are predicted to give steeper pedestals than conventional-aspect-ratio. Both wide and narrow branches have been attained in tokamak experiments.