10.7910/DVN/EMCEVCParisi, J.F.; Guttenfelder, W.; Nelson, A.O.; Gaur, R.; Kleiner, A.; Lampert, M.; Avdeeva, G.; Berkery, J.W.; Clauser, C.; Curie, M.; Diallo, A.; Dorland, W.; Kaye, S.M.; Mcclenaghan, J.; Parra, F.I.Harvard Dataverse2025Physicsconventional aspect ratio tokamaksgyrokinetic instabilityideal-ballooning plasma instabilitykinetic-ballooning-limited pedestalslinear gyrokineticslow-aspect-ratio high- β tokamak NSTXnovel Gyrokinetic Critical Pedestal constraintNSTX pedestalspedestal width-height Diallo scalingself-consistent pedestal equilibrium variationspherical tokamak pedestalsspherical tokamak plasmaswidth-height scaling expressions2025-06-093358500application/pdf1.0CC0 1.0A theoretical model is presented that for the first time matches experimental measurements of the pedestal width-height Diallo scaling in the low-aspect-ratio high-β tokamak NSTX. Combining linear gyrokinetics with self-consistent pedestal equilibrium variation, kinetic-ballooning, rather than ideal-ballooning plasma instability, is shown to limit achievable confinement in spherical tokamak pedestals. Simulations are used to find the novel Gyrokinetic Critical Pedestal constraint, which determines the steepest pressure profile a pedestal can sustain subject to gyrokinetic instability. Gyrokinetic width-height scaling expressions for NSTX pedestals with varying density and temperature profiles are obtained. These scalings for STs depart significantly from that of conventional aspect ratio tokamaks.<a href="http://library.psfc.mit.edu/catalog/reports/2020/24ja/24ja126/abstract.php">PSFC REPORT PSFC/JA-24-126</a><br /><br />This work was supported by the U.S. Department of Energy under Contract Numbers DE-AC02-09CH11466, DE-SC0022270, DE-SC0022272, and the Department of Energy Early Career Research Program. The United States Government retains a non-exclusive, paid-up, irrevocable, world-wide license to publish or reproduce the published form of this manuscript, or allow others to do so, for United States Government purposes.<br /><br />If this record does not contain the full text, then the manuscript has been embargoed by the publisher thus restricting open access for 12 to 24 months after publication.