pedestal is the narrow band of steep pressure gradient at the edge of an H-mode plasma — the raised platform on which the temperature of the fusion core stands.
The pedestal is what the edge 📝transport barrier of 📝H-mode builds: with turbulence suppressed in a layer a centimeter or two wide, pressure climbs steeply across it, so the confined 📝plasma begins not at zero but at the pedestal top. Its leverage comes from a property of the core called profile stiffness — turbulence limits how steep core gradients can get, so the central temperature rides up and down almost in lockstep with the pedestal height. Raising the pedestal raises the whole profile, and with it the 📝fusion power.
The pedestal cannot be raised without limit. When its gradient and the current flowing in it get steep enough, the edge crosses a 📝magnetohydrodynamic stability boundary — the peeling-ballooning limit — and erupts in an 📝edge localized mode that flattens the pedestal before the cycle repeats. Predictive models built on that stability physics, most prominently EPED, anticipate pedestal height for future machines and underpin performance projections for 📝ITER and for compact high-field tokamaks.