The Plasma Pedestal

The pedestal is the steep edge pressure barrier of H-mode — the thing that drives ELMs. Kronos's L-mode-like NT edge deliberately does without a strong one.

What

A steep pressure barrier at the plasma edge

Comes with

H-mode confinement — and ELMs

Kronos edge

L-mode-like, no strong pedestal (NT)

Benefit

No pedestal → no ELMs

The pedestal is the steep "shoulder" of pressure at the very edge of an H-mode plasma — an edge transport barrier that sharply raises the whole pressure profile and roughly doubles confinement. It is the source of H-mode's performance, but also the reservoir of free energy that periodically releases as ELMs.

Kronos MetroVolt deliberately does without a strong pedestal. Its negative-triangularity edge is L-mode-like — no steep edge barrier, and therefore no ELMs — while core turbulence reduction recovers the confinement a pedestal would otherwise have provided. Giving up the pedestal to protect the direct-energy converter from ELMs is the central trade of the design.