H-mode (High-Confinement Mode)

A spontaneous transition to roughly doubled confinement, standard in modern tokamaks.

Above a power threshold, tokamak plasmas jump into a high-confinement regime — H-mode — in which an edge transport barrier roughly doubles the energy confinement time relative to L-mode. The confinement multiplier H₉₈ = 1 denotes standard H-mode performance.

HYPERION's confinement target of H₉₈ = 1.0 places it squarely at established H-mode performance rather than beyond it — a deliberately unaggressive assumption.

The H-mode transition is one of fusion's most important empirical discoveries: above a power threshold, an edge transport barrier forms and roughly doubles confinement. Reaching and sustaining it shapes the heating requirement. HYPERION is designed at H₉₈ = 1 — standard H-mode — rather than betting on an enhanced regime.