Elongation (κ)

How vertically stretched the plasma cross-section is; taller plasmas carry more current and pressure.

Elongation κ is the ratio of the plasma's height to its width. A circular plasma has κ = 1; shaping it into a tall D raises the current it can carry and the pressure it can hold.

HYPERION is designed at κ = 2.0, a strong elongation that spherical tokamaks naturally support. Higher elongation must be balanced against vertical-stability control.

Higher elongation increases the plasma cross-sectional area and the current it can carry at fixed edge safety factor, both of which raise fusion performance. It comes at the cost of vertical instability: a tall plasma drifts up or down and must be held by fast feedback control. HYPERION's κ = 2.0 is well within what spherical tokamaks demonstrate, and the control coils and power supplies are sized for it.