Negative Triangularity delta -0.30
Hyperion runs a negative-triangularity plasma, delta -0.30, whose D-shape points outward — a choice made for edge stability and heat handling.
What triangularity is
Triangularity, delta, measures how the D-shaped plasma cross-section leans. Positive triangularity points the corners of the D toward the center column, the conventional choice. Negative triangularity, delta -0.30 for Hyperion, flips the shape so the corners point outward, toward the low-field side.
The interest in negative triangularity is that it can access good confinement while suppressing the edge-localized instabilities that trouble conventional high-confinement operation. An edge that does not periodically expel bursts of energy is gentler on the first wall and divertor — a meaningful advantage for a machine whose inboard components already run in a hard environment.
Confinement and the trade
Negative-triangularity plasmas in experiments elsewhere have shown confinement comparable to standard operation without the usual edge pedestal and its instabilities. The trade is geometric: a negative-triangularity shape is harder to fit around a tight center column and constrains the achievable elongation and volume. Hyperion adopts delta -0.30 as its canonical shape and treats the confinement and stability consequences as design-and-simulation results, not settled facts. The choice is a considered bet: the machine forgoes the well-characterized high-confinement pedestal of conventional operation in exchange for an edge that is intrinsically calmer, wagering that the shape itself supplies enough confinement to reach the gain target without the instabilities the pedestal brings.
- delta -0.30: D-shape corners point outward
- Motivates edge-instability suppression and gentler heat exhaust
- Trade: geometric fit against a tight ST center column
This page describes a design-and-simulation study, not a built machine. Construction begins Q2 2027; first-of-a-kind first tritium is targeted near 2030. No hardware net-gain is claimed before FOAK.