Negative Triangularity and Confinement

The open question for negative triangularity is whether it holds confinement comparable to conventional operation at Hyperion's field and size.

Confinement without a pedestal

Energy confinement is usually helped by the edge pedestal that negative triangularity removes. The reason negative triangularity is attractive anyway is that experiments elsewhere have found core confinement can remain strong even without the pedestal, because the shape itself stabilizes turbulence that would otherwise transport heat out of the core.

For Hyperion this is the crux: the machine adopts delta -0.30 for its stability and heat-handling benefits and requires that confinement stay high enough to reach Q_sci 3.076. Whether the confinement holds at 8 T on-axis, R0 1.2 m, and this current is a design-and-simulation finding that the program treats as something to prove, not to assert.

What the simulations must show

• Core turbulence stabilization sufficient to reach the design triple product
• Confinement robust without an edge pedestal
• No hidden dependence on parameters outside the demonstrated range

The candid position is that negative triangularity trades a known confinement helper (the pedestal) for a shape-based one (turbulence suppression). The design point assumes the trade nets out favorably; the FOAK build is what tests that assumption in hardware. This is the honest crux of the whole shape choice: negative triangularity is adopted for reasons the design considers sound, but the confinement it must deliver at Hyperion's field and size is asserted as a target to be demonstrated, not as an established property carried over unchanged from smaller, cooler experiments.

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.