Validating the Equilibrium Reconstruction

The breeder's magnetic equilibrium — its negative-triangularity shape at 9.66 MA — is solved and cross-checked, with the caveat that low-aspect-ratio validation data is limited.

Getting the shape right

Everything downstream depends on the plasma's magnetic equilibrium: the shape, the current distribution, and the field. The breeder (Hyperion) equilibrium is a strongly shaped, negative-triangularity (delta -0.30) configuration at 9.66 MA and 8 T on-axis. The reconstruction is solved by a Grad-Shafranov solver and checked for self-consistency.

How it is checked

• Force balance: the solution satisfies the Grad-Shafranov equation to tolerance.
• Solver verification via MMS and convergence, as above.
• Cross-comparison against an independent equilibrium code where possible.
• Consistency with the prescribed current and pressure profiles.

The honest caveat

Solving an equilibrium correctly is verification; confirming it matches a real plasma is validation. Negative triangularity at low aspect ratio is thinly represented in existing data, so the equilibrium's fidelity to a real breeder plasma is a FOAK-era question. The field prediction that the equilibrium implies is pre-registered so it can be tested directly.

A subtle risk with strongly shaped equilibria is that a solver can converge to a mathematically valid solution that a real control system cannot hold. The record therefore treats controllability of the negative-triangularity shape as a separate question from existence of the equilibrium, and defers the controllability claim to FOAK rather than inferring it from a converged solve.

This page describes a design-and-simulation study, not a built machine. Construction of the breeder (Hyperion) begins Q2 2027; first-of-a-kind first tritium is targeted near 2030. No hardware net-gain claim is made before FOAK.