Validating the Transport Model
The transport model behind the breeder's confinement and gain is the least certain link; the record benchmarks it against other machines and pre-registers its FOAK test.
The softest link in the chain
Turbulent transport sets the energy confinement time, and confinement sets the gain. Transport is also the hardest fusion physics to predict from first principles, so it is the breeder (Hyperion) model most in need of validation. The record treats it accordingly: it does not overstate confidence in the confinement prediction behind Q_sci 3.076.
How it is checked
- Benchmarking predicted confinement against IPB98(y,2) and the ST database.
- Comparison of the transport model against experimental confinement where geometry overlaps.
- Propagating transport-model uncertainty into the reported gain interval.
- A pre-registered confinement prediction with a stated falsifier.
Why honesty here matters most
If any single model is going to be surprised by hardware, transport is the candidate. Stating that plainly — and pre-registering the confinement falsifier — is more credible than presenting the confinement number as settled. FOAK is the arbiter.
It is worth being precise about what a transport disagreement would and would not overturn. A confinement shortfall would erode or break the Q_sci 3.076 case, but it would not touch the neutron kinematics or the measured field; those rest on firmer ground. Isolating the soft link keeps a possible surprise contained to the claims that actually depend on it, rather than casting doubt across the whole record.
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.