Deep Dive: The Field-Lever Upgrade Path
The deposited S78 field-lever study mapped a constraint-checked B₀/R_c move; on 24 July 2026 the ratified Mode-D basis adopted the lever at the build limit — R_c = 1.50 m, B₀ = 6.37 T, 24.42 T peak.
- What
- A B₀/R_c toroidal-field lever (S78)
- As studied
- Hold peak at the demonstrated 24.4 T, or +6% Pfus (2409→2557 MW)
- As adopted (Mode D)
- R_c → 1.50 m + B₀ → 6.37 T ⇒ 24.42 T peak
- Status
- Adopted into the ratified Mode-D basis, 24 July 2026
Beyond the frozen design point, Kronos deposits forward-looking design-space studies that ask "can it be better?" — and publishes the answers honestly, favourable or not. The field-lever study (S78) is a favourable one.
As deposited, it examined a small, fully constraint-checked move — shifting the peak-field radius R_c from 1.40 to 1.44 m and the on-axis field B₀ from 6.0 to 6.11 T — offering either a peak conductor field held at the demonstrated 24.4 T (down from the 24.6 T Mode-C-era stress basis) with improved Troyon and kink margins, or +6% fusion power (2409 → 2557 MW) at unchanged confinement. Every number survives the coupled systems code's simultaneous constraint check.
On 24 July 2026 the ratified Mode-D re-basis adopted the lever at the build limit: R_c = 1.50 m, B₀ = 6.37 T, and a 24.42 T peak — exactly the demonstrated single-coil field — now the frozen MetroVolt operating basis. The record shows both steps: the option mapped transparently first, then adopted through the same constraint chain rather than quietly baked in.