The Kronos magnet systems.

High field is what makes both Kronos machines compact — but each uses it differently. The breeder leans on compact HTS coils; the burner leans on high-field end plugs.

Breeder

Compact high-temperature-superconductor (HTS) coils

Burner end-plug throat

26.49 T (frozen A11)

Why high field

Power density scales steeply with field

Superseded

The earlier 24.42 T single-tokamak magnet

Fusion power density rises steeply with magnetic field, which is why compact machines chase the highest field their superconductors allow. Kronos applies that principle twice, in two different geometries.

• The breeder — compact HTS. HYPERION is a small spherical tokamak (major radius 1.2 m). It reaches its performance with compact high-temperature-superconductor coils rather than the very large low-field magnets of a conventional tokamak.
• The burner — high-field end plugs. The tandem mirror confines its central cell with strong magnetic plugs at each end; the frozen ion-end throat field is 26.49 T. That throat is also what sets the burner's end-expander requirement — the field must be expanded ~53× (down to ~0.5 T) to spread the axial exhaust over enough collector area.

An earlier Kronos design centered on a single 24.42 T tokamak magnet (about 5.75 m). That belonged to the tokamak-era architecture and is superseded by the two-machine design above.