Why a Spherical Tokamak
The breeder uses a spherical (low aspect ratio) tokamak because it reaches high plasma pressure at accessible field and stays compact.
The configuration choice
Hyperion is a spherical tokamak: a tokamak with a low aspect ratio, where the plasma is more nearly spherical than the classic doughnut shape. This choice follows directly from the foundry mission of reaching gain in a compact machine.
Why low aspect ratio helps
- Higher plasma pressure (beta) for a given magnetic field, improving fusion output efficiency
- Compact size, which shortens the build and concentrates the hard engineering
- Strong plasma shaping, which supports the chosen negative triangularity
The trade it accepts
The spherical geometry concentrates stress and heat in a slender centerpost, which becomes the hardest engineering problem in the machine. The design accepts this trade because compactness and high beta serve the gain-only foundry mission better than a large, low-field conventional tokamak would.
How it shapes the rest of the design
The spherical choice drives the centerpost engineering, the high 16.84 T peak field, the 9.66 MA plasma current, and the negative triangularity of -0.30. These are not independent choices; they are a coherent set that follows from deciding to reach gain in a compact machine.
The configuration is a design decision for a machine not yet built. Its merits, high beta at accessible field, compactness, are the reasons the breeder can plausibly be the first machine Kronos builds.