The Center-Post Conductor

The center post carries the return current of the toroidal field at the smallest radius in the machine, where current density and forces peak.

The most loaded conductor

The toroidal field is made by current flowing the long way around the torus and returning through the center. In a spherical tokamak that return path is the center post, and because it sits at the smallest radius it carries the highest current density anywhere in the machine. Delivering a 16.84 T peak field with roughly 8 T on the plasma axis depends on what this single column can carry.

Forces and cooling

The toroidal-field coils are pulled inward toward the axis by large centering forces; the center post reacts them in compression while the current tries to heat it. Its cooling must remove that heat and, in the neutron environment, the coolant and structure must tolerate activation and radiation damage. These constraints set the post's diameter, and its diameter sets how much shielding, if any, can sit between it and the plasma.

A designed-in compromise

The center post is where the spherical-tokamak bargain is paid in full: compact, high-beta plasma in exchange for a central conductor working near its limits with minimal shielding. Hyperion treats the post as a serviceable component with a finite life rather than a permanent structure, so degradation is planned for and scheduled around, not deferred until failure.

• Highest current density in the machine
• Reacts inward centering forces in compression
• Serviceable, finite-life component by design

This page describes a design and simulation study, not a built machine. Construction begins Q2 2027; first-of-a-kind first tritium is targeted near 2030.