Divertor Heat Exhaust

The divertor removes the plasma's exhaust heat and particles; on a compact spherical tokamak the heat is concentrated onto a small area — a hard problem.

Where the exhaust goes

Not all of the plasma's energy leaves as neutrons; a substantial fraction flows out along field lines and must be exhausted at a material surface. The divertor is that surface: magnetic geometry channels the scrape-off-layer plasma to divertor targets, away from the main first wall, where the heat and particles are absorbed and pumped.

On a compact spherical tokamak this is acute. The power crossing the last closed flux surface is concentrated onto a narrow channel landing on a small target area, giving very high local heat flux — among the most demanding steady heat loads in any engineered system. The tight ST geometry leaves little room to spread that load.

Mitigation and the shape connection

Heat flux is managed by spreading the strike point, tilting the target, and encouraging partial detachment, where edge radiation and neutral gas dissipate power before it reaches the surface. Hyperion's negative triangularity is relevant here: an edge without violent instabilities makes the exhaust steadier and more manageable. Whether the divertor solution holds at the machine's power density is a design-and-simulation question tied to the confinement and materials work.

• Divertor exhausts the non-neutron power and particle flux
• Compact ST geometry concentrates heat onto a small target
• Managed by strike-point spreading and detachment; aided by a quiet edge

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. No hardware net-gain is claimed before FOAK.