Confinement Modes and Transport

Turbulent transport, not collisions, sets confinement in a tokamak; the operating mode determines how much heat leaks out of the core.

What limits confinement

If plasmas lost heat only through particle collisions, confinement would be excellent. In practice small-scale turbulence — drift-wave instabilities driven by the temperature and density gradients — dominates transport and carries heat out of the core far faster. Understanding and suppressing that turbulence is most of what confinement physics is about.

Operating modes differ in how they handle this turbulence. High-confinement modes form an edge transport barrier that steepens gradients and improves tau_E, at the cost of the edge instabilities discussed elsewhere. Negative-triangularity operation, Hyperion's choice, aims for strong core confinement through shape-based turbulence suppression without relying on that edge barrier.

Why the mode matters for Hyperion

The gain of Q_sci 3.076 assumes a confinement level that a particular transport state delivers. The design bets that a negative-triangularity plasma can suppress core turbulence enough to reach the target triple product without an edge pedestal. Whether the achieved transport state matches the assumed one at Hyperion's parameters is a design-and-simulation question the FOAK build is meant to answer. The distinction matters because two plasmas with identical density, temperature, and current can confine heat very differently depending on which turbulent modes are active; the design's confidence in Q_sci 3.076 is therefore only as strong as its confidence that the intended, low-transport state is the one the machine will actually settle into.

• Turbulent transport, not collisions, dominates heat loss
• Operating mode sets how much the core leaks
• Hyperion targets shape-suppressed core turbulence over an edge pedestal

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.