Plasma Current Formation

Hyperion sustains 9.66 MA of plasma current, the source of the poloidal field that, with the toroidal field, confines the plasma.

Why the plasma carries current

A tokamak plasma is itself a conductor, and the 9.66 MA it carries generates the poloidal component of the magnetic field. Without that current there is no confining twist to the field lines. Plasma current also heats the plasma ohmically during startup and sets the pressure and stability limits the machine can reach.

Getting to 9.66 MA

Current is initiated inductively by the central solenoid, which breaks down the gas and ramps the current. As the plasma heats, its resistance falls and inductive drive becomes less efficient, so non-inductive sources, neutral-beam and RF current drive, plus the self-generated bootstrap current, take over to reach and hold 9.66 MA on flat-top. A spherical tokamak's limited solenoid flux makes this hand-off essential rather than optional.

Current and performance

Higher plasma current improves energy confinement and raises the density and pressure the plasma can hold, which is why 9.66 MA is central to reaching Q_sci 3.076 at 85.0 MW in so small a machine. But high current also raises the stakes of a disruption, a sudden loss of confinement, because the stored magnetic and thermal energy must go somewhere. Sustaining the current cleanly and terminating it safely are both design requirements.

• 9.66 MA sustained plasma current
• Source of the confining poloidal field; heats plasma at startup
• Started inductively, sustained non-inductively plus bootstrap

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.