The End Plugs
Each end of the machine carries a high-field plug that both mirror-confines and builds the electrostatic potential that seals the central cell.
The workhorses of confinement
The two end plugs are where the extreme engineering lives. Each combines the highest fields in the machine — a 26.49 T peak in the plug coils and 17 T at the mirror throat — with intense local heating that raises the plasma potential. Together these produce the axial confinement the central cell relies on.
Two jobs at once
- Magnetic mirroring: the field rises steeply toward the throat, reflecting most ions back by conserving magnetic moment
- Potential formation: hot, dense plug plasma raises the local ambipolar potential, electrostatically plugging the central cell for ions
Sloshing ions
The plug plasma is sustained as a sloshing-ion population created by angled neutral-beam injection. Sloshing ions have a density that peaks away from the mirror midplane, which shapes the potential correctly and improves microstability. Electron-cyclotron heating is applied in the plug to control the electron temperature and the potential profile.
The plug is also the machine's most demanding thermal and structural region: high field means large Lorentz stresses in the REBCO conductor, and the local heating and particle flux drive the cryogenic and first-wall designs. Everything downstream — the expander and direct converter — receives the plasma the plug lets escape.
Because both jobs happen in the same compact region, the plug is where plasma physics and structural engineering are most tightly coupled, and where the burner's hardest validation work is concentrated ahead of the test unit.