divertor detachment is an operating regime of a magnetically confined 📝fusion plasma in which radiation and neutral gas cool the exhaust stream before it strikes the divertor surface.
The name marks the contrast with attached operation, the default state in which the exhaust 📝plasma flows along field lines and slams directly into the 📝divertor targets at full force. Detachment interposes a buffer: raising the density of the divertor plasma and radiating away its energy — typically through 📝impurity seeding — cools the exhaust from millions of degrees to just a few electron-volts. At those temperatures ions recombine into neutral atoms and the plasma loses its momentum to the resulting neutral gas cloud, so what finally reaches the target is a cooled, diffuse flow rather than a concentrated beam. Heat flux at the surface can fall by an order of magnitude or more.
Detachment matters because reactor-scale machines have no alternative: their exhaust power, if attached, would exceed what any material — including 📝tungsten — can continuously absorb. The open challenge is control. Detachment sits near operational cliffs: pushed too far, the cold front migrates toward the confined core and degrades confinement. Real-time detachment control is therefore one of the defining plasma-control problems of first-generation power plants.