Impurity Seeding

Injecting trace impurities to radiate exhaust power and protect the divertor.

Seeding small amounts of impurities (such as neon or nitrogen) makes the plasma edge radiate more, cushioning the divertor. It must be balanced against fuel dilution and core radiation — a controlled trade-off.

Seeding a trace of neon or nitrogen makes the plasma edge radiate more and cushions the divertor, but every seeded ion also dilutes the fuel and can radiate from the core. Getting the balance right — enough edge radiation, not too much core contamination — is an active control problem tied to the divertor's radiated-fraction target.