Impurity evolution in a beam-heated tokamak

Impurity evolution during neutral beam injection has been investigated in a large tokamak with The first wall made of low-Z (carbon), medium-Z (titanium) and high-Z (molybdenum), based on a simple model of wall-released impurity behavior. The use of low-Z material seems helpful in reducing impurity contamination in a high-tempeature plasma with material limiters. A divertor is effective for controlling of wall-sputtered impurities for any of the wall materials. (author)