Erosion/Redeposition Analysis of the International Thermonuclear Experimental Reactor Divertor

Sputtering erosion of the proposed International Thermonuclear Experimental Reactor (ITER) divertor has been analyzed using the REDEP computer code. A carbon-coated plate, as well as beryllium and tungsten plates, have been examined at medium and low plasma edge temperatures. Peak net erosion rates for carbon and beryllium are very high (∼20 to 80 cm/burn · yr) though an order of magnitude less than the gross rates. Tritium buildup rates in co-deposited carbon surface layers may also be high (∼50 to 250 kg/burn · yr). Plasma contamination from divertor sputtering, however, is low (≲0.5%), Operation with low-Z divertor plates at high duty factors, therefore, appears unacceptable due to erosion, but may work for low duty factor (∼2%) “physics phase” operation. Sweeping of the poloidal field lines at the divertor can reduce erosion, typically by factors of ∼2 to 8. A tungsten-coated plate works well, from the erosion standpoint, for plasma plate temperatures of ∼40 eV or less.