Recent Progress In Tritium Codeposition Modeling

Abstract

Tritium codeposition in sputtered and redeposited surface layers may be a critical issue for next generation tokamak fusion reactors. We review recent codeposition/erosion code/model improvements, and calculations. Updated models for carbon include chemical sputtering yields, sputtered hydrocarbon species, and atomic and molecular processes. Calculations show that a carbon coated divertor with a semi or fullydetached plasma may behave poorly, with predicted codeposition rates of order 10 gT/1000s pulse, and peak net erosion rates of order 10 nm/s. Other materials such as beryllium, tungsten, lithium, or carbon with a non-detached plasma regime, look better. Outstanding research issues include reflection/sticking properties of redeposited carbon/hydrocarbon particles, possible flux dependence of chemical sputtering, and dopant effects.