The relative importance of surface phenomena in CTR first-wall designs

Plasma-wall interactions are modeled using physical sputtering theory. Sputtering yields are calculated for incoming D-T ions that have a monoenergetic or Maxwellian distribution in energy. The yield curves assuming the Maxwellian energy distribution are flatter than the monoenergetic curves. The consequences of sputtering considered here are surface composition and microtopography changes of the first-wall surface. For the iron-carbon system, the surface becomes enriched with carbon when deuterons are incident on the target. The number of cycles for crack initiation at the first-wall surface is linearly proportional to differences in sputtering yield of two adjacent areas. These effects are of first order and appear to be dominant in limiting the life of the first wall. (Auth.)