Analysis of C-MOD molybdenum divertor erosion and code/data comparison

We analyze an important 15 year old Alcator C-MOD study of campaign-integrated molybdenum divertor erosion in which the measured net erosion was significantly higher (∼X3) than originally predicted by a simple model [1], [2]. We perform full process sputtering erosion/redeposition computational analysis including the effect of a possible RF induced sheath. The simulations show that most sputtered Mo atoms are ionized close to the surface and strongly redeposited, via Lorentz force motion and collisional friction with the high density incoming plasma. The predicted gross erosion profile is a reasonable match to MoI influx data, however, the critically important net erosion comparison with post-exposure Mo tile analysis is poor, with ∼X10 higher peak erosion measured than computed. An RF sheath increases predicted erosion by ∼45%, thus being significant but not fundamental. We plan future analysis.