Composition and hydrogen isotope retention analysis of co-deposited C/Be layers

Abstract

A neutral Be atom source and deposition probe have been installed on PISCES-B to simulate ITER diverter erosion and deposition phenomena where Be impurity concentration in the plasma, up to 10%, is expected due to first wall erosion. Graphite target erosion by deuterium plasma is found to be significantly reduced with as little as ∼0.1% Be impurities in the plasma [K. Schmid, M.J. Baldwin, R. Doerner, these Proceedings]. Deposited Be on the target is re-eroded and leads to deposited layers in the target vicinity, that are sampled with the deposition probe. These layers are Be rich and contain only small C concentrations (<3at.%). The ratio of co-deposited deuterium to deposited beryllium (D/Be) decreases rapidly with increasing probe temperature up to 573K. D/Be values are systematically lower and O/Be values higher compared to similar experiments in TPE [R.A. Causey, D.S. Walsh, J. Nucl. Mater. 254 (1998) 84]. The difference is likely due to different target-collector geometries and incident hydrogen isotope fluxes during collection.