Transport and deposition of 13C from methane injection into partially detached H-mode plasmas in DIII-D

Abstract

Experiments are described which examine the transport and deposition of carbon entering the main plasma scrape-off layer in DIII-D. 13CH4 was injected from a toroidally symmetric source into the crown of lower single-null partially detached ELMy H-mode plasmas. 13C deposition, mapped by nuclear reaction analysis of tiles, was high at the inner divertor but absent at the outer divertor, as found previously for low-density L-mode plasmas. This asymmetry indicates that ionized carbon is swept towards the inner divertor by a fast flow in the scrape-off layer. In the private flux region between inner and outer strike points, carbon deposition was low for L-mode but high for the H-mode plasmas. OEDGE modeling reproduces observed deposition patterns and indicates that neutral carbon dominates deposition in the divertor from detached H-mode plasmas.