Abstract
An experiment was conducted in DIII-D to examine carbon deposition when a secondary separatrix is near the wall. The magnetic configuration for this experiment was a biased double-null, similar to that foreseen for ITER. C-13 methane was injected toroidally symmetrically near the secondary separatrix into ELMy H-mode deuterium plasmas. The resulting deposition of C-13 was determined by nuclear reaction analysis. These results show that very little of the injected C-13 was deposited at the primary separatrix, whereas a large fraction of injected C-13 was deposited close to the point of injection near the secondary separatrix. Six of the tiles were put back into DIII-D, where they were baked at 350-360 degrees C for 2 h at similar to 1 kPa in a 20% O-2/80% He gas mixture. Subsequent ion beam analysis of these tiles showed that about 21% of the C-13 and 54% of the deuterium were removed by the bake.