13C transport studies in L-mode divertor plasmas on DIII-D

13CH4 was injected with a toroidally-symmetric gas system into 22 identical lower-single-null L-mode discharges on DIII-D. The injection level was adjusted so that it did not significantly perturb the core or divertor plasmas, with a duration of ∼3 s on each shot, for a total of ∼300 T L of injected particles. The plasma shape remained very constant; the divertor strike points were controlled to ∼1 cm at the divertor plate. At the beginning of the subsequent machine vent, 29 carbon tiles were removed for nuclear reaction analysis of 13C content to determine regions of carbon deposition. It was found that only the tiles inboard of the inner strike point had appreciable 13C above background. Visible spectroscopy measurements of the carbon injection and comparisons with modeling are consistent with carbon transport by means of scrape-off layer flow.