Investigation of Divertor Heat Flux Width in DIII-D for 2010 Joint Research Target

The 2010 Joint Research Target for NSTX, C-Mod, and DIII-D aims to improve prediction of divertor heat flux profile width for future divertors. In DIII-D we varied input power, toroidal field, plasma current I_p, and density. Divertor heat flux was obtained using IR thermography. We find that w_q,div is most sensitive to I_p. Mapped to the outer midplane w_q,div scaled like w_q,mid (mm) = 5.38/I_p^1.24 (MA). Scrape-off layer and pedestal density and temperature fluctuations were measured using midplane and x-point plunging Langmuir probes at the lower powers. From midplane fluctuation data, we obtained energy transport measurements, which we compare with transport coefficients obtained from onion-skin modeling using density profiles, and with experimentally determined heat flux widths in the divertor.