Effect of the Surface Temperature on Net Carbon Deposition and Deuterium Co-deposition in DIII-D Divertor

We report a strong effect of a moderately elevated surface temperature on net C deposition and D co-deposition in DIII-D divertor under detached conditions. A DiMES sample with a gap 2~mm wide and 15~mm deep was exposed to L-mode plasmas first at room temperature then at 200$^{\circ}$C. At the elevated temperature deuterium co-deposition in the gap was reduced an order of magnitude and net carbon erosion at a rate of 3~nm/s was measured at the plasma-facing surface of the sample. In another experiment visible deposits were produced on molybdenum mirrors recessed 2~cm under the divertor floor and exposed to ELMing H-mode plasmas for 25~seconds at room temperature. In contrast, virtually no deposits were observed on mirrors exposed to similar plasmas for 70~seconds at elevated temperatures, between 140$^{\circ}$ and 80$^{\circ}$C.