Heat flux measurements based on Surface Eroding Thermocouple in Small Angle Slot divertor target on DIII-D

The new Surface Eroding Thermocouples (SETC) in the small angle slot (SAS) divertor target have been used as a fast (sub-10ms) heat flux measurement in DIII-D. In recent experiments, measurable heat flux profiles were obtained by the SETCs when the outer strike point was swept along the SAS target. Those results showed that heat flux decreases on the target as plasma density increases during density scans. During density ramping experiments with the ion B×∇B drift away from the divertor target, a significant reduction in heat flux in the outer Scrape-Off-Layer (SOL) region was observed at the onset of detachment, which was consistent with the occurrence of the rollover of the ion saturation current as density increases. In addition, heat flux on the SAS target also showed a strong relationship with neutral pressure build up in the SAS divertor. Further detailed comparisons will be made with different E×B drift directions and outer strike point locations.