Development of Surface Eroding Thermocouples in Small Angle Slot Divertor in DIII-D

The surface eroding thermocouple (SETC) has proved to be a useful fast local temperature and heat flux diagnostic since its application in DIII-D. The SETC system in DIII-D was upgraded, and seven new SETCs were installed in the small angle slot (SAS) divertor to create a localized poloidal array to provide heat flux profiles with sub-10-ms temporal resolution. In addition, a smaller SETC was developed to increase the spatial resolution and simplify installation in the SAS divertor. The SETC-containing tiles were re-engineered with a double-wide format so that the distance between the SETCs and the tile edges is extended to 10 cm on both sides, giving additional tolerance for tile-to-tile misalignments. Mineral insulated thermocouple cable with a metal sheath has also been implemented to further reduce noise and magnetic pickup. Recent measurements obtained from the SETCs indicate that the newly installed SETC array in the SAS divertor is able to provide important heat flux information to various physics experiments in closed divertors.