A Method to Identify the Heat Flux From Photons and Neutrals at the Divertor Target

The surface eroding thermocouple (SETC) is a diagnostic designed for fast surface heat flux measurement and has been successfully applied in DIII-D tokamak to investigate divertor detachment. A novel method has been developed of using a combination of surface-facing and recessed SETCs to distinguish between the heat flux from charged particles, and that from neutrals and radiative heating. This technique suggests that at least 20% of the total incident heat flux is attributable to the latter sources not trapped in the magnetic field in a fully detached open divertor condition. It not only indicates the noncharged particle heating significantly contributes to the total surface heat flux in detached divertor conditions but also demonstrates the feasibility of using two operational modes of SETCs to distinguish between the two surface heating mechanisms.