Hot Spot Cause Analysis and Shaping Optimization Design of the Monoblock Divertor Target Plate in EAST

The monoblock divertor target plate (MDTP) is a mainstream divertor target plate. MDTP was installed in EAST and in WEST and will be used in ITER. Local high-temperature hot spots (HS) were observed on MDTP during a plasma experiment. HS will reduce the lifetime of MDTP. In this paper, the causes of HS on MDTP are determined through theoretical analysis and are verified by numerical simulations. The HS on MDTP seem to be caused by small high-density heat load areas on the toroidal and poloidal direction surfaces facing the incident direction of the plasma strike line (PSL) of the MDTP tungsten block. When toroidal HS and poloidal HS appear simultaneously, a super local high-temperature HS will be formed at the corner (facing the incident direction of PSL) of the MDTP tungsten block. The HS on MDTP can be eliminated by optimizing the geometry of the MDTP tungsten block, when the plasma configuration is determined. A method and the scope of application of the method, which can be used for tungsten block geometry optimization, are given in this paper. In order to facilitate the selection of a divertor configuration, the heat flux–carrying performance of the optimized MDTP was evaluated. In order to attain a maximum temperature within MDTP of less than 900 K, it was found that if the poloidal incidence angle between PSL and MDTP can be stably controlled as 5 deg (or 35 deg), MDTP can directly withstand PSL with a peak heat flux density of no more than 90 (or 40 ).