R&D issues of W/Cu divertor for EAST

To improve plasma performance of EAST device, the SiC-coated doped C tiles in the divertor region will be replaced by tungsten coated CrZrCu heat sink in 3-5 years. Vacuum plasma spraying (VPS) tungsten coatings on Cu substrate are being developed in collaboration with Guangzhou Research Institute of Nonferrous Metals (GZRINM) and Shanghai Institute of Ceramics, Chinese Academy of Sciences (ASSIC). In order to reduce thermal stresses, several kinds of interlayer structures have been considered to be coated on the heat sink before preparing the pure tungsten layer to the final thickness, and the castellation concepts also taken into account. An actively cooled VPS-W/Cu movable limiter (ML) has been tested in HT-7 and a Material and Plasma Evaluation System (MAPES) will be built soon on EAST. High heat flux testing and non-destructive testing are also being studied. Plasma-wall interaction (PWI) issues like recycling and retention of H isotopes in the coatings, surface and bulk modification of the coatings and service life of the plasma-facing material and component (PFMC) are being studied not only on tokamaks but also in laboratories.