Limiter material experiments towards long pulse operation in the HT-7 superconducting tokamak

Selection and testing of candidate materials for plasma facing components (PFC) in next-step fusion devices is an important and strongly addressed point in the research programme of HT-7 device. A kind of B, Si and Ti doped graphite with thick SiC gradient coatings has been chosen as the main limiter material for the HT-7 device. From only a 0.3 m2 of poloidal limiter to a total covered area of 2.5 m2 new belt limiter plus up and down toroidal limiters with actively water-cooled, the change in the HT-7 device was very successful, the plasma performance has been significantly improved and the longest discharge duration has been more than 306 s. These results have demonstrated that new carbon armored PFC can also be used in the first phase of the EAST device, and might be an attractive choice for the first wall of steady state fusion devices.