Surface diversifying and deuterium retention characteristics of doped graphite with SiC coating exposed to plasma discharges in East Tokamak

Carbon-based material is widely used as plasma facing material (PFM) in fusion device, for its high thermal conductivity and good mechanical strength, such as the multi-element (B, Si, Ti) doped graphite with SiC coating in the divertor PFM in EAST tokamak. To study its service performance, surface diversifications were analyzed for the pristine sample and the samples after exposure to plasma discharges. The exposed samples have different structures in the SiC coating, depending on the different level of plasma heating loads. The nano-rods obtained from the higher heat loaded area are with diameters in the range of 200-500 nm and lengths in the range of 4-10 μm. While in the lower heat loaded area, the morphologies characterized by scanning election microscope show a transition stage between the pristine big crystals and the nano-rods. The SiC nanorods were further exposed to pure deuterium plasmas generated by linear plasma generator STEP and afterwards was analyzed by thermal desorption spectroscopy. The result indicates that the deuterium retention is increased remarkably.