Deposition Mitigation of the First Mirrors Exposed in EAST with Metal and Carbon Mixed Wall Materials

In order to investigate the effect of aperture geometry on deposition mitigation, stainless steel (SS) first mirrors (FMs) were fixed on the holders of protective aperture geometry with different depth-diameter ratios (DDRs) and exposed in the deposition dominated environment of EAST. A baffle was used during the wall conditioning. The surface properties and reflectivity of the FMs were characterized before and after exposure. It is shown that using aperture geometry and a baffle can effectively mitigate the impurities deposition. The degradation of the surface and specular reflectivity of the FMs is reduced with the increase of DDRs in the range of 0 to 2. The main contaminated elements in a low-Z and high-Z mixed wall materials environment were still carbon and oxygen.