Development of multi-band and high-speed visible endoscope diagnostic on EAST with catadioptric optics

A new multi-band and high-speed endoscope diagnostic for the observation of visible light has been successfully developed on the Experimental Advanced Superconducting Tokamak. The mirror with an aperture is designed at the head of the optical system. Based on two dichroic mirrors, the system is divided into three imaging mirror groups with different bands, i.e. B (380–500 nm), G (500–580 nm) and R (580–750 nm) bands, and its focal length is 16 mm with a relatively large aperture of D/f=1:4. The spatial resolution is less than 5 mm near the object distance of 1750 mm with the camera NAC ACS-1 M60. This optical system will be used to contrastively study both the spatial distribution and time evolution of different impurities in the same field of view. The experimental results confirm that it can be applied to the recognition of plasma boundary and related physical research.