Design study of the optical system in the port plug for edge Thomson scattering diagnostics for ITER

Kajita, Shin; Hatae, Takaki; Katsunuma, Atsushi*; Kusama, Yoshinori

The design of the collection optics for edge Thomson scattering diagnostics for ITER is provided. Since the neutron and ray radiation fluxes generated by the nuclear fusion reaction are considerably high near the plasma in ITER, available optical components are limited. Near the plasma, namely in the front-end optics, only metal mirrors can be used; moreover, optical fiber may be used only outside the vacuum window, which is located far from the front-end optics. In this design, three metal mirrors are used for the front-end optics, and the light ray is transmitted in the slender port plug through a relay optical system. To compensate the aberrations and increase the coupling efficiency to the fibers, two types of optical system with Catadioptric system are proposed for fiber-coupling optical system. It has been revealed that refraction type and reflection type system are not adequate for the fiber-coupling optical system. The image qualities are discussed based on the spot diagram and so on for the Catadioptric optical system.