Optical design of ex-vessel components for the Wide Angle Viewing System diagnostic for ITER

The equatorial visible and infrared Wide Angle Viewing System (WAVS) for ITER is one of the key diagnostics for machine protection, plasma control and physics analysis. To achieve these objectives, the WAVS will monitor the surface temperature of the Plasma Facing Components by infrared (IR) thermography (3–5 μm range) and will image the edge plasma emission in the visible range. It will be composed of 15 lines of sight installed in four equatorial ports (no. 3, 9, 12 and 17) and will survey more than 80% of the overall area of the vacuum vessel. This paper presents the optical design of the ex-vessel optics, which is at Preliminary Design Status by the time this paper is published. The main function of the ex-vessel optics is to relay the scene image, and also the pupil image, coming from the Port-Plug Optics into a dedicated set of detectors, while keeping the required performance. The optics will work in two bands simultaneously, visible and Mid IR, and will use common refractive optics all along the optical path until it splits into the dedicated sensors at the Port Cell Cabinet. The optical system consists of several modules that comply with the different system interfaces and environmental constraints. A full description of the different modules, its function and performance, and the end to end optics performance will be described in this paper. The optics alignment strategy will be also described and the corresponding assembly and manufacturing tolerances.