Final Design and Tests of the In-Vessel Shutter of the ITER Wide Angle Viewing System (WAVS) in Equatorial Port 12

The ITER wide angle viewing system (WAVS) is a major diagnostic for machine protection, plasma control, and physics analysis. It will measure the surface temperature of the plasma-facing components by infrared thermography and will image the plasma emission in the visible range. The global system is composed of 15 lines of sight (LoS) located in four equatorial ports, covering 70% of the Tokamak internal surface. This article focuses on an in-vessel component, the shutter, present in each line of sight of the WAVS. Indeed, the shutter will protect the first mirrors from direct erosion due to fast particles from the plasma and/or direct contamination due to slow particles from glow discharges during first wall conditioning. Integrated within each first mirror unit, this mechanism is a critical component since it undergoes severe constraints, while it has to perform a robust cinematic to achieve 30000 cycles over all ITER phases. The shutter mechanism consists of a pneumatic actuated bellows, which rotates a lever blade, thanks to its linear displacement through two pivots. Two electrical end switches monitor its stroke. On top of the protection function, the shutter incorporates an in situ infrared calibration source. This calibration source consists in a heater, regulated by a thermocouple and inserted on its moving blade. The shutter is fully water-cooled, except all mobile parts, such as the bellows and the blade. A prototype of this shutter has been developed, manufactured and tested. Over 100000 actuations have been achieved under representative conditions while keeping its full operability. This article presents the shutter’s design presented at the FDR and describes its validation thanks to the thermal cycling tests.