In-vessel final design of the ITER Wide Angle Viewing System in equatorial port 12

Abstract

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 located in four equatorial ports, covering more than 80% of the tokamak internal surface.This article focuses on the In-Vessel components of the three lines of sight of the diagnostic in equatorial port 12, which have to be installed for the “first plasma” of ITER.The main components of the system are the First Mirror Unit (FMU) and the Hot Dog-Leg (HDL). The FMU contains two mirrors and all associated equipment allowing their support, protection, cleaning and monitoring. It is a critical component since it has to sustain severe constraints (harsh nuclear environment, plasma proximity, complex interfaces) while it has to achieve challenging optical performances. All elements of the FMU are actively cooled. Furthermore, a pneumatic shutter to avoid direct contamination of the mirrors during first wall conditioning phases can close the FMU. The HDL is composed of two mirrors generating a labyrinth avoiding the direct neutron streaming and transmitting the optical beam toward the windows and the Ex-Vessel components of the WAVS.The main design aspects of the FMU and HDL are presented in this paper. These In-Vessel components have been presented to their Final Design Review (FDR) in July 2022 and their design is mature enough to outline the main features to comply with all the challenging requirements of the ITER machine.