The ITER Equatorial Visible/Infra-Red Wide Angle Viewing System: Status of design and R&D

The Equatorial Visible/Infra-Red Wide Angle Viewing System (WAVS) is one of the ITER key diagnostics owing to its role in machine investment protection through the monitoring of Plasma Facing Components (PFCs) by Infra-Red thermography and visible imaging. Foreseen to be installed in 4 equatorial port plugs to maximize the coverage of divertor, first wall, heating antennas and upper strike zone, the WAVS will likely be composed of 15 lines of sight and 15 optical systems transferring the light along several meters from the PFCs through the port plug and interspace up to detectors located in the port cell. After a conceptual design phase led by ITER Organization, the design is being further developed through a Framework Partnership Agreement signed between the European Domestic Agency, Fusion for Energy, and a consortium gathering CEA, CIEMAT (with INTA as third party) and Reran Technologies company. The next design step is the System Level Design (SLD) which will enable to consolidate the WAVS specifications as well as the performance realistically achievable (taking into account ITER and project constraints). The SLD has been preceded by a preparatory phase aiming at clarifying the WAVS functions and identifying critical prototyping. The outcomes of this preparatory phase are reported in this paper. First a review by the consortium of the WAVS measurement specifications is presented, for the purpose of a clearer separation of measurement parameters mandatory for machine protection (with stringent requirements) from those relevant for machine control and physics studies. Secondly the main features of the diagnostic are summarized, including a description of its current design, a preliminary analysis of its interfaces and a high level functional analysis. Finally the status of the R&D which may be necessary to validate the diagnostic design is presented. On the one hand, this R&D could consist in testing materials and coatings of optical components to characterize their behavior under the harsh environment of ITER. On the other hand R&D activities could concern prototyping and testing of subsystems of the diagnostic which have been identified as critical, such as the first mirrors and their associated devices (shutter and cleaning system) and the differential movement compensation system. (c) 2015 Elsevier B.V. All rights reserved.