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The WEST platform aims at testing ITER like W divertor targets in an integrated tokamak environment. To operate long plasma discharges, IR thermography is required to monitor the main plasma facing components by means of real time surface temperature measurements, while providing essential data for various physics studies. To monitor the new divertor targets, the WEST IR thermography protection system has been deeply renewed, to match the new tokamak configuration. It consists of 7 endoscopes located in upper ports viewing the whole lower divertor and the 5 heating devices. Electronic devices and computers allow data storage of ≈3 Gb/s IR images and real time video frames processing at 50 Hz rate, to ensure the protection of the main plasma facing components during plasma discharges by a feedback control of the power injected by the heating systems. Each endoscope provides 2 views covering 2 divertor sectors of 30° (toroidally) and 1 view of a heating antenna. Each optical line is composed of a tight entrance window followed by a head objective which forms an image transported through the endoscope by a series of 4 optical relays and mirrors, up to a camera objective. Finally, 12 IR cameras specially developed for WEST environment capture the thermographic data, at the wavelength of 3.9 μm, with a 640 × 512 pixels frame size. The paper describes the design constraints and diagnostic technologies: optics, mechanics, electronics, hard & software, cameras. Tvhe laboratory characterization procedures (Modulation Transfer Function, slit response, calibration), and the measurement performance results are given (spatial resolution, temperature threshold). Finally, first results obtained during experimental campaigns in WEST are presented. [ABSTRACT FROM AUTHOR]

This paper presents the method toward quantifying the global uncertainty on the blackbody temperature measurement from the infrared (IR) diagnostics of WEST. To address this goal, the main functional elements of the IR diagnostics are identified. Then the temperature calibration and calculation principles are presented and analysed to extract the main potential uncertainty contributors, such as the optical transmission coefficients and their stray lights, or the accuracy of temperature references used for calibration. These contributors are individually estimated, or experimentally measured when a supposed effect on the overall uncertainty is identified, like environmental conditions or parasitic radiations. In particular, effects of environmental temperature on the transmission lines and camera is thoroughly studied. All contributions are then aggregated in the uncertainty propagation calculation and results in an overall temperature uncertainty versus the temperature estimation. The uncertainty is in the range of 5–10% for blackbody temperatures above 200 °C, and progressively worsens when temperature decreases. [ABSTRACT FROM AUTHOR]

• Unique 0.1 mm/pixel IR thermography diagnostic for plasma-wall interaction studies. • Improved accuracy and reliability on field of view positioning. • Operational on WEST tokamak since 2020. • Diagnostic is accurate to the monoblock. The Very High spatial Resolution (VHR) infrared thermography diagnostic developed by CEA-IRFM is installed in the WEST tokamak to measure surface temperature of the actively cooled W-monoblocks (MB) of the Plasma Facing Units (PFUs), which are similar to the International Thermonuclear Experimental Reactor (ITER) ones. It is a major diagnostic to investigate the behavior of PFU during experimentation thanks to its very high spatial resolution (0.1 mm / pixel), movable field of view (FoV) and the wide-range temperature measurement. In particular, it can study the evolution of monoblocks mounted in the tokamak, the influence of the shaping of these components submitted to high heat load and the behavior of the leading edges regarding the assembling tolerances between adjacent monoblocks. Finally, such diagnostic directly contributes to the specification assessment of the ITER divertor units. This diagnostic was operational during the 2019 WEST experimentation and its enhanced design for the 2020 WEST experimentation campaign. In order to monitor 30 × 12 mm monoblocks temperature, the VHR IR diagnostic is able to move its narrow FoV (64 × 51 mm) to specific targets on the observable divertor area (360 × 420 mm). Position and focus steering are achieved through motor-controlled mirrors and lenses operated by a dedicated Labview application on a remote unit. Mirror positioning occurs between pulses under normal WEST operation conditions, and can withstand thermal radiation and disruptions during pulses. Repeatability, hysteresis, mechanical components reliability are critical parameters to provide accurate positioning (<1 mm) of the FoV. The tuning and calibration of these actuators in accordance with WEST environment is crucial to guarantee the best position of the FoV and optical performances. This paper gives the FoV positioning implementation details and performance of the VHR in WEST. [ABSTRACT FROM AUTHOR]