A new infrared thermography system has been installed in the WEST tokamak to observe the thermal scene of the first wall and components in a wide-angle tangential view of the poloidal cross-section.
The objective of this system is to provide a thermal map of the chamber and the inner components. About one-sixth of the chamber is observed, including sectors of the baffle, the lower and upper divertors, one inner bumper, vertical displacement event (VDE) protections, one ICRH antenna, and parts of the wall. Measurements will be used for machine protection by means of monitoring temperature thresholds in delimited region of interest, and for analysis of heat load during operation and specific events such VDE, ELM, disruption or runaways.
This wide angle view uses one aspherical and one on-axis plane mirrors, a Sapphire window and 3 lenses for the objective of the camera which is home-made camera designed by CEA. The optical path is optimized in the range 1.5 to 5µm. The field of view is 60 degrees on a 512*640 pixels Focal Plane Array. Since the head of the endoscope is close to the surface of the first wall, it is actively cooled.
The thermal scene is complex due to various viewing angles and different components and materials observed. In addition, spurious signals (reflecting light) and performances of the diagnostic (like the spatial resolution) have to be taken into account to obtain the best accurate temperature. Hence, emissivity and angle dependences on materials have been measured on test-beds and used for the interpretation of surface temperatures. Also a superimposition of CAD image with IR imaging is performed to help in the location of the thermal events on components.
Last update : 06/25 2018 (674)