Data Merging of Infrared Images for Plasma Facing Components Inspection

For steady state magnetic thermonuclear fusion devices, actively cooled plasma facing components (PFC) have been developed in order to enable a large power exhaust capability up to 10 to 20 MW/m2. Therefore, PFC commissioning became a key issue for actively cooled fusion devices. The thermal and mechanical behaviour of the PFC's must be assessed in order to guarantee the integrity of the components during the requirement lifetime. In order to improve the thermal discontinuity detection capability of the SATIR method, the possibility of infrared data amalgamation with LOCKIN test has been assessed. The SATIR method - French acronym of Station d'Acquisition et Traitement Infrarouge - is based on infrared measurements of tile surface temperature during a thermal transient produced by successive hot/cold water flowing through the heat sink cooling channel. The LOCKIN technique is based on an external sinusoidal thermal excitation generated by a set of modulated flash lamp pulses. The phase shifting of the thermal response of the inspected component is recorded by means of an infrared device. It depends on the thermal diffusivity along the heat path, indicating the presence of cracks or failures in the component. A data combination by these two techniques led to an improvement of the global interface control. The data merging of the two infrared images - SATIR and LOCKIN - on W7X targets improved significantly the detection sensibility and reliability in the sense of defect location and size, both at the first (CFC/Cuofhc) and second (CuCrZr/Cuofhc) bonding interface. This original study showed a detection improvement of 24% for LOCKIN and 10% for SATIR method. This method has been developed on a calibrated strip defect of 2 mm and then applied on a natural defect. The data merging method of infrared images using the fuzzy logic and Dempster-Shafer's model will be presented. Remember that W7X targets are made of Carbon Fiber Composite flat tiles, thickness of 8 mm, bonded to a Copper-Chromium-Zirconium alloy heat sink through a compliant layer of soft copper. (author)