Réduction de modèle thermique par Méthode d'Identification Modale (MIM) pour déterminer la température de surface des composants de machine de fusion

National audienceUne méthode de réduction de modèle par Méthode d’Identification Modale a été mise en place afin de simuler la température de surface de composants face au plasma dans les machines de fusion. Une des difficultés à la mise en place de cette méthode est la prise en compt e d’un flux de chaleur très hétérogène sur la surface du composant. La méthode permet de fournir la température de surface transitoire du composant en un temps très réduit par rapport à des méthodes de référence de type éléments finis (MEF) (12 000 fois plus vite) pour une erreur en température de l’ordre de quelques pourcents

Inverse Radiation Problem with Infrared Images to Monitor Plasma-Facing Components Temperature in Metallic Fusion Devices

International audienceInfrared (IR) diagnostics are used to measure plasma-facing components (PFC) surface temperature in fusion devices. However, the interpretation of such images is complex in all-reflective environments because of unknown emissivity and multiple reflections issues. In order to assess these challenges an iterative inversion method based on a fast photonic model, the radiosity method, has been developed. The radiosity method is based on strong hypotheses including all diffuse surfaces. The inversion method allows retrieving the true surface temperature of PFC in two steps: a step of the target emissivity estimation in a baking scene and the use of the emissivity map to retrieve the temperature of metallic components with errors up to 3% during a plasma scenario

Real-Time Detection of Overloads on the Plasma-Facing Components of Wendelstein 7-X

Wendelstein 7-X (W7-X) is the leading experiment on the path of demonstrating that stellarators are a feasible concept for a future power plant. One of its major goals is to prove quasi-steady-state operation in a reactor-relevant parameter regime. The surveillance and protection of the water-cooled plasma-facing components (PFCs) against overheating is fundamental to guarantee a safe steady-state high-heat-flux operation. The system has to detect thermal events in real-time and timely interrupt operation if it detects a critical event. The fast reaction times required to prevent damage to the device make it imperative to automate fully the image analysis algorithms. During the past operational phases, W7-X was equipped with inertially cooled test divertor units and the system still required manual supervision. With the experience gained, we have designed a new real-time PFC protection system based on image processing techniques. It uses a precise registration of the entire field of view against the CAD model to determine the temperature limits and thermal properties of the different PFCs. Instead of reacting when the temperature limits are breached in certain regions of interest, the system predicts when an overload will occur based on a heat flux estimation, triggering the interlock system in advance to compensate for the system delay. To conclude, we present our research roadmap towards a feedback control system of thermal loads to prevent unnecessary plasma interruptions in long high-performance plasmas