Thermal analysis of the FILD head in the ASDEX Upgrade Tokamak

Abstract

Fusion power is set to be an important energy agent in the mid future. Magnetic confinement fusion is the current most advanced technology for fusion energy. An important fraction of the plasma energy is stored in fast ions, high temperature ions that tend to abandon the magnetic confinement due to different physical phenomena. To be able to make a self sustained fusion (ignition) those fast ions must not escape. The fast Ions Loss Detector (FILD) have been set in numerous Tokamaks to study the behavior of those ions. This work develops a numerical tool in order to simulate the thermal fluxes a FILD will be facing during operation. Particle orbits within a Tokamak were approximated by magnetic field lines for this purpose. OcTree algorithm and a preliminary analysis of the position of the frontier between wet or dry zones (with or without particle impact) have been implemented to reduce computational time during simulations. As thermal model, the cosine model has been chosen, where the parallel heat flux is taken as dominant and then weighted in function of the intersection angle between magnetic field line and the FILD head. An example case has been run for one of the FILDs installed in the ASDEX Upgrade Tokamak. This machine is an important ITER physics testing site for its unique divertor configuration, taking advantage of its huge plasma shot library. The thermal analysis for this example case has been carried out using ANSYS software for FILD 4. The resulting tool comes as highly customizable as the magnetic equilibrium, tokamak, chosen FILD and FILD position are easily exchangeable, making it a good solution for a wide range of configurations.