CFD analysis and optimization of a liquid lead-bismuth loop target for ISOL facilities

The concept of a high-power target based on a liquid Pb-Bi loop incorporating a heat-exchanger and a diffusion chamber was proposed within EURISOL DS and is being developed within the LIEBE1 project. Due to the non-static character of the target, specific hydrodynamics issues are of concern. In this paper, these issues are studied mostly based on three-dimensional (3D) Computational Fluid Dynamics analysis of the flow of the Lead Bismuth Eutectic (LBE) target, resulting in optimized designs. The concept and hydrodynamic challenges of generating RIBs from a liquid-metal-loop target irradiated with a high-power primary beam are presented. The optimization of the target design has been conducted keeping in mind the need for a fast and efficient release of short-lived isotopes. This study shows that approximately 100 ms after the proton pulse the irradiated liquid-metal is entirely and uniformly evacuated from the irradiation volume and spread in a shower of small droplets (100-mu m radii), in order to reduce the diffusion length of isotopes. Solutions to deal with the typical cavitation risk due to the presence of low-pressure zones in the liquid have also been found and simulated.