EURISOL-DS Multi-MW Target Preliminary Study of the Liquid Metal Proton-to-Neutron Converter

This technical note summarises the design calculations performed within Task #2 of the European Isotope Separation On-Line Radioactive Ion Beam Facility Design Study (EURISOL-DS) [1]. A preliminary study was carried out in order to determine the optimum value of relevant parameters in the target design. Different scenarios were simulated using the Monte Carlo code FLUKA [2]. Namely, sensitivity studies were performed to assess the impact of the projectile particle energy on the neutronics and energy deposition in the spallation target. The optimal target dimensions were also studied for every case as well as the proper target material for the liquid metal proton-to-neutron converter, since mercury and lead-bismuth eutectic are reasonable options. The effect of the beam width on the power densities was also evaluated, taking into account the geometrical limitations of the facility. Finally, a comparison between protons and deuterons as primary particles was performed, acknowledging the limitations of using FLUKA for these simulations. The results of these calculations show the benefit of using protons as primary particles and increasing their energy, in order to reduce the high power densities occurring in the first few centimetres downstream from the interaction point. Particularly, a 2 GeV proton beam with a  ~15 mm Gaussian distribution on a 15 cm radius 50 cm long target seems a suitable trade between increasing the neutron and fission yields and reducing the power densities in both, the liquid metal and fission targets.