Development and benchmark of an analytical model for isotope release from ISOL thin-foils targets

ISOL@MYRRHA is the Isotope Separation On Line (ISOL) facility for radioactive ion beam (RIB) production which will be built at the Belgian Nuclear Research Centre SCK-CEN. In the early stages of the process, a proton beam is sent towards the target material placed inside a container where nuclear reactions between the incoming beam and the target atoms take place. The products of these interaction diffuse out of the target material, effuse out of the cylindrical container and are subsequently ionized and extracted in a RIB which is mass purified by the magnetic separator. In this work, a detailed analytical model has been developed to simulate isotope release curves from thin-foils targets. It involves the separate modelling of diffusion with first and second Fick's law, and effusion with the Monte Carlo code MolFlow+. The two processes have been convoluted and radioactive decay was included to obtain an overall analytical description of the isotope release curve. This model was benchmarked with experimental data on release curve from two target geometries operated at ISOLDE (CERN). Moreover, the isotope in-target production was simulated with the Monte Carlo code FLUKA and it was corrected by the efficiency of the transport process calculated through the model so that a comparison with experimental data on yields at the counting station was possible. The good agreement between the model results and experimental data hints at a future applicability of this model for predicting yields and optimizing the geometry in future targets. ISOL targets have to withstand very harsh environments. This work also reports on the literature study to assess the possibility of employing a new class of materials for ISOL targets. It is derived from MAX phases, nanolaminated materials which can be treated to produce porous carbide structures which seem promising for enhancing diffusion of isotopes and withstand the severe conditions. Moreover, thermal calculations have been run to assess the possibility of using a simplified approach to compute the temperature profile in a high-power target where the input heat is provided by the beam-energy deposition.