Analytical model for release calculations in solid thin-foils ISOL targets

A detailed analytical model has been developed to simulate isotope-release curves from thin-foils ISOL targets. It involves the separate modeling of diffuiosn and effusion inside the target. The former has been modeled using both first and second Fick's law. The latter, effusion from the surface of the target material to the end of the ionizer, was simulated with the Monte Carlo code MolFlow+. The claculated dleay-time distribution for this process was then fitted using a double-expontnetial function. The release curve obtained from the convolution of diffusion and effusion shwows good agreement with experimental data from two different target geometries used at ISOLDE. Moreover, the experimental yyields are well reproduced when combining the release fraction with calculated in-target production.