Optimized production of Tb-155 by mass separation using Ta-based target materials at the CERN-MEDICIS facility

Abstract Terbium isotopes are of considerable interest for medical theranostics; however, their efficient off-line mass separation is constrained by short half-lives and limitations of indirect collection techniques. In this work, an optimized strategy for the production and separation of $$^{155}$$ 155 Tb at the CERN-MEDICIS facility is presented through a comparative study of three tantalum-based target materials: metallic Ta foils, TaC pellets, and a TaC-MWCNT (multi-walled carbon nanotube) composite. Metallic Ta foils exhibit low collection efficiency and are significantly affected by pseudo-isobaric contamination from 139 Ce. In contrast, TaC-based targets, when operated with CF 4 injection, enable direct molecular extraction of 155 Tb as volatile $$\\hbox {TbF}_{X}$$ TbF X species, avoiding reliance on indirect 155 Dy collection and effectively suppressing Ce contamination. The modified TaC+C configuration achieved the highest initial collection efficiency (up to 1.74%); however, their performance degraded upon repeated use. By comparison, the TaC-MWCNT composite showed encouraging consistency across the two high-temperature collection runs performed, with process efficiencies of 0.40% and 0.37%. Complementary microstructural characterization indicates that MWCNT incorporation is associated with reduced grain growth and greater retention of open porosity after high-temperature treatment. These results identify CF $$_4$$ 4 -assisted molecular extraction from carbide-based targets as a promising route for high-purity $$^{155}$$ 155 Tb separation. The TaC–MWCNT composite shows encouraging repeatability across the two runs performed, while additional reuse cycles are required to establish long-term reproducibility and thermal stability.