Co-production of 155Tb and 152Tb irradiating 155Gd / 151Eu tandem target with a medium energy α-particle beam

Abstract

Introduction: Four terbium isotopes ^{149,152,155,161}Tb emitting various types of radiation can be used for both diagnostics and therapy. ¹⁵²Tb emits positrons and is ideal for PET. ¹⁵⁵Tb is considered a promising Auger emitter and a diagnostic pair for other terbium therapeutic isotopes. Several methods for the production of ¹⁵⁵Tb using charged particle accelerators have been proposed, but they all have significant limitations. The restricted availability of this isotope hinders its medical applications. We have proposed a new method for production of ¹⁵⁵Tb, irradiating enriched ¹⁵⁵Gd by alpha particles. The possibility of simultaneous production of two isotopes of terbium, ^152,155Tb, was also studied for more efficient cyclotron beam use.

Methods: Irradiation of ¹⁵⁵Gd enriched targets and ¹⁵⁵Gd / ¹⁵¹Eu tandem target with alpha-particles with an energy of 54 MeV was carried out at the U-150 cyclotron at the NRC "Kurchatov Institute". The cross sections of nuclear reactions on ^enr-155Gd were measured by the stack foil technique, detecting the gamma-radiation of the activation products. The separation of rare earth elements was performed by extraction chromatography with the LN Resin. ¹⁵⁵Tb was produced via ¹⁵⁵Dy decay.

Results: The cross sections for the ^155,156Tb and ^155,157Dy production were measured by the irradiation of a gadolinium target enriched with the ¹⁵⁵Gd isotope with alpha-particles in an energy range of 54 → 33 MeV. The yield of ¹⁵⁵Dy on a thick target at 54 MeV was 130 MBq/μAh, which makes it possible to obtain 1 GBq of ¹⁵⁵Tb in 11 hour-irradiation with 20 μA beam current. The possibility of simultaneous production of ^152,155Tb by irradiation of ¹⁵⁵Gd and ¹⁵¹Eu tandem target with medium-energy alpha-particles is implemented. Optimal irradiation energy ranges of alpha -particles as 54 → 42 MeV for ¹⁵⁵Tb and 42 → 34 MeV for ¹⁵²Tb were suggested. Product activity and radionuclidic purity were calculated.

Keywords: Cross section; Cyclotron; Nuclear reaction; Tandem target; Terbium-152; Terbium-155.