Orateur
Description
The medical radioisotope Ac-225 is produced at a handful of accelerator facilities by high energy proton irradiation of thorium-based targets. The current standard separation protocol of this isotope and its generator parent Ra-225 from irradiated targets is based on radiochemistry. This method can recover Ac-225 and Ra-225 with high radiochemical yields of >90%. Nonetheless, a major issue is that the recovered Ac solutions contain the long-lived Ac-227 with an activity potentially unsafe for medical use. In order to address this, the method of resonant laser ionization and mass separation can instead be performed on Ac-225-containing samples including irradiated ThO2 matrices, or as solutions dried on refractory foils. This contribution will provide a comprehensive overview of the multiple collections of Ac-225 that have been performed with this method at CERN MEDICIS from different starting samples. For each collection, the total separation efficiency as measured by complementary alpha- and gamma-spectroscopy techniques will be reported and discussed. Furthermore, the separation factor of Ac-225 compared to Ac-227 through this method and hence its suitability for producing medically relevant Ac-225 samples will be reported where applicable. During the discussion, emphasis will be placed on the systematics of the laser ionization efficiency, as well as Ac-225 release as a function of its chemical environment and temperature. The contribution will conclude by recommending an optimum method for separating medical grade Ac-225 from thorium-based targets irradiated with protons.
