Resonant Laser Ionization and Mass Separation of 225Ac

Abstract 225 Ac is a radio-isotope that can be linked to biological vector molecules to treat certain distributed cancers using targeted alpha therapy. However, developing 225 Ac-labelled radiopharmaceuticals remains a challenge due to the supply shortage of pure 225 Ac itself. Several techniques to obtain pure 225 Ac are being investigated, amongst which is the high-energy proton spallation of thorium or uranium combined with resonant laser ionization and mass separation. As a proof-of-principle, we perform laser ionization and mass separation on two samples of 225 Ac, each with a known activity, in different chemical environments. We report overall operational collection efficiencies of 10.1(2)% and 9.9(8)% for the cases in which the 225 Ac was deposited on a rhenium surface and a ThO 2 mimic target matrix respectively. The bottleneck of the technique was the laser ionization efficiency, which was deduced to be 15.1(6)%.