Production and purification of molecular 225Ac at CERN-ISOLDE

Abstract

The radioactive nuclide 225Ac is one of the few promising candidates for cancer treatment by targeted-α-therapy, but worldwide production of 225Ac faces significant limitations. In this work, the Isotope Separation On-Line method was used to produce actinium by irradiating targets made of uranium carbide and thorium carbide with 1.4-GeV protons. Actinium fluoride molecules were formed, ionized through electron impact, then extracted and mass-separated as a beam of molecular ions. The composition of the mass-selected ion beam was verified using time-of-flight mass spectrometry, α- and γ-ray decay spectrometry. Extracted quantities of 225Ac19F2+ particles per μC of incident protons were 3.9(3)×107 from a uranium carbide target and 4.3(4)×107 for a thorium carbide target. Using a magnetic mass separator, the long-lived contamination 227 Ac is suppressed to <5.47×10-7 (95% confidence interval) with respect to 225Ac by activity. Measured rates scale to collections of 108 kBqμA-1h-1 of directly produced 225Ac19F2+.