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-\(\alpha\)-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, \(\alpha\)- and \(\gamma\)-ray decay spectrometry. Extracted quantities of \(^{225}\textrm{Ac}^{19}\textrm{F}_2^{+}\) particles per \(\upmu\)C of incident protons were \(3.9(3)\times 10^7\) from a uranium carbide target and \(4.3(4)\times 10^7\) for a thorium carbide target. Using a magnetic mass separator, the long-lived contamination ²²⁷ Ac is suppressed to \(<5.47\times 10^{-7}\) (95% confidence interval) with respect to ²²⁵Ac by activity. Measured rates scale to collections of 108 kBq\(\upmu\)A\(^{-1}\)h\(^{-1}\) of directly produced \(^{225}\textrm{Ac}^{19}\textrm{F}_2^{+}\).