Production and purification of molecular ²²⁵Ac at CERN-ISOLDE

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