Separation of manganese isotopes by resonance ionization mass spectrometry for Mn-53 half-life determination

We report on the production of ultra-pure samples of the long-lived radioisotope Mn-53 for precision measurements of its half-life. Activated samples from a copper beam dump from PSI, which was irradiated with 590 MeV protons, were used for extraction of the manganese fraction. Following initial radiochemical purification, efficient three-photon laser resonance ionization of manganese inside a hot-cavity laser ion source was applied for subsequent isotope selection in a 30 keV high transmission magnetic mass separator. A new ionization scheme was developed and characterized for Mn-53 implantation. In this way the isobar Cr-53 and the Mn isotopes Mn-54,Mn-55 are quantitavely removed, with a special focus on the radioactive Mn-54 isotope. Microgram quantities of Mn-53 were implanted into Al targets with an isotopic and isobaric purity of well above 10(3). An overall efficiency of the enrichment process of about 15% was demonstrated.