Production study of Fr, Ra and Ac radioactive ion beams at ISOLDE, CERN.

The presented paper discusses the production of radioactive ion beams of francium, radium, and actinium from thick uranium carbide (UC ) targets at ISOLDE, CERN. This study focuses on the release curves and extractable yields of francium, radium and actinium isotopes. The ion source temperature was varied in order to study the relative contributions of surface and laser ionization to the production of the actinium ion beams. The experimental results are presented in the form of release parameters. Representative extractable yields per C are presented for Ac, several Ra and Fr isotopes in the mass ranges 214 A 233 and 205 A 231 respectively. The release efficiency for several isotopes of each of the studied elements was calculated by comparing their yields to the estimated in-target production rates modeled by CERN-FLUKA. The maximal extraction efficiency of actinium was calculated to be 2.1(6)% for a combination of surface ionization using a Ta ion source and resonant laser ionization using the two-step 438.58 nm, and 424.69 nm scheme.