Production of radioactive beams of francium

We describe the production of francium beams from the fusion–evaporation reaction Au197(O18,kn)215-kFr generated by a ∼100∼100 MeV O6+18 beam on a thick gold target. The physics of the production process is discussed, together with estimates of expected production rates. The production target is heated to ∼1200K and kept at a potential of +3kV to enhance Fr diffusion and surface desorption, and to accelerate surface-ionized ions. Details are given on its design and construction. The performance of the target is measured as a function of primary beam energy and flux, target temperature and extraction voltage. Average production rates are 0.7×106ions/s for 210Fr with a primary beam flux of 1012particles/s, with peaks of 2×106ions/s. From these measurements, information on the efficiency of the release processes is inferred.