Production of radioactive beams of francium

We describe the production of francium beams from the fusion–evaporation reaction Au 197 ( O 18 , kn ) 215 - k Fr generated by a ∼ 100 MeV O 6 + 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 ∼ 1200 K and kept at a potential of + 3 kV 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 × 10 6 ions / s for 210Fr with a primary beam flux of 10 12 particles / s , with peaks of 2 × 10 6 ions / s . From these measurements, information on the efficiency of the release processes is inferred.