Production of high intensity radioactive ion-beams by means of thick target technique

Target and ion-source techniques which allow rapid separation of thermalized radioactive nuclei from 1-500 g/cm2 thick irradiated target material and continuously convert them into a mono-isotopic ion-beam present themselves as a new method of radiochemical separation. These techniques combine nuclear reactions with high temperature chemistry, metallurgy, solid state diffusion and ionization phenomena. Developed at the many mass separators on-line at various accelerators or reactors they are today widely used to produce radioactive ion-beams for physics experiments. For some years they have reached a stage of development that allows the production of low-energy high-intensity beams of radioactive isotopes of most elements in the periodical system. In this paper the parameters that determine the intensities of these most often singly charged ion-beams are discussed in view of injection into a post accelerator. First a short introduction is given to the technique of on-line mass separation. This is followed by a detailed discussion of the three factors which determine the production rates in the target: i.e. reaction cross sections, beam properties and target thicknesses and by a discussion of the more decisive factors which control the efficiency with which the radioactive nuclei produced in the target can be transformed into a final ion-beam of typically 10-60 keV energy. Throughout the discussion the influence and direction of new developments are assessed. Finally, selected examples of realistic beam intensities are given, which may be used for comparison of the different production methods