Comparison of radioactive ion-beam intensities produced by means of thick targets bombarded with neutrons, protons and heavy ions

Abstract

Target and ion-source techniques which allow rapid separation of thermalized radioactive nuclei from 1–500 g cm 2 thick irradiated target material and continuously convert them into a mono-isotopic ion beam have been proven to be a powerful 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 to various accelerators or reactors they are today widely used to produce low-energy (10–60 keV) radioactive ion-beams for physics experiments. Since some years they have reached a stage of development that allows the production of high-intensity beams of up to 10 12 ions/s of radioactive isotopes of most elements in the periodic system. Such on-line mass separators seem to be excellent injectors to a second accelerator which accelerates up to 20 MeV/u. This paper discusses the radioactive beam intensities that may be injected into proposed or working European radioactive ion-beam facilities which make use of such injectors. 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 that determine the production rates in the target, i.e. reaction cross-sections, primary beam properties, and target thicknesses, and by a discussion of the more decisive factors that control the efficiency with which the radioactive nuclei produced in the target can be transformed into an injection ion-beam of typically 10–60 keV energy. Throughout the discussion the influence of new developments is assessed. Finally, selected examples of realistic beam intensities are given, which are used for intercomparison of the different production methods used by the various European projects.