Materials science and biophysics applications at the ISOLDE radioactive ion beam facility

The ISOLDE isotope separator facility at CERN provides a variety of radioactive ion beams, currently more than 800 different isotopes from ∼70 chemical elements. The radioisotopes are produced on-line by nuclear reactions from a 1.4 GeV proton beam with various types of targets, outdiffusion of the reaction products and, if possible, chemically selective ionisation, followed by 60 kV acceleration and mass separation. While ISOLDE is mainly used for nuclear and atomic physics studies, applications in materials science and biophysics account for a significant part (currently ∼15%) of the delivered beam time, requested by 18 different experiments. The ISOLDE materials science and biophysics community currently consists of ∼80 scientists from more than 40 participating institutes and 21 countries. In the field of materials science, investigations focus on the study of semiconductors and oxides, with the recent additions of nanoparticles and metals, while the biophysics studies address the toxicity of metal ions in biological systems. The characterisation methods used are typical radioactive probe techniques such as Mössbauer spectroscopy, perturbed angular correlation, emission channeling, and tracer diffusion studies. In addition to these “classic” methods of nuclear solid state physics, also standard semiconductor analysis techniques such as photoluminescence or deep level transient spectroscopy profit from the application of radioactive isotopes, which helps them to overcome their chemical “blindness” since the nuclear half life of radioisotopes provides a signal that changes in time with characteristic exponential decay or saturation curves. In this presentation an overview will be given on the recent research activities in materials science and biophysics at ISOLDE, presenting some of the highlights during the last five years, together with a short outlook on the new developments under way.