The 6 MV pelletron at Stuttgart - an accelerator for ions, positrons and electrons

After a short introduction and a description of the accelerator facility the paper surveys the experiments which were performed with the ion and positron beams of this accelerator since its installation in Stuttgart. Selected examples are presented for either characteristic or novel applications in more detail. They comprise: (i) The ion beam analysis of solids by means of RBS (stoichiometry of high-Tc superconductors), NRA (trace analysis by a novel p-γ-coincidence technique), ion channeling (structure of quasicrystals), and high resolution RBS and ERDA of surfaces and near-surface layers with a recently set up electrostatic spectrometer for MeV ions (oxidation of metal surfaces, stoichiometry of multi-layers, high resolution ERDA of hydrogen). (ii) Measurement of the energy dependence of the elastic (Bhabha) scattering of positrons by electrons and of the annihilation-in-flight cross-section of positron-electron pairs (search for resonant neutral particle states), beam-based β+-γ-coincidence positron-lifetime measurements (high-temperature thermal-equilibrium studies on Ge in the solid and molten state and on Si up to the melting point), triple-coincidence β+γΔE Age - Momentum Correlation (AMOC) measurements (positronium formation in fused quartz, time-resolved observation of spin conversion of positronium in a paramagnetic solution (HTEMPO/methanol), trapping of positrons at defects in diamonds and at thermally generated vacancies in aluminium). (orig.)