Positron Annihilation Spectroscopy at a Superconducting Electron Accelerator

High-power superconducting linear electron accelerators allow producing a variety of secondary beams. At the Helmholtz-Zentrum Dresden-Rossendorf a 40 MeV superconducting electron accelerator is operated at beam currents up to 1.6 mA in continous-wave mode delivering neutrons from photo-production off lead, tunable coherent laser light from free-electron lasers, intense Bremsstrahlung for nuclear (astro-) physics, and positrons from pair production. New developments now enable for the first time positron annihilation lifetime experiments in bulk materials, fluids, gases and organic tissue. A 3-D tomographic annihilation lifetime imaging systems has been developped for new classes of experiments for quantitative and qualitative crystal-defect characterizations, chemsitry of positronium in insulators and porous materials. Some recent applications will be presented.