ELectron-Ion Scattering in a Storage Ring (eA collider) - ELISe

The FAIR facility will provide intense, high-quality secondary beams of ions and antiprotons. A new double synchrotron ring system will provide 1012 ions/s up to uranium with an energy of 1.5 GeV/u. Intense, secondary ion beams will be produced and separated with the Super-FRS. A system of storage-cooler rings will be used to reduce the emittance and energy spread of secondary beams created via fragmentation or fission reactions. Scattering experiments at internal targets are being planned in the New Experimental Storage Ring (NESR) with radioactive ions at energies up to 740 MeV/u. Additionally, an intersecting electron ion ring (eA collider) will allow to scatter electrons with an energy of 125-500 MeV off exotic nuclei. The eA collider will enable for the first time to perform elastic, inelastic and quasielastic electron scattering off shortlived radioactive isotopes. The collider kinematics has the advantage that it will be possible to detect electrons and target like ejectile in coincidence. One of the most challenging aspects in this context is the design of a high-resolution electron spectrometer with large acceptance adapted to the specific demands of an in-ring experiment. Charge distributions, transition form factors in giant resonance or electrofission experiments and spectral functions can be measured with a clean electromagnetic probe.