The Antiproton‐Ion‐Collider at FAIR

For the FAIR Project at Darmstadt an antiproton‐ion collider has been proposed to independently determine rms radii for protons and neutrons in stable and short lived nuclei by means of antiproton absorption at medium energies. The experiment makes use of the electron ion collider complex to store, cool and collide antiprotons of 30 MeV energy with short lived radioactive ions in the NESR that are produced by projectile fragmentation and projectile fission separated in the Super FRS. The total absorption cross‐section for antiprotons on the stored ions with mass A will be measured by detecting the loss of stored ions by means of the Schottky method. Cross sections for the absorption on protons and neutrons, respectively, will be measured by the detection of residual nuclei with A‐1 either by the Schottky method or by detecting them in recoil detectors after the first dipole stage of the NESR following the interaction zone. Theoretical calculations show that the absorption cross sections are in first order directly proportional to the mean square radii.