Highly charged ions in storage rings

Abstract

The possibilities for experiments with highly-charged ions have decisively been enlarged by the new generation of heavy ion storage rings employing cooling of the stored beams. Some of the basic operation principles of heavy-ion storage rings and of electron cooling as the most commonly used method will be discussed. In combination with appropriate in-beam targets, the cooled, brilliant beams in the heavy-ion storage ring ESR offer a unique access to the determination of the binding energies of hydrogen-like, very heavy ions by the precise measurement of the energies of corresponding x-ray transitions. These investigations provide an experimental access to a special domain of quantum electrodynamics (QED), namely the radiative corrections to the binding energies of states bound in very strong nuclear Coulomb fields. In contrast to light ions, the electrons are relativistic and nonperturbative methods have to be applied for the calculations of the QED effects in order to properly treat the interaction between the electron and the nucleus. Since these corrections are largest for electrons in the ground states, special emphasis is given to measurements of x-ray transitions into the ground states of hydrogen-like ions up to uranium. The present status of the experimental and theoretical results will be discussed together with further experimental perspectives.