Electron Targets / Using Storage Ring Electron Coolers as Targets for Free Electrons

Electron Ion Collisions

Collisions between free electrons and ions belong to the most fundamental process in atomic physics.  Within the AOF department, primarily electron-ion collisions with stable heavy highly charged ions and with artificially synthesized radioisotopes are pursued. In a storage ring, the circulating ions repeatedly interact with the target electrons thus allowing investigations of low-intensity projectiles and/or of processes with low cross sections to be carried out. In addition, the storage ring environment provides very clean experimental conditions owing to phase-space cooling and dedicated control of the isotope and charge state of the ion.

At present, at ESR and at CRYRING@ESR three different classes of electron-ion collision experiments are carried out:

  • Photon or electron spectroscopy produced in collisions between free target electrons and stored ions.
  • Precision spectroscopy and lifetime studies utilizing energy-sharp resonant features in the electron-ion cross section (‘collisions spectroscopy’). More details about collision spectroscopy can be found here. With the same approach cross sections and resonance strengths are determined on an absolute scale, thus providing an in-depth understanding of electron-ion collisions and their dynamical aspects.
  • Determination of absolute rate coefficients for applications in astrophysics and fusion research

Three main experimental installations will be used to reach these goals: