For four decades, the technique of beam cooling has made many varied and ambitious physics programs at CERN possible. The observation of the intermediate vector bosons predicted by the unifying electro-weak theory and the trapping of anti-hydrogen atoms are just two examples of such achievements. More recently, lead-lead and proton-lead ion collisions in the LHC have been made possible thanks to the cooling and accumulation of lead ions in the low energy ion ring LEIR.
Electron cooling in particular has been used extensively on the storage rings of the CERN accelerator complex, primarily for the accumulation of ions or for the improvement of the beam quality for precision experiments at very low energies. Since the first cooling experiments on ICE (Initial Cooling Experiment) the coolers have evolved to incorporate the latest advances in electron cooling technology and many unique experiments have also been performed when they are not used for everyday operations.
After a brief introduction to the process of electron cooling, the history of coolers operational at CERN will be presented culminating with the successful commissioning of a third device operating at energies below 350 eV on the Extra Low ENergy Antiproton ring (ELENA).