Overview of Energy Recovery Linacs

Existing Energy Recovery Linacs (ERLs) are successfully operated as kW-class average power infrared Free Electron Lasers (FELs). Various groups worldwide actively pursue ERLs as a technology of choice for a number of new applications. These include high brilliance light sources in a wide range of photon energies utilizing both spontaneous and FEL radiation production techniques, electron cooling of ion beams, and ERL-based electron-ion collider. All of these projects seek in various ways to extend performance parameters possible in ERLs beyond what has been achieved in existing relatively small scale demonstration facilities. The demand is for much higher average currents, significantly larger recirculated beam energies and powers and substantially improved electron sources. An overview of the ongoing ERL projects will be presented along with the summary of the progress that is being made in addressing the outstanding issues in this type of accelerators.