ASP Online Seminars: Energy Recovery Linacs - a way towards the energy sustainability of particle accelerators
Energy Recovery Linacs (ERL) are emerging as a new generation of particle accelerators that promises the maximum energy sustainability. Based on Super-conducting Radio-Frequency cavities, and a smart multiple propagation of the electron beam through the Linear accelerator, they aim at reaching beam average current levels typical of storage rings (from tens up to hundreds of mA), normally forbidden to linear accelerators (Linacs) due to the large beam power levels involved (well above the MW scale). In fact ERLs will be able to deliver high brightness electron beams, as requested by advanced radiation sources like FEL’s or ICS, together with very large average beam current/power, while recovering after use (by means of beam deceleration in the Linac) the large amount of power stored in the beam. They grant users/experiments with full access to the beam phase space, but only perturbative access to the beam power (no fixed target experiments allowed): the user can degrade the beam quality but cannot waste particles of beam. Consequently, only radiation emission and/or beam collisions experiments can be carried out with ERLs. A discussion of the basics of acceleration/deceleration process will be presented, followed by an overview of ongoing projects that are demonstrating the basic ERL principle, and future designs of large scale ERLs for the high energy frontier (electron-positron or electron-hadron collisions for Higgs factories and fundamental physics, secondary muon beams for muon colliders, etc).