In the design of particle accelerators, longitudinal beam dynamics plays a critical role in delivering beams with the desired properties to the interaction regions by controlling the energy distribution and current profile. Variable bunch compressors are therefore a fundamental tool to provide flexibility in any accelerator. This variability is implemented in the MAX IV bunch compressors employing variable strength dipoles capable of delivering high-quality beams with a wide range of available longitudinal dispersions.
Energy recovery linacs have the potential to outperform traditional linacs and storage rings by delivering simultaneously high brilliance beams at a high repetition rate. In an ERL, a self-consistent longitudinal match is not only necessary to optimize the beam delivered to the interaction regions but also to enable the energy recovery mechanism. We present a detailed study of self-consistent longitudinal matches for collider and FEL applications. We conclude that choosing common return transport beamlines severely restricts the availability of a self-consistent match, in particular when synchrotron radiation
losses are important. Finally, we apply this method to two distinct projects: ER@CEBAF as a high energy ERL FEL driver and PERLE as a high-charge ERL for nuclear physics experiments.