Control is difficult in particle accelerators when bunches with different characteristics have to travel through the same beam pipe and see the same optics. Controlling bunches of different types with the same magnets is a challenge. Optimizing the lattice for one type of bunch typically worsens control for the other types of bunches. Unfortunately, no knobs are available that affect only one type of bunch while leaving the others untouched. As an example, in a recirculator energy recovery linacs (ERL) having a single linac, the accelerated and decelerated beams have the same energy and thus cannot be separated by a spreader/recombiner.
As an example, JLAMP (JLab AMPlifier), a 4th generation light source covering the range 10 eV-100 eV in the fundamental mode with harmonics to 1 keV, includes common recirculation transport of accelerated and recovered beams. The common recirculation transport imposes significant constraints on both performance and operability, as multiple beams must be managed using a common set of accelerator components. Common transport is therefore a significant problem in multi-pass ERL designs having a single linac.
Accordingly, what is needed is a method for achieving independent control over the bunch types in common transport lines. As an example, independent control over the bunch types could be used to increase the power of an extreme ultra violet (EUV) free electron laser (FEL), which would be of interest in lithography systems, or in ERL-based light sources such as JLAMP, eRHIC, LHeC, CERN, and KEK.