Staging of plasma-wakefield accelerators

Abstract

Reaching high energies with a plasma-wakefield accelerator may require use of multiple stages. This coupling of beams from one stage to another can be nontrivial due to a combination of high divergence and non-negligible energy spreads. In addition, a number of other requirements must be met, such as space-efficient in- and out-coupling of the driver, matching of beta functions, dispersion cancellation, and ensuring synchronization and alignment to within extremely tight tolerances. Satisfying all these requirements takes up space between the stages, which can significantly reduce the effective gradient of the accelerator. We review the challenges, the technical requirements, and some currently proposed methods for solving (or circumventing) the staging problem.