Longitudinal phase space control in the Berkeley Femtosecond X-ray light source LUX

LUX, the proposed Berkeley Femtosecond X-ray light source, is a ∼2.5 GeV recirculating linear accelerator, where electrons reach their final energy in four passes through a 600 MeV superconducting linac after injection at ∼120 MeV. An important consideration for this machine is the preservation of the electron beam longitudinal emittance through the various stages of acceleration including injection linac, bunch compression, and various passages through the linac and magnetic arcs. In this paper we analyze the longitudinal dynamics of electrons and define a strategy for the electron beam manipulation leading to a successful conservation of the longitudinal emittance. Particular attention is given to the management of the correlated energy spread induced by collective effects such as longitudinal wake fields and coherent synchrotron radiation (CSR).