A high-brightness beam bunch-compression test stand

There is a growing need for high-brightness electron beams. Applications include next-generation linear colliders, single-pass free-electron lasers, and advanced wiggler/undulator diagnostics beamlines. Longitudinally compressing the bunch while minimizing emittance growth will play a key role in obtaining high-brightness beams. At the Advanced Photon Source a test stand is being designed specifically to allow testing of bunch compression techniques enroute to high-brightness electron sources. The beamline consists of an rf gun initially suitable for a traditional thermionic cathode but also capable of supporting a photocathode; a 3 m SLAC-type traveling wave linac; low- and possibly high-energy magnetic chicanes; rf bunching and deflecting cavities; beam-control magnets; and beam diagnostics both before and after the linac. The gun mount is designed to allow simple replacement and upgrade of the rf gun in order to permit comparison of different gun types. The diagnostics will allow rapid characterization of the electron beam emittance, energy spread and bunch length in both the low- and high-energy portions of the line. This information will be used to study the effects of both magnetic and ballistic bunch compression on the beam and will allow one to optimize gun performance for a given application.