Transverse-to-longitudinal emittance exchange to improve performance of high-gain free-electron lasers

P. Emma, Z. Huang, K.-J. Kim, P. Piot
2006 Physical Review Special Topics. Accelerators and Beams  
The ability to generate small transverse emittance is perhaps the main limiting factor for the performance of high-gain x-rays free-electron lasers (FELs). Noting that beams from an rf photocathode gun can have energy spread much smaller than required for efficient FEL interaction, we present a method to produce normalized transverse emittance at or below about 0.1 µm, which will lead to a significantly shorter length undulator as well as a lower electron beam energy for an x-ray FEL project.
more » ... -ray FEL project. The beam manipulation consists of producing an unequal partition of the initially equal emittances into two dissimilar emittances by a flat beam technique and exchanging the larger transverse emittance with a small longitudinal emittance. We study various issues involved in the manipulation. In particular, a new emittance exchange optics we found enables an exact emittance exchange necessary for this scheme.
doi:10.1103/physrevstab.9.100702 fatcat:zqh7eljptbdx5botkbw7wwrakm