  We report our comparison study on the first stage electron bunch compression
schemes at 750 MeV using a conventional and a double C-chicane for the X-ray
free electron laser (XFEL) under development for the Matter-Radiation
Interactions in Extremes (MaRIE) project at Los Alamos National Laboratory.
Compared to the performance of the conventional C-chicane bunch compressor, the
double C-chicane scheme exhibits the capability of utilizing the transverse
momentum shift induced by the coherent synchrotron radiation (CSR) in the
second C-chicane to compensate that generated in the first C-chicane, resulting
in a compressed electron bunch with minimized transverse momentum along the
beam. It is also found that the double C-chicane scheme can be designed to
significantly better preserve the beam emittance in the course of the bunch
compression. This is particularly beneficial for the MaRIE XFEL whose lasing
performance critically depends on the preservation of the ultralow beam
emittance.
