Initial characterization of coherent synchrotron radiation effects in the APS bunch compressor

A chicane bunch compressor was recently installed in the Advanced Photon Source (APS) linac in support of the Low-Energy Undulator Test Line (LEUTL) free-electron laser (FEL) project. As in any magnetic compression system, the use of bending magnets raises concerns about corruption of the emittance by coherent synchrotron radiation (CSR). In this paper, we present results of an initial characterization of these effects in the APS system. We also compare the measurements to simulations with the program elegant. The horizontally bending compressor is equipped with numerous diagnostics to aid in the exploration and reduction of CSR effects. These include: a flag in the chicane center for imaging the energy distribution; a flag for critical beam size tuning at the exit of the final chicane dipole; a vertical-bending spectrometer line downstream of the chicane with two flags for imaging CSR-induced correlations between horizontal and energy coordinates; and a three-flag emittance measurement system downstream of the chicane