An asymmetric four-bend S-chicane compressor immune to coherent synchrotron radiation effects

The most significant advances in x-ray free electron lasers (FELs) have been driven by the development of ingenious bunch compressors and high-brightness sources in the last several decades. Coherent synchrotron radiation (CSR) is considered a disruptive effect that hinders the reach of design targets, and its control is of essential importance for bunch compression to avoid beam phase-space quality degradation, especially transverse emittance dilution. Herein, we demonstrate a design to cancel the CSR-driven emittance excitation by arranging four adjacent bends into an asymmetric S-chicane without any use of additional components. The CSR-induced emittance growth of the proposed chicane is found to be drastically reduced by nearly one order of magnitude compared with the nominal symmetric C-chicane by particle tracking simulation. This breakthrough opens the door for the bunch compressors to meet the ever-increasing demands of future accelerator applications, especially important in the field of FELs.