Multicolor Operation and Spectral Control in a Gain-Modulated X-ray Free Electron Laser.

摘要

We show that modulating the gain in magnetic undulators can control the spectral properties of a SASE x-ray free-electron laser, producing one or several spectral lines within a single few femtosecond pulse. By varying the magnetic field along the undulator and the electron beam transport line, the system we propose can tailor the X-ray spectrum to optimally meet numerous experimental requirements such as spectral narrowing, broadening, or multi-color operation.