Atomic inner-shell radiation seeded free-electron lasers

Abstract

In order to effectively improve the output quality of x-ray free electron laser (XFEL), we theoretically propose an XFEL scheme seeded by atomic inner-shell laser. Atomic inner-shell lasers based on neutral atoms and pumped by XFEL have been experimentally demonstrated [Rohringer et al., Nature (London) 481, 488 (2012)NATUAS0028-083610.1038/nature10721, Yoneda et al., Nature (London) 524, 446 (2015)NATUAS0028-083610.1038/nature14894], which produced sub-femtosecond X-ray pulses with increased temporal coherence. It shows that, by using the inner-shell laser as a seed to modulate the electron bunch, very stable and almost fully-coherent short-wavelength XFEL pulses can be generated. The proposed scheme holds promising prospects in x-ray wavelengths, and even shorter.