Schematic design of fully coherent X-ray generation using self-seeded harmonic lasing free-electron lasers

Abstract

This paper studies the self-seeded harmonic lasing scheme and analyzes the feasibility of its application in the SHINE project. The scheme is used to improve the longitudinal coherence and extend the operating spectral range of the X-ray free electron lasers (FELs). Combining the benefits of traditional self-seeding and harmonic lasing schemes, the scheme would be compatible with existing facilities without any device modification. We have compared the harmonic performances under different monochromator types with numerical simulations. And considering the sensitivity to energy spread of the scheme, we also propose several possible solutions. The numerical simulation results show that the third harmonic radiation with GW-level peak power and quasi-full coherence can be achieved. The scheme will be helpful for improving the performance of the SHINE and other X-ray FEL facilities.