The Free-Electron Laser in Hamburg (FLASH) has been operated so far in the Self-Amplified-Spontaneous-Emission (SASE) mode. The FEL process starts from noise and as a result the output radiation has poor longitudinal coherence. An option to improve coherence is to stimulate the FEL radiation with an external so-called "seed" laser beam. This concept has been implemented in the framework of the seeding project "sFLASH" at FLASH. In this work, the wavefront of the seed laser at 38 nm is investigated. The influence of aberrant wavefronts on the experiment is studied in numerical simulations as...
The Free-Electron Laser in Hamburg (FLASH) has been operated so far in the Self-Amplified-Spontaneous-Emission (SASE) mode. The FEL process starts fro...