Stable Generation of High Power Self-seeded XFEL at SACLA

A self-seeded XFEL system using a transmitted beam under Bragg diffraction has been developed at the compact XFEL facility SACLA, in order to generate a brilliant single-mode XFEL with high temporal coherence. The self-seeding setup composed of a small magnetic chicane that can generate up to 50 fs temporal delay and a diamond single crystal with the thickness of 180 m were installed by 2013. In the beam commissioning, a monochromatic X-ray enhancement at 10 keV due to the self-seeding was observed using the single-shot spectrometer. The integrated peak intensity over 100 shorts was 5 times higher than that without seeding. The spectral bandwidth of the seeded FEL was about 3 eV in FWHM, about 1/10 of that of SASE. The hit rate was more than 80%, which was promising for future practical use. Further optimization and a long-term stabilization will be planned in the next commissioning.