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TY - UNPB AU - Inoue, I. AU - Hara, T. ED - Schaa, Volker R.W. ED - Decking, Winfried ED - Sinn, Harald ED - Geloni, Gianluca ED - Schreiber, Siegfried ED - Marx, Michaela TI - Reflection Self-Seeding at SACLA J2 - Proc. of FEL2019, Hamburg, Germany, 26-30 August 2019 CY - Hamburg, Germany T2 - Free Electron Laser Conference T3 - 39 LA - english AB - XFEL are widely operated based on the self-amplified spontaneous emission (SASE) scheme, where spontaneous radiation originating from density modulations in the electron beam is amplified along periodic magnetic field in undulators. Although the SASE scheme effectively produces intense X-ray beams, the stochastic starting-up processes cause poor temporal coherence and a broad spectrum. To narrow the bandwidth while keeping high intensity, we have recently developed an efficient seeding scheme at SACLA, called reflection self-seeding; the SASE-XFEL beam in the first-half undulators is monochromatized via Bragg reflection of a silicon channel-cut crystal, and the monochromatic seed is amplified in the remaining undulators. By applying this scheme to SACLA, we succeeded in producing nearly Fourier-transform-limited XFEL pulses, corresponding to an increase of spectral brightness by a factor of six with respect to the SASE-XFEL [1]. In this presentation, I will talk about the concept of the reflection self-seeding and technical details. Also, I will report on the current operation status and future perspectives of the reflection self-seeding at SACLA. PB - JACoW Publishing CP - Geneva, Switzerland ER -