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A machine-learning-based beam optimizer has been implemented to maximize the spectral brightness of the X-ray free-electron laser (XFEL) pulses of SACLA. A new high-resolution single-shot inline spectrometer capable of resolving features of the order of a few electronvolts was employed to measure and evaluate XFEL pulse spectra. Compared with a simple pulse-energy-based optimization, the spectral width was narrowed by half and the spectral brightness was improved by a factor of 1.7. The optimizer significantly contributes to efficient machine tuning and improvement of XFEL performance at SACLA. [ABSTRACT FROM AUTHOR]

A simple spectrometer using diffraction from diamond microcrystals has been developed to diagnose single-shot spectra of X-ray free-electron laser (XFEL) pulses. The large grain size and uniform lattice constant of the adopted crystals enable characterizing the XFEL spectrum at a resolution of a few eV from the peak shape of the powder diffraction profile. This single-shot spectrometer has been installed at beamline 3 of SACLA and is used for daily machine tuning. [ABSTRACT FROM AUTHOR]

This paper proposes and demonstrates a simple method using the intensity correlation of X‐ray fluorescence to evaluate the focused beam size of an X‐ray free‐electron laser (XFEL). This method was applied to the sub‐micrometre focused XFEL beam at the SPring‐8 Angstrom Compact Free Electron Laser, and the beam size evaluated using the proposed method was consistent with that measured using the knife‐edge scan method. The proposed method is readily applicable to extremely small X‐ray spots and can be applied for the precise diagnostics of sub‐10 nm focused X‐ray beams which have recently emerged. [ABSTRACT FROM AUTHOR]

The SPring‐8 Ångstrom Compact free‐electron LAser (SACLA) began parallel operation of three beamlines (BL1–3) in autumn 2017 to increase the user beam time of the X‐ray free‐electron laser. The success of the multiple‐beamline operation is based on two technological achievements: (i) the fast switching operation of the SACLA main linear accelerator, which provides BL2 and BL3 with pulse‐by‐pulse electron beams, and (ii) the relocation and upgrade of the SPring‐8 Compact SASE Source for BL1, for the generation of a soft X‐ray free‐electron laser. Moreover, the photon beamlines and experimental stations were upgraded to facilitate concurrent user experiments at the three beamlines and accommodate more advanced experiments. The parallel operation of three free‐electron laser (FEL) beamlines was first conducted using the SPring‐8 Ångstrom Compact free‐electron LAser (SACLA), to offer more opportunities for advanced studies using X‐ray FELs. [ABSTRACT FROM AUTHOR]

An experimental platform using X‐ray free‐electron laser (XFEL) pulses with high‐intensity optical laser pulses is open for early users' experiments at the SACLA XFEL facility after completion of the commissioning. The combination of the hard XFEL and the high‐intensity laser provides capabilities to open new frontiers of laser‐based high‐energy‐density science. During the commissioning phase, characterization of the XFEL and the laser at the platform has been carried out for the combinative utilization as well as the development of instruments and basic diagnostics for user experiments. An overview of the commissioning and the current capabilities of the experimental platform is presented. An experimental platform using X‐ray free‐electron laser (XFEL) pulses with high‐intensity optical laser pulses has been developed at the SACLA XFEL facility. An overview of the commissioning and the capabilities of the experimental platform is presented. [ABSTRACT FROM AUTHOR]

An X‐ray prism for the extraction of a specific harmonic of undulator radiation is proposed. By using the prism in a grazing incidence geometry, the beam axes of fundamental and harmonics of undulator radiation are separated with large angles over 10 µrad, which enables the selection of a specific harmonic with the help of apertures, while keeping a high photon flux. The concept of the harmonic separation was experimentally confirmed using X‐ray beams from the X‐ray free‐electron laser SACLA. [ABSTRACT FROM AUTHOR]

X‐ray free‐electron laser (XFEL) pulses from SPring‐8 Ångstrom Compact free‐electron LAser (SACLA) with a temporal duration of <10 fs have provided a variety of benefits in scientific research. In a previous study, an arrival‐timing monitor was developed to improve the temporal resolution in pump–probe experiments at beamline 3 by rearranging data in the order of the arrival‐timing jitter between the XFEL and the synchronized optical laser pulses. This paper presents Timing Monitor Analyzer (TMA), a software package by which users can conveniently obtain arrival‐timing data in the analysis environment at SACLA. The package is composed of offline tools that pull stored data from cache storage, and online tools that pull data from a data‐handling server in semi‐real time during beam time. Users can select the most suitable tool for their purpose, and share the results through a network connection between the offline and online analysis environments. [ABSTRACT FROM AUTHOR]

Direct metrology of coherent short-wavelength beamlines is important for obtaining operational beam characteristics at the experimental site. However, since beam-time limitation imposes fast metrology procedures, a multi-parametric metrology from as low as a single shot is desirable. Here a two-dimensional (2D) procedure based on high-resolution Fresnel diffraction analysis is discussed and applied, which allowed an efficient and detailed beamline characterization at the SACLA XFEL. So far, the potential of Fresnel diffraction for beamline metrology has not been fully exploited because its high-frequency fringes could be only partly resolved with ordinary pixel-limited detectors. Using the high-spatial-frequency imaging capability of an irradiated LiF crystal, 2D information of the coherence degree, beam divergence and beam quality factor M2 were retrieved from simple diffraction patterns. The developed beam metrology was validated with a laboratory reference laser, and then successfully applied at a beamline facility, in agreement with the source specifications. [ABSTRACT FROM AUTHOR]

A data processing pipeline for serial femtosecond crystallography at SACLA was developed, based on Cheetah [] and CrystFEL []. The original programs were adapted for data acquisition through the SACLA API, thread and inter-node parallelization, and efficient image handling. The pipeline consists of two stages: The first, online stage can analyse all images in real time, with a latency of less than a few seconds, to provide feedback on hit rate and detector saturation. The second, offline stage converts hit images into HDF5 files and runs CrystFEL for indexing and integration. The size of the filtered compressed output is comparable to that of a synchrotron data set. The pipeline enables real-time feedback and rapid structure solution during beamtime. [ABSTRACT FROM AUTHOR]

Obituary for Hiromichi Kamitsubo [ABSTRACT FROM AUTHOR]