A self-seeded X-ray free-electron laser (XFEL) is a promising approach to realize bright, fully coherent free-electron laser (FEL) sources in the hard X-ray domain that have been a long-standing ...issue with longitudinal coherence remaining challenging. At the Pohang Accelerator Laboratory XFEL, we have demonstrated a hard X-ray self-seeded XFEL with a peak brightness of 3.2 × 1035 photons s–1 mm–2 mrad–2 0.1% bandwidth (BW)–1 at 9.7 keV. The bandwidth (0.19 eV) is about 1/70 times as wide (close to the Fourier transform limit) and the peak spectral brightness is 40 times higher than in self-amplified spontaneous emission (SASE), with substantial improvements in the stability of self-seeding and noticeably suppressed pedestal effects. We could reach an excellent self-seeding performance at a photon energy of 3.5 keV (lowest) and 14.6 keV (highest) with the same stability as the 9.7 keV self-seeding. The bandwidth of the 14.6 keV seeded FEL was 0.32 eV, and the peak brightness was 1.3 × 1035 photons s–1 mm–2 mrad–2 0.1%BW–1. We show that the use of seeded FEL pulses with higher reproducibility and a cleaner spectrum results in serial femtosecond crystallography data of superior quality compared with data collected using SASE mode.A hard X-ray self-seeded X-ray free-electron laser at the Pohang Accelerator Laboratory provides X-ray pulses with peak brightness of 3.2 × 1035 photons s–1 mm–2 mrad–2 0.1%BW–1 at 9.7 keV and a very small shot-to-shot electron energy jitter of 0.012%.
Characterization of the Percival detector with soft X‐rays Marras, Alessandro; Correa, Jonathan; Lange, Sabine ...
Journal of synchrotron radiation,
January 2021, 2021-Jan-01, 2021-01-01, 20210101, 2021, Volume:
28, Issue:
1
Journal Article
Peer reviewed
Open access
In this paper the back‐side‐illuminated Percival 2‐Megapixel (P2M) detector is presented, along with its characterization by means of optical and X‐ray photons. For the first time, the response of ...the system to soft X‐rays (250 eV to 1 keV) is presented. The main performance parameters of the first detector are measured, assessing the capabilities in terms of noise, dynamic range and single‐photon discrimination capability. Present limitations and coming improvements are discussed.
Characterization of the Percival 2Megapixel detector with soft X‐rays is presented.
A wake monochromator based on a large‐area diamond single crystal for hard X‐ray self‐seeding has been successfully installed and commissioned in the hard X‐ray free‐electron laser (FEL) at the ...Pohang Accelerator Laboratory with international collaboration. For this commissioning, the self‐seeding was demonstrated with a low bunch charge (40 pC) and the nominal bunch charge (180 pC) of self‐amplified spontaneous emission (SASE) operation. The FEL pulse lengths were estimated as 7 fs and 29.5 fs, respectively. In both cases, the average spectral brightness increased by more than three times compared with the SASE mode. The self‐seeding experiment was demonstrated for the first time using a crystal with a thickness of 30 µm, and a narrow bandwidth of 0.22 eV (full width at half‐maximum) was obtained at 8.3 keV, which confirmed the functionality of a crystal with such a small thickness. In the nominal bunch‐charge self‐seeding experiment, the histogram of the intensity integrated over a 1 eV bandwidth showed a well defined Gaussian profile, which is evidence of the saturated FEL and a minimal electron‐energy jitter (∼1.2 × 10−4) effect. The corresponding low photon‐energy jitter (∼2.4 × 10−4) of the SASE FEL pulse, which is two times lower than the Pierce parameter, enabled the seeding power to be maximized by maintaining the spectral overlap between SASE FEL gain and the monochromator.
Hard X‐ray self‐seeding based on a diamond wake monochromator has been commissioned at PAL‐XFEL using various bunch charges and crystals. The performances of self‐seeding and low electron‐energy jitter (∼10−4) are discussed.
The past, current and planned future developments of X-ray imagers in the Photon-Science Detector Group at DESY-Hamburg is presented. the X-ray imagers are custom developed and tailored to the ...different X-ray sources in Hamburg, including the storage ring PETRA III/IV; the VUV-soft X-ray free electron laser FLASH, and the European Free-Electron Laser. Each source puts different requirements on the X-ray detectors, which is described in detail, together with the technical solutions implemented.
The hard X-ray free-electron laser at the Pohang Accelerator Laboratory (PAL-XFEL) in the Republic of Korea achieved saturation of a 0.144 nm free-electron laser beam on 27 November 2016, making it ...the third hard X-ray free-electron laser in the world, following the demonstrations of the Linac Coherent Light Source (LCLS) and the SPring-8 Angstrom Compact Free Electron Laser (SACLA). The use of electron-beam-based alignment incorporating undulator radiation spectrum analysis has allowed reliable operation of PAL-XFEL with unprecedented temporal stability and dispersion-free orbits. In particular, a timing jitter of just 20 fs for the free-electron laser photon beam is consistently achieved due to the use of a state-of-the-art design of the electron linear accelerator and electron-beam-based alignment. The low timing jitter of the electron beam makes it possible to observe Bi(111) phonon dynamics without the need for timing-jitter correction, indicating that PAL-XFEL will be an extremely useful tool for hard X-ray time-resolved experiments. The Pohang Accelerator Laboratory X-ray Free Electron Laser (PAL-XFEL) in South Korea has now entered operation with a timing jitter of just 20 fs.
The Pohang Accelerator Laboratory X‐ray Free‐Electron Laser (PAL‐XFEL) is a recently commissioned X‐ray free‐electron laser (XFEL) facility that provides intense ultrashort X‐ray pulses based on the ...self‐amplified spontaneous emission process. The nano‐crystallography and coherent imaging (NCI) hutch with forward‐scattering geometry is located at the hard X‐ray beamline of the PAL‐XFEL and provides opportunities to perform serial femtosecond crystallography and coherent X‐ray diffraction imaging. To produce intense high‐density XFEL pulses at the interaction positions between the X‐rays and various samples, a microfocusing Kirkpatrick–Baez (KB) mirror system that includes an ultra‐precision manipulator has been developed. In this paper, the design of a KB mirror system that focuses the hard XFEL beam onto a fixed sample point of the NCI hutch, which is positioned along the hard XFEL beamline, is described. The focusing system produces a two‐dimensional focusing beam at approximately 2 µm scale across the 2–11 keV photon energy range. XFEL pulses of 9.7 keV energy were successfully focused onto an area of size 1.94 µm × 2.08 µm FWHM.
Microfocusing of hard X‐ray free‐electron laser pulses using Kirkpatrick–Baez mirrors at the nano‐crystallography and coherent imaging hutch of the Pohang Accelerator Laboratory X‐ray Free‐Electron Laser facility is reported.
A thin-film deposition system was developed for the surface coating of X-ray mirrors of up to 1 m in length. With two coating process areas and four sputtering cathodes, various combinations ...employing a single layer, multilayered, and co-sputtered thin films are possible. Furthermore, it is possible to correct and modify the mirror surface shape by controlling the speed of the substrate stage. In this study, to evaluate the performance of the proposed coating system, the static coating distribution was measured to check the vertical direction. In a 10 mm area, a 0.9% peak-to-valley error and 0.2% root mean square error occurred. A differential deposition test was also performed for the horizontal direction (stage scan direction). In this study, arbitrary shapes were deposited on 100-mm and 400-mm-long mirrors. After removing the measurement error, the deposition error was less than 1 nm (peak-to-valley). The results demonstrate that this system can correct the surface of an X-ray mirror with ultra-high precision.
Display omitted
•System developed for surface coating of X-ray mirrors of up to 1 m long.•Differential deposition by two coating process areas and four sputtering cathodes.•Mirror surface shape corrected and modified by control of substrate stage speed.•The deposition error was less than 1 nm (peak-to-valley).•This system can correct the surface of an X-ray mirror with ultra-high precision.
PDF
