High-brightness self-seeded X-ray free-electron laser covering the 3.5 keV to 14.6 keV range

Abstract

We demonstrate a hard-X-ray self-seeded (HXRSS) free-electron laser (FEL) at Pohang Accelerator Laboratory with an unprecedented peak brightness (3.2 × 10 35 photons/(s•mm 2 •mrad 2 •0.1%BW)). The self-seeded FEL generates hard X-ray pulses with improved spectral purity; the average pulse energy was 0.85 mJ at 9.7 keV, almost as high as in SASE mode; the bandwidth (0.19 eV) is about 1/70 as wide, the peak spectral brightness is 40 times higher than in self-ampli ed spontaneous emission (SASE) mode, and the stability is excellent with > 94% of shots exceeding the average SASE intensity. Using this self-seeded XFEL, we conducted serial femtosecond crystallography (SFX) experiments to map the structure of lysozyme protein; data-quality metrics such as R split , multiplicity, and signal-to-noise ratio for the SFX were substantially increased. We precisely map out the structure of lysozyme protein with substantially better statistics for the diffraction data and signi cantly sharper electron density maps compared to maps obtained using SASE mode.

Studying ultrafast Rabi dynamics with a short-wavelength seeded free-electron laser

“…Together with our experimental approach of using two-photon ionization as an in-situ probe of the coherent population transfer, which does not rely on any additional laser probe field, the scheme proposed here becomes applicable to other quantum systems as well. With the ongoing developments of seeded FEL facilities around the world 35,36 capable of providing coherent light pulses down to few-ångstrom wavelength, our findings can inspire future studies involving core-level electrons in multi-electronic targets, such as molecules, and nano-objects at ultrafast timescales.…”

Achievement and prospect of the PAL-XFEL

“…At the PAL-XFEL, we demonstrated a hard-X-ray selfseeded (HXRSS) XFEL with an unprecedented peak brightness at 9.7 keV [11]. The self-seeded mode had 12 times higher average peak spectral intensity than the SASE mode (Fig.…”

A perfect X-ray beam splitter and its applications to time-domain interferometry and quantum optics exploiting free-electron lasers

“…Here, the strongest contribution arises from the shot-to-shot fluctuation in the electron-beam parameters due to the micro-bunch instability. In seeded FELs, this becomes apparent in the so-called pedestal of the spectra ( 18 , 19 , 43 ). For our application, this results in a loss of coherence between the two pulses (damping of first-order correlation function shown in Fig.…”