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Results for “self-seeding”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 19 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2021

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

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. Additionally, at the Pohang Accelerator Laboratory XFEL, we have demonstrated a hard X-ray self-seeded XFEL with a peak brightness of 3.2 × 10 35 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 × 10 35 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.

47 OTHER INSTRUMENTATION↗
DOE OSTI2020

Two-stage reflective self-seeding scheme for high-repetition-rate X-ray free-electron lasers

X-ray free-electron lasers (XFELs) open a new era of X-ray based research by generating extremely intense X-ray flashes. To further improve the spectrum brightness, a self-seeding FEL scheme has been developed and demonstrated experimentally. As the next step, new-generation FELs with high repetition rates are being designed, built and commissioned around the world. A high repetition rate would significantly speed up the scientific research; however, alongside this improvement comes new challenges surrounding thermal management of the self-seeding monochromator. Here, a new configuration for self-seeding FELs is proposed, operated under a high repetition rate which can strongly suppress the thermal effects on the monochromator and provides a narrow-bandwidth FEL pulse. Three-dimension time-dependent simulations have been performed to demonstrate this idea. Finally, with this proposed configuration, high-repetition-rate XFEL facilities are able to generate narrow-bandwidth X-ray pulses without obvious thermal concern on the monochromators.

38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEA↗
DOE OSTI2020

Enhanced Self-Seeding with Ultrashort Electron Beams

In this paper, we describe a new method to produce intensity stable, highly coherent, narrow-band x-ray pulses in self-seeded free electron (FEL) lasers. The approach uses an ultrashort electron beam to generate a single spike FEL pulse with a wide coherent bandwidth. The self-seeding monochromator then notches out a narrow spectral region of this pulse to be amplified by a long portion of electron beam to full saturation. In contrast to typical self-seeding where monochromatization of noisy self-amplified spontaneous emission pulses leads to either large intensity fluctuations or multiple frequencies, we show that this method produces a stable, coherent FEL output pulse with statistical properties similar to a fully coherent optical laser.

43 PARTICLE ACCELERATORS↗
DOE OSTI2020

High-Brightness Self-seeded X-ray Free Electron Laser to Precisely Map Macromolecular Structure

Two datasets were uploaded. Run numbers #r0101~#r0112 were collected from self-seeded XFEL mode. Run numbers #r0079~#r0088 and #r0090 were collected from SASE mode. The run number is shown in the file name as "ue_191027_SFX_runnumber-c00.cxi.". To understand the effect of self-seeded XFEL source, we used the datasets from run numbers #r0102 to #r0112. Datasets used were randomly chosen. - SS1 is from #r0102~#r0112. - SS2 is from #r0102~#r0105 and #r0109. - SS3 is from #r0104 and #r0105. To compare self-seeded mode and SASE mode, we also used corresponding three SASE datasets labeled as SASE1, SASE2, and SASE3 from run numbers #r0079 to #r0089. Datasets used were randomly chosen. - SASE1 is from #r0079~#r0089. - SASE2 is from #r0080, #r0081, #r0085, #r0087. - SASE3 is composed of #r0079, #r0080.

Lysozyme↗
DOE OSTI2022

Characterization of a hard X-ray self-seeding diamond crystal orientation

We present a method to accurately control the photon energies for hard X-ray Self-seeding schemes with a single crystal monochromator in transmissive geometry. The energy calibration is performed by measuring which pairs of the machine pitch and yaw angles for different crystallographic planes reflect the X-ray at the same wavelength. The free parameters of an analytical formula for the self-seeding energies are determined by fitting the observed intersections and the normalized derivative with respect to the pitch and yaw angles in the observed intersections. The method requires a hard X-ray spectrometer, but it does not rely on its absolute energy calibration. Instead, identifying the self-seeded energies above the SASE background or the monochromatic notches within the SASE bandwidth is sufficient for the calibration.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2023

Cascaded hard X-ray self-seeded free-electron laser at megahertz repetition rate

High-resolution X-ray spectroscopy in the sub-nanosecond to femtosecond time range requires ultrashort X-ray pulses and a spectral X-ray flux considerably larger than that presently available. X-ray free-electron laser (XFEL) radiation from hard X-ray self-seeding (HXRSS) setups has been demonstrated in the past and offers the necessary peak flux properties. So far, these systems could not provide high repetition rates enabling a high average flux. We report the results for a cascaded HXRSS system installed at the European XFEL, currently the only operating high-repetition-rate hard X-ray XFEL facility worldwide. A high repetition rate, combined with HXRSS, allows the generation of millijoule-level pulses in the photon energy range of 6–14 keV with a bandwidth of around 1 eV (corresponding to about 1 mJ eV –1 peak spectral density) at the rate of ten trains per second, each train including hundreds of pulses arriving at a megahertz repetition rate. At 2.25 MHz repetition rate and photon energies in the 6–7 keV range, we observed and characterized the heat-load effects on the HXRSS crystals, substantially altering the spectra of subsequent X-ray pulses. We demonstrated that our cascaded self-seeding scheme reduces this detrimental effect to below the detection level. This opens up exciting new possibilities in a wide range of scientific fields employing ultrafast X-ray spectroscopy, scattering and imaging techniques.

47 OTHER INSTRUMENTATION↗
DOE OSTI2022

Self-seeded growth of very large open-structured zeolite nanosheet assemblies with extraordinary micropore accessibility

Zeolite nanosheets (ZNs) offer improved micropore accessibilities and transport properties for enhanced molecular catalysis and separations. However, practical application of the ZN materials is hampered by the lack of efficient synthesis methods. Here, in this work, a ZN self-seeded method is demonstrated for single-step reproduction of flower-like assemblies of very large MFI ZN plates. The ZN plates are ~60 nm-thick stacks of 4-nm-thick single-crystal sheets. The ZN flower growth involves terrace nucleation on the seed surfaces and subsequent ZN epitaxial growth in [010] orientation directed by a diquaternary agent. The open architecture of the assemblies prevented collapse and agglomeration of ZNs during thermal activation that effectively preserved the interconnected intra-sheet and inter-sheet micropore system. Thus, the ZN assemblies exhibited markedly enhanced molecular adsorption capacity and transport diffusivity for the probing xylene molecules as compared to the conventional crystals. The ZN assembly and its harvestable very large-sized ZNs have the potential for developing high-performance ZN adsorbents, catalysts, and molecular-sieve membranes.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Thermal loading on self-seeding monochromators in x-ray free electron lasers

One approach to achieve longitudinally coherent hard X-ray free electron laser (XFEL) radiation is to introduce a single-crystal monochromator in the beam path to generate a co-propagating, time-synchronized self-seeding radiation pulse. For modern high-repetition rate XFELs, however, thermal loading on the crystal can degrade the quality of the seed pulse. To assess limitations on the maximum XFEL pulse repetition rate imposed by the seeding crystal, a comprehensive study of thermomechanical, and X-ray diffraction effects within the crystal is presented in this paper for two consecutive self-amplified spontaneous emission pulses incident on both reflective and transmissive crystal monochromators.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2020

Dynamic pulse-to-pulse thermal load effects in pulse-train-mode self-seeded X-ray free-electron laser

Thermal load has been a haunting factor that undermines the brightness and coherence of the self-seeded X-ray free-electron laser. Additionally, different from uniformly pulsed mode, in pulse train mode a thermal quasi-steady state of the crystal monochromator may not be reached. This leads to a dynamic thermal distortion of the spectral transmission curves and seed quality degradation. In this paper, the pulse-to-pulse thermal load effects on the spectral transmission curves and seed quality are shown, and some instructive information for the tuning process is provided.

47 OTHER INSTRUMENTATION↗
DOE OSTI2020

Split-pulse X-ray photon correlation spectroscopy with seeded X-rays from X-ray laser to study atomic-level dynamics

Abstract With their brilliance and temporal structure, X-ray free-electron laser can unveil atomic-scale details of ultrafast phenomena. Recent progress in split-and-delay optics (SDO), which produces two X-ray pulses with time-delays, offers bright prospects for observing dynamics at the atomic-scale. However, their insufficient pulse energy has limited its application either to phenomena with longer correlation length or to measurement with a fixed delay-time. Here we show that the combination of the SDO and self-seeding of X-rays increases the pulse energy and makes it possible to observe the atomic-scale dynamics in a timescale of picoseconds. We show that the speckle contrast in scattering from water depends on the delay-time as expected. Our results demonstrate the capability of measurement using the SDO with seeded X-rays for resolving the dynamics in temporal and spatial scales that are not accessible by other techniques, opening opportunities for studying the atomic-level dynamics.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Numerical characterization of quasi-steady thermal load for thin crystal at cryogenic temperature with nondiffusive heat transfer

With dramatically improved brightness and repetition rate, the thermal load for crystal optics in x-ray free-electron laser applications has also significantly increased. To mitigate the thermal load, one effective method is cryogenic cooling. However, the emerging nondiffusive heat transfer phenomenon at cryogenic temperature may cause design failure if overlooked. To evaluate the optical performance of thin crystal optics under thermal load at cryogenic temperature, an integrated numerical tool is presented and applied to characterize the thermal load on thin crystals with nondiffusive phenomena accounted. Significant thermally induced distortion of the rocking curve is observed from numerical simulation, leading to potential seed power reduction in hard x-ray self-seeding application. Cryogenic cooling is confirmed necessary by simulation to handle the thermal load at high repetition rate operation.

42 ENGINEERING↗
DOE OSTI2022

Time-dependent dynamical Bragg diffraction in deformed crystals by the beam propagation method

Herein, this paper describes how to efficiently solve time-dependent X-ray dynamic diffraction problems in distorted crystals with a fast Fourier transform based beam propagation method. Examples are given of using the technique to simulate the propagation of X-ray beams in deformed crystals in space and time domains relevant to the cavity-based X-ray free-electron lasers and X-ray free-electron laser self-seeding systems.

36 MATERIALS SCIENCE↗
DOE OSTI2024

High Power Density Thermal Energy Storage With Phase Change Material in Enhanced Compact Heat Exchangers

Abstract Performance of a novel ultracompact thermal energy storage (TES) heat exchanger, designed as a microchannel finned-tube exchanger is presented. With water as the heating–cooling fluid in the microchannels, a salt hydrate phase change material (PCM), lithium nitrate trihydrate (LiNO3 · 3H2O), was encased on the fin side. To establish the hypothesis that small-length-scale encasement (<3 mm) of PCM substantially enhances heat transfer to yield very high power-density energy storage, heat exchanger designs with 10 and 24 fins/inch were considered. They were subjected to thermal cycling, or repeated heating (melting) and cooling (freezing), with inlet fluid flow mimicking diurnal variation between 42 °C and 25 °C (representing typical arid-region conditions) over an accelerated time period. By employing salt self-seeding to obviate subcooling during cooling or recrystallization, the TES was found to exhibit stable long-term (100 heating–cooling cycles) operation with very high PCM-side heat transfer coefficients (∼100–500 W/m2 K) and storage power density (∼160–175 kW/m3). In fact, with optimization of heating–cooling fluid flowrate for given charging–discharging time period and exchanger size, power density >300 kW/m3 can be achieved. The results clearly establish that highly compact heat exchangers used as TES units can provide very high-performance alternatives to conventional ones.

Engineering↗
DOE OSTI2023

49 W carrier-envelope-phase-stable few-cycle 2.1 µm OPCPA at 10 kHz

We demonstrate a mid-infrared optical parametric chirped pulse amplifier (OPCPA), delivering 2.1 µm center wavelength pulses with 20 fs duration and 4.9 mJ energy at 10 kHz repetition rate. This self-seeded system is based on a kW-class Yb:YAG thin-disk amplifier driving a CEP stable short-wavelength-infrared (SWIR) generation and three consecutive OPCPA stages. Our SWIR source achieves an average power of 49 W, while still maintaining excellent phase and average power stability with sub-100 mrad carrier-envelope-phase-noise and 0.8% average power fluctuations. These parameters enable the OPCPA setup to drive attosecond pump probe spectroscopy experiments with photon energies in the water window.

47 OTHER INSTRUMENTATION↗
DOE OSTI2023

Advanced Photon Acceleration Schemes for Tunable XUV/Soft X-Ray Sources

We report on the advances made under the purview of DOE award number DE-SC0019135 that was active during the period: 09/01/2018–08/31/2021. The grant investigated the application of a “flying focus” to the problem of photon acceleration—in which a dynamic refractive index gradient is used to continuously upshift a probe beam’s frequency. Codes were written to describe the creation of ionization waves of arbitrary velocity (IWAVs) for use as a photon-accelerating medium, as well as the behavior of a witness pulse residing in said medium. Experiments first verified the spatiotemporal control over laser intensity provided by a chromatic flying focus, then used that ability to produce small-diameter IWAVs in the far-field with the expected dynamics, and finally demonstrated even further flexibility by producing large-diameter IWAVs in the laser quasi-far-field that maintained the beneficial dynamics. Multiple innovative diagnostics—spectrally resolved Schlieren and spectrally resolved interferometry—were pioneered in order to diagnose the IWAVs. For IWAV production in the laboratory, however, beam quality was identified as a key limitation in the quasi-far-field. Since the original chromatic flying focus was found to result in relatively long (ps duration) intensity peaks, which could limit some applications including photon acceleration, additional techniques were invented to provide similar spatiotemporal control while also retaining ultrashort intensity peaks. While simulations have identified several interesting regimes for photon acceleration—first predicting the upshift of a counterpropagating witness pulse from the optical to the extreme ultraviolet in less than 1 cm, and later obtaining similar shifts in less than 100 μm in a simpler self-seeded configuration—experimental demonstration is left for future work.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗