Synchrotron Radiation Light Source Research Articles

Valence and Rydberg excitations of 3-fluorotoluene in the 4.4–10.8 eV photoabsorption energy region

The absolute photoabsorption cross sections for 3-fluorotoluene in the 4.4–10.8 eV energy-range were obtained for the first-time using a synchrotron radiation light source. New theoretical calculations, providing vertical excitation energies and oscillator strengths, were performed at the time-dependent density functional theory and the equation-of-motion coupled cluster method restricted to single and double excitations to qualitatively support the experimental data. The electronic transitions discernible in the photoabsorption spectrum have been assigned to valence, mixed valence-Rydberg and Rydberg transitions. Additionally, a comprehensive assignment of the vibronic structure was performed with the main contribution of C–H in plane bending mode progressions dictating the spectroscopy of the lowest-lying absorption band. From the absolute photoabsorption cross sections, the photolysis lifetimes of 3-fluorotoluene in the Earth's atmosphere were also obtained.

Synchrotron light source X-ray detection with Low-Gain Avalanche Diodes

Low Gain Avalanche Diodes (LGADs) represent the state-of-the-art in timing measurements and will instrument the future Timing Detectors of ATLAS and CMS for the High-Luminosity LHC. While initially conceived as a sensor for charged particles, the intrinsic gain of LGADs makes it possible to detect low-energy X-rays with good energy resolution and excellent time resolution (tens of picoseconds). Using the Stanford Synchrotron Radiation Lightsource (SSRL) at SLAC, several LGADs designs were characterized with energies from 5 to 70 keV. The SSRL provides 10 ps pulsed X-ray bunches separated by 2 ns intervals with an energy dispersion (ΔE/E) of 10-4. LGADs from Hamamatsu Photonics (HPK) and Brookhaven National Laboratory (BNL) with different thicknesses ranging from 20 μm to 50 μm and different gain layer designs were read out using fast amplification boards and digitized with a high bandwidth and high sampling rate oscilloscope. PIN devices from HPK and AC-LGADs from BNL were characterized as well. A systematic and detailed characterization of the devices' energy linearity, resolution, and time resolution as a function of X-ray energy was performed for different biasing voltages at room temperature and are reported in this work. The charge collection and multiplication mechanism were simulated using Geant4 and TCAD Sentaurus, providing an important handle for interpreting the data.

Remote and automated high-throughput powder diffraction measurements enabled by a robotic sample changer at SSRL beamline 2-1.

The general-purpose powder diffractometer beamline (BL2-1) at the Stanford Synchrotron Radiation Lightsource (SSRL) is described. The evolution of design and performance of BL2-1 are presented, in addition to current operating specifications, applications and measurement capabilities. Recent developments involve a robotic sample changer enabling high-throughput X-ray diffraction measurements, applicable to mail-in and remote operations. In situ and operando capabilities to measure samples with different form factors (e.g. capillary, flat plate or thin film, and transmission) and under variable experimental conditions are discussed. Several example datasets and accompanying Rietveld refinements are presented.

Solution phase high repetition rate laser pump x-ray probe picosecond hard x-ray spectroscopy at the Stanford Synchrotron Radiation Lightsource.

We present a dedicated end-station for solution phase high repetition rate (MHz) picosecond hard x-ray spectroscopy at beamline 15-2 of the Stanford Synchrotron Radiation Lightsource. A high-power ultrafast ytterbium-doped fiber laser is used to photoexcite the samples at a repetition rate of 640 kHz, while the data acquisition operates at the 1.28 MHz repetition rate of the storage ring recording data in an alternating on-off mode. The time-resolved x-ray measurements are enabled via gating the x-ray detectors with the 20 mA/70 ps camshaft bunch of SPEAR3, a mode available during the routine operations of the Stanford Synchrotron Radiation Lightsource. As a benchmark study, aiming to demonstrate the advantageous capabilities of this end-station, we have conducted picosecond Fe K-edge x-ray absorption spectroscopy on aqueous [FeII(phen)3]2+, a prototypical spin crossover complex that undergoes light-induced excited spin state trapping forming an electronic excited state with a 0.6-0.7 ns lifetime. In addition, we report transient Fe Kβ main line and valence-to-core x-ray emission spectra, showing a unique detection sensitivity and an excellent agreement with model spectra and density functional theory calculations, respectively. Notably, the achieved signal-to-noise ratio, the overall performance, and the routine availability of the developed end-station have enabled a systematic time-resolved science program using the monochromatic beam at the Stanford Synchrotron Radiation Lightsource.

Exploring beam size measurement based on the Talbot effect at BEPCII.

Vertical beam size measurements were carried out at Beijing Electron-Positron Collider II (BEPCII) using a phase grating and an absorption grating based on the Talbot effect. The transverse coherence of synchrotron radiation is closely related to beam size. Due to the partial coherence of the synchrotron radiation source, the coherence length can be calculated by measuring the visibility decay of interferograms recorded at different distances behind the gratings. A vertical beam size of 68.19 ± 2 µm was obtained based on the relationship between the coherence length and beam size at the 3W1 beamline of BEPCII. A comparison of the vertical emittance derived from the grating Talbot method and the synchrotron radiation visible light interferometer method was presented. The vertical emittances from the two methods are 1.41 nm rad and 1.40 nm rad, respectively. The 0.1% difference indicates that the grating Talbot method for beam size measurement is reliable. This technique has great potential for small beam size measurement of fourth-generation synchrotron radiation light sources, considering its small diffraction limitation and simple experimental setups.

Remote-access X-ray spectroscopy at the Stanford Synchrotron Radiation Lightsource

Remote-access X-ray spectroscopy at the Stanford Synchrotron Radiation Lightsource

Phase Engineering and Synchrotron-Based Study on Two-Dimensional Energy Nanomaterials.

In recent years, there has been significant interest in the development of two-dimensional (2D) nanomaterials with unique physicochemical properties for various energy applications. These properties are often derived from the phase structures established through a range of physical and chemical design strategies. A concrete analysis of the phase structures and real reaction mechanisms of 2D energy nanomaterials requires advanced characterization methods that offer valuable information as much as possible. Here, we present a comprehensive review on the phase engineering of typical 2D nanomaterials with the focus of synchrotron radiation characterizations. In particular, the intrinsic defects, atomic doping, intercalation, and heterogeneous interfaces on 2D nanomaterials are introduced, together with their applications in energy-related fields. Among them, synchrotron-based multiple spectroscopic techniques are emphasized to reveal their intrinsic phases and structures. More importantly, various in situ methods are employed to provide deep insights into their structural evolutions under working conditions or reaction processes of 2D energy nanomaterials. Finally, conclusions and research perspectives on the future outlook for the further development of 2D energy nanomaterials and synchrotron radiation light sources and integrated techniques are discussed.

Visualizing Catalytic Dynamics Processes via Synchrotron Radiation Multitechniques.

The importance of catalysts today as workhorses in most modern industrial fields cannot be downplayed. As a result, rational design and engineering of targeted catalysts have emerged as key objectives and are dependent on in-depth understanding of complex catalytic dynamics. Synchrotron radiation (SR) light sources with rich advanced experimental methods are being recognized as a comprehensive characterization platform, which can draw a full picture on such multiparameter-involved catalysis under actual working conditions. Herein, the recent progress of catalytic dynamics process studied by the means of various SR techniques is summarized. In particular, SR-based spectroscopic, scattering, and imaging investigations on true catalysts are first introduced with the potential of in situ and operando characterizations. Apparently, the limitations from single SR technique naturally prompt a simple combination of SR techniques to better understand the whole catalysis process. Moreover, the discrepancies among various online testing facilities and batches of samples, along with random/systematic errors introduced by traditional intermittent/asynchronous measurement make it imperative to develop more prolific systems, complementary of multiple SR techniques for deep probing of dynamic catalytic processes. It is believed that the booming new light sources can further enrich the current multiple SR techniques, and thus may realize the true visualization on future catalytic dynamic processes.

Lattice misorientation at domain boundaries in β‐Ga2O3 single‐crystal substrates observed via synchrotron radiation X‐ray diffraction imaging and X‐ray reticulography

AbstractTo evaluate the lattice misorientation at domain boundaries (DBs) in β‐Ga2O3, we performed X‐ray diffraction imaging (XRDI), X‐ray reticulography (XRR), and X‐ray topography (XRT) using a synchrotron radiation light source. Four reciprocal lattice vectors (g‐vectors) were applied, and the DBs showed different visibilities in the XRDI maps depending on the g‐vector. By analyzing possible characteristics of the misorientation, the XRDI results suggested that the DB being investigated was associated with a misorientation on the () plane and contained twist and tilt components. The apparent peak change in XRDI caused by the two components was calculated. We further succeeded in separating the tilt and twist components using XRR images in conjunction with simulation. Dislocation arrays at the DBs were observed using XRT, and the average distance between the dislocations in the array was consistent with the misorientation obtained using XRDI and XRR. The distribution of DBs across a wide area was acquired by a combination of XRR images recorded on a charge‐coupled device camera and X‐ray films. The fringe‐patterned XRR on X‐ray films provided a powerful and nondestructive tool to characterize DBs distributed across a large‐diameter wafer with an angular resolution on the order of several arc sec (low 10−5 rad).

Physics design of the Shenzhen innovation light source storage ring

The Shenzhen innovation light source facility (SILF) is a fourth generation of medium energy synchrotron radiation light source, which focuses on supporting the development of the domestic core industries, basic science frontier research and major strategic requirement, such as integrated circuits, biomedicine, advanced materials and advanced manufacturing. With the Shenzhen Municipal Government's approval of the SILF project proposal on Sep10 2020, the feasibility study of the SILF was completed in 2022, and the preliminary design of the SILF are in progress. The accelerator complex is composed of the 200 MeV linac, the 0.2–3.0 GeV booster and the 3.0 GeV storage ring. The circumference of the storage ring is 696.0 m, which includes 28 hybrid seven-bend achromat lattice periodic units to achieve the emittance below 100 pm·rad. The detailed physics design of the SILF storage ring will be presented in this paper.

Experimental verification and analysis of the beam loading effect based on precise bunch-by-bunch 3D position measurement

The beam loading effect is one of the main bottlenecks in further improving the performance of synchrotron radiation light sources. Although theoretical analysis and numerical simulation of the beam loading effect have been very well performed, the corresponding diagnostic tools were rather poor, and in most cases, only streak cameras were used to observe the synchronous phase distribution and the intensity distribution in bunch trains. SSRF developed a precise bunch-by-bunch 3D beam position measurement system. This system allows precise measurement and recording of both transient state data and steady-state beam parameters (filling pattern, synchronous phase). Therefore, experimental verification and analysis of the beam loading effect can be more comprehensive and accurate. In this paper, the measurement results of the synchronous phase, synchrotron frequency and synchrotron damping time with and without a third harmonic cavity are introduced and discussed.

Abstract TP92: Early Hyperacute Ion Dysregulation Following A Temporary Large Vessel Occlusion Stroke

Introduction: Ion dysregulation is a hallmark of energy failure after onset of ischemic stroke. To better understand the nature of the ion concentration changes in the early hyperacute phase after stroke onset we have quantitatively imaged the trace element distribution in the stroke lesion territory after a 30-minute temporary large vessel occlusion stroke. Methods: A temporary large vessel occlusion stroke was generated with the middle cerebral artery occlusion (MCAO) mouse model (insertion of an occluding filament via the ECA) with reperfusion after 30 minutes (occluding filament withdrawn). C57BL/6 mice (5 per time point) were euthanized at 5-, 30-, 60-, 90-, and 120-minutes post reperfusion. Shams included all surgical procedures, however the occluding filament was withdrawn immediately after insertion. Heads were immediately frozen post mortem and sectioned for trace element mapping. Quantitative X-ray fluorescence microscopy was performed at the Stanford Synchrotron Radiation Lightsource. Results: Loss of potassium is observed throughout the affected tissue at all post-reperfusion time points, with most of the initial loss occurring in the 30-minutes prior to reperfusion. Loss of essential zinc began to be observed 1-hour post reperfusion. No significant elevations in chlorine or calcium were observed during the early hyperacute phase. At subsequent post reperfusion time points the lesion (as defined by diminished potassium) grew steadily for 90-minutes. After 90-minutes post reperfusion some lesions demonstrated a distinct pattern consistent with a central infarct core surrounded by an ischemic penumbra. Conclusions: At all early hyperacute time points the stroke lesion demonstrated on-going potassium dysregulation, despite reperfusion. The loss of potassium was a bulk phenomenon in the tissue. Potassium is essential for maintenance of neuronal membrane potential and therefore function. Restoration of normal blood flow is insufficient to protect the brain from the enduring reduction in vital potassium levels or expansion of the region of ion dysregulation. The lack of available potassium within the affected tissue may hinder recovering neuronal cells from restoring action potentials, even after tissue perfusion is restored.

Experimental setup for high-resolution characterization of crystal optics for coherent X-ray beam applications.

Stanford Synchrotron Radiation Lightsource serves a wide scientific community with its variety of X-ray capabilities. Recently, a wiggler X-ray source located at beamline 10-2 has been employed to perform high-resolution rocking curve imaging (RCI) of diamond and silicon crystals. X-ray RCI is invaluable for the development of upcoming cavity-based X-ray sources at SLAC, including the cavity-based X-ray free-electron laser and X-ray laser oscillator. In this paper, the RCI apparatus is described and experimental results are provided to validate its design. Future improvements of the setup are also discussed.

Beam orbit shift due to BPM thermal deformation using machine learning

Stabilizing beam orbit is critical for advanced synchrotron radiation light sources. The beam orbit can be affected by many sources. To maintain a good orbit stability, global orbit feedback systems (OFB) has been widely used. However, the BPM thermal deformation would lead to BPM misreading, which can not be handled by OFB. Usually, extra diagnostics, such as position transducers, is needed to measure the deformation dependency of BPM readings. Here, an alternative approach by using the machine operation historic data, including BPM temperature, insertion device (ID) gaps and corrector currents, is presented. It is demonstrated at Hefei Light Source (HLS). The average orbit shift due to BPM thermal deformation is about 34.5 μm/°C (horizontal) and 20.0 μm/°C (vertical).

Study on support for HALF beam position monitor displacement measurement system

Hefei Advanced Light Facility (HALF), is a fourth-generation vacuum ultraviolet and X-ray diffraction limit synchrotron radiation (DLSR) light source under preliminary research and construction. Beam position monitor (BPM) displacement measurement system with nanometer resolution is used to correct the BPM data and achieve sub-micron beam orbit stability. In order to make full use of the performance and meet the requirement of HALF’s beam orbit stability, the supports of the system are particularly crucial. The purpose of this paper is to develop a set of support for the BPM displacement system that meet the stability requirements of HALF. A hybrid support with Invar 36 and carbon fiber/epoxy is creatively proposed to achieve stability requirements. Through the calculation of thermal expansion, the analysis of mechanical vibration and finite element analysis (FEA), the hybrid support is adjusted to higher stability. Experiments are conducted and show that the hybrid support has higher stability than traditional support. On the existing experimental platform, the vibration RMS of the hybrid support was measured at 42.6 nm in horizontal and 29.9 nm in vertical and the hybrid support could meet the requirement of HALF’s beam orbit stability.

A new μ-high energy resolution fluorescence detection microprobe imaging spectrometer at the Stanford Synchrotron Radiation Lightsource beamline 6-2.

Here, we describe a new synchrotron X-ray Fluorescence (XRF) imaging instrument with an integrated High Energy Fluorescence Detection X-ray Absorption Spectroscopy (HERFD-XAS) spectrometer at the Stanford Synchrotron Radiation Lightsource at beamline 6-2. The X-ray beam size on the sample can be defined via a range of pinhole apertures or focusing optics. XRF imaging is performed using a continuous rapid scan system with sample stages covering a travel range of 250 × 200mm2, allowing for multiple samples and/or large samples to be mounted. The HERFD spectrometer is a Johann-type with seven spherically bent 100mm diameter crystals arranged on intersecting Rowland circles of 1m diameter with a total solid angle of about 0.44% of 4π sr. A wide range of emission lines can be studied with the available Bragg angle range of ∼64.5°-82.6°. With this instrument, elements in a sample can be rapidly mapped via XRF and then selected features targeted for HERFD-XAS analysis. Furthermore, utilizing the higher spectral resolution of HERFD for XRF imaging provides better separation of interfering emission lines, and it can be used to select a much narrower emission bandwidth, resulting in increased image contrast for imaging specific element species, i.e., sparse excitation energy XAS imaging. This combination of features and characteristics provides a highly adaptable and valuable tool in the study of a wide range of materials.

Complementarity of neutron, XFEL and synchrotron crystallography for defining the structures of metalloenzymes at room temperature.

Room-temperature macromolecular crystallography allows protein structures tobe determined under close-to-physiological conditions, permits dynamic freedom in protein motions and enables time-resolved studies. In the case of metalloenzymes that are highly sensitive to radiation damage, such room-temperature experiments can present challenges, including increased rates of X-ray reduction of metal centres and site-specific radiation-damage artefacts, as well as in devising appropriate sample-delivery and data-collection methods. It can also be problematic to compare structures measured using different crystal sizes and light sources. In this study, structures of a multifunctional globin, dehaloperoxidase B (DHP-B), obtained using several methods of room-temperature crystallographic structure determination are described and compared. Here, data were measured from large single crystals and multiple microcrystals using neutrons, X-ray free-electron laser pulses, monochromatic synchrotron radiation and polychromatic (Laue) radiation light sources. These approaches span a range of 18 orders of magnitude in measurement time per diffraction pattern and four orders of magnitude in crystal volume. The first room-temperature neutron structures of DHP-B are also presented, allowing the explicit identification of the hydrogen positions. The neutron data proved to be complementary to the serial femtosecond crystallography data, with both methods providing structures free of the effects of X-ray radiation damage when compared with standard cryo-crystallography. Comparison of these room-temperature methods demonstrated the large differences in sample requirements, data-collection time and the potential for radiation damage between them. With regard to the structure and function of DHP-B, despite the results being partly limited by differences in the underlying structures, new information was gained on the protonation states of active-site residues which may guide future studies of DHP-B.

Linearly and circularly polarized radiation with a low on-axis heat load from an asymmetric magnet pole undulator

The heavy heat load on optical components from the normal planar undulator has become a serious problem in the synchrotron radiation light source, especially for generating the low-energy photon in a high-energy storage ring and/or a diffraction-limited storage ring. The asymmetric magnet pole undulators have different period lengths between the upper and lower magnet poles. Taking the advantage of the asymmetric magnet pole undulators in building various magnetic fields, this paper proposes a new class of undulators to obtain the specific magnetic fields which can scatter the electron velocity away from the undulator axis. It consists of four magnet arrays and has a similar structure compared to the DELTA/APPLE-X undulator; however, each couple of magnet arrays has a different period length with the period ratio of ${n}_{1}:{n}_{2}$. Taking the one-to-two and two-to-three period ratios as examples, a novel Figure 8 undulator and a novel Knot undulator are demonstrated. The polarization state can be flexibly switched from the linear polarization to the circular polarization by tuning the phase shifts of magnetic fields, with the on-axis heat load greatly suppressed. The heat-load suppressions of linear polarization at two predetermined orthogonal directions are almost the same and fully effective. Analysis and simulations of undulator designs with the corresponding radiation characteristics are reported.

Development of a novel high gradient quadrupole magnet

High gradient quadrupoles are key components for advanced synchrotron radiation light sources. This paper presents the magnet design, the mechanical structure and the magnetic field measurements of a novel high gradient quadrupole magnet. This high gradient quadrupole magnet with a gradient greater than 100 T/m uses permanent magnets (PMs) on the poles to improve the excitation efficiency. The magnetic field measurement results show the feasibility of this magnetic design.

A laser powder bed fusion system for operando synchrotron x-ray imaging and correlative diagnostic experiments at the Stanford Synchrotron Radiation Lightsource.

Laser powder bed fusion (LPBF) is a highly dynamic multi-physics process used for the additive manufacturing (AM) of metal components. Improving process understanding and validating predictive computational models require high-fidelity diagnostics capable of capturing data in challenging environments. Synchrotron x-ray techniques play a vital role in the validation process as they are the only in situ diagnostic capable of imaging sub-surface melt pool dynamics and microstructure evolution during LPBF-AM. In this article, a laboratory scale system designed to mimic LPBF process conditions while operating at a synchrotron facility is described. The system is implemented with process accurate atmospheric conditions, including an air knife for active vapor plume removal. Significantly, the chamber also incorporates a diagnostic sensor suite that monitors emitted optical, acoustic, and electronic signals during laser processing with coincident x-ray imaging. The addition of the sensor suite enables validation of these industrially compatible single point sensors by detecting pore formation and spatter events and directly correlating the events with changes in the detected signal. Experiments in the Ti-6Al-4V alloy performed at the Stanford Synchrotron Radiation Lightsource using the system are detailed with sufficient sampling rates to probe melt pool dynamics. X-ray imaging captures melt pool dynamics at frame rates of 20 kHz with a 2 µm pixel resolution, and the coincident diagnostic sensor data are recorded at 470 kHz. This work shows that the current system enables the in situ detection of defects during the LPBF process and permits direct correlation of diagnostic signatures at the exact time of defect formation.