Advanced Light Source Research Articles

Polarization control at the microscopic and electronic structure observatory

The new Microscopic and Electronic Structure Observatory (MAESTRO) at the Advanced Light Source (ALS) in Berkeley provides X-rays of variable polarization, produced by an elliptically polarized undulator (EPU), for angle resolved photoemission (ARPES) and photoemission electron microscopy (PEEM) experiments. The interpretation of photoemission data, in particular of dichroism effects in ARPES, requires the precise knowledge of the exact polarization state. Numerical simulations show that the first harmonics of the EPU at MAESTRO provides soft X-rays of almost 100% on axis polarization. However, the higher harmonics as well as the downstream optical elements of the beamline, have a considerable impact on the polarization of the light delivered to the experimental end-station. Employing a simple reflective polarimeter, the polarization is characterized for variable EPU and beamline settings and the overall degree of polarization in the MAESTRO end-stations is estimated to be on the order of 83%.

Simulation of trajectory correction in early commissioning of the Advanced Light Source upgrade

The ALS upgrade into a diffraction-limited soft x-rays light source requires a small emittance, which is achieved by much stronger focusing than in the present ALS. Very strong focusing elements and a relatively small vacuum chamber make the required rapid commissioning a significant challenge. This paper will describe the progress towards a start-to-end simulation of the machine commissioning and present first simulation results.

Experimental research of inside mechanical behavior based on advanced light source

Failure of key materials is a significant problem in various important engineering fields including aerospace, bridge, architecture, military-industrial, and high-speed train, etc. Materials failure and fracture are the fundamental causes of many engineering disasters and safety accidents. As we all know, visible macroscopic material failure is determined by the internal microscopic mechanical behavior which can not be directly observed. Therefore, precise experimental observation and research of internal microscopic mechanical behavior are the important foundation for revealing the mechanisms of materials failure and fracture. Conventional experimental techniques based on ultrasonic, visible light, electromagnetism, etc., are unavailable for direct observation with high resolution of internal mechanical behavior. Fortunately, the development of advanced light sources including synchrotron radiation and neutron source in recent years makes it possible to conduct in situ experimental research of materials inside failure processes. Both domestic and overseas research works of internal mechanical behavior experiments on the basis of advanced light sources are reviewed in this manuscript in two aspects of space and time. In spatial scale, the research works are organized into three scales of millimeter and micrometer, micrometer and sub-micrometer, nanometer according to spatial resolution. As for time scale, the research works are divided into static and quasi-static tests, and dynamic tests according to time resolution. At last, the challenges of experimental methods for internal observation in solving the problem of material failure and fracture are analyzed. And the development tendency of internal mechanical behavior experimental theories, methods and techniques based on advanced light sources are also discussed.

The COSMIC Imaging Beamline at the Advanced Light Source: a new facility for spectro-microscopy of nano-materials

The COSMIC Imaging Beamline at the Advanced Light Source: a new facility for spectro-microscopy of nano-materials

Synchrotron X-ray Micro Tomography at the Advanced Light Source: In-Situ Sample Environments for Advanced Aerospace Materials

Synchrotron X-ray Micro Tomography at the Advanced Light Source: In-Situ Sample Environments for Advanced Aerospace Materials

Nanoscale Visualization of Magnetic Contrasts with Soft X-ray Spectro-Ptychography at the Advanced Light Source

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Implementation and application of the peak scaling method for temperature measurement in the laser heated diamond anvil cell.

A new design for a double-sided high-pressure diamond anvil cell laser heating set-up is described. The prototype is deployed at beamline 12.2.2 of the Advanced Light Source at Lawrence Berkeley National Lab. Our compact design features shortened mechanical lever arms, which results in more stable imaging optics, and thus more user friendly and more reliable temperature measurements based on pyrometry. A modification of the peak scaling method was implemented for pyrometry, including an iterative method to determine the absolute peak temperature, thus allowing for quasi-real time temperature mapping of the actual hotspot within a laser-heated diamond anvil cell without any assumptions on shape, size, and symmetry of the hotspot and without any assumptions to the relationship between fitted temperature and peak temperature. This is important since we show that the relationship between peak temperature and temperature obtained by fitting the Planck function against the thermal emission spectrum averaged over the entire hotspot is not constant but depends on variable fitting parameters (in particular, the size and position of the fitting window). The accuracy of the method is confirmed through measuring melting points of metal wires at ambient pressure. Having absolute temperature maps in real time allows for more differentiated analyses of laser heating experiments. We present such an example of the pressure variations within a heated hotspot of AgI at a loaded base pressure of 3.8 GPa.

Investigation of Oxidation Reaction Products of 2-Phenylethanol Using Synchrotron Photoionization.

A photolytically Cl-initiated oxidation reaction of 2-phenylethanol (2PE) was carried out at the Advanced Light Source (ALS) in the Lawrence Berkeley National Laboratory. Using the multiplex photoionization mass spectrometer, coupled with the tunable vacuum ultraviolet radiation of the ALS, data were collected at low pressure (4-6 Torr) and temperature (298-550 K) regimes. Data analysis was performed via characterization of the reaction species photoionization spectra and kinetic traces. Products and reaction pathways are also computed using the CBS-QB3 composite method. The present results suggest primary products m/ z = 30 (formaldehyde), 106 (benzaldehyde), and 120 (phenylacetaldehyde) at 298 K, and m/ z = 120 (phenylacetaldehyde) at 550 K. Branching fractions at room temperature are 27 ± 6.5% for formaldehyde, 24 ± 4.5% for benzaldehyde, and 25 ± 5.8% for phenylacetaldehyde and 60 ± 14% for phenylacetaldehyde at 550 K.

(Invited) Interactions in Ionomers: From Cations to Confinement

Ion-conductive polymers (ionomers) have been widely used as the solid-electrolyte in energy conversion devices, such as polymer-electrolyte fuel cells (PEFCs) fuel cells, redox flow batteries and water-splitting devices. Ionomers, such as perfluorosulfonic-acid (PFSA), function as the separator-electrolyte in these devices due their high proton conductivity and chemical-mechanical stability.1 In PEFCs, however, ionomers play another key role in Catalyst Layer (CL) structure, where they exist as nanometer-thick electrolyte “thin film" to facilitate transport of ionic and gaseous species to the catalytic particles. As a cathode catalyst film, an ionomer is expected to transport the oxygen molecules to the catalytic sites, which differs dramatically from its gas-separator functionality.2 Once confined to these nanometer thicknesses (< 100 nm), ionomer properties change drastically from the bulk (solid-electrolyte PEM), and are significantly more influenced by its interfaces with the free surface (air) and the catalytic surfaces comprised of carbon and platinum(Pt)-alloyed particles.1,2 In particular, mass-transport limitations in CLs are believed to be related to the transport resistances at the ionomer thin-film, mitigation of which requires a fundamental understanding of ionomer interfaces.3-5 In addition, ionomers, whether as PEMs or in CLs, are exposed to various cations arising from contamination, migration of radical scavengers (such as Cerium), dissolution of catalyst particles (such as Co-alloys), all of which alter the ionomer’s interactions and impact the cell performance.3,6 Thus, throughout this thickness range, it is not only the functionality of ionomer that differs, but also its morphology and transport properties, which are controlled by various interactions. This talk will present an overview of various interactions, from cationic and catalytic particles to dynamic interfaces, and how they influence an ionomer’s intrinsic morphology and transport properties across lengthscales, with a focus on thin films. The latter is in particularly important as the interactions and confinement-driven changes in thin films create an intriguing interplay governing ionomer functionality. We will explore structure-property relationship PFSA ionomers of several chemistries and thicknesses (from micrometer to 10’s of nanometers) in the presence of various types and doping levels of cations to elucidate the underlying origins of governing interactions. Water uptake and swelling behavior as well as nano-morphology of cation-exchanged PFSA membranes and thin films are studied to identify the key factors and interactions impacting their behavior. We will also discuss the role of side-chain chemistry in these interactions, especially in nano-confined thin films. Lastly, I will summarize recent progress in ionomer thin-film research, including improved model systems for thin films that can mimic fuel-cell catalyst structure and environment, and advanced characterization techniques, such as Grazing-Incidence X-ray scattering (GIXS), and how they can be used to probe various interactions. Acknowledgements We acknowledge Adam Z. Weber and Douglas Kushner of Berkeley Lab for helpful discussions, and Michael Yandrasits and Andrew Haug of 3M for helpful discussions and supplying ionomer materials. This work made use of facilities at the Advanced Light Source (ALS), supported by the Office of Science, Office of Basic Energy Sciences, of the U.S. Department of Energy, and was funded under the Fuel Cell Performance and Durability Consortium (FC-PAD), by the Fuel Cell Technologies Office, of the office of the Energy Efficiency and Renewable Energy (EERE), of the U. S. Department of Energy (under contract number DE-AC02-05CH11231). References A. Kusoglu and A. Z. Weber, Chem. Rev., 117, 987 (2017).A. Kusoglu, in Encyclopedia of Sustainability Science and Technology, R. A. Meyers Editor, p. 1, Springer New York, New York, NY (2018).A. Kongkanand and M. F. Mathias, J Phys Chem Lett, 7, 1127 (2016).A. Z. Weber and A. Kusoglu, J Mater Chem A, 2, 17207 (2014).M. Tesfaye, A. N. MacDonald, P. J. Dudenas, A. Kusoglu and A. Z. Weber, Electrochem Commun, 87, 86 (2018).A. M. Baker, R. Mukundan, D. Spernjak, E. J. Judge, S. G. Advani, A. K. Prasad and R. L. Borup, J. Electrochem. Soc., 163, F1023 (2016).

The collaborative crystallography program at the Advanced Light Source

The collaborative crystallography program at the Advanced Light Source

Synchrotron X-ray Microdiffraction and Fluorescence Imaging of Mineral and Rock Samples

In this report, we describe a detailed procedure for acquiring and processing x-ray microfluorescence (μXRF), and Laue and powder microdiffraction two-dimensional (2D) maps at beamline 12.3.2 of the Advanced Light Source (ALS), Lawrence Berkeley National Laboratory. Measurements can be performed on any sample that is less than 10 cm x 10 cm x 5 cm, with a flat exposed surface. The experimental geometry is calibrated using standard materials (elemental standards for XRF, and crystalline samples such as Si, quartz, or Al2O3 for diffraction). Samples are aligned to the focal point of the x-ray microbeam, and raster scans are performed, where each pixel of a map corresponds to one measurement, e.g., one XRF spectrum or one diffraction pattern. The data are then processed using the in-house developed software XMAS, which outputs text files, where each row corresponds to a pixel position. Representative data from moissanite and an olive snail shell are presented to demonstrate data quality, collection, and analysis strategies.

Synchrotron X-ray Microdiffraction and Fluorescence Imaging of Mineral and Rock Samples

In this report, we describe a detailed procedure for acquiring and processingx-ray microfluorescence (μXRF), and Laue and powder microdiffraction two-dimensional (2D) maps at beamline 12.3.2 of the Advanced Light Source (ALS), Lawrence Berkeley National Laboratory. Measurements can be performed on any sample that is less than 10 cm x 10 cm x 5 cm, with a flat exposed surface. The experimental geometry is calibrated using standard materials (elemental standards for XRF, and crystalline samples such as Si, quartz, or Al2O3 for diffraction). Samples are aligned to the focal point of the x-ray microbeam, and raster scans are performed, where each pixel of a map corresponds to one measurement, e.g., one XRF spectrum or one diffraction pattern. The data are then processed using the in-house developed software XMAS, which outputs text files, where each row corresponds to a pixel position. Representative data from moissanite and an olive snail shell are presented to demonstrate data quality, collection, and analysis strategies.

Simulating X-ray Spectroscopies and Calculating Core-Excited States of Molecules.

During the past decade, the research field of computational X-ray spectroscopy has witnessed an advancement triggered by the development of advanced synchrotron light sources and X-ray free electron lasers that in turn has enabled new sophisticated experiments with needs for supporting theoretical investigations. Following a discussion about fundamental conceptual aspects of the physical nature of core excitations and the concomitant requirements on theoretical methods, an overview is given of the major developments made in electronic-structure theory for the purpose of simulating advanced X-ray spectroscopies, covering methods based on density-functional theory as well as wave function theory. The capabilities of these theoretical approaches are illustrated by an overview of simulations of selected linear and nonlinear X-ray spectroscopies, including X-ray absorption spectroscopy (XAS), X-ray natural circular dichroism (XNCD), X-ray emission spectroscopy (XES), resonant inelastic X-ray scattering (RIXS), and X-ray two-photon absorption (XTPA).

Quantitative Scanning Laue Diffraction Microscopy: Application to the Study of 3D Printed Nickel-Based Superalloys

Progress in computing speed and algorithm efficiency together with advances in area detector and X-ray optics technologies have transformed the technique of synchrotron radiation-based scanning Laue X-ray microdiffraction. It has now evolved into a near real-time quantitative imaging tool for material structure and deformation at the micrometer and nanometer scales. We will review the achievements of this technique at the Advanced Light Source (Berkeley, CA, USA), and demonstrate its application in the thorough microstructural investigations of laser-assisted 3D printed nickel-based superalloys.

Vacuum ultraviolet photoionization cross section of the hydroxyl radical.

The absolute photoionization spectrum of the hydroxyl (OH) radical from 12.513 to 14.213 eV was measured by multiplexed photoionization mass spectrometry with time-resolved radical kinetics. Tunable vacuum ultraviolet (VUV) synchrotron radiation was generated at the Advanced Light Source. OH radicals were generated from the reaction of O(1D) + H2O in a flow reactor in He at 8 Torr. The initial O(1D) concentration, where the atom was formed by pulsed laser photolysis of ozone, was determined from the measured depletion of a known concentration of ozone. Concentrations of OH and O(3P) were obtained by fitting observed time traces with a kinetics model constructed with literature rate coefficients. The absolute cross section of OH was determined to be σ(13.436 eV) = 3.2 ± 1.0 Mb and σ(14.193 eV) = 4.7 ± 1.6 Mb relative to the known cross section for O(3P) at 14.193 eV. The absolute photoionization spectrum was obtained by recording a spectrum at a resolution of 8 meV (50 meV steps) and scaling to the single-energy cross sections. We computed the absolute VUV photoionization spectrum of OH and O(3P) using equation-of-motion coupled-cluster Dyson orbitals and a Coulomb photoelectron wave function and found good agreement with the observed absolute photoionization spectra.

The Effect of Pulsed Current and Organic Additives on the Hydrogen Incorporation in Electroformed Copper Used in High Vacuum Applications

The trend in electron accelerators design consists in approaching the poles of the steering magnets close to the electron beam. This implies reducing the bore hosting the vacuum chamber and using very small diameter vacuum pipes [1]. The application of functional thin films by physical vapour deposition in such small diameter chambers becomes then very difficult. A new approach relies on copper electroforming to build the vacuum chamber onto a pre-deposited thin film coating [2]. In this method, unlike the usual process, the pipe is built from the inside out. An aluminium mandrel is coated with a functional thin film first, then by a copper film and finally followed by a thick electroplated copper (1-3mm) structural layer. The replacement of high-purity copper parts by electroformed ones may nevertheless lead to the incorporation of various impurities among which hydrogen, which is generated by solvent reduction and thus trapped into the coating. The aim of the present study is the evaluation of the effect of two main triggers, namely polarization wave modulation and copper electrolyte composition by the addition of organic additives. For this purpose, transient curves in response to pulsed currents have been studied for various cathodic current densities. Two main patterns have been observed as shown in figure 1a in the absence of additive. At low current densities, i.e. below 50 A/dm2, the potential increases rapidly and reaches an average constant value. For higher current densities, two characteristic plateaux can be observed: the first one corresponds to the faradic reduction of copper below the diffusion limit, and the second one, at higher potential, is attributed to the diffusion-limited range that is well known for promoting the hydrogen generation. When adding 33 mg/L of d-xylose, it is possible to reach higher current densities before the occurrence of the transition between the faradic reduction of copper, near the electrode, and the diffusion-limited mechanism. The d-xylose acts clearly by inhibiting the hydrogen discharge. Thank to this, four singular situations have been identified on the curves (marked by the stars on figure 1). They correspond to four pulse sequences (40A/dm2, Ton=20 ms), (40A/dm2, Ton=80 ms), (70A/dm2, Ton=20 ms), (70A/dm2, Ton=80 ms), which were used to prepare samples for characterization in terms of hydrogen outgassing by Thermal Desorption Spectroscopy (TDS) and X-Ray Diffraction (XRD) measurements. TDS experiments show two peaks (figure 2), corresponding to the release of hydrogen trapped into the copper under different forms. The temperature of desorption of the first peak (around 420°C for a ramp of 10K/min) corresponds well to hydrogen interstitial diffusion in the copper deposit [3]. The nature of the second peak (around 600°C) is not yet understood. [1] C. Steier, A. Anders, D. Arbelaez, J.M. Byrd, K. Chow, S. De Santis, R.M. Duarte, J.-Y. Jung, T.H. Luo, A. Madur, H. Nishimura, J.R. Osborn, G.C. Pappas, L.R. Reginato, D. Robin, F. Sannibale, D. Schlueter, C. Sun, C.A. Swenson, W.L. Waldron, E.J. Wallen and W. Wan, "Progress of the R&D towards a diffraction limited upgrade of the Advanced Light Source", in Proceedings of IPAC, Richmond, USA (2015), p. 1840. [2] L. Lain Amador, P. Chiggiato, L. M.A Ferreira, V. Nistor, A. T. Perez Fontenla, M. Taborelli, W. Vollenberg, M-L Doche, J-Y Hihn “Development of copper electroformed vacuum chambers with integrated non-evaporable getter thin film coatings” Journal of Vacuum Science and Technology A, accepted. [3] Y. Fukai “Formation of superabundant vacancies in M–H alloys and some of its consequences: a review” Journal of Alloys and Compounds 356–357 (2003) 270–273. Figure 1

Collective resonances of atomic xenon from the linear to the nonlinear regime

XUV nonlinear spectroscopy has recently discovered that there is more than one collective dipole resonance state in the energy range of the giant dipole resonance (GDR) of atomic Xe. This resonance-state substructure, hidden in the linear regime, raises imminent questions regarding our understanding of the collective electronic behavior of Xe, which has been largely founded on linear spectroscopic studies. Here, we approach the collective response of Xe from a new perspective: we study directly the resonance eigenstates, and then analyze their spectroscopic manifestations. We find that linear spectroscopy captures only partial information on the resonance substructure as a result of quantum interferences. Moreover, we show that the resonance state dominating the GDR in linear spectroscopy has no adiabatic connection to the resonance state governing the corresponding cross section when multielectron interactions are neglected. Going beyond the dipole-allowed correlated electronic structure, we predict the existence of collective multipole resonances of Xe. Unlike any known collective feature in atoms, these resonances live exceptionally long (more than 100 attoseconds), thus providing a new playground for studying the collective nonlinear response of Xe using advanced light sources.

Efficient proton acceleration from a 3 TW table-top laser interacting with submicrometric mass-produced solid targets

Thin layer membranes with controllable features and material arrangements are often used as target materials for laser driven particle accelerators. Reduced cost, large scale fabrication of such membranes with high reproducibility, and good stability are central for the efficient production of proton beams. These characteristics are of growing importance in the context of advanced laser light sources where increased repetition rates boost the need for consumable targets with design and properties adjusted to study the different phenomena arising in ultra-intense laser-plasma interaction. We present the fabrication of sub-micrometric thin-layer gold or aluminum membranes in a silicon wafer frame by using nano/micro-electro-mechanical-system (N/MEMS) processing which are suitable for rapid patterning and machining of many samples at the same time and allowing for high-throughput production of targets for laser-driven acceleration. Obtained targets were tested for laser-proton acceleration through the Target Normal Sheath Acceleration mechanism (TNSA) in a series of experiments carried out on a purpose-made table-top Ti:Sa running at 3 TW peak power and 10 Hz diode pump rate with a contrast over ASE of 108.

A photoemission moments model using density functional and transfer matrix methods applied to coating layers on surfaces: Theory

Recent experimental measurements of a bulk material covered with a small number of graphene layers reported by Yamaguchi et al. [NPJ 2D Mater. Appl. 1, 12 (2017)] (on bialkali) and Liu et al. [Appl. Phys. Lett. 110, 041607 (2017)] (on copper) and the needs of emission models in beam optics codes have lead to substantial changes in a Moments model of photoemission. The changes account for (i) a barrier profile and density of states factor based on density functional theory (DFT) evaluations, (ii) a Drude-Lorentz model of the optical constants and laser penetration depth, and (iii) a transmission probability evaluated by an Airy Transfer Matrix Approach. Importantly, the DFT results lead to a surface barrier profile of a shape similar to both resonant barriers and reflectionless wells: the associated quantum mechanical transmission probabilities are shown to be comparable to those recently required to enable the Moments (and Three Step) model to match experimental data but for reasons very different than the assumption by conventional wisdom that a barrier is responsible. The substantial modifications of the Moments model components, motivated by computational materials methods, are developed. The results prepare the Moments model for use in treating heterostructures and discrete energy level systems (e.g., quantum dots) proposed for decoupling the opposing metrics of performance that undermine the performance of advanced light sources like the x-ray Free Electron Laser. The consequences of the modified components on quantum yield, emittance, and emission models needed by beam optics codes are discussed.

X-Ray Diffraction under Extreme Conditions at the Advanced Light Source

The more than a century-old technique of X-ray diffraction in either angle or energy dispersive mode has been used to probe materials’ microstructure in a number of ways, including phase identification, stress measurements, structure solutions, and the determination of physical properties such as compressibility and phase transition boundaries. The study of high-pressure and high-temperature materials has strongly benefitted from this technique when combined with the high brilliance source provided by third generation synchrotron facilities, such as the Advanced Light Source (ALS) (Berkeley, CA, USA). Here we present a brief review of recent work at this facility in the field of X-ray diffraction under extreme conditions, including an overview of diamond anvil cells, X-ray diffraction, and a summary of three beamline capabilities conducting X-ray diffraction high-pressure research in the diamond anvil cell.