A dedicated superbend x-ray microdiffraction beamline for materials, geo-, and environmental sciences at the advanced light source

Abstract

SynopsisA new facility for microdiffraction strain measurements and microfluorescence mapping has been developed at the Advanced Light Source. Details of the mechanics and performance of the beamline and endstation will be given. AbstractA new facility for microdiffraction strain measurements and microfluorescence mapping has been built on beamline 12.3.2 at the Advanced Light Source (ALS) of the Lawrence Berkeley National Laboratory (LBNL).This beamline benefits from the hard x-radiation generated by a 6 Tesla superconducting bending magnet (superbend). This provides a hard x-ray spectrum from 5 keV to 22 keV and a flux within a 1 µm spot of ~ 5 · 10 9 photons per seconds (0.1% bandwidth at 8 keV). The radiation is relayed from the superbend source to a focus in the experimental hutch by a toroidal mirror. The focus spot is tailored by two pairs of adjustable slits, which serve as secondary source point. Inside the lead hutch, a pair of Kirkpatrick-Baez (KB) mirrors placed in a 2 vacuum tank re-focuses the secondary slit source onto the sample position. A new KB-bending mechanism with active temperature stabilization allows for more reproducible and stable mirror bending and thus mirrorfocusing. Focus spots around 1 µm are routinely achieved and allow a variety of experiments, which have in common the need of spatial resolution. The effective spatial resolution (~0.2 µm) is limited by a convolution of beam size, scan-stage resolution and stage stability. A 4-bounce monochromator consisting of 2 channel-cut Si(111) crystals placed between the secondary source and KB-mirrors allows for easy changes between whitebeam and monochromatic experiments while maintaining a fixed beam position. High resolution stage scans are performed while recording a fluorescence emission signal or an x-ray diffraction signal coming from either a monochromatic or a white focused beam. The former allows for elemental mapping, whereas the latter is used to produce 2-dimensional maps of crystal-phases,-orientation, -texture and -strain/stress. Typically achieved strain resolution is in the order of 5 · 10 -5 strain units. Accurate sample positioning in the x-ray focus spot is achieved with a commercial laser-triangulation unit. A Si-drift detector serves as a high-energy-resolution (~150 eV FWHM) fluorescence detector. Fluorescence scans can be collected in continuous scan mode with up to 300 pixels per second scan-speed. A CCD area detector is utilized as diffraction detector. Diffraction can be performed in reflecting or transmitting geometry. Diffraction data are processed using XMAS, an in-house written software package for Laue and monochromatic microdiffraction analysis.

Impact of deposition conditions on the crystallization kinetics of amorphous GeTe films

“…The diffraction patterns were collected with a DECTRIS Pilatus 1 M pixel area detector (active area of 179 mm 9 169 mm), which was placed at a distance of approximately 140 mm from the sample. More detailed information on the setup at this beamline can be obtained elsewhere [12,13].…”

Improving aluminum particle reactivity by annealing and quenching treatments: Synchrotron X-ray diffraction analysis of strain

“…The 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 8 measured relative small shifts in the reflection positions in the Laue pattern provides the deviatoric strain tensor of the material while the measurement of the energy of one reflection provides the dilatational component. Data were processed using XMAS software [31]. The beamline experimental setup and capabilities have been described elsewhere [32].…”

Visualization of Charge Distribution in a Lithium Battery Electrode

“…Here we present a novel experimental method for direct determination and visualization of the charge distribution in a composite electrode using synchrotron x-ray microdiffraction. 13 LiFePO 4 was chosen as active material for this study, because (i) it is a safe and promising cathode material for plug-in hybrid electric vehicle application; 14 (ii) its twophase charge-discharge reaction produces a charge distribution that is "frozen" when the current is interrupted. 15 Since non-uniform charge distribution may develop either in the cross section or in the plane of the electrode depending on cell configuration and current density, two LiFePO 4 composite electrodes in different cell configurations were studied.…”

“…The x-ray scan diffraction data were processed by XMAS software and an in-house software package for monochromatic microdiffraction analysis. 13 µXRD data collected in stereographic projection (Figure 3) was integrated along the 2θ arcs to create 1-D powder diffraction patterns. Peak areas for the 020 reflections for each phase were used for quantitative analysis due to their relatively high intensity/noise ratios (see Supporting information).…”