13 ID-E : X-ray Microprobe
The X-ray microprobe and spectroscopy beamline, GSECARS station 13-ID-E, provides users with a world-class micro-focused X-ray beam for X-ray fluorescence and absorption spectroscopy and imaging, with some capabilities for X-ray diffraction and fluorescence-mode X-ray computed tomography. The microprobe emphasizes the techniques of fast X-ray fluorescence (XRF) mapping with X-ray absorption spectroscopy (XAS) and the scientific areas of earth, planetary, and environmental sciences. Micro-scale XAS using crystal analyzers for high energy resolution fluorescence detection (HERFD) is being commissioned and may be available for particular elements for interested users. Contact the beamline staff if you are interested in this.
The available X-ray energy range is 2.4 to 28 keV, allowing access to the X-ray absorption edges of sulfur and heavier elements. The beamline uses dynamically bent Kirkpatrick-Baez mirrors to focus the X-ray beam, with a typical spatial resolution of 1.5 x 2 μm (V x H), though the beam can be made as large as 100 x 100 μm if needed. X-ray flux varies from about 5e10 Hz to 1e13 Hz depending on energy range and beam size.
Analyses are typically done with samples at ambient conditions, in air. Some high-pressure work with samples in diamond-anvil cells has been done. We have a Peltier cold stage (~-15C) which may be available for some experiments. For low X-ray energies and redox-sensitive samples, we can work with samples in a helium-filled environment.
X-ray Absorption Fine Structure (µXAFS)
Microfocused XAFS can be be used to determine the speciation (local chemistry, quantitative determination of the local geometric structure around the absorbing atom) of the elements. Both µ-XANES and µ-EXAFS are possible, depending on concentration, as is oxidation state mapping. The beamline monochromator has both Si(111) and Si(311) crystal sets available.
X-ray Fluorescence (µXRF) mapping
Compositional analysis and mapping for elements with X-ray emission energies between ~ 2-28 keV. Multiple elements can be analyzed simultaneously. Minimum detection limits depend strongly on sample and spectral overlaps in the XRF spectra. Parts-per-million level detection is typical, and ppb level detection is possible for some samples. Mapping utilizes continuous scanning approach with practical pixel times as low as 5-10 milliseconds. Non-destructive compositional mapping (diffusion, zonation), sector zoning in minerals, compositions of microparticles (soils, micrometeorites, aerosols), trace element distributions in cells, etc. Samples can be analyzed in air, in a moist or wet state, biological samples can be analyzed intact.
X-ray Diffraction (µXRD)
Microdiffraction analysis for mineral identification with spatial resolutions of <1 µm. Area detector readout at frame rates < 20 msec per frame possible using Eiger 500K area detector (Eiger 1M will be available in mid-2021) allowing for diffraction mapping and tomography, etc.
Fluorescence Computed Microtomography (fCMT)
Element specific X-ray fluorescence tomography with micrometer spatial resolution. Our fCMT analysis employs a continuous scanning approach similar to that utilized in fast 2D mapping, with practical pixel times as low as 10-20 milliseconds. X-ray fluorescence (full EDS) from a sample is measured as it is translated (X) and rotated (theta) through the focused beam to generate a sinogram (top image shown below). In our implementation of the technique we use theta as the fast scan direction to improve stability. Tomographic slices of XRF intensity through the object are then reconstructed following the same methods utilized for absorption tomography.
Using fCMT methods researches can non-destructively examine trace element distributions in materials without the need for physical sectioning. The bottom image below of a reconstructed slice through a 150 micrometer diameter Arabidopsis seed (Punshon – Dartmouth College) shows the high resolution imaging possible at elemental concentrations below 100 ppm.
- 2.4-m long, 36 mm period undulator.
- High heat-load, LN2-cooled monochromator with air-bearing and high-torque motor for continuous XAS scanning, with Si(111) and Si(311) crystal sets.
- double horizontal mirrors to create secondary-source for improved horizontal focusing.
- Beam-position monitor upstream of secondary source aperture for improved beamline stability.
- 200-mm long Kirkpatrick-Baez mirrors in endstation to focus the beam down to 1×1 μm.
- high-quality visible light-microscope for sample viewing.
- Sample stages with both large travel range (>100 mm) and high precision (< 0.25 μm) for precise and fast XRF mapping. A rotation stage available, allowing for X-ray fluorescence tomography.
- High-stability synthetic granite block for the experimental table with state-of-the-art vibration isolation.
- Continuous slew scanning with hardware triggering for both XRF mapping and XAFS spectra.
- Intuitive GUIs for interactive data collection and visualization, with easy-to-build scripting of sequences of data collection.
- remote-access with mail-in samples available.
- Canberra SXD-7 7-element Si drift detector (SDD) detector with Xspress3 electronics, giving excellent resolution and count rate for energy-dispersive (EDS) X-ray fluorescence spectra.
- Eiger 500K detector used for XRD and HERFD measurements. micro-XRD can be collected either as single images or at each pixel in a 2-D map (combined XRD and XRF mapping). An Eiger 1M detector is expected in mid-2021.
- Crystal analyzer system (in commissioning) with up to 3 analyzers in a 1-m Rowland circle geometry and allowing HERFD and RIXS plane measurements while leaving EDS detector in place for XRF mapping.
- Optem microscope with Point Grey camera 1 mm field of view.
- optional UV lamp for imaging fluorscence of stained samples.
- Access to GSECARS laboratories including microscopy instrumentation, wet lab, fume hood, laminar-flow hood, glove box, sample prep areas.
- Benchtop SEM.
- Offline Sample Registration and Coordinate System (OSCAR) provides users an offline microscope in the beamline control area to view samples and select areas for X-ray analysis before putting the sample in the X-ray beam.
- Peltier-cooled sample stage
- Helium sample environments
|Source||3.6 cm undulator|
|Monochromator Type||cryo-cooled Double-crystal monochromator, Si(111), Si(311)|
|Energy Range||2.4-28 keV|
|resolution (deltaE/E)||1.1 x 10-4|
|flux (photons/sec)||6 x 1012 @ 10 keV|
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X-ray Absorption Fine Structure (XAFS)