GSECARS Synchrotron Facility for Planetary Science Research

SEM photomicrograph of Murchison fragment analyzed tomographically using focused beam XRF/XRD. Dashed yellow line shows the position of the reconstructed tomographic slice. (middle) XRF tomographic reconstruction of Mn, Fe and Ni Kα fluorescence intensity. (right) XRD tomographic reconstruction of the measured intensity of scattering vectors (Q) at 1.50, 1.76 and 1.78 Å-1. Reconstructed Q-intensity patterns show that blue area in the lower right is consistent with a mixture of forsteritic olivine and hedenbergite, while green areas are largely serpentine group minerals

Overview

Beginning in February 2023, GSECARS will receive funding from NASA’s Research Facilities for Planetary Science program (https://science.nasa.gov/researchers/planetary-science-enabling-facilities) to support planetary science research conducted by NASA-funded investigators using some of our beamlines. This support is focused primarily on experiments using the 13-ID-E X-ray microprobe and the 13-BM-D the full-field computed microtomography (CMT) instrument, which are the GSECARS instruments most heavily used by researchers in this field. NASA-funded researchers will receive assistance in experiment design and sample preparation to ensure that prepared samples are optimized for synchrotron analysis, particularly to take full advantage of beamline capabilities provided by the planned Advanced Photon Source upgrade (APS-U; see below). This funding will also support data collection, data interpretation, and publication preparation using these beamlines. Access to the facility will be through the APS General User Program involving peer-review of beam time proposals. Support for focused ion beam section preparation at the University of New Mexico will also be a capability offered to planetary science researchers through this program.

Main Techniques

X-ray Fluorescence (µXRF) mapping: Compositional analysis and mapping for elements with ~ 1 µm focused spot size and 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, but 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.

X-ray Absorption Fine Structure (µXAFS): Microfocused XAFS can 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 absorption fine structure (XAFS) spectroscopy has proven to be a valuable tool in defining valence states of multivalent elements in minerals and glasses that can then be used as oxybarometry proxies in cosmochemical studies. Multivalent elements of particular importance to earth and planetary science studies include S, Ti, V, Mn, Cr, Eu, and Fe.

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 1M area detector allowing for diffraction mapping and tomography, etc.

Fluorescence and Diffraction Computed Microtomography (fCMT and dCMT): Both element specific X-ray fluorescence tomography and X-ray diffraction tomography with micrometer spatial resolution are available. Tomographic slices of XRF and XRD intensity through the object are then reconstructed following the same methods utilized for absorption tomography.

Full-field X-ray Computed Microtomography (CMT): Absorption tomography using the 13-BM-D bending magnet source for non-destructive 3D characterization of internal microstructures of larger samples. A 3D representation of the phases and their textures can identify primary minerals, chemical zoning within crystallites, orientation relations, as well as secondary reaction products. The unique detection system for the full-field absorption CMT apparatus consists of a single crystal scintillator (which converts X-rays to visible light), a microscope objective (that magnifies the scintillator image), and a 1920×1200 pixel fast CMOS camera. Three modes can be used. Monochromatic beam mode uses a high-resolution Si(111) double crystal monochromator for element-specific applications, such as “above-edge, below-edge” subtraction imaging. Pink beam mode provides more than 1,000 times higher intensity than the monochromatic mode, and thus allows much faster data collection. White beam mode provides the highest flux and the highest energy X-ray spectrum, at the expense of vertical beam size.

FIB Sectioning Capability: This project will include funds to support preparation of focused ion beam sections for use at 13-ID-E using the University of New Mexico ion beam facilities. These resources would be available on an as-needed basis to users of the GSECARS facilities that require this specialized sample preparation procedure.

APS-U

In April 2023, the APS will undertake a year long, major upgrade (APS-U) that will dramatically enhance microanalytical studies relevant to planetary sciences, improving the spatial resolution and flux density at the XRM beamline. Examples of experiments that will be enhanced by these improvements include analyses of fine-grained materials that are prepared as FIB sections, such as asteroidal materials returned by Hayabusa 2 and eventually OSIRIS-REx, and studies of secondary veins in primary minerals.

Science Highlights

Contacts

 

Tony Lanzirotti

PSEF PI and Primary Contact
University of Chicago
lanzirotti@uchicago.edu

Steve Sutton

PSEF Co-I
University of Chicago
sutton@cars.uchicago.edu

Adrian Brearley

PSEF Co-I
University of New Mexico
brearley@unm.edu

Important Links

Research Facilities for Planetary Science
APS Upgrade

Recent Publications