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The WHOI XRF Scanning Lab

Jess loading the XRF
Loading a core sample into the XRF Scanner. Photo Credit: Tom Kleindinst, WHOI. Enlarge »
xrf scan
The XRF excels at analyzing laminated sediments. Photo Credit: Tom Kleindinst, WHOI. Enlarge »
xrf scanning lab
The XRF Scanning Lab at WHOI. Enlarge »
xrf scanner data
Photo, X-radiography, and XRF data from the scanner. Data credit: William D'Andrea, Brown University. Enlarge »

The XRF Scanning Lab at Woods Hole Oceanographic Institution offers nondestructive, high-resolution elemental analysis, x-radiography and digital photos of split sediment cores using an ITRAX model XRF Corescanner built by Cox Analytical Systems, Sweden. The scanner provides unprecedented analytical resolution and speed, allowing for the determination of chemical composition of entire core sections within a matter of hours. With a flexible mounting system, the XRF scanner can easily accommodate split cores between 6-12 cm in diameter and up to 180 cm in length. The instrument is capable of scanning at a resolution as fine as 200 microns and performing radiography at a maximum resolution of 20 microns, ideal for analysis of laminated marine and lacustrine sediments. Other types of samples, such as tree ring sections, speleothems, and corals may be run through the machine as well.

Digital Photography
The scanner is equipped with a camera that collects digital photos of the sediment cores prior to the radiographic/XRF scan. The maximum resolution of these photos is 100 microns, allowing the user to digitally align visible features in the sediment core with changes in density and sediment chemistry.

Radiographic Imaging
Flat-beam optics focus X-rays into a 13 x 0.2 mm rectangular beam perpendicular to the sample surface. A slit system located below the sample further focuses the rays down to a maximum resolution of 20 microns. Exposure times are on the order of 400-800 milliseconds per point, so that very high-resolution images are collected within an hour or two per core.

X-ray Fluorescence Elemental Analysis
The scanner employs a Si-drift detector coupled with a digital multi-channel analyzer to handle high count rates and provide sensitivity at relatively low exposure times (10-30 seconds per point). To accommodate for uneven core surfaces and maintain a constant
sample-detector distance, a laser triangulation system is used to measure the surface of the core and adjust the motorized detector accordingly.

Applications
The WHOI scanner provides non-destructive records of elemental composition at resolutions and speeds difficult to achieve utilizing discrete sampling methods. The 200 micron resolution is appropriate for studying laminated sediments. Data produced by the scanner can be used for detecting sediment source area based on
bulk geochemistry, for constructing inter-core correlations and event stratigraphy, for developing paleoclimatic and paleoceanographic proxies, for pollution histories, and for examining and developing proxies for textures, sedimentary structures, and lithologies.

For more information on the scanner, including pricing, contact:

Liviu Giosan
lgiosan@whoi.edu

Jeff Donnelly
jdonnelly@whoi.edu

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