September 18-20, 2007

A Course on Quantitative Hard X-ray Micro-Fluorescence Imaging

Twenty-one graduate, postdoctoral, and research scientists came to the NSLS on September 18-20, 2007 for a workshop on the analysis techniques that are necessary to identify and quantify x-ray fluorescence (XRF) spectra from synchrotron microprobe facilities. These now-standard instruments are typically able to focus x-rays in the range of 50 nm to a few microns, thus providing spatially resolved spectroscopic information. Because the samples analyzed at these facilities differ in composition and thickness and many times have a multi-elemental nature due to research areas as varied as geology and biophysics, the resulting x-ray spectra often are complicated and can suffer from severe fluorescence line overlap and detector artifacts. The purpose of this workshop was to give users of the NSLS microprobe beamlines X26A and X27A the necessary know-how and analysis tools for unraveling and quantifying their micro-fluorescence data through a series of hands-on tutorials dispersed with research-based talks.

Participants in the Quantitative Hard X-ray Micro-Fluorescence Imaging Workshop.

Workshop speakers included: Chris Ryan, Australia’s Commonwealth Scientific and Industrial Research Organisation, Exploration and Mining; Tony Lanzirotti, Consortium for Advanced Radiation Sources (CARS), University of Chicago, at X26A; Stefan Vogt, Experimental Facilities Division at the Advanced Photon Source (APS), at 2ID-D & 2ID-E; and Peter Siddons, BNL, NSLS.

Lanzirotti kicked off the workshop with a talk on the various issues involved in x-ray micro-fluorescence experiments (such as sample matrix effects and spectral overlap) and gave a very detailed description of the analysis software (NRLXRF and routines developed by Mark Rivers and Steve Sutton at CARS, and used at the NSLS) that can help users analyze their data. During the afternoon session, Ryan gave a presentation about the features of the powerful GeoPIXE software, for PIXE and XRF microprobe analysis, that was to be used in the subsequent hands-on analysis tutorials. Then, point x-ray fluorescence spectra were collected at the X27A microprobe beamline for a hands-on analysis session conducted by Lanzirotti, and a large area micro-fluorescence map on an ancient sea specimen was initiated for analysis the next day.

During the morning session of the second day, Siddons gave a rigorous review of detector systems that users encounter on microprobe beamlines and described some revolutionary developments in multi-element detectors for real-time micro-fluorescence imaging that he is working on with Ryan. In the next talk, Vogt gave a presentation on XRF analysis for trace metals in biological systems in which x-ray probes of 200 nm at the APS can be used to identify metals in cells at extremely low detection limits. Lanzirotti began the afternoon session with a presentation of the research conducted by the CARS team, which included work on Martian meteorites, interplanetary dust particles, and impressive fluorescence computed micro-tomography data collected at X26A. After the research talks, hands-on tutorials using the GeoPIXE software were given by Ryan, and the workshop participants worked with this very powerful software to analyze pre-recorded data and micro-fluorescence data taken the previous day at X27A.

The last day of the workshop began with an absorbing research-based talk by Vogt on biomedical applications of XRF microscopy that touched on topics such as cardiac hypertrophy, marine biology, copper angiogenis, nanocomposites, and mercury in teeth. For the remainder of the day, workshop participants once again took out their laptops to work on other XRF data analysis.

This workshop was supported by the NSLS, and special thanks go to Gretchen Cisco and Liz Flynn of the NSLS User Administration Office for their work in making it such a successful event.

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ARTICLE BY: James Ablett, Spokesperson for NSLS beamline X27A