George J. Havrilla

Monolithic polycapillary x-ray optics engineered to meet a wide range of applications

Two new applications of monolithic polycapillary x-ray optics were explored. One was to improve the detection sensitivity of microbeam x-ray fluorescence analysis for radioactive samples. One focusing optic was used to focus x-rays onto a small area of the sample, and the second focusing optic was used as a spatial filter to collected x-ray fluorescence from the area defined by the first optic. The radiation background from the radioisotope in the sample was significantly reduced, and therefore the detection sensitivity for such samples was greatly enhanced. The other application was using a focusing optic to improve performance of position-sensitive-detector-based wavelength- dispersive x-ray fluorescence analysis. The small, intense excitation beam obtained with a focusing optic greatly increased the count rate of the measurement, thus improving the detection sensitivity of the system. Some new progresses achieved in monolithic polycapillary optics design and manufacturing are also discussed.

Attenuated Total Internal Reflection Infrared Microspectroscopic Imaging Using a Large-Radius Germanium Internal Reflection Element and a Linear Array Detector

The number of techniques and instruments available for Fourier transform infrared (FT-IR) microspectroscopic imaging has grown significantly over the past few years. Attenuated total internal reflectance (ATR) FT-IR microspectroscopy reduces sample preparation time and has simplified the analysis of many difficult samples. FT-IR imaging has become a powerful analytical tool using either a focal plane array or a linear array detector, especially when coupled with a chemometric analysis package. The field of view of the ATR-IR microspectroscopic imaging area can be greatly increased from 300 × 300 μm to 2500 × 2500 μm using a larger internal reflection element of 12.5 mm radius instead of the typical 1.5 mm radius. This gives an area increase of 70× before aberrant effects become too great. Parameters evaluated include the change in penetration depth as a function of beam displacement, measurements of the active area, magnification factor, and change in spatial resolution over the imaging area. Drawbacks such as large file size will also be discussed. This technique has been successfully applied to the FT-IR imaging of polydimethylsiloxane foam cross-sections, latent human fingerprints, and a model inorganic mixture, which demonstrates the usefulness of the method for pharmaceuticals.

INTEGRATION OF ELEMENTAL AND MOLECULAR IMAGING TO CHARACTERIZE HETEROGENEOUS INORGANIC MATERIALS

Spatially resolved elemental and molecular information has been obtained for complex inorganic mixed-phase systems, including plutonium-contaminated ash samples, with the use of micro-X-ray fluorescence (MXRF), micro-Raman, and micro-infrared imaging spectroscopies. Approaches for spatially guided analysis and the combination of multispectral data sets to improve assignment of chemical composition are discussed for two heterogeneous materials. This novel integrated experimental approach provides the advantages of a very small sample size and the ability to correlate elemental analysis with molecular functional group analysis for species identification, as well as insight into chemical interactions in complex matrices.

Micro X-ray fluorescence in materials characterization

Micro X-ray fluorescence (MXRF) offers the analyst a new approach to materials characterization. The range of applications is expanding rapidly. Single point analysis has been demonstrated for nanoliter volumes with detection limits at the 0.5 ng level. MXRF can be used as an element specific detector for capillary electrophoresis. Elemental imaging applications include analysis of sample corrosion and polymers, use as a combinatorial chemistry screening tool, and integration with molecular spectroscopic imaging methods to provide a more comprehensive characterization. Three-dimensional elemental imaging is a reality with the development of a confocal X-ray fluorescence microscope. Stereoview elemental X-ray imaging can provide unique views of materials that flat two-dimensional images cannot achieve. Spectral imaging offers chemical imaging capability, moving MXRF into a higher level of information content. The future is bright for MXRF as a materials characterization tool.

Infrared Microspectroscopic Imaging Using a Large Radius Germanium Internal Reflection Element and a Focal Plane Array Detector

Previously, we established the ability to collect infrared microspectroscopic images of large areas using a large radius hemisphere internal reflection element (IRE) with both a single point and a linear array detector. In this paper, preliminary work in applying this same method to a focal plane array (FPA) infrared imaging system is demonstrated. Mosaic tile imaging using a large radius germanium hemispherical IRE on a FPA Fourier transform infrared microscope imaging system can be used to image samples nearly 1.5 mm × 2 mm in size. A polymer film with a metal mask is imaged using this method for comparison to previous work. Images of hair and skin samples are presented, highlighting the complexity of this method. Comparisons are made between the linear array and FPA methods.

Raman/SEM Chemical Imaging of a Residual Gallium Phase in a Mixed Oxide Feed Surrogate

An integrated analytical approach, which combines elemental [scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM/EDS)] and molecular (Raman) chemical imaging techniques, has been utilized for the characterization of a residual phase of gallium in mixed oxide (MOX) surrogate material. Surrogate MOX materials are comprised of CeO2 in place of PuO2. In real MOX materials, PuO2 is mixed with UO2 as a commercial fuel source. A Ga phase remains in the surrogate sample following reductive heating experiments designed to explore the removal of gallium from weapons-grade plutonium. The SEM/EDS data reveal the concentration of Ga within the grain boundaries of the sample and a distribution of Ce and O throughout the sample matrix. Molecular analysis provided by Raman chemical matrix imaging correlates with the SEM/EDS elemental imaging results. Specifically, the Raman data suggest that the matrix is comprised of CeO2 and grain boundaries are a mixed phase comprised of CeO2 with a form of Ga, most likely a CeGaO3 perovskite phase having a cubic structure.

Integrating X-ray fluorescence and infrared imaging microspectroscopies for comprehensive characterization of an acetaminophen model pharmaceutical.

The integration of full spectral images using the complementary microspectroscopic imaging techniques X-ray fluorescence and Fourier transform infrared is demonstrated. This effort surpasses previous work in that a single chemometric software package is used to elicit chemical information from the integrated spectroscopic images. Integrating these two complementary spectroscopic methods provides both elemental and molecular spatial distribution within a specimen. The critical aspect in this work is using full spectral maps from each pixel within the image and subsequent processing with chemometric tools to provide integrated chemical information. This integration enables a powerful approach to more comprehensive materials characterization. Issues addressed include sample registration and beam penetration depth and how each affects post-processing. An inorganic salt and an acetaminophen pharmaceutical model mixture demonstrate the power of integrating these techniques with chemometric software.

Applications of x‐ray microfluorescence to materials analysis

X-ray microfluorescence provides the analytical scientist with a powerful tool to solve a variety of materials-based problems. Spatially resolved non-destructive elemental analyses can rapidly address a number of problems using qualitative analysis. Point spectra, line profiles and elemental maps offer different approaches for characterization information on a wide variety of materials. Applications are presented which span customer service complaints to experimental ceramic materials to fossils.

Combining X-ray Fluorescence Spectrometry and Vibrational Microscopy to Assess Highly Heterogeneous, Actinide-Contaminated Materials

Combining X-ray fluorescence (XRF) spectrometry with micro-Raman and infrared spectroscopies is shown to be a powerful experimental approach in providing information on components present in highly heterogeneous materials which contain or have been in contact with actinides. In this initial study, the quantitative XRF data demonstrate a correlation in the relative amounts of plutonium with other elements such as strontium and yttrium. The XRF mapping provides further evidence for correlation of these (and other) elements and identifies regions of interest within the sample to be further studied. These regions were then examined by vibrational microscopy to supply information on molecular species present and their spatial distribution. This experimental approach provides insight into very complex samples and provides a technique capable of exploring interactions of molecular components with actinides in complex media.

NONDESTRUCTIVE INVESTIGATIONS OF A COPPER-AND ARGON-DOPED SPUTTERED BERYLLIUM CAPSULE USING X-RAYS IN THREE DIMENSIONS

Abstract Three-dimensional (3-D) computed micro X-ray tomography (micro CT) and 3-D confocal micro X-ray fluorescence (MXRF) combined are very useful nondestructive metrology techniques for determining the unique compositional and morphological information of fusion targets and target materials. Micro CT and confocal MXRF are being used in concert to examine a beryllium ablator capsule that has been sputtered and graded doped with copper and argon. In this manuscript, we will show that two-dimensional (2-D) MXRF imaging in concert with a simple radiograph is very useful for approximating the copper and argon profiles in the x and y dimensions, but because of the lack of signal discrimination in the z direction, image “bleed” from the sample regions where the X-rays are out of focus is prevalent. Data collected using the micro CT and overlapped with the confocal MXRF data produce absorbance and elemental line profiles without the signal bleed. Overlapping the 3-D data from these techniques provides a more accurate picture of the composition of these capsules than 2-D nondestructive techniques.