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Preliminary comparison of monolithic and aperture optics for XRMF

Description: Comparisons between standard aperture optics and a custom designed monolithic capillary x-ray optic for the Kevex Omicron are presented. The results demonstrate the feasibility of retrofitting an Omicron with a monolithic capillary. Increased flux is observed especially at lower energies which results in an increase in sensitivity and potentially an increase in spatial resolution. Alignment is a critical factor in achieving optimal performance of the monolithic capillary. Further improvements in flux output, spot size and overall sensitivity are expected with better alignment.
Date: August 1, 1997
Creator: Havrilla, G.J. & Worley, C.G.
Partner: UNT Libraries Government Documents Department

Nanodroplet quantification: pushing the detection limits of micro x-ray fluorescence

Description: In this study, detection limits for a variety of elements were determined on an EDAX Eagle I1 MXRF system equipped with a polycapillary and a Rh X-ray source. Both mass, volume, and spot diameter detection limits were established using dried spot technology, where various volumes and/or masses of different elements were deposited on different substrates, dried, and quantitatively analyzed by MXRF. Preliminary results have shown that sub-nanogram levels of material can be detected in less than 200 pm diameter spot sizes deposited on thin polymer films. Specifically, detection limits were found for a given element as a function of mass deposited for a given spot volume, and volume deposited for a given mass. The effect of the presence of multiple elements in a droplet on the detection limit was also investigated. For example, the detection limit for copper was determined when it was deposited as a single Cu solution and in various multielement mixtures containing from 2 up to 10 different elements. To determine how the substrate affects the detection limit of different species, elemental dried spots were analyzed on different polymer films, including polypropylene and AP 1 . Comparisons were also made to elements deposited on different spherical, resin substrates such as polystyrene beads.
Date: January 1, 2002
Creator: Miller, T. C. (Thomasin C.) & Havrilla, G. J. (George J.)
Partner: UNT Libraries Government Documents Department

Ce-MXRF: the power of separation with bench top element sensitive detection

Description: Capillary electrophoresis (CE) is a proven separation technique that offers highly efficient separation, rapid analysis, and minute sample consumption. When combined with a element specific detection scheme, it can be used for chemical speciation of biologically and environmentally relevant species such as metal containing proteins. In this study, a new tool was developed for separation and elemental detection. Specifically, a simple CE apparatus was constructed using a thin-walled fused Si capillary and interfaced with a bench top micro x-ray fluorescence (MXRF) system. X-ray excitation and detection of the separated sample volumes was performed using an EDAX Eagle II micro x-ray fluorescence system equipped with a Rh target excitation source and a SiLi detector. It was demonstrated that the system could be used for the separation and detection of two metals from one another, specifically Cu{sup 2+} and Co{sup 2+}. Free Co{sup 2+} could also be isolated from Co{sup 2+} bound to cyanocobalamin (Vitamin B-12). Other systems that were explored were the separation of two organics, ferritin from cyanocobalamin as well as the separation of the different Cu and Zn isoforms of metallothinein. CE-MXRF was also used to separate the important serum isoforms of transferrin. Direct comparisons were made between CE-MXRF system and other elemental separation techniques such as CE-PIXE, CE-synchrotron-XRF, and CE-ICPMS.
Date: January 1, 2002
Creator: Miller, T. C. (Thomasin C.); Joseph, M. R. (Martha R.) & Havrilla, G. J. (George J.)
Partner: UNT Libraries Government Documents Department

Materials characterization using micro-x-ray fluorescence elemental imaging.

Description: Materials characterization continues to be a key challenge in a variety of programs. Although bulk elemental composition provides overall concentration of both major and trace elements, the distribution of these elements both on micro and macro scales can determine the performance and ultimately the physical properties of the materials. Hence elemental imaging can provide a new level of information for major and in some cases bulk trace concentrations of elements. Micro X-ray fluorescence (MXRF) offers unique capabilities in terms of elemental imaging. This approach is based on a meso scale level of resolution around 50 micrometer X-ray spot size. When coupled with a moveable stage, specimens several inches on a side can be imaged with surprising detail. In most instances, qualitative images are sufficient to illustrate the elemental heterogeneity. This information can then be used to determine if the material meets the desired physical characteristics and whether this is due to the observed heterogeneity or in spite of it. Several examples of elemental imaging will be presented. These will include the aging of polymers and the effects of residual organotin catalyst. The tin can be imaged using MXRF and has been show to be mobile within the polymeric material over time. Corrosion is a serious issue throughout the industrial world. A specific example of chloride attack on a metal, which creates problems in waste storage. Finally, MXRF used in high throughput screening in the development of novel peptide receptors will be shown. The advantage of MXRF is that no fluorescent tags need be added to the target molecules. This insures the unhindered interaction of the target molecules and allows for additional characterization using molecular spectroscopic techniques.
Date: January 1, 2002
Creator: Havrilla, G. J. (George J.); Miller, T. C. (Thomasin C.) & Joseph, M. R. (Martha R.)
Partner: UNT Libraries Government Documents Department

Nuclear fuels technologies: Thermally induced gallium removal system (TIGRS), fiscal year 1998 research and development test plan

Description: This document details the research and development (R and D) activities that will be conducted in Fiscal Year 1998 (FY98) by the Thermally Induced Gallium Removal System (TIGRS) team for the Department of Energy Office of Fissile Materials Disposition. This work is a continuation and extension of experimental activities that have been conducted in support of using weapons-derived plutonium in the fabrication of mixed-oxide (MOX) nuclear fuel for reactor-based plutonium disposition. The ultimate purpose of this work is to demonstrate adequate Thermally Induced Gallium Removal with a prototypic system. This Test Plan presents more than the FY98 R and D efforts in order to frame the Task in its entirety. To achieve the TIGRS Program objectives, R and D activities during the next two years will be focused on (1) process development leading to a prototypic TIGRS design, and (2) prototypic TIGRS design and testing leading to and including a prototypic demonstration of TIGRS operation. Both the process development and system testing efforts will consist of a series of surrogate-based cold tests and plutonium-based hot tests. Some of this testing has already occurred and will continue into FY99.
Date: December 24, 1997
Creator: Buksa, J.J.; Butt, D.P.; Chidester, K.; DeMuth, S.F.; Havrilla, G.J.; James, C.A. et al.
Partner: UNT Libraries Government Documents Department