R.M. Wheeler

Trace element analysis using proton-induced x-ray emission spectroscopy

Abstract A system for trace element analysis by proton-induced X-ray emission spectroscopy developed at the T. W. Bonner Nuclear Laboratories at Rice University is presented. Some characteristic problems are discussed and applications to the study of trace element concentrations in environmental and biological targets are described.

Trace element analysis of seawater and fish samples by proton induced x-ray emission spectroscopy

Abstract Proton induced X-ray emission spectroscopy has been used for trace element analysis of seawater and fish (trout-Salmo gairdneri) samples. To test the applicability of the technique for large-scale analysis of seawater and fish samples, the consistency of results from equivalent samples was checked. Also, a volatilization study was made at several different beam intensities to determine the effects of the beam on trace elements in the samples. The reproducibility of the results was found to be within acceptable limits.

Techniques for trace element analysis: x-ray fluorescence, x-ray excitation with protons, and flame atomic absorption.

Trace element concentrations in human blood serum have been measured by x‐ray fluorescence and by x‐ray excitation with protons to test the current effectiveness of each technique for routine analysis of biological samples. Results are compared with those obtained from analysis by flame atomic absorption.

M-shell ionization of rare earth elements by proton impact in the energy range 0.6–4.6 MeV

M-shell X-ray production cross sections of the rare-earth elements 57La, 60Nd, 62Sm, 63Eu, 64Gd, 66Dy, 67Ho, 66Dy, 67Ho, 68Er, 70Yb, 71Lu, and 72Hf were measured for proton bombardment in the energy range 0.6–4.6 MeV. The efficiency of the windowless Si(Li) detector for X-rays in the energy range 0.5–5.0 keV was determined by using the known atomic-field bremsstrahlung cross sections for low energy electron beams, K-shell X-ray measurements with protons, and calibrated radioactive sources. The measured X-ray production cross sections are compared to the predictions of the first Born approximation and the ECPSSR theories.

Trace elements in human nasal cavity bones

In recent years, the use of synchrotron radiation for high-sensitivity trace multielement analysis has been well established. We have used a white X-ray beam from the Brookhaven National Synchrotron Light Source to analyze trace elements in nasal cavity bones from both males and females of various ages. Ca, Fe, Cu, Zn, Pb, and Sr were routinely identified. A 30 × 60 μm photon beam was used to scan the samples to see variations in elemental concentrations. Results of our preliminary analysis as well as future plans to analyze more bone and other biomedical samples will be discussed.

Geologic assessment of environmental impact in Lake Macatawa, Michigan

A historical record of the effects of human development upon Lake Macatawa is established using geologic criteria. Significant cultural events are recognized using the pollen record, particularly ambrosia/vesiculate pollen ratios, and occurrences of detrital and chemical contaminants within the more recent sedimentary column. Detrital contaminants include such things as cinder and ash from coal burning power plants and animal hair from early tanning operations. Trace metal contaminants, frequently associated with specific industrial events, are particularly useful in establishing a modern sedimentary chronology.The impact of human activity upon Lake Macatawa is measured using fossil diatoms. The advantage of this method of environmental impact assessment is that it provides a historical perspective in which changes within an environment are related to its natural conditions.

M-shell X-ray production cross sections of rare-earth elements by 4He2+ impact in the energy range 0.7–7.0 MeV

Abstract M-shell X-rays of the rare-earth elements 57La, 60Nd, 62Sm, 63Eu, 64Gd, 66Dy, 67Ho, 66Dy, 67Ho, 68Er, 70Yb, 71Lu, and 72Hf were measured for 4He2+ bombardment in the energy range 0.7–7.0 MeV. The M-shell X-rays with energies of 0.64–1.90 keV were detected with a windowless Si(Li) detector. The efficiency of the detector was determined by using the known atomic-field bremsstrahlung cross sections from low energy electron beams, K-shell X-ray measurements with light projectiles, and calibrated radioactive sources. The measured cross sections are compared to the predictions of the first Born approximation and the ECPSSR (energy loss and Coulomb deflection effects, perturbed stationary state approximation with relativistic correction) theories.

X-ray production in fluorine by highly charged boron, carbon, and oxygen ions *

Abstract K-shell X-ray production cross sections of fluorine have been measured as a function of ion charge state for boron and carbon ions at 10 MeV and oxygen ions at energies of 8, 10, and 12 MeV. From the projectile charge-state dependence of the cross sections, both direct-ionization and electron-capture contributions were extracted for comparison to the Coulomb ionization theory, ECPSSR, which accounts for energy loss and Coulomb deflection of the projectile as well as for relativistic and perturbed stationary states of the inner-shell electrons.

Direct ionization in K-shell X-ray production in fluorine by highly-charged lithium, boron, and oxygen ions

Abstract Measurements of fluorine K-shell X-ray production cross sections are reported for thin solid targets of YF 3 for 1.5–4.0 MeV 7 Li + 2–10 MeV 10 B 2,3+ and 3–12 MeV 16 O 3,4,5,+ ions. In order to determine target thicknesses corresponding to near single-collision conditions. X-ray measurements were made using targets of thickness 2–66 μg/cm 2 deposited on 5 μg/cm 2 carbon backings. Experimental procedures as well as comparisons to the ECPSSR theory are discussed.

Trace element analysis of steel samples with synchrotron radiation

Abstract X-ray fluorescence by synchrotron radiation (SRXRF) has been used to determine elemental concentrations of elements from Ti to Mo in power generating turbine assemblies. Measurements were made at the Cornell High Energy Synchrotron Source using 7.0 and 20.5 keV X-ray fluxes. Absolute concentrations were made by comparison to an NIST steel standard. These same samples have recently been studied using the PIXE technique. Because of its sensitivity to elements with higher atomic numbers, the synchrotron radiation method is seen as complementary to PIXE for trace element analysis of steel samples. Advantages and disadvantages of the SRXRF technique are discussed.