The PGI is not only a consortium of people, projects, and ideas, but also one of facilities in the greater Knoxville metropolitan area, most noteably those at the University of Tennessee (UT) and those available at the Oak Ridge National Laboratory (ORNL),approximately 25 miles from UT. The facilities available for research include the Electron Microprobe Laboratory and the Laboratory of Analytical Geochemistry, which includes laminar flow benches and fume hoods for mineral separations as well as a new class 100, trace-element chemistry lab. The Institute for Rare Isotope Measurements (IRIM), located at UT's Pellessippi Research Facility 15 miles from the main campus includes gas separation system and three unique mass spectrometers that have been desiged for the analysis of very small quantities of rare-gas isotopes in natural materials. Those facilities at ORNL include the High Flux Isotope Reactor (HFIR) and associated neutron-activation counting lab, and the laboratories in the Analytical Chemistry Division which include an ion microprobe, an inductively coupled plasma mass spectrometer, and thermal ionization mass-spectrometers.

Electron Microprobe Laboratory, UT
Mr. Allan Patchen, Technician
The major analytical instrument utilized in most, if not all, of the PGI research endeavors is the electron microprobe. The Department of Geological Sciences has a Cameca SX-50 microprobe, with four wavelength spectrometers and and energy dispersive system (EDS). This computer-based instrument is capable of performing fully automated, non-destructive chemical analyses on 1-5 micron spots on polished surfaces. The Oxford Instruments (formerly Link) software on the EDS unit permits detailed back-scattered electron (BSE) and x-ray digital-imaging analysis to obtain modal data, as well as various shape values. This imaging capability has found particular application with lunar resource (ISRU) beneficiation studies, as well as to addressing the effects of “space Weathering” on lunar soils.

Laboratory of Analytical Geochemistry (LAG), UT
Dr. Gregory Snyder, Research Associate Professor, working in the Clean Lab.
The LAG is located in the new Science and Engineering Research facility adjacent to the Geology Department. The LAG consists of two distinct portions: 1) a semi-clean laboratory space for mineral separations that includes a Frantz isodynamic/magnetic separator, laminar flow benches for mineral picking with binocular microscopes, and a fume hood dedicated to heavy liquid separations, and 2) a Class 100 clean lab, for ion exchange, wet-chemical, separations of trace elements and radiogenic isotopic studies. Attached to the clean lab is an anteroom for weighing of rock powders. This clean lab is currently operational with two separate HEPA-filtered, plexiglass, chemistry work-stations (see photo). Isotopic analyses are performed in the Division of Analytical Chemistry at ORNL (30 miles away) on a VG 354 multi-collector mass-spectrometer. Currently, we are developing protocols for the analysis of trace-elements (specifically the REE) by isotope dilution, and Sm-Nd, and Rb-Sr isotopic studies of lunar samples, meteorites, and terrestrial mantle xenoliths and their constituent minerals. Protocols for Pb isotopic studies are planned for the future.

The Institute for Rare Isotope Measurements (IRIM), UT

The staff at IRIM, left to right: Michael Mobley (MS student in Physics), Katherine Ocker (PhD student in Geology), Charles Joyner (IRIM Technician), Karla Kuebler (MS student in Geology) and Norbert Thonnard (IRIM Director). The time-of-flight noble gas mass spectrometer and some of its associated laser system is in the foreground.

The Institute for Rare Isotope Measurements (IRIM), UT was established in 1993 to provide the research facilities and collaborative environment to further develop and to initiate new research opportunities by utilizing the nascent ultra-sensitive analytical technique based on resonance ionization. Research at IRIM is currently concentrating on isotope measurements of extremely small krypton and xenon noble gas samples. The technique has already demonstrated detection limits (for Kr-85) of less than 100 atoms, and isotopic discrimination (for Kr-81) of one part in 1013, opening new research opportunities in fields as diverse as particle physics, hydrogeology, glaciology and astrophysics.
Collaborators include members of the departments of Geological Sciences, Physics and Astronomy, and Environmental Engineering at UT, more than a dozen universities and research institutions in the US, and researchers at five foreign institutions. IRIM is funded with grants from NASA, NSF, DOE and JPL, and by research incentive awards from the Science Alliance and the Office of Research at UT.
Facilities include a gas separation system for efficient extraction of parts-per-million krypton samples from 0.1 to 10 liters of air, two specialized static mass spectrometers for reducing interfering isotopes in the sample, a resonance ionization laser system that can be tuned to krypton and xenon, or most elements in the periodic table, and a unique static time-of-flight noble gas mass spectrometer. Other equipment includes a residual gas analyzer system for gas separation system development and vacuum leak detection, a high-vacuum evaporator for preparing clean films for sample storage and calibrators, and the usual profusion of electronic, vacuum and mechanical test equipment found in a mass spec lab. When fully operational by mid-1998, IRIM will be the only laboratory world-wide capable, for example, of dating 200,000 year-old polar ice with Kr-81, or making Kr and Xe isotope measurements using the few thousand atoms available in micron-sized interstellar dust grains.

High-Flux Isotope Reactor (HFIR), ORNL
The HFIR and associated neutron-activation counting facilities offer unique opportunities to collaborate with physicists and chemists who are actively involved in trace-element analyses of a variety of earth materials. This facility includes two pneumatic tubes, one with a thermal neutron flux of 4 x 1014 n cm-2 s-1, which is the highest flux available to a pneumatic tube in the world. Such a high flux allows routine analysis of elements that are not possible with other reactors. Two PC-based gamma spectrometers, and six Ge detectors (four coaxial, one well, one x-ray) are available for counting. Approximately 65 elements can be determined at levels ranging from parts-per-million to parts-per-trillion or below. If the matrix to be analyzed does not become too radioactive when activated with neutrons, or if the activity decays quickly, then groups of trace elements can often be measured simultaneously. Extremely low quantities of certain elements (such as Ir) can be measured utilizing microwave digestion facilities available at ORNL and straightforward chemical separation techniques. Research and collaboration with Universities and Industry have been a hallmark of the work at HFIR. Cooperative programs currently exist with the University of Tennessee, University of Kentucky, Florida A & M, University of Missouri, and Montana State University. Among Industry, research has been undertaken with General Electric, ALCOA, and IBM.


Analytical Chemistry Laboratories, ORNL

Dr. Lee Riciputi, Group Leader

• Secondary Ion Mass-Spectrometry laboratory.
  The ORNL-geochemistry secondary ion mass-spectrometry (SIMS; or ion probe) facility has been utilized for high-precision measurement of light stable isotope ratios and is centered around a Cameca 4f ion microprobe. This instrument allows the in-situ analysis of elemental abundances and isotopic ratios for a wide variety of elements using normal thin-sections, and has a spatial resolution typically in the 5-30 mm range. Most work has been focused on the analysis of oxygen and sulfur isotope ratios, although hydrogen, carbon, lithium, and boron isotope analyses have also been performed. Typical 1-sigma precisions (limited by counting statistics) for 15-30 mm spot sizes are: +0.2 per mil for d34S in sulfides (12 minute analysis) and +0.6 per mil for d34S in sulfate (30 minute analysis); +0.6 per mil d18O in silicates, carbonates, and phospates (25 minute analysis) and +1.0 per mil d17O (60 minute analysis); +5 per mil D/H (40-60 minute analysis) in various hydrous phases; +2 per mil 13C/12C in carbonates (40 minute analysis). Standards are available for the analysis of a variety of phases, including quartz, feldspar, garnet, olivine, and carbonates. In addition to the stable isotope capabilities, the ion probe has been used to determine the abundances of trace-elements at the ppm to ppb level with precision on the order of 2-10% relative. Secondary ion imaging is also possible utilizing this instrument. Research is conducted on a wide range of geologic problems, with an emphasis on stable isotope research. Collaborative projects have included researchers from UT, the universities of Michigan, Wisconsin, Georgia, Florida, Princeton, Auburn, Virginia Polytechnic, Alberta, Indiana, Nevada-Las Vegas, Missouri, Queen’s-Belfast, the Scottish Universities Research and Reactor Centre, and Exxon Production Research
• Other Mass-Spectrometery Facilities.
  A class 100 clean lab for the high-purity separation of elements for thermal ionization mass-spectrometry is currently nearing completion. Instrumentation for thermal ionization isotope ratio measurements include a commercial VG-354 multi-collector mass-spectrometer and three in-house constructed, single-collector tandem mass-spectrometers for very low-abundance, high-sensitivity measurements. A VG Plasma-54 multicollector ICP instrument is also available for isotopic ratio measurements.

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