U-PB SYSTEM Equipment

NBS-12", purchased in 1963, is a semi-automated isotope-ratio thermal ionization mass spectrometer (TIMS). It has single-sample capability and is not equipped with any type of electron multiplier or photomultiplier. Because of the slow throughput and the inability to analyze very small beams, the instrument is no longer used, and its electronic parts are being used as backups to other working instruments. Located in Denver. Tandem, purchased in 1973, is a semi-automated isotope-ratio TIMS. It is a double-focusing magnetic sector instrument and has both a Faraday collector and an electron multiplier. It has only a single-sample capability. It is primarily used for extremely low-level (<1ng) Pb isotopic analyses and low-level concentration analyses of metals such as Cd, In, Sb, Tl, and Ag. It was used extensively in the analysis of lunar material and meteorites. Located in Denver. VG-MM54E, purchased in 1979, is a fully-automated, isotope-ratio TIMS. It is equipped with a 16-sample turret, which increases sample throughput because of the ability to load and evacuate multiple samples at the same time. A photomultiplier system enables measurement of beams of <10-16 amperes. The external adjustable collector slit allows the user to adjust the resolution without needing to break vacuum. It is primarily used to analyze uranium and thorium isotopes for U-series disequilibrium age determinations, uranium isotope tracer studies, lead-uranium-thorium for age determinations, and lead isotope tracer studies. Located in Denver. VG-MM54R, purchased in 1981, is nearly identical in design and capability to the VG-MM54E. It is primarily used for U-Th-Pb, neodymium-samarium, and rubidium-strontium isotopic analyses. Located in Denver. VG-MM54 Sector, acquired in 1990, is a fully-automated isotope-ratio TIMS. It is equipped with a 20-sample turret, a pulse-counting photomultiplier and seven Faraday collectors, six of which are adjustable. Multiple collectors increase the throughput and quality of the data. Movable collectors allow measurement of any set of isotopes from lighter masses, such as calcium, to higher masses, such as uranium, on the same instrument with only a small amount of effort. It is primarily used for U-Th-Pb isotopic analyses for age determinations and tracer studies and high precision (+/-.00001) Sr-isotopic composition analyses for age determinations and tracer studies. Located in Denver. KEVEX 770 X-ray Fluorescence Spectrometer, purchased in 1991, allows rapid turnaround and inexpensive analyses for a wide range of elements. These elements can be analyzed quantitatively if suitable standards exist, or semi-quantitatively. The XRF instrument is fully-automated and holds sixteen samples at a time. It uses source-tuned incident x-rays for optimal analysis conditions for a given element and has a high-resolution energy dispersive detector. Located in Denver. MAT 262, purchased in 1993, is a fully-automated isotope- ratio TIMS. It is equipped with seven Faraday collectors, six of which are adjustable. The instrument is equipped with a 13-sample turret and an ion-counting electron multiplier. It is primarily used to analyze U and Th isotopes for U-series disequilibrium studies and Sr-isotope ratios for tracer studies. It is occasionally used for Pb and Sm-Nd isotopic analyses. Located in Denver. MAT 262, purchased in 1993, multicollector (9 collectors), multi-sample (13 samples), mass spectrometer. Fully automated, equipped with an electron multiplier. The instrument is updated with a better water chiller and a newer computer system. Located in Reston.

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URL http://geology.cr.usgs.gov/capabilities/gronemtrac/geochron/uthpb/equip.html