| The VG Sector 54, seven-collector thermal
ionization mass spectrometer has been in operation since August 1991. It is
fully automated with a 20-position sample turret, and 6 movable Faraday
collectors, and a Daly ion counting system. It is used for high precision
isotope ratio analysis of radiogenic isotopes and their parent daughter
abundance ratios by isotope dilution. Most of the work is with Sr (Rb/Sr),
Nd (Sm/Nd), and Pb (U/Th/Pb) systems and U-Pb geochronology. These isotopic
systems provide natural radiogenic tracers of geological processes as well
as clocks for determining the age of geologic events. In thermal ionization mass spectrometry the element of interest is deposited as a salt on a filament. The element is ionized by heating the filament. The ions are separated according to mass-to-charge ratio as they pass through an electromagnetic field. Precision on isotope ratios < 10 ppm are possible with this instrument. |
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