Nu TIMS AppNote
High-Precision U-Pb Geochronology on Nu TIMS Using
All-Faraday Collectors with 10¹³ Ω Resistors
U-Pb geochronology by Isotope Dilution Thermal Ionization Mass Spectrometry (ID-TIMS) remains the most precise method for determining geological ages. Application note TI09 demonstrated the capabilities of the Nu TIMS at the Pacific Centre for Isotopic and Geochemical Research (PCIGR), University of British Columbia, using a Daly photomultiplier for Pb peak-jumping in combination with static Faraday collectors for U.
This follow-up note presents results from a new instrumental configuration: an all-Faraday acquisition of both Pb and U using 1013 Ω resistors, which offer inherently lower electronic noise, significantly improved per-analysis precision for small-to-medium ion beams,
and reduced analysis time by ~70%.
and reduced analysis time by ~70%.
The 1013 Ω resistors provide a ten fold increase in gain compared to the 1012 Ω resistors used in the TI09 study two years ago, decreasing Johnson–Nyquist thermal noise by a factor of √10 (approx. ×3.2) with the same integration times. This makes them particularly useful for low-Pb ion beams, which are common in ID-TIMS geochronology on single grains or individual standard fragments (5–50 pg Pb), where amplifier noise is the primary limit to precision.
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