Facilities

The LLNL noble gas analysis facilities include three mass spectrometers with associated gas introduction and purification systems. One remaining 1989 VG5400 is dedicated to noble gas analyses in natural waters as well as tritium concentration measurements in environmental samples by the helium-3 accumulation method. Two Nu Noblesse multicollector instruments are housed in a separate laboratory space and used for nuclear physics and nuclear forensics applications as well as Earth and planetary science research, including cosmogenic-nuclide geochemistry, geochronology, and the evolution of planetary atmospheres.

mass spectrometer
Noblesse 6-Faraday/4-multiplier detector block.

Mass Spectrometry

  • A VG5400 NGMS with one Faraday and one ion-counting collector is optimized for low-level helium measurements and used primarily for analysis of natural waters.
  • A Nu Noblesse NGMS acquired in 2013 is equipped with six Faraday detectors and four electron multipliers used in ion-counting mode. This instrument is used primarily for routine xenon and krypton analyses for nuclear science applications.
  • A second Nu Noblesse with a high-resolution ion source and five coaxial, switchable Faraday/multiplier detectors was installed in 2018 and is used for a variety of purposes including nuclear forensics and Earth and planetary science applications of cosmogenic noble gases.
  • A Pfeiffer Prisma Plus quadrupole mass spectrometer is coupled to the same extraction line as the 2013 Noblesse and is mainly used for sample screening, QC, and process development.
  • A standalone benchtop noble gas membrane inlet mass spectrometer (NG-MIMS) utilizes a Stanford Research Systems quadrupole RGA200 to rapidly measure dissolved noble gas concentrations in environmental waters (see  Visser et al., 2013)

Gas extraction

Noble gases are extracted from samples using a variety of methods. A dedicated line for gas extraction from natural water systems is coupled to the VG5400, and several laser heating systems can be coupled to either of the Noblesse instruments:

  • A Photon Machines Fusions laser “microfurnace” system includes both 70W and 140W laser diodes used in a control loop with an optical pyrometer allowing precise temperature control of samples heated in metal envelopes. This system allows both controlled-temperature extractions and simultaneous acquisition of isotopic data and diffusion kinetics.
  • A Photon Machines CO2 laser allows direct heating and melting of mineral and other solid samples.
  • In-situ noble gas isotope measurements can be performed with a Photon Machines Analyte G2 ultra-short-pulse excimer laser ablation system.

Gas processing and calibration

All three mass spectrometers are equipped with fully automated gas processing and purification systems including getters and stainless steel and charcoal cryogenic traps, as well as an array of standard gas introduction pipettes for introduction of calibrated gas standards. Gas standards include atmospheric noble gases used for determining spectrometer mass discrimination as well as mono-isotopic spikes used for abundance determinations by isotope dilution.