Laboratory

The Fluids and Volatiles Laboratory at Scripps is equipped with a state-of-the-art, magnetic-sector, noble gas mass spectrometer (MAP 215) with Channeltron multiplier (operated in ion counting mode) and electrostatic analyser. This instrumentation is optimized for the precise isotopic measurement of helium (3He/4He) – over a wide range of concentrations and from a variety of natural samples. Sample preparation and input is made via a fully-automated, all-metal line containing a Janis He-cooled cryogenic trap (to separate He from Ne), a Zr-Al bulk getter (for reaction of active gases), and an on-line dual-collector quadrupole mass spectrometer - for He/Ne ratio (and CO2 abundance) measurement and aliquot determination for MAP 215 inlet. The preparation/input line is interfaced to our Merchantek dual laser extraction system and to two on-line magnetic-slug-driven hardened-steel crushers.

The laboratory also houses the VG5440 – a modified version of the VG5400 noble gas mass spectrometer. The SIO VG5400 instrument has an enhanced Nier-type electron bombardment source (the VG “bright source”) and a nominal radius of 27 cm extended to 54 cm by use of stigmatic focusing. The primary design modifications of the SIO machine include the following alterations to the standard model. The machine is designed for static mode, triple collection of the isotopes of neon and nitrogen on four off-axis Faraday collectors and two axial collectors - switchable between a Faraday cage and a Daly multiplier. The instrument underwent a complete electronics overhaul in 2008. There are tow extraction lines interfaced to the VG5440 - a line dedicated to He-Ne-Ar isotope analysis and a different line built for the measurement of N2 isotopes.


A separate all-metal, groundwater and geothermal fluid extraction and noble gas isotopic dilution system is interfaced to a quadrupole mass spectrometer (SRS RGA200 equipped with electron multiplier) and is dedicated to the analysis of the noble gas concentrations in fluid samples. This system uses two mixed spikes (3He-22Ne and 78Kr-136Xe) which are aliquoted into the extraction system prior to sample extraction. Release of samples effectively mixes the ‘spike’ with the sample’s indigenous noble gases. Three separate noble gas fractions (containing He-Ne, Kr and Xe) are inlet into the quadrupole section for isotopic determination following active gas removal (gettering), sequential adsorption onto stainless-steel frits and U-tubes, and manometric measurement of the Ar partial pressure. The system is designed to give accurate determinations of the noble gas concentrations (± 0.5%) in fluids.


A glass extraction system for measurement (and collection) of CO2 and H2O is available for basalt analysis. The system consists of a temperature-regulated furnace for incremental step-heating of samples, a variable temperature trap for gas resolution, and a calibrated volume housing a Baratron capacitance manometer for pressure measurement. Following extraction and measurement, both water and CO2 can be collected for transfer to mass spectrometers for stable isotope analysis. A related glass extraction system is used for geothermal samples whereby CO2 is purified and manometrically measured before being aliquoted for stable isotope analysis.