Caltech
Noble Gas Lab
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My laboratory
consists of a MAP 215-50 noble gas mass spectrometer and associated vacuum
systems for the analysis of the abundance and isotopic composition of helium,
neon, argon, krypton, and xenon. A second system,
based on a Pfeiffer-Balzers
Prisma quadrupole mass spectrometer, is used for high precision noble gas
abundance determinations using isotope dilution. Both instruments are fully
automated for high sample throughput and improved reproducibility. We can
extract noble gases from a variety of geological materials including water
and gas samples, for example as collected from volcanic hotsprings. We can
also release noble gases from rocks, minerals and sediments using vacuum
crushing, conventional vacuum fusion, and heating with a Q-switched Nd-YAG
laser. After extraction the noble gases are purified of contaminants such as
CO2 and N2 using SAES getters, and adsorbed on a
variable temperature (8 - 450 kelvin) cryogenic cold trap built by Janis Research. The individual noble gases
are then thermally desorbed and analyzed with the mass spectrometers. The
laboratory automation system is run by custom software created with Labview. In 2005 I received a newly
designed split-tube noble gas mass spectrometer (Helix SFT) manufactured by GV instruments. This instrument is
specifically designed for simultaneous detection of 4He (on a Faraday
collector) and 3He (on an electron multiplier). The split tube
design and a secondary electrostatic filter in front of the multiplier will
provide very high abundance sensitivity for measuring extremely low 3He/4He
ratios and 3He concentrations. This instrument is performing
extremely well. In addition to commercial
instrumentation my group is collaborating with Dr. Ara Chutjian at JPL to
design and test a static-vacuum-mode Paul ion trap mass
spectrometer for noble gases. The goal of this project is to assess the
sensitivity and resolution of the instrument. |
