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Noble Gas Mass Spectrometer

Noble Gas Mass Spectrometer

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The noble gas mass spectrometer is a low volume instrument operated under static vacuum, and has a high sensitivity ion source (Nier-type). Typical sensitivity is 0.23 mA per torr for 4He and 1.7 mA per torr for 40Ar at 400 mA. The instrument is all-metal construction and can be baked to reach low background levels and low static gas rise rates, particularly important for the isotope analysis of small amounts of noble gases.

The OSU Noblesse instrument is fitted with a single faraday cup and 3 ion counting detectors. The high mass ion counter position is shared with the faraday with switching via an electrostatic deflector. The central and low mass ion counting detectors have a special filter to eliminate scattered, low energy ions that may interfere with small ion beams (especially important when trying to measure very small amounts of 3He in the presence of large amounts of 4He, for example).

The Noblesse is a variable dispersion instrument employing patented, electrostatic "zoom optics" derived from the Nu Plasma ICP-MS. It performs the 3He/4He measurement in a pseudo high-resolution mode that partially resolves 3He from HD++H3+, but any tailing from the HD+ +H3+ beneath the peak-flat where 3He is measured is virtually absent. The instrument also allows simultaneous collection of 20Ne, 21Ne and 22Ne, and rapid peak switching to measure 40Ar+ and CO2+ during the Ne analysis to monitor potential contributions of doubly charged interfering species. 36Ar, 38Ar and 40Ar can be measured simultaneously, with a choice between ion counting or faraday detection for the 40Ar peak depending upon sample size. Kr and Xe isotopes can be measured via peak jumping.