Neon isotopic measurements using high-resolution, multicollector noble gas mass spectrometer: HELIX-MC

Y. Marrocchi (1, 2) , P. G. Burnard (1) , D. Hamilton , A. Colin (1) , M. Pujol (1) , L. Zimmermann (1) , B. Marty (1, 3)

1 CRPG - Centre de Recherches Pétrographiques et Géochimiques
2 LMCM - Laboratoire de Minéralogie et Cosmochimie du Muséum
3 ENSG - Ecole Nationale Supérieure de Géologie

We describe a new high-resolution, multicollection, noble gas mass spectrometer, the HELIX-MC, developed by GV instruments. The instrument uses a collector housing that holds five "MiniDual" detection systems, each detector containing two devices: a Faraday cup collector and channel electron multiplier. Each detector is 5.2 mm wide, which permits collecting adjacent beams separated by 1 atomic mass unit (amu) at mass 136. The HELIX-MC operates at high mass resolution (m/Δm > 1500), which allows the interference of ⁴⁰Ar⁺⁺ on ²⁰Ne⁺ to be resolved. We report the results of some tests on the "MiniDual" collectors, in which we have achieved precise Ne abundance and isotopic measurements. After a correction for doubly ionized CO₂ (0.37-1.5%), our results show that the HELIX-MC produces only very limited instrumental Ne isotopic mass fractionation (≈-0.5%.amu^-1). The sensitivity of the HELIX-MC for neon measurement performed on 10¹² ohms collector is around 1.4 × 10^-3 A torr^-1 for quantities of ²⁰Ne analyzed comprised between 1.27 × 10^-15 and 4.71 × 10^-15 moles. Within this range, the reproducibility of the isotopic measurements of standard gas falls in the range between 0.5 and 0.8% (1σ) for ²⁰Ne/²²Ne and 1 and 1.5% for ²¹Ne/²²Ne over a period of several days. The machine characteristics for measuring He are also reported.

Domains: Sciences of the Universe [physics]; Earth Sciences

Y. Marrocchi, P. G. Burnard, D. Hamilton, A. Colin, M. Pujol, et al.. Neon isotopic measurements using high-resolution, multicollector noble gas mass spectrometer: HELIX-MC. Geochemistry, Geophysics, Geosystems, 2009, 10, ⟨10.1029/2008GC002339⟩. ⟨insu-03619251⟩