Performance of the 3F4M Noblesse–HR Noble Gas Mass Spectrometer for Multicollection Ne-Ar-N2 Analyses

Abstract

The Noblesse–HR noble gas mass spectrometer was designed for multicollection analyses of different sets of noble gas isotopes with a fixed detector array under static conditions. At the Centre de Recherches Pétrographiques et Géochimiques (CRPG, Nancy, France), we developed a novel procedure to measure nitrogen (N₂) abundance and isotope ratio (²⁸N₂/²⁹N₂) using the 3 Faraday–4 Multiplier (3F4M) system. This procedure simultaneously acquires ion signals for ¹⁴N¹⁴N⁺ (Fa2), ¹⁵N¹⁴N⁺ (Fa1), and ¹⁵N¹⁵N⁺ (IC0). An in-house-built purification system ensures ultra-low blank levels (≤1 × 10⁻¹² mol N₂), while air standard measurements monitor detector sensitivity and instrumental mass fractionation. Here, we assess the effects of the source and zoom optics settings on mass resolution (MR), mass resolving power (MRP), and peak alignment, and identify potential contributions from interfering species. The performance of the Noblesse–HR for multicollection Ne-Ar-N₂ analyses was evaluated over several months and across varying gas quantities introduced into the mass spectrometer. Average sensitivities, with 1σ relative scatter, were 5.05 × 10⁻⁵ A/Torr ±1.02% for ²⁰Ne, 2.86 × 10⁻⁴ A/Torr ±1.37% for ³⁶Ar, and 1.18 × 10⁻⁴ A/Torr ±1.90% for N₂. Corresponding isotopic ratios were ²⁰Ne/²²Ne = 9.80 ± 0.34%, ²¹Ne/²²Ne = 2.90 × 10⁻² ± 1.53%, ⁴⁰Ar/³⁶Ar = 296.19 ± 0.10% (over 20 days), ³⁸Ar/³⁶Ar = 0.1876 ± 0.28%, and ²⁸N₂/²⁹N₂ = 135.92 ± 0.05%. These results demonstrate that the 3F4M Noblesse–HR provides precise, accurate, and reproducible data, adapted for studying planetary materials.