Enabling Isotope Ratio Measurements on an Ion Trap Mass Spectrometer.

For portable, remotely operated systems in space and defense, relaxed vacuum requirements are a strong advantage of ion trap mass analyzers. However, ion traps are believed to have insufficient capability for isotope ratio measurement because they fundamentally restrict sampling capacity. Focusing on modifications to the detection sequence of a digitally driven 3D quadrupole ion trap, operating in resonance ejection mode, we investigated improved performance for isotope ratio precision and accuracy. Due to xenon's inert nature and wide span of isotopes, xenon isotope ratios provide an excellent marker of processes (e.g. radioactive decay and planetary atmospheric escape) which would be ideally measured by in situ mass spectrometry. To target xenon isotope ratio analysis specifically, we implemented data acquisition system modifications for enhanced y-axis resolution measurements and signal filtering. In this manner, we show measurement precision improvements from ~±100 0/00 to ~±0.1 0/00 and accuracy improvements from ~30 0/00 to ~0.5 0/00 for our targeted isotopes of interest.