Speaker
Description
Lunar exploration and in-situ resource utilization require reliable analysis of lunar soil and its resources. Orbitrap mass spectrometers offer high resolving power and mass accuracy, but charged regolith particles, plasma, and local surface potentials can disturb the electric fields that control ion injection and motion. This study investigates these effects using a three-stage physics-based approach linking grain-scale regolith charging to electric-field perturbations and Orbitrap performance. LIGGGHTS is used to model regolith packing and triboelectric and photoemission charging of individual grains. The resulting charge distribution is imported into COMSOL Multiphysics, where a nonlinear Poisson--Boltzmann/Bohm-flux model calculates sheath potentials and local electric-field variations. These perturbed fields are applied to ion trajectories in a validated Orbitrap geometry using Charged Particle Tracing. Fourier analysis determines changes in trapping frequency, resolving power, and mass accuracy, while Sobol analysis identifies the dominant factors affecting performance. Lunar charging conditions from approximately +10 V on illuminated surfaces to -50--100 V near the terminator and nightside are considered. For approximately 100 $\mu$m regolith-simulant grains, charges exceeding $10^5e$ ($\sim1.6\times10^{-14}$ C) are modeled. The results show that differently charged grains can create spatially varying injection-interface fields even at the same mean surface potential. Increasing field nonuniformity produces greater ion-energy dispersion and axial-frequency variation, causing shifts in measured $m/z$, mass accuracy, and resolving power. The results are compared with field-free Orbitrap performance of up to approximately 150,000 FWHM and 2--5 ppm mass accuracy. This work provides a quantitative framework for assessing how lunar regolith charging can affect Orbitrap accuracy, resolution, and ion transmission during lunar surface measurements.