Design method and construction of the Schwarzschild microscope with high numerical aperture for secondary ion mass spectrometry.

This article focuses on the design, optimization, and construction of a Schwarzschild microscope with a high numerical aperture (NA) of 0.47 for use in secondary ion mass spectrometry (SIMS). The authors propose an improved Schwarzschild optic (ISO) model to reduce high-order geometric aberrations that limit imaging quality at high NA values, demonstrating superior aberration correction compared to previous models. Tolerance analysis revealed that while thickness and curvature errors can be compensated by adjusting mirror spacing or object position, tilt and decenter misalignments remain critical factors restricting spatial resolution, necessitating precise mirror alignment. The constructed microscope integrated into a home-built SIMS achieved a spatial resolution of 2.19 µm, validating the design approach for enhanced sample navigation in SIMS applications.