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This SBIR Phase II project will significantly improve the quality of elemental analysis in SEMS under partial pressure conditions by using a polycapillary x-ray optic in front of the energy dispersive spectrometer (EDS) in low-vacuum scanning electron microscopes (LV-SEM) or environmental SEMs (ESEM). LV-SEMS and ESEMs are designed to work at elevated sample chamber pressures to allow analysis of nonconductive or moist specimens. An undesirable consequence results from the broadening electron beam due to the presence of the gas. This degrades the elemental-detection sensitivity, because the fluorescent x rays generated far from the center of the electron probe create high background. It also greatly reduces spatial resolution for elemental mapping. The Phase I results have successfully demonstrated the feasibility of the proposed approach. In the Phase II, a fully-functional prototype polycapillary optic-based EDS will be built and demonstrated in a commercial LV-SEM system. This will include an optimized polycapillary x-ray optic with a large collecting angle, optic detector mounting, detector-SEM mounting which provides fine alignment, an operating procedure, and examples of application data. The team involved world leaders in developing and commercially providing x-ray optics and EDS systems.