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The Ultrachron project is an effort to create a more specialized analytical instrument which will expand the capabilities of electron probe micro-analysis (EPMA) beyond traditional performance "limitations". EPMA instruments have historically been constructed to achieve rapid,efficient, in-situ chemical microanalyses of major and minor elements from a broad array of solid materials.

The Ultrachron project represents a major philosophical departure in that every aspect of the instrument has been re-evaluated in order to achieve specific goals, sacrificing the versatility of traditional EPMA where necessary. In this case, the development has three major goals: 1) Improved spatial resolution; 2) Improved precision; and 3) Improved accuracy. These are extraordinary challenges given that enhanced spatial resolution typically requires lower scattering volumes produced at lower voltage and smaller beam diameter produced at lower current, and that these effects are counter to enhancement of precision (count rates) produced with higher beam current and voltage.

This development takes advantage of the small electron scattering volumes in high Z accessory phases such that improvements in beam diameter make a substantial difference in the spatial resolution of the compositional analysis. Higher brightness sources and improved column optics do make a difference under these circumstances.

This development has also saught to improve precision by both developing higher current density and improving X-Ray counting efficiency. The achievement of extremely high current density presents new issues, particularly with internal space charge effects and sample damage potentially affecting accuracy.

ultrachron overview
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