EES-1 has a Cameca Camebax SX50, a fully automated electron microprobe that was acquired in 1992. This microprobe is equipped with four vertical wavelength spectrometers, long acknowledged as the method of choice for high-precision quantitative analysis, plus a fully integrated Princeton Gamma Tech energy-dispersive X-ray analysis system. In terms of both maximum acceptable count rate and spectral resolution, wavelength spectrometry enjoys a nearly ten-fold advantage over energy-dispersive spectrometry. As well as traditional element measurement capabilities, the SX50 contains two, large d-spacing, multilayer, pseudocrystals capable of detecting and measuring light elements from fluorine down to berylium. Spectrometer precision is provided for by an optically encoded, totally linear, fully geared direct-drive mechanism. Beam current regulation, essential for consistent quantitative analysis, is provided by a continuous beam current monitoring and feedback system. Stage positioning is provided by fixed ruled-glass markers and moving photocell detectors that ensure a respositioning repeatability of 1 micron. Multiple sample carriers allow study of conventional geologic petrographic thin sections or one-inch rounds. Both reflected or transmitted plane or polarized light is available. Imaging functions include both secondary electron and backscattered electron capabilities. Microprobe automation is provided by a SUN 4/330 work station with 32-bit VME-bus hardware. Software includes SUN/Unix operating system and utilities and the Cameca software. Cameca software consists of the following application groups:
(1) Local instrument control;
(2) Quantitative analysis using Pouchou and Pichoir matrix corrections acquired in either manual or unattended, automated mode and utility menus for summary, averaging, and comparison and plotting of quantitative data;
(3) Qualitative analysis comprising acquisition of line scans in either beam or stage mode, acquisition of wavelength scans, and display and processing of qualitative data; and
(4) Cameca image processing programs designed to acquire and process X-ray and secondary or backscattered electron images.
This instrument is used routinely to provide staff researchers with fully quantitative analyses of a variety of mineral species. Detection limits are estimated to be as low as 100 ppm (or 0.01 wt.%) for most common elements.
For more information, contact:
Peg Snow (505-667-8007
or snow@lanl.gov)