Electron Probe Microanalysis Laboratory

Instrumentation and Facilities

The Department of Earth and Planetary Science purchased an electron microprobe analyzer with a generous grant from the National Science Foundation in 1994. The principle investigator of the proposal, "Purchase of a New Electron Microprobe", was Dr. Ian S. E. Carmichael and the proposal was co-investigated by Drs. Raymond Jeanloz, George Brimhall, Hans-Rudolf Wenk and Donald DePaolo.

The microprobe instrument is a Cameca SX-51 with 5 vertical high resolution wavelength dispersive spectrometers (WDS) and a atmospheric thin window (ATW) energy dispersive spectrometer (EDS). The instrument is under the direction of Dr. Ian. S. E. Carmichael.

The SX-51 includes a TV rate secondary electron (SE), backscattered electron (BSE), cathodo-luminescence (CL) and coaxial optical imaging capabilities. The instrument is completely computer controlled for automation of both the beam (high voltage, beam current, beam size, scan magnification, etc), spectrometer (analyzing crystal, Bragg position, PHA baseline/window/gain/bias/deadtime, count time, etc) and stage (x, y, z position).

In addition, new Windows PC based software has been developed (Win95/NT OS) to facilitate rapid and accurate acquisition, automation and quantitative analysis for all specimen types on the microprobe.

Summary of Specifications

· Cameca SX-51 electron microprobe with 5 wavelength spectrometers
· Oxford Si(Li) EDS detector, ATW thin window, 138 eV resolution
· Secondary, backscattered, cathodo-luminescence and optical analog and digital imaging
· Analytical range from Be to U
· Analytical sensitivity from 100 % to 10 ppm
· Analytical sensitivity typically from 100 % to 100 ppm
· Analytical accuracy typically 1 - 5 % (major and minor elements)
· Typical analysis time 10 sec (major elements) to 300 sec (traces)
· Sample size range typically from 10 microns to 25 mm or larger
· Analysis volume typically 1 - 10 cubic microns depending on x-ray energy
· Reflected and Transmitted Light Optics in all configurations
· Pentium PC based Windows multi-tasking acquisition and analysis interface
· Numerical, graphical and false-color image hard copy and file output