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Brown University Electron Microprobe Facility

The Cameca SX-100 electron microprobe is one of the primary and fundamental research instruments in the Department of Earth, Environmental and Planetary Sciences.

In 2014, through an internal research grant from Brown University, the microprobe was upgraded with a new computer running Windows 7, version 5 of Cameca's Peaksight software, an improved vacuum system, a new electron gun that houses a LaB6 filament, and a joystick.

The electron microprobe laboratory

The Cameca SX-100 microprobe at Brown University.

Installed Options

Capable of analyzing most solid, non-organic materials, it is fully equipped with 5 wavelength dispersive spectrometers (WDS), a Rontec energy dispersive spectrometer (EDS), a secondary electron (SE) detector and a monochromatic cathodoluminescence (CL) detector.

Lanthanum boride filament

The installed LaB6 (lanthanum boride) filament (left) provides superior imaging capabilities, as well as a significantly longer lifespan over standard tungsten wire filaments.

A software option called beam tracking is also installed on this microprobe. This allows the instrument to deflect the electron beam slightly, when necessary, and guarantee that stored stage positions be precisely analyzed within a micron of their original setup position, even hours to days later, despite minor stage drift.

The microprobe can accommodate a variety of sample types including 6 one inch round slides or mounts, 4 rectangular slides or short mounts, or simple hand samples that have been flat polished.

See photos of the different holders.

The laboratory has acquired a full spectrum of mineral standards for the microprobe, including most silicate groups, glasses, carbonates, oxides, metals, phosphates, and sulfides.

The dept has a full suite of sample preparation tools and equipment for cutting, grinding and polishing most materials. A carbon coater is also present.

Brown University Electron Microprobe Facility

The Brown University Electron Microprobe Facility is located in the GeoChem building, room 027.

Schematic of the electron microprobe


The WDS spectrometers each contain two or four diffracting crystals and presently include LTAP, TAP (2), LPET (2), PET, LLIF (2), LIF, LPCO, PC1 and PC2. The last three crystals are used to measure the light elements (boron to sodium). The absolute detection limits for the instrument are approximately 50-200 ppm, depending on the element and available standards.

The EDS spectrometer is capable of detecting all elements above sodium (Na).

Element X-ray and Phase Mapping

Element x-ray maps can easily be acquired with the microprobe. Using 512x512 pixel maps, up to nine element maps (5 elements on WDS, 4 on EDS), plus a backscattered electron (BSE) image, can be obtained simultaneously. Maximum resolution on any one map is one micron per pixel. Utilizing the stage coordinate system, maps of entire thin sections can be generated. Individual element maps can subsequently be stitched together using ImageJ software. Finally, red-green-blue (RGB) phase maps can be generated by overlaying different element maps. An example is below.

Magnesium map of the eucrite meteorite Chaves

Magnesium, calcium and aluminum element x-ray maps (left) of the basaltic meteorite, Chaves, and a combined RGB mosaic map of those elements (below). Chaves, a howardite, is a breccia from the asteroid, Vesta.
Calcium map of the eucrite meteorite ChavesA combined RGB map of Chaves using magnesium, calcium and aluminum
Aluminum map of the eucrite meteorite Chaves

In the RGB phase map above, red shows the compositional zoning in the mineral, pigeonite (a type of low calcium pyroxene), blue shows plagioclase feldpsar, while green shows augite (a high calcium pyroxene).

Need to do some analysis or generate element maps?

Laboratory Fees and Contact Information

Download Microprobe Related Documents