Cameca SX 100

X-ray electron microanalysis is a non-destructive analytical method with high spatial resolution for measurement of elemental concentrations in geological samples.

Within the microprobe a tungsten cathode produces electrons that are accelerated towards the sample using high voltage. The interaction of the electron beam with the sample leads to emission of characteristic X-rays, the intensity of which is measured. By comparison with measurements of reference materials, the elemental concentrations within the sample can be calculated. With the exception of the light elements (H, He and Li), all elements can be detected by electron microprobe. In addition to quantitative analyses the instrument can produce element distribution maps as well as secondary and backscatter electron images (similar to a scanning electron microscope)

Our lab at the Department of Geosciences of the University of Bremen is equipped with a Cameca SX100 electron microprobe. This machine contains an energy-dispersive system (EDS) as well as four wavelength-dispersive spectrometers (WDS). The latter are equipped with TAP (2x; 2d= 25.7Å), LIF (2x; 2d= 4.03Å), PC1 (1x; 2d= 61Å) und PET (3x; 2d= 8.75Å) analyzing crystals, which enables us to measure all elements starting with carbon (or heavier). In addition, the SX100 has a built-in optical microscope and detectors for secondary electrons and backscattered electrons.

Samples must have a planar polished surface and must be resistant to vacuum (they must not degas). Possible sample formats are thin sections 28 x 48 mm in size ("Gießen format") and 1-inch mounts (25 mm diameter, 4-10 mm thickness). Prior to analysis samples are sputtered with carbon. For calibration standards the lab possesses the complete series of the Smithsonian National Museum of Natural History (Jarosewich et al. 1980), USGS glasses, and further silicates and sulfides.

Note: We thank the GFZ Potsdam for the generous donation of the microprobe, and Dr. Dieter Rhede (GFZ) and Dr. Niels Jöns (Uni Bochum) for their support during buildup of the lab.

User regulations electron microprobe (only in German)