Electron Microprobe Laboratory

The electron microprobe technique employs an electron beam, which is accelerated to a selected voltage, normally 15-20 kV, and focused on the surface of the sample. The electron beam is typically operated at probe currents of 10-50nA with a spot size of 0.1-20 µm. The volume excited by the electron beam is nominally about 1.5 cubic microns, corresponding to a sample size of a few picograms. The target (sample) generates characteristic X-rays, whose intensities are measured with wavelength or energy dispersive spectrometers.

Quantitative analysis can be made of the elements from Be to U. Detection limits are typically between 50 - 300 ppm depending on the mean atomic number of the rock matrix, target elements and X-ray counting times.
Digital X-ray maps show variations in chemical compositions on the surface of a sample. The resolution of the image depends of the pixel number in each direction, whereby every pixel represent an individual analysis. For example, a pixel map of 512 x 512 contains 262144 analyses for each selected element.

Contact persons:

• Dr. Dieter  Rhede
• Oona  Appelt [Section 4.1]
• Dr. Wolfgang  Seifert [Section 3.1]

JEOL JXA-8500F

 

• Accelerating voltage: 1 to– 30 kV
• Electron Gun: Schottky-Fieldemitter
• Beam current: 0.01 to– 4500 nA
• Minimum Beam Size: 40 nm at 10 kV and 10 nA
• 5 Spectrometers

 

CAMECA SX-100

 

• 4 two-crystal spectrometers and  Princeton Gamma Tech IMIX - energy dispersive spectrometer (with Be-window).
• Utility program for chained acquisition in un-attended operation mode
• Coaxial optical microscope with reflected and polarized transmitted light, CCD color camera and frame grabber
• Optical encoded specimen stage, reproducible step size to 0.5 µm
• Full quantitative WDS and EDS data acquisition either alone or in combination, up to 40 elements
• Image acquisition by beam or stage scanning and mapping, up to  2 video, 4 WDS and 16 EDS images simultaneously