Electron Microprobes

 The JEOL Superprobe JXA-8230 has the following parameters (manufacturer information):

  • Electron Gun: LaB6 or W-emitter
  • 5 Spectrometers
  • Crystals (for e.g.): LDE1 (F), LDE5H (N), TAP (Na, Si), PET (Ca, P, S), LIF (metals)
  • Cold trap (liquid nitrogen)

 

The JEOL Hyperprobe JXA-8500F has the following parameters (manufacturer information):

  • Accelerating voltage: 1 to 30 kV • Beam current: 0.01 to 4500 nA
  • Minimum Beam Size: 40 nm at 10 kV and 10 nA
  • Electron Gun: Schottky-Field emitter
  • 5 Spectrometers
  • Crystals (for e.g.): LDE1 (F), LDEB (Be, B), TAP (Na, Si), PET (Ca, P, S), LIF (metals, REE)
  • Cold trap (liquid nitrogen)

 

The electron microprobe technique employs an electron beam accelerated to a selected voltage of 3-20 kV, and focused on the surface of the sample. The electron beam is typically operated at probe currents of 5 to 50nA and the beam spot size can vary from 0.4 to 20 µm. The volume excited by the electron beam varies in the range of about 0.5 to 4.5 cubic microns, depending on sample density and acceleration voltage, corresponding to a sample mass of a few picograms. The sample generates characteristic X-rays, whose intensities are measured with wavelength (WDS) or energy dispersive spectrometers (EDS).

Employing these characteristic X-rays to reference standards make it a quantitative analysis. Elements from Be to U can be measured and quantified. Detection limits are typically between 5 and 800 ppm depending on the beam current and voltage, the X-ray line chosen and the counting time. Digital X-ray maps show variations in chemical compositions on the surface of a sample e.g. within a selected mineral. The resolution of the image and time of acquisition depend of the number of pixel 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.

The GeoForschungsZentrum maintains two electron microprobes, a JEOL Hyperprobe JXA-8500F with a thermal field-emission cathode (see Figure) and a JEOL Superprobe JXA 8230 with a tungsten or LaB6 cathode.

 

Samples can be analysed within the frame of an scientific cooporation. Beside that, analyses are possible in return for a financial contribution. For the latter case, please read the user regulations and the Appendix1. Prices can be given upon request, please send an e-mail to the contact person.

 

 

 

Contact

Franziska Wilke
Scientist
Dr. Franziska Wilke
Inorganic and Isotope Geochemistry
Telegrafenberg
Building D , Room 222
14473 Potsdam
+49 331 288-1317
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