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-8530F PLUS has the following parameters (manufacturer information):

  • Accelerating voltage: 1 to 30 kV
  • Electron Gun: Schottky-Field emitter with In-lens condenser lense
  • Minimum Beam Size: 50 nm at 10 kV and 100 nA
  • Resolution in SE-mode: 3nm at 30kV
  • Beam current adjustable between 1pA and 2µA
  • 5 Spectrometer
  • Crystals (for e.g.): LDE1 & LDE1L (F), LDEB (Be, B), TAP and TAPL (Na, Si), PETL (Ca, P, S), LIFL (metals, REEs), LDE5H (N)
  • Cold trap (liquid nitrogen)

 

The German Centre for Geosciences (GFZ) maintains two electron microprobes, a JEOL Hyperprobe JXA-8530F PLUS with a thermal field-emission cathode and a JEOL Superprobe JXA 8230 with a tungsten or LaB6 cathode.

The electron microprobe technique employs an electron beam accelerated to a selected voltage of mostly 5-20 kV, and focused on the surface of the sample. The electron beam is typically operated at probe currents of 5 to 50nA. At high voltages and small currents, the beam diameter can be focused into the nm range and set to a maximum of 20 µm on the sample surface.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. The detection limits are usually between 5 and 800 µg/g, depending on the comparability of the concentration of the element sought from the standard and sample, the intensity of the selected X-ray line, and thus also on the excitation voltage and the beam current as well as the counting time.

Element distribution maps are recorded over a certain area of the sample or in a certain mineral either by scanning the electron beam over the sample or by moving the sample under the electron beam. The size of the area determines the type of recording. The resolution of the images depends on the number of pixels in each direction (e.g. 512 * 512 pixels), with each pixel corresponding to an individual analysis. 

Prior to an appointment on the microprobe, samples need a special treatment. Samples can be analysed within the frame of a scientific cooperation. Besides that, analyses are possible in return for a financial contribution. In any case, please read the "Sample preparation and user regulations". Prices can be given upon request, please send an email to the contact person.

Sample preparation and user regulations

 

 

 

Contact

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