Electron Microprobe Standard Block
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SATURATING THE FILAMENT

CAUTION: Greatly exceeding the plateau voltage risks burning out the filament. Proceed very carefully during saturation.  If you are not sure if you are close to the plateau, back the filament voltage down and begin again.

1) Move to the Brass Saturation Spot on the Standard Block

2) Begin to saturate the filament by SLOWLY raising the filament voltage.

  • Carefully watch the PICOAMMETER and make sure the beam is unblanked.

3) As the filament begins to saturate it will go through a false peak

  • Be careful not to go past the plateau.
  • Also do not exceed 2 amps on the filament current gauge.

4) If the Beam Current is going off scale adjust using the C2 Condenser Lens knob.

  • Once the plateau is reached, back the BEAM CURRENT down.

5) Centering the filament

  • Use the 4 large knurled knobs on top of the electron gun.
  • DO THIS VERY CAREFULLY SO YOU DON'T GET THE GUN OUT OF ALIGNMENT.

6) Set the Emission Current

  • Set the gauge above the Gun High Voltage Switch to 100 microamps using the bias knob.

7) Adjust the Sample Current

  • Turn the Signal Selector Knob from BC to SC.
  • Make sure that you are on the Brass Saturation Spot.
  • Change the Range of the Picoammeter from .1 to .03.
  • Use the C2 Condenser knob to set the Sample Current to 15 nanoamps.