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Safety Precautions
Element Basic User Guide
Page 9 of 21
2.6.2 PREVENT PARTICLE CONTAMINATION INSIDE THE SAMPLE CHAMBER
Particulates inside the sample chamber have a tendency to become entrained in the gas flow while
venting the sample chamber. The gas flow during a chamber vent or increase in chamber pressure is
generally turbulent meaning that entrained particles can fly in all directions, including toward the
detector window. Particulates which impact the window can cause micro cracks compromising the
vacuum seal of the window. In more extreme situations, particles can fully penetrate the window
causing what is known as a “bullet hole”, which causes a larger leak in the detector. It is also possible to
dislodge particles from the sample via the electron beam. If these particles are charged, they may be
accelerated toward the detector, which is at ground potential.
Recommendations :
□
Always use particle free gloves when loading samples or working in the sample chamber.
□
Be certain that there are no loose particles on the sample before placing the sample in the
chamber. Sample surfaces, fractures and powdered samples stuck to an adhesive should be
cleaned with compressed air to ensure the surfaces are clean and free of loose particles.
□
Avoid venting the sample chamber too quickly. Specifically, do not exceed 10 cm/s gas velocity
into the chamber, as this can increase the risk of particle-induced detector window damage. This
may require a small aperture in the vent port or decrease in supply pressure if N2 purge is used
to reduce the gas velocity.
□
If there is a high risk of particulates becoming dislodged during some operation in the
microscope, fully retract the detector to minimize the risk of damaging the detector window.
2.6.3 PROPER CARE WHEN USING A COMPRESSED GAS TO VENT THE SAMPLE CHAMBER
Ensure that the gas pressure does not exceed 2 atm.
Recommendations
:
□
Release any latching mechanism that is designed to keep the chamber door closed.
□
Make certain that the chamber door will open normally when the chamber reaches atmospheric
pressure.
□
Avoid venting the chamber too quickly as this can cause unsafe pressure-induced vibrations on
the window. See recommendations in section
2.6.2 above.
2.6.4 AVOID HITTING THE DETECTOR OR INDUCING MECHANICAL VIBRATIONS IN THE
DETECTOR OR WINDOW
The detector window can be ruptured by excessive physical vibration or shock.
Recommendations :
□
Be careful not to run samples into the EDS detector.
□
Close the sample chamber door gently.
□
Do not pull the sample chamber door open while venting the sample chamber. This may lead to
unsafe pressure fluctuations inside the sample chamber which could damage the detector
window.