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Cooling the MCT Detector
If the microscope is fitted with an MCT (mercury cadmium telluride) detector, the detector
must be cooled to −196 °C before you collect spectra. It is mounted in a dewar that can be
filled with liquid nitrogen. As you fill the dewar, the temperature of the detector drops, and
the preamp supplies power to the detector. Use the following procedure to cool the MCT
detector.
NOTE: If your Spotlight 200 is fitted with a DTGS or InGaAs detector, cooling with liquid
nitrogen is not required.
The extremely low temperature of liquid nitrogen can burn skin and
eyes. Avoid exposure by wearing heavy gloves and safety goggles
whenever you work with it.
WARNING
When liquid nitrogen warms to room temperature, nitrogen gas
vaporizes so rapidly that resulting pressures can send a funnel or
detector cap suddenly and forcefully shooting upward from the top of
the microscope.
WARNING
Be sure to wait the specified time when filling the funnel and before
replacing the detector cap. This enables the bubbling nitrogen to settle
down and the pressure to dissipate. In addition to wearing safety
goggles at all times, stand back from the microscope after each time
WARNING
you fill the funnel.
Do not site the instrument in a poorly ventilated area.
Oxygen depletion in an enclosed space does not trigger a gasping reflex,
and errors of judgment, confusion, or unconsciousness can occur in
WARNING
seconds and without warning.
Getting Ready to Use the Spotlight 200 . 43
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