Routine Maintenance . 81
Cooling the MCT Detector (Spectrum 100)
Optionally, the Spectrum 100 may be fitted with an MCT (mercury cadmium telluride)
detector. When it is fitted in the instrument it must be cooled to 77 K before you collect
spectra. The detector is mounted in a dewar that can be filled with liquid nitrogen. The
detector is not enabled until it has been sufficiently cooled.
WARNING
Be sure to wait the specified time when filling the funnel and before
replacing the plug. 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 instrument after each time you fill
the funnel.
1. Remove the MCT coolant cover (Figure 28).
Figure 28 Location of MCT Coolant Cover
2. Remove the plug from the dewar.
3. Ensure that the funnel guide, which helps prevent overspill entering the instrument
body rather than the dewar, is in place.
WARNING
The extremely low temperature of liquid nitrogen can burn skin and
eyes. Avoid exposure by wearing protective gloves and safety
goggles whenever you work with it.
WARNING
As liquid nitrogen cools the detector it evaporates so rapidly that the
resulting pressures can send a funnel or detector cap suddenly and
forcefully shooting upward from the top of the dewar.
MCT coolant cover
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