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18 NTE/CCD Detector Manual Version 2.A
4.
On the top side of the Temp knob is a rectangular window that denotes hundreds of
degrees C. Each complete turn of the knob is -100°C. Around the moveable part of
the knob are numbers from 0 to 99, in increments of 2. Turn the knob until the
correct value (0) appears in the hundreds’ box.
5.
Then turn the knob until the desired value between 0 and 70 appears below the box.
6.
Turn the locking tab clockwise to lock the Temp knob in place.
Figure 9 exhibits the position of the dial for a temperature of -50°C. Position 1 shows the
locking tab in the unlocked position. Position 2 is the locked position.
Once cooling has been initiated, it takes from 10-20 minutes for the NTE/CCD to reach
and lock at the set temperature. With an ST-138 controller, the cooler status indicator
will turn from orange to green. Once lock is established, temperature is stable to within
±0.050°C.
Cooling Troubleshooting
Detector doesn’t achieve Temperature Lock
If the indicator doesn’t turn green after 30 minutes, the temperature setting may be at a
temperature colder than the specified limit or the environment could be particularly
warm. If this occurs, try a higher temperature setting. Make sure you are selecting a
temperature that is acceptable for your particular detector and CCD array.
Cooling and Vacuum Level
With time, there will be a gradual deterioration of the detector’s vacuum. This, in turn,
will eventually affect temperature performance and it may no longer be possible to
achieve temperature lock at the lowest temperatures. In the kind of low-light imaging
applications for which cooled CCD detectors are so well suited, it is highly desirable to
maintain the system’s temperature performance because lower temperatures provide less
thermal noise and better signal-to-noise ratio.
Vacuum deterioration occurs primarily as a result of outgassing of components in the
vacuum chamber. Because outgassing normally diminishes with time, the rate of vacuum
deterioration in new detectors will be faster than in old ones. As a result, each time the
detector is repumped, the new vacuum will remain good for a longer time than the
previous one. In any case, should you notice a gradual deterioration in temperature
control performance, the detector should be repumped.
If you have the appropriate equipment and personnel with the necessary expertise
available, you may wish to pump down the detector at your facility. Contact the
factory Technical Support Dept. for information on how to refresh the vacuum. See
page 50 for contact information.
If the necessary equipment and expertise is not available, simply contact the factory to
make arrangements for returning the detector to have the vacuum restored.
The CCD array is subject to damage from condensation if exposed to the atmosphere
when cold. For this reason, the detector should be kept properly evacuated or backfilled
with dry nitrogen, free of oil or other contaminants.
WARNING