PerkinElmer Spotlight 400 Series, User Manual

Page: 42 / 120

42 . Spotlight 400 Series User’s Guide
Open the flap covering the dewar.
1. Remove the dewar cap.
2. Place the small funnel supplied with the imager in the opening in the detector dewar
(Figure 14).
Figure 14 The dewar opening with the funnel inserted
CAUTION
Stand where you can see the inside of the funnel as you pour the
nitrogen in. Pour slowly, so that neither the funnel nor the dewar
overflows. If liquid nitrogen runs down the outside of the dewar, it can
damage the optics of the imager.
3. Carefully fill the funnel with liquid nitrogen. Stand back and let the funnel empty
completely.
The liquid nitrogen bubbles rapidly as it drains into the dewar. This first amount of
liquid nitrogen vaporizes completely as it cools the dewar.
4. Add another one and a half funnels of liquid nitrogen. Stand back and wait two minutes.
This nitrogen also vaporizes as the dewar continues to cool. The two minute wait
enables the bubbling to settle down and the pressure of the vaporizing nitrogen to
dissipate.
5. Continue to pour liquid nitrogen into the funnel, adding a little more each time the
funnel empties.
The funnel takes longer to empty as the dewar fills. This happens after two to three
more funnels of liquid nitrogen. Because the dewar has now cooled, the liquid nitrogen
does not vaporize, but instead fills the dewar.
6. Remove the funnel and wait two minutes.
The liquid nitrogen settles down and bubbling slows.
7. When the nitrogen stops bubbling, refit the detector cap.
The filled dewar cools the MCT to the correct operating temperature for several hours.
After that, the dewar begins to return to room temperature, and the preamp switches
off power to the MCT.