PerkinElmer Spotlight 150, User Manual

Page: 36 / 107

36 . Spotlight 150 User's Guide
1. Open the flap covering the dewar.
2. Remove the dewar cap.
3. Place the small funnel supplied with the microscope in the opening in the detector
dewar (Figure 11).
Figure 11 The dewar opening with the funnel inserted
CAUTION
Stand where you can see the inside of the funnel as you pour the
nitrogen in, but without positioning your head over the funnel itself.
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 microscope.
4. 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.
5. 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.
6. 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.
Now the dewar has cooled, the liquid nitrogen does not vaporize, but instead fills the
dewar.