Model SMM 770 Scanning Magnetic Microscope System
TRISTAN TECHNOLOGIES --Page
52
Boil 0ff SMM770#3
run#1- 5/20/05
0.00
5.00
10.00
15.00
0
1
2
3
4
5
6
7
8
Days
Level (cm)
Depth=15.3 cm
2.29 liter volume
Figure 5-1
Measured boil off rate
5.2.3 Sensor Maintenance
The sensor window is .002” (51 microns
)
Sapphire.
WARNING
The Sapphire widow is very fragile! It must never be touched with the sample or
anything else. It is not covered by any warranties.
If the window is broken and vacuum is lost while the Dewar is cold, several things will happen:
1.
There will be a rapid loss of liquid nitrogen from the reservoir.
This could form a
violent stream of Liquid Nitrogen, which could be hazardous. Use caution.
When the
Dewar has emptied itself, and the danger of liquid nitrogen “burns “ has passed, the
window must be sealed and the Dewar evacuated as soon as possible.
2.
To reduce the chance that the SQUID sensor itself is not damaged by moisture,
temporarily seal the window with tape or other appropriate plug. Attach a vacuum pump
hose to the Cryolab valve operator and open the valve with a clockwise twisting motion.
Keep pumping until the Dewar is at room temperature (many hours).
3.
The cold inner parts will condense moisture from the available air. This moisture, if
allowed to collect, will destroy the superinsulation and the SQUID sensor itself. If the
Dewar is warm when the vacuum is lost, the available moisture in air is enough to ruin
the SQUID within ~20 minutes. If an emergency seal and vacuum pump cannot be
applied immediately, an airtight bag with desiccant packets can be used to store the
