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Purging the cooling tube
The low temperature nitrogen gas path in the cooling
tube maybe blocked sometimes (such as by foreign particles and ice). In
this case, you'll have to purge the tube using dry air. Do the following.
1. Disconnect the control station (make a note how it was connected
before disconnect it) from the cooling tube. Dismount the tube from the
cryo tank (undo four screws). Cover the tank top with a plate.
2. Lay the tube on floor and reconnect the control station exactly
the same way. You do not have to turn on the control station for this job.
3. Find the spare (and special) connection board in the lab that's
supposedly for connecting a helium cylinder to the mirror box. Take a plastic
tubing in a tool drawer and connect it to the connection board. You need
to take a look how it is connected. The other end of the connection board
goes to the dark gray tubing, which has an "easy connect" connector, to
the control station (and then to the cryo tube). Now, hook up the plastic
tubing to a "house air" outlet (the closest one in Lab 17 next to the x-ray
lab).
4. Turn the switch on the control station to "fill" position and
open the house air. Also, you need to adjust both the flow gauges on the
control station and the connection board to generate a strong enough dry
air flow passing througn the cryo tube. Let it purge to a few hours and
then put the cryo tube back on the cryo tank.
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