Back when I worked with cryo-LNA's, we had helium for the cryo's and
nitrogen for the waveguide (to pressurize it). The cryo's were located
in a tropical environment and we had to add helium every day.
Then you get a new person, who comes back and ask if they were suppose
to use the pink bottle or green bottle. Before you could get to the
cryo's, you would hear the displacers grinding away on the frozen nitrogen.
I took about 3 days to repair, you spent one day letting the unit come
up to ambient, then you cleaned it with freon and let it dry out, and
then you spent a day or two vacuuming the unit back down and purging it.
These units were for early day's satellite communications and they were
cooled down to 18 degree's kelvin. Use to use a hydrogen temp gauge to
measure that low.
Brian
On 9/1/2010 7:40 PM, Robert Darlington wrote:
And cryo means ultra high purity helium. I learned about that the hard
way. They don't like pumping gravel (solidified trace amounts of oxygen,
argon, etc.)
-Bob
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