[time-nuts] Fwd: Re: homebrew H maser

J. Forster jfor at quik.com
Thu Sep 2 03:08:05 UTC 2010

They should never leak He. Were the lines between the compressor and the
head very long?



> 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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