[time-nuts] homebrew H maser

J. Forster jfor at quik.com
Thu Sep 2 04:58:01 UTC 2010


The combination of high vacuum and milliKelvin temperatures is far, far
worse.

-John

================


> J. Forster wrote:
>>
>> If you try to cut corners with high vacuun technology, you will be
>> disappointed. Even with all new parts and carefull assembly, you will
>> almost certainly have to He Leak Detect the system to get it tight. I've
>> done this stuff. It is doable but certainly not trivial. And you cannot
>> be
>> sloppy.
>>
>
>
> not trivial is an understatement..
>
> High vacuum seems straightforward until you sweat blood on it.  Oh. that
> fingerprint that serves as a virtual leak for weeks.  That Kapton tape
> that trapped a few molecules of whatever under it and outgassed.
> The gas diffusing out through the drilled bolt.. sure it's drilled, but
> the conductance is so patheticaly low, you're literally waiting until
> the gas molecules happen to randomly bounce their wey up the hole.
>
>
> It is the most horribly frustrating experience you will have. Unless
> you're running HUGE fast pumps.. then you just don't care.. Back when I
> sweated this kind of thing, I would have killed for the size pumps we
> run at JPL on the big vacuum chambers.. Outgas, what outgas, it just
> gets pumped away... But when you're running a 2 or 3 inch diff or turbo
> pump...
>
>
>





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