[time-nuts] homebrew H maser

Bruce Griffiths bruce.griffiths at xtra.co.nz
Thu Sep 2 07:58:16 UTC 2010


jimlux wrote:
> Hal Murray wrote:
>> jimlux at earthlink.net said:
>>> 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. 
>>
>> I've never worked with vacuum gear.
>>
>> I assume "drilled bolt" refers to a bolt through a drilled hole so 
>> there is some slop between the bolt and the hole.
> No... the bolt has a hole through it, to provide a gas path when you 
> install it into a blind tapped hole. Otherwise, the trapped gas in the 
> bottom of the hole slowly leaks out past the threads.
>
>>
>> Can I use vacuum grease as a seal around the bolt?  Or does it outgas 
>> too much if you are going for seriously low pressures?
>
> For the most part, grease is more trouble than it's worth. Knife edge 
> seals are where it's at.
>
>>
>> Can I use a soft(er) metal washer and mash it to a gas tight fit by 
>> tightening the bolt enough?
>
> Not exactly.. what you see is a knife edge cutting into a softer 
> metal... "mashing" implies gas trapped between layers.. That kind of 
> thing crops up in TWT manufacturing, where they stack all the parts of 
> the gun or the collector...
>>
>>
>> How low a pressure does a H maser need?   Where is it relative to say 
>> fingerprints outgassing?
>
> That's a good question.. I don't know.
>
>
http://www.dtic.mil/cgi-bin/GetTRDoc?Location=U2&doc=GetTRDoc.pdf&AD=ADA503712 
<http://www.dtic.mil/cgi-bin/GetTRDoc?Location=U2&doc=GetTRDoc.pdf&AD=ADA503712>

Indicates that the operating pressure at the hydrogen dissociator is 
likely to be a few Torr or so.

Bruce




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