[time-nuts] homebrew H maser

[Richard W. Solomon]

This discussion reminds me of a time long ago when I 
worked at a University. We had one rather obnoxious 
Grad Student, who, although brilliant, was a Royal PITA.

So, while constructing his vacuum system, and getting 
hassled by him, I located one of the Universities residents, 
a large water bug. Which I let loose in the vacuum plumbing.

He was beside himself for about a week, wondering why he 
could not get pumped down to the level he expected.

73, Dick, W1KSZ


-----Original Message-----
>From: jimlux <jimlux at earthlink.net>
>Sent: Sep 2, 2010 6:29 AM
>To: Discussion of precise time and frequency measurement <time-nuts at febo.com>
>Subject: Re: [time-nuts] homebrew H maser
>
>Poul-Henning Kamp wrote:
>> In message <4C7F5918.7030101 at xtra.co.nz>, Bruce Griffiths writes:
>> 
>>> Indicates that the operating pressure at the hydrogen dissociator is 
>>> likely to be a few Torr or so.
>> 
>> The pressure is basically: "As low as possible" in order to minimize
>> hydrogen collisions (other hydrogen, walls) as much as possible.
>> 
>
>
>A few torr is actually not a particularly high vacuum (e.g. your run of 
>the mill neon sign is pumped down a lot lower before being filled to a 
>few torr).
>
>PHKs comment implies you're looking for mean free path somewhat greater 
>than physical dimensions...
>That would imply pressures less than a micron (0.001 Torr)..  MFP = 
>5E-3/P with P in Torr.. 1 micron pressure == 5cm MFP
>
>The other thing is when you're looking at MFP comparable to dimensions, 
>you're looking at molecular pumping in some form (no more pistons or 
>rotary vanes or ...)
>
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