[time-nuts] homebrew H maser

Bruce Griffiths bruce.griffiths at xtra.co.nz
Thu Sep 2 08:31:04 UTC 2010

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.
i.e. the mean free path of the atomic hydrogen needs to be somewhat 
larger than the dimensions of the (fused silica) gas containment bulb.

The mean free path will be comparable to the bulb dimensions at a 
pressure of around 1 ubar (100 uPa) or so.

Since the Hydrogen atom bounces of the fluoropolymer coated walls 
thousands of times before phase coherence is lost the mean free path 
needs to be several thousand times the containment bulb dimensions to 
avoid degrading the maser performance. This requires a pressure of 
around 1 nanobar (100nPa) or below within the storage bulb..

The (gas) conductance of the exit aperture of the dissociator is 
selected to achieve the required atomic hydrogen flux of  at most around 
3E-5 liter-Torr/sec or so for a typical hydrogen dissociator pressure of 
50Torr or so.


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