[time-nuts] homebrew H maser
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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