[time-nuts] homebrew H maser
Bruce Griffiths
bruce.griffiths at xtra.co.nz
Thu Sep 2 09:00:29 UTC 2010
The effect of some residual gas species can be gauged from the results of:
http://cos.cumt.edu.cn/jpkc/dxwl/zl/zl1/Physical%20Review%20Classics/atomic/106.pdf
Bruce
Bruce Griffiths wrote:
> Bruce Griffiths wrote:
>> 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.
>>
>> Bruce
>>
>>
> Oops!, the pressures given in Pa above are out a few orders of
> magnitude.
> Correct values are:
>
> The mean free path will be comparable to the bulb dimensions at a
> pressure of around 1 ubar (0.1Pa) 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 (100uPa) 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.
>
> Bruce
>
>
>
>
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