[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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