[time-nuts] Hydrogen Maser KIT! Update #1
magnus at rubidium.dyndns.org
Sun Nov 2 18:09:43 EST 2014
Yes, but your Q will suffer.
Yes, I've dug out *aged* papers. I was sad to see that JPLs server was
taken down before I got to download their wealth of papers. Naturally it
happen just after I found out it also had a hydrogen maser section, but
also Chuck's papers was lovely to have collected in that form.
I have been lazy not to read up on all the hydrogen maser I have in
book-form at home... should definitely read up more on those.
It is interesting to see how variation on themes got considerable
narrower somewhere in the 60/70s shift to the rubidium gas-cell, active
and passive hydrogen maser and finally cesium atomic beam. It seems like
the knowledge of why they narrowed down to that set is somewhat lost to
most, but as one reads up on the old stuff one learns of the variation
of these themes that have been tested. The CSAC thus belongs to the gas
cell type for instance, with that set of problems, but with a few twist
and turns. The fountains (Cs or Rb) is a variation of the beam
apparatus, but with a few twist and turns. The ion clocks is really an
extension of the hydrogen maser's bouncing box in it's attempt to create
long observations times.
I think I recall that someone attempted a cryogenic hydrogen maser,
which would have benefits as to the lower temperature and thus speed of
the hydrogen atoms, producing even longer observations times. Hydrogen
being so darn light get into high speed for the temperature. Oh, some
doppler benefits would also to be expected.
On 11/02/2014 11:20 PM, Bob Camp wrote:
> OK, it works better if it bounces off the wall. The line width is narrower. Does it work at all (is there a line you can find) without the coating?
> Yes you would need to find a paper from the 1960’s to find anybody trying to run one that way.
>> On Nov 2, 2014, at 5:04 PM, Magnus Danielson <magnus at rubidium.dyndns.org> wrote:
>> Hi Attila,
>> On 11/02/2014 10:43 PM, Attila Kinali wrote:
>>> On Sun, 2 Nov 2014 16:28:47 -0500
>>> Bob Camp <kb8tq at n1k.org> wrote:
>>>> It’s been way too many years since my last Maser play session …
>>>> Will it fire up *without* the Teflon coating on the bulb? Yes it works
>>>> *better* with the Teflon (less wall interaction). Getting the bulb
>>>> re-coated might be a major pain.
>>> According to some of the papers i've read, parafin might be an alternative
>>> to Teflon. The interaction of Hydrogen with Teflon is lower than with
>>> Parafin, but it might be acceptable (Curiously, if it were a Rb maser,
>>> you'd use a parafin coating instead of a Teflon coating).
>> Parafin was used early, but in the strive to even further increase the interaction time with the hydrogen in the "bouncing box", telfon was preferred.
>> In the early days they experimented with different coatings. The goal was to increase the time (and thus narrowing the bandwidth) of interaction before the hydrogen atoms loose state and cause a frequency shift. Rubidium gas cells have similar wall-shift, but advancements have stabilized the wall-shift by buffer-gas selection.
>> A way to estimate the wall-shift is to run different sizes of glas-bulbs, and notice the maser frequency shift.
>> The old hydrogen masers where really experimental platsforms to a much higher degree, but that also meant that validation was done.
>> Then again the cavity shift is there, something that can be measured and compensated as a separate control loop, which has contributed to increase the stability and thus performance. Some hydrogen masers have proven themselves to be much more pressure sensitive than others.
>> Finding the lack of hydrogen masers in my lab disturbing.
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