[time-nuts] Hydrogen Maser KIT! Update #1

[Magnus Danielson]

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.

Cheers,
Magnus