Magnus Danielson wrote:
On 09/01/2010 09:39 PM, Poul-Henning Kamp wrote:
In message<24c547b54ea34a69bacc4f823bb40...@pc52>, "Tom Van Baak"
writes:
I found the original copies of both EFOS manuals, along with
a few photos. See:
http://www.leapsecond.com/museum/efos/
Interesting.
Page 4/3 in the service manual states:
For the Hydrogen Maser, this unperturbed frequency
is
f(H) = 1 420 405 751.768 +/- 0.002 Hz
In practice, this frequency is perturbed by
interaction of the hydrogen atoms with the walls
of the interaction volume container, doppler
effects, interactions between the atoms themsel-
ves, etc. The resulting frequency for the EFOS
Maser is taken to be
F(o) = 1 420 405 751.689 Hz
I have no idea where the EFOS was produced, but somebody should try
to calculate the relativistic correction for their height above the
geoid, and see how much of the systematic 0.079Hz frequency difference
that explains...
Neuchatel, which still leaves a bit of unspecified height.
However, this effect would be cancelled as their cesium clocks would
be on the same height above the geoid (give or take a few meters).
So, their indication is correct. The C-field also pulls the atoms of
course, which they failed to point out in the cited text.
If I were to build a maser myself, I would probably not attempt
to copy the EFOS, as the large mechanical dimensions add significant
cost in materials and machining.
I would be much more tempted by a sapphire loaded cavity design like
this one:
http://www.nict.go.jp/publication/shuppan/kihou-journal/journal-vol50no1.2/0304.pdf)
As that brings the mechanics inside the work envelope of main-stream
CNC machines with the required tolerances.
Yes, but what is the issues relating to sapphire loading? What's the
cost of the sapphire block and having it machined?
The tempco of the dielectric constant of sapphire is quite large so the
cavity resonance tempco is somewhat larger than that of an unloaded
copper or aluminium cavity.
There is a NIST paper detailing a somewhat earlier attempt to use a
dielectric cavity:
http://tf.nist.gov/general/pdf/156.pdf
Again the dielectric constant tempco is a significant issue.
Cheers,
Magnus
Bruce
_______________________________________________
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
