[time-nuts] Re: ammonia, cesium, masers, etc.

[paul swed]

Jim
I did download and read that article. Its pretty interesting as it
explained some things on the Amonium reference that I never understood as
to why Cesium was preferable to Amonia. With todays technology it does seem
that a Amonia reference would be far more reasonable to build. Though
honestly bending 23 GHz waveguide might be tricky. Or simply leave it
straight after all it Amatuer grade.
There was a note that there was the belief that even that reference could
be significantly improved.
Then a good explaination on why cesium and the use of parts from radar
systems of the time. Makes sense.
Lastly they discussed an Amonia maser. Never knew. Wonder if it actually
vented amonia slowly. Sort of sounds that way.
Thanks for sharing
Regards
Paul

On Sun, Sep 19, 2021 at 6:59 PM Tom Van Baak <tvb at leapsecond.com> wrote:

> Thanks for posting that Sci-Am article, Jim.
>
> -- Also online is the classic and very approachable book:
>
> "From Sundials To Atomic Clocks: Understanding Time And Frequency"
> by James Jespersen, Jane Fitz-Randolph (NBS Monograph 155)
>
> https://nvlpubs.nist.gov/nistpubs/Legacy/MONO/nistmonograph155e1999.pdf
>
> That's 1996 edition. The older 1977 edition, in color, and highly readable:
>
>
> https://archive.org/details/FromSundialsToAtomicClocksUnderstandingTimeAndFrequency
>
> -- I recommend either of the above two editions for anyone new to the
> field of precise time & frequency. For something fresher try:
>
> https://nvlpubs.nist.gov/nistpubs/jres/122/jres.122.029.pdf
>
> which is a recent review of atomic clock history at NIST, with a nice
> collection of photos ;-)
>
> -- For deeper and more technical discussion of time & frequency topics
> these two are good:
>
> "Introduction to time and frequency metrology", by Judah Levine
> https://tf.nist.gov/general/pdf/1288.pdf
>
> "Fundamentals of Time and Frequency", by Michael Lombardi
> https://tf.nist.gov/general/pdf/1498.pdf
>
> Many of these are mentioned in the curated reading list:
>
>
> https://www.nist.gov/pml/time-and-frequency-division/general-interest-tf-publications
>
> /tvb
>
>
> On 9/19/2021 12:14 PM, Lux, Jim wrote:
> > A nice article from the late 50s in Scientific American that describes
> > the various schemes for timekeeping (including zenith transit
> > detectors, etc.)
> >
> > https://tf.nist.gov/general/pdf/1568.pdf
> >
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