
HP 5061A Cesium Clock [video] - brudgers
https://www.youtube.com/watch?v=eOti3kKWX-c
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fsh
Amazing piece of technology. Its successor, the 5071A (now made by microsemi)
is still the most common primary frequency standard. HP used to be such a
great company. Now they make crappy consumer printers and network cables with
DRM chips.

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Gibbon1
HP spun off the good parts in 1999 to form Agilent. The Test Equipment
division was spun off in 2014 as Keysight

[https://en.wikipedia.org/wiki/Agilent_Technologies](https://en.wikipedia.org/wiki/Agilent_Technologies)
[https://en.wikipedia.org/wiki/Keysight](https://en.wikipedia.org/wiki/Keysight)

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NovemberWhiskey
The atomic clock product line was sold off before the latter event in 2005 to
Symmetricom, which was then acquired by Microsemi in 2013, and Microsemi
itself was itself acquired by Microchip a year or two ago!

The 5071A (the evolution of the product in the video) is still in the product
line:

[https://www.microsemi.com/product-directory/cesium-
frequency...](https://www.microsemi.com/product-directory/cesium-frequency-
references/4115-5071a-cesium-primary-frequency-standard)

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iAm25626
If you like this type of stuff: [http://leapsecond.com/time-
nuts.htm](http://leapsecond.com/time-nuts.htm)

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abjecton
I find this video quite interesting.

I had no idea how Cesium clocks work, other than the SI definition of a second
is 9xxxx transitions between two states of a cesium atom.

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fsh
"Transition frequency" seems to be a common source of confusion here. In the
context of the SI definition it means "frequency corresponding to the energy
difference between the two states". This is the frequency of radiation that
can _most efficiently_ drive transitions between the states. How fast the atom
transitions between the states depends on the frequency, polarization, and
power of the driving radiation and can in principle take any value. To avoid
confusion this is called the "Rabi frequency" in atomic physics.

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jonshariat
Great video, bonus I learned how spectrometry works!

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jmcguckin
Why cesium? Why not Rb?

