[time-nuts] Updating the unit of,time: the second.

[Richard (Rick) Karlquist]

On 5/29/2019 6:16 AM, Attila Kinali wrote:
> On Tue, 28 May 2019 22:56:35 +0200
> Mike Cook <michael.cook at sfr.fr> wrote:

> 
>> c. The first commercial cesium clocks were available in 1956, but the second did not get redefined until 1967.  There is no rush.
> 
> Which caesium beam standards were available in 1956? AFAIK the first one
> was the HP5061 and that came much later. Essen and Parry built their
> clock in the 1950s and published the results in 1955. The picture of the
> beam tube is only a small fraction of the clock itself. There are multiple
> racks full of RF equipment not shown. I would be very surprised if there
> was any company that was able to commercialize this contraption within
> only a year. Even in this large size.

Before the HP5061 was the HP5060, which used CBT's made by Varian in the
early 60's.  The old Varian factory site is just about next door to the 
present 5071 production line in MA by a strange coincidence.  Back to
the future.

FWIW, there is a nice article in IEEE Spectrum, Oct. 2014, page 42 on
OLC's that starts out by showing the 1956 (non-commerical) clock by
Parry and Essen.  It has a tutorial on OLC's and a history of the
second.  The author is Prof. Lodewyck from France who actually
builds these things.  Highty recommended, even though now 5 years out
of date.

Rick N6RK