[time-nuts] So what’s inside that Cs Beam Tube anyway?

Magnus Danielson magnus at rubidium.dyndns.org
Thu Nov 3 08:18:34 UTC 2016


Hi Tom,

That's more relevant text. Thanks.

Cheers,
Magnus

On 11/03/2016 08:34 AM, Tom Van Baak wrote:
> Hi Magnus,
>
> About the high-perf CBT, I wrote: "The difference would be in things like the oven temp and detector gain, both of which are controlled outside the tube. My first hint of this was in a paper by Carroll Alley."
>
> Since you're curious, let me explain the hint in the paper by Alley [1][2]. He says:
>
> "The clocks were modified in order to give the performance needed. Following suggestions by Len Cutler and others at Hewlett Packard, we increased the beam current by a factor of 2, we added an integrating loop in the crystal control, and there was a proprietary modification of the beam tube (now standard on all high performance tubes)."
>
> "All in all, we could achieve stabilities over the 15 hours at a couple of parts in 10^14 with standard commercial clocks, as shown in Figure 29. We paid much attention to providing a stable environment for the clocks. Let us look at some pictures to show you the equipment and give you some feeling for the experiment."
>
> I hope that answers your question.
>
> /tvb
>
>
> [1] C.O.Alley, "Proper Time Experiments in Gravitational Fields with Atomic Clocks, Aircraft, and Laser Light Pulses" in "Quantum Optics, Experimental Gravity, and Measurement Theory".
>
> https://books.google.com/books?id=GLwGCAAAQBAJ
> This article / book is behind paywalls. I can send you a PDF off-list. But...
>
>
> [2] There's papers with about the same content. C.O.Alley, "Introduction to some fundamental concepts of general relativity and to their required use in some modern timekeeping systems", PTTI, 1981.
>
> And this PDF for this is freely available, from all the usual suspects:
>
> http://tycho.usno.navy.mil/ptti/1981papers/Vol%2013_37.pdf
> https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19820012654.pdf
> http://www.dtic.mil/dtic/tr/fulltext/u2/a494262.pdf
>
> The quote above is from page 710.
>
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