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

Magnus Danielson magnus at rubidium.dyndns.org
Wed Nov 2 20:02:37 EDT 2016


Hi Tom,

On 11/02/2016 06:23 PM, Tom Van Baak wrote:
> Hi Rick,
>
> That's consistent with what I've seen and heard as well. Most of the 5061B / 5071A on eBay with dead tubes are opt 001 (high-performance) tubes. The surplus units with standard performance tubes are more likely to power up and lock. And if they don't, it's probably something simple rather than a dead Cs tube.
>
> I've also heard that the choice of high- vs std-performance is made *after* the tube is built. 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...
>
> You know the famous 1971 Hafele-Keating experiment with four 5061 cesium clocks flying around the world. Several years later, a more precise measurement was made by Carroll Alley using better clocks. What I read is that he got Len Cutler to hack the 5061A so that its beam current would be higher, thereby improving performance for the duration of the experiment. Same tube, just different operating parameters.
>
> See page 3 of:
> http://www.hp.com/hpinfo/abouthp/histnfacts/publications/measure/pdf/1977_04.pdf

Nice find, except, that's not what it says there.
"I also modified the cesium standards, which already had the new 
high-beam flux tubes, for further improve their performance."

This implicates that the high-beam flux tubes already existed, and that 
he did other tweakings to the clocks.

I'm not disputing that beam-current changes might be completely 
controlled by the resistors rather than being a physical aspect.

Cheers,
Magnus


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