[time-nuts] RE: Zeeman effect and tuning cesium clocks

Tom Van Baak tvb at leapsecond.com
Sun Jan 23 02:10:30 UTC 2005


> By the way, one of the things Boulder corrects for
> is altitude. Their clocks run about 5e-13 fast due to
> General Relativistic effects. I'm at 1000 ft here in
> Bellevue so mine run only 1e-13 fast.

Let me correct myself. The relativistic effect due to
altitude is on the order of 1e-16 per meter not foot
(hey, now I can work for NASA). So NIST's altitude
correction is 1.8e-13 and mine about 3e-14.

To get a feel for the type of corrections one needs to
make to a cesium standard to achieve the ultimate
frequency standard, read the article below; my favorite
example of a precise physics experiment. NIST-7 was
the most accurate cesium beam tube (an approach
recently replaced by cesium fountains).

Accuracy evaluation of the primary frequency standard NIST-7
http://www.boulder.nist.gov/timefreq/general/pdf/1497.pdf (1.84 MB)

/tvb








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