[time-nuts] Sensitivity to g in atomic clocks
rk at timing-consultants.com
Wed Jan 12 22:43:40 UTC 2011
I've got some data that FEI released on g sensitivity enhancements in their OCXOs.
I'll dig it out.
From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On Behalf Of John Ackermann N8UR
Sent: 11 January 2011 6:58 PM
To: Tom Van Baak; Discussion of precise time and frequency measurement
Cc: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Sensitivity to g in atomic clocks
FWIW, I have an FTS militarized Cesium that has an accelerometer as part of the OCXO assembly to reduce vibration sensitivity. I'm told -- but can't document -- that it was for the Navy and the idea was to counteract the effects of the ship's guns. FTS engineers had a couple of PTTI articles describing their accelerometer research.
On Jan 11, 2011, at 1:37 PM, "Tom Van Baak" <tvb at LeapSecond.com> wrote:
>> While sensitivity to g is an usually specified parameter for crystal
>> oscillators, I've been unable to find any indications for atomic
>> clocks, say 5071A, or more modestly LPRO. Can anybody point me to any
>> source of info on the subject?
>> Antonio I8IOV
> Hi Antonio,
> You may find some information on g-sensitivity of rubidium in old FCS
> or PTTI papers. There are high-rel rubidium for the military and space
> applications, so practical issues of acceleration and jerk sensitivity
> have been well researched.
> The other thing you could do is quickly and/or very slowly turn over a
> running LPRO and report what happens. Like what we do with quartz, try
> it on all three axis. It would be a fun experiment.
> For a 5071A the frequency shift is gh/c . Earth tides cause a couple
> of ten cm change during the day; this change in local g affects the
> output by parts in 10^17; way too low to be detected with a 5071A but
> getting near to the capabilities of ion clocks. See:
> For some info on g, tides, and clocks see:
> To detect changes in g with a 5071A you can raise the clock by many
> meters. For example, g is about 9.808 m/s at sea level in Seattle but
> 1 km up it's closer to 9.805 m/s . A 5071A runs about 1e-13 faster at
> 1 km elevation compared to one at sea level. This is large enough to
> be measurable. See:
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