[time-nuts] 12.6GhZ Yb clock - was Cs tube pics
bob at evoria.net
Wed Nov 2 21:17:24 EDT 2016
I figured it was the same as for the Cs, but I thought I'd ask. I should have realized what was going on when I saw the word "cryogenic" in close proximity to "oscillator".
GFS GPSDO list:
From: Magnus Danielson <magnus at rubidium.dyndns.org>
To: time-nuts at febo.com
Cc: magnus at rubidium.se
Sent: Wednesday, November 2, 2016 6:42 PM
Subject: Re: [time-nuts] 12.6GhZ Yb clock - was Cs tube pics
Essentially all atomic clocks is really passive clocks, the only real
exception is the active hydrogen maser, even if other active masers or
lasers could be considered. They all use a fly-wheel oscillator of some
sort, typically a crystal oscillator for simpler devices, hydrogen maser
or cryogenic sapphire whispering gallery oscillators for the more
Flywheel is what keeps things running at about the right rate while
interrogation of the passive system occurs. Over time more and more
advanced schemes of interrogation has been devised in order to handle
more effects. One such is to measure the side peaks in order to servo
the C-field, which stabilize things which would otherwise be open-loop.
On 11/02/2016 10:10 PM, Michael Wouters wrote:
> Dear Bob,
> The error signal (readout is optical, with a laser) you get from tuning the
> microwaves from your synthesis chain to the 12.6 GHz hyperfine transition
> in Yb is not continuous. There's a measurement sequence of state
> preparation etc that means you only get an error measurement every 10 to
> 100 s. so you need a good flywheel in between.
> On Thursday, 3 November 2016, Bob Stewart <bob at evoria.net> wrote:
>> Hi Michael,
>> I've got a dumb question about the need for a really good flywheel
>> oscillator for the 12.6Ghz Yb clock: What is the signal that is locking
>> that oscillator? Is it a 1PPS, or is it something in the RF domain, such
>> as 10MHz or higher?
>> I still hope to make a modern version of the old water-hydrogen generator
>> from the 40s or whatever it was. But, my copious free time seems to be
>> taken up now that I have the time to do it.
>> Bob - AE6RV ------------------------------------------------------
>> GFS GPSDO list:
>> To: Discussion of precise time and frequency measurement <
>> Sent: Wednesday, November 2, 2016 3:42 PM
>> Subject: Re: [time-nuts] Cs tube pics
>> I worked on a trapped ion frequency standard 20 years ago, a 12.6Ghz Yb
>> clock. It's still in the lab across from me and looking at it, and the
>> electronics, I think it is the sort of thing that a physicist might
>> contemplate building in his/her garage but ...
>> Building it took about 10 man years of concentrated effort so the time you
>> would need for a project like this would be the killer, assuming you could
>> buy the spectroscopic lasers and UHV equipment you needed at a price that
>> didn't require refinancing your mortgage.
>> One other vital component is the flywheel oscillator you need to take
>> advantage of the fabulous stability you now have at hand.We had a cryogenic
>> sapphire oscillator for our (microwave) clock.
>> For an optical clock, you're also going to need a frequency comb to get
>> back into the RF domain.
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