Dear Bob,
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
expensive setups.
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.
Cheers,
Magnus
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.
Cheers
Michael
On Thursday, 3 November 2016, Bob Stewart <b...@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 ------------------------------------------------------
-----------
AE6RV.com
GFS GPSDO list:
groups.yahoo.com/neo/groups/GFS-GPSDOs/info
From: Michael Wouters <michaeljwout...@gmail.com <javascript:;>>
To: Discussion of precise time and frequency measurement <
time-nuts@febo.com <javascript:;>>
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.
Cheers
Michael
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