Cs tube pics
On Wed, 02 Nov 2016 10:02:53 +0000
"Poul-Henning Kamp" phk@phk.freebsd.dk wrote:
In message 20161102104103.0c58d35a72b7b36253b3d6b2@kinali.ch, Attila Kinali writes:
I still would like to try to build my own atomic clock at some point,
even if it would be a quite costly, and a many years project.
If you like lasers, build an ion trap.
If you only like lasers a little bit, build an optically pumped standard.
If you really like lasers, build a fountain.
If you reallyreally* like lasers build an neutral atom optical clock :-)
A fountain is a quite intricate design. Beside doing the MOT one needs
to launch the atoms in a precisely determined direction with precisely
controlled speed, such that they pass trough the cavity with a constant
timing. If multiple cavities are used, the alignment is sligtly more
difficult (not just launching straigth up, but in a parabola and mistakes
make the atoms get lost completely, and not just arrive early/late).
It might be easier to just let the atoms fall freely within the cavity
and do the Ramsey probing using lasers instead of a microwave cavity.
Of course this reduces the time avaible and induces a Doppler shift which
needs to be calculated and compensated.
The one thing nobody has done or even tried yet, (as far as I know),
is optically excite a solid crystal.
This has been done. Ok, not the whole crystal, but single atoms within
the crystall. The most popular is probably diamond nitrogen vacancy defects:
"Timekeeping with electron spin states in diamond", by Hodges, Yao,
Maclaurin, Rasogi, Lukin, Englund, 2013
http://link.aps.org/doi/10.1103/PhysRevA.87.032118
https://arxiv.org/abs/1109.3241
"Solid-state electronic spin coherence time approaching one second",
by Bar-Gill, Pham, Jarmola, Budker, Walsworth, 2013
http://dx.doi.org/10.1038/ncomms2771
"High-resolution correlation spectroscopy of 13C spins near a
nitrogen-vacancy centre in diamond", by Laraoui, Dolde, Burk, Reinhard,
Wrachtrup, Meriles, 2013,
http://dx.doi.org/10.1038/ncomms2685
But these all suffer from one problem: mounting and temperature effects.
Because the nitrogen atom is not in free space, but bond trough its
valence electrons to the surrounding carbon atoms, it is directly influenced
by them. Any change in distance or strain directly affects the energy levels.
Attila Kinali
--
It is upon moral qualities that a society is ultimately founded. All
the prosperity and technological sophistication in the world is of no
use without that foundation.
-- Miss Matheson, The Diamond Age, Neil Stephenson
A comment to the thread.
Desired a C, obtained a C. Discovered they take care, feeding and power.
Mine is after all a rag-tag C.
So thats why they run them on UPS systems....
Anyhow happy that I have one and learned so much.
But for a large group of time-nuts GPSDO may simply be good enough.
No concerns for the C's running out....
So desire is good education is great, but a consideration in reality.
Regards
Paul
WB8TSL
On Wed, Nov 2, 2016 at 6:51 AM, Attila Kinali attila@kinali.ch wrote:
On Wed, 02 Nov 2016 10:02:53 +0000
"Poul-Henning Kamp" phk@phk.freebsd.dk wrote:
In message 20161102104103.0c58d35a72b7b36253b3d6b2@kinali.ch, Attila
Kinali writes:
I still would like to try to build my own atomic clock at some point,
even if it would be a quite costly, and a many years project.
If you like lasers, build an ion trap.
If you only like lasers a little bit, build an optically pumped standard.
If you really like lasers, build a fountain.
If you reallyreally* like lasers build an neutral atom optical clock :-)
A fountain is a quite intricate design. Beside doing the MOT one needs
to launch the atoms in a precisely determined direction with precisely
controlled speed, such that they pass trough the cavity with a constant
timing. If multiple cavities are used, the alignment is sligtly more
difficult (not just launching straigth up, but in a parabola and mistakes
make the atoms get lost completely, and not just arrive early/late).
It might be easier to just let the atoms fall freely within the cavity
and do the Ramsey probing using lasers instead of a microwave cavity.
Of course this reduces the time avaible and induces a Doppler shift which
needs to be calculated and compensated.
The one thing nobody has done or even tried yet, (as far as I know),
is optically excite a solid crystal.
This has been done. Ok, not the whole crystal, but single atoms within
the crystall. The most popular is probably diamond nitrogen vacancy
defects:
"Timekeeping with electron spin states in diamond", by Hodges, Yao,
Maclaurin, Rasogi, Lukin, Englund, 2013
http://link.aps.org/doi/10.1103/PhysRevA.87.032118
https://arxiv.org/abs/1109.3241
"Solid-state electronic spin coherence time approaching one second",
by Bar-Gill, Pham, Jarmola, Budker, Walsworth, 2013
http://dx.doi.org/10.1038/ncomms2771
"High-resolution correlation spectroscopy of 13C spins near a
nitrogen-vacancy centre in diamond", by Laraoui, Dolde, Burk, Reinhard,
Wrachtrup, Meriles, 2013,
http://dx.doi.org/10.1038/ncomms2685
But these all suffer from one problem: mounting and temperature effects.
Because the nitrogen atom is not in free space, but bond trough its
valence electrons to the surrounding carbon atoms, it is directly
influenced
by them. Any change in distance or strain directly affects the energy
levels.
Attila Kinali
--
It is upon moral qualities that a society is ultimately founded. All
the prosperity and technological sophistication in the world is of no
use without that foundation.
-- Miss Matheson, The Diamond Age, Neil Stephenson
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/
mailman/listinfo/time-nuts
and follow the instructions there.
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
On Wednesday, 2 November 2016, Attila Kinali attila@kinali.ch wrote:
On Tue, 1 Nov 2016 09:10:25 -0700
"Tom Van Baak" tvb@LeapSecond.com wrote:
I really would like to do that. But they are a tad bit expensive.
Especially on this side of the big pond. If anyone is willing
to part with a Cs standard and want to have it a good home, feel
free to contact me :-)
It's true that a cheap GPS receiver is more accurate long-term than
a surplus cesium standard, but you're right about the "just because"
part.
To me at least, this time nut hobby is not so much about the pursuit of
accuracy as it is an appreciation for the variety, ingenuity and
complexity
of timekeeping. In some cases "how it works" is far more interesting that
"does it work".
I think, most of us are in it for the "how it works" and
"how far can I push it". :-)
A used but known working cesium standard can be expensive, but like most
of
you almost all my gear comes from eBay via automated daily keyword
searches.
Many of my mil- or telecom-surplus FTS 4050 and HP 5061 were obtained for
just a couple hundred dollars. You may search for months or even years,
but
amazing bargains show up. Not all of them work, of course, but the op/svc
manuals are superb, the design / construction is very repair-friendly,
and
there's a weird group called time nuts with helpful advice.
It still is prohibitevly expensive in Europe. There are much fewer
Cs standards going around than in the US in the first place, and there
is also less a tinkering mentality. Ie a lot of companies just say
"it's broken, it's no use for anyone anymore, let's just scrap it" and
thus a lot of stuff ends up in recycling instead of on ebay. Heck, a couple
of years ago i got an 3458 because the company wanted to throw it away.
Mind you, it was in full working condition, only the NVRAM batteries were
low.
I still would like to try to build my own atomic clock at some point,
even if it would be a quite costly, and a many years project.
IMHO the easiest to build would be an Rb or Cs vapor cell using either
dual resonance or coherent population trapping. Cells can be bought
for 300-500€. For a bit more you can get them made to spec. Machining
a resonant cavity from aluminium is pretty easy and cheap these days,
if one wants to go for the dual resonance. The biggest issue for both
types would be the laser system. Either getting the laser diodes selected
(makes them expensive) or build an external cavity for them (creates
the need of a complex control system and not so simple mechanically).
Putting all toghether would probably cost something in the order of
1000€ to 5000€.
One up in difficulty would be a passive hydrogen maser. This requires a
vacuum system and things like platinum leaks to generate atomar hydrogen
and state selection magnets. If one knows glass blowing, part of it can
be made using pyrex tubes, which simplifies some stuff (like keeping the
state selection magnets outside the vacuum system). Also, the cavity
needed would be quite big. A normaly used TE011 cavity is huge. One can
load it with aluminia and get it down to 15-20cm diameter, but this
requires
crystaline aluminia to maintain low loss. Maybe one could use other
resonating
structures that are smaller, TE111 or loop-gap resonators have been
proposed.
The biggest cost here is definitely the needed vacuum system. Although
the rough pumps are rather cheap (around 500-1000€ if one does not need
fast pumping) and some of these actually end up on ebay without being
destryoed by "testing", the high vacuum pumps (ion pumps, turbo pumps etc)
are not cheap and need to bought new (the stuff you see on ebay are either
systems that were removed from labs because they don't work anymore, or
were destroyed by "testing" them in free air).
An active hydrogen maser should not be that much more difficult. It mostly
involves a low loss, correctly tuned cavity and low noise detection
electronics.
The input stream of hydrogen atoms needs to be more precisely controlled as
well...
Another step up in difficulty would be a system using a magneto optical
trap.
Glass cavities with flanges for vacuum system are readily available and
also cheap. Again, the vacuum system is one difficulty, though probably
simpler than for the hydrogen maser (less parts that need to be custom
made).
But the requirements for the vacuum are a bit higher. The laser system
poses
a similar difficult as with the CPT system above, but now there are more
lasers and all need to be locked to eachother. The traping laser also need
to be directed at the cavity from 6 sides, all meeting in the center of the
cavity, which makes alignment problematic. This is also the first system
that offers to be a primary standard, although it probably does not get to
the stability of a 5071, as the trapping lasers will induce a light shift
that is not so easy to control unless one goes for the expensive laboratory
grade lasers.
Next on the list would be an Hg ion trap. But there are so many parts
in such a system that are not easily bought and require a very good
understanding of the physics involved to design custom parts, that
it becomes almost unrealistic that an amateur could be build one at home.
Same goes for ion and neutral atom optical clocks. Yes, they can be build,
yes the principle is simple, but getting it actually to work needs a lot
of understanding and tinkering.
Ah... I'm dreaming again :-)
Attila Kinali
--
It is upon moral qualities that a society is ultimately founded. All
the prosperity and technological sophistication in the world is of no
use without that foundation.
-- Miss Matheson, The Diamond Age, Neil Stephenson
time-nuts mailing list -- time-nuts@febo.com javascript:;
To unsubscribe, go to https://www.febo.com/cgi-bin/
mailman/listinfo/time-nuts
and follow the instructions there.
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 <michaeljwouters@gmail.com>
To: Discussion of precise time and frequency measurement time-nuts@febo.com
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
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 bob@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 <michaeljwouters@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
time-nuts mailing list -- time-nuts@febo.com javascript:;
To unsubscribe, go to https://www.febo.com/cgi-bin/
mailman/listinfo/time-nuts
and follow the instructions there.
On Thu, 3 Nov 2016 07:42:13 +1100
Michael Wouters michaeljwouters@gmail.com wrote:
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.
Yes, a lot of the optical clocks are using a hydrogen maser as local
oscillator. Ie you need an atomic clock to build an atomic clock.
For an optical clock, you're also going to need a frequency comb to get
back into the RF domain.
If i were able to build a working optical clock, i would just buy
a frequency comb. The 10k€ for a comb would be cheap compared to the
money spend on the rest of the clock :-)
Attila Kinali
--
Malek's Law:
Any simple idea will be worded in the most complicated way.
On Thu, 3 Nov 2016 07:42:13 +1100
Michael Wouters michaeljwouters@gmail.com wrote:
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 ...
BTW: can you take a couple (ie a lot) of pictures of it and put them online?
I'd be interested to see how it looks like and how it works
Attila Kinali
--
Malek's Law:
Any simple idea will be worded in the most complicated way.
Poul-Henning,
On 11/02/2016 11:02 AM, Poul-Henning Kamp wrote:
In message 20161102104103.0c58d35a72b7b36253b3d6b2@kinali.ch, Attila Kinali writes:
I still would like to try to build my own atomic clock at some point,
even if it would be a quite costly, and a many years project.
If you like lasers, build an ion trap.
If you only like lasers a little bit, build an optically pumped standard.
If you really like lasers, build a fountain.
If you are more chemically inclined, there are a ton of gasses you
can work with, methane, amonia, CO2 etc.
The one thing nobody has done or even tried yet, (as far as I know),
is optically excite a solid crystal.
Actually, that's how lasers got started, by getting ruby crystals to
laze, which really use the chromium dopant of sapphire:
https://en.wikipedia.org/wiki/Ruby_laser
Surely you know that.
Being able to utilize it for clock purposes is another thing.
NaCl crystal stable HeNe laser is used for meter standards, which is
kind of associated.
I have not seen anyone optical excite atoms for microwave frequencies. I
wonder if the chemical bonds can be prohibitive enough for meaningful use.
Cheers,
Magnus
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 bob@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 <michaeljwouters@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
time-nuts mailing list -- time-nuts@febo.com javascript:;
To unsubscribe, go to https://www.febo.com/cgi-bin/
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Hi Magnus,
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".
Bob
-----------------------------------------------------------------
AE6RV.com
GFS GPSDO list:
groups.yahoo.com/neo/groups/GFS-GPSDOs/info
From: Magnus Danielson <magnus@rubidium.dyndns.org>
To: time-nuts@febo.com
Cc: magnus@rubidium.se
Sent: Wednesday, November 2, 2016 6:42 PM
Subject: Re: [time-nuts] 12.6GhZ Yb clock - was Cs tube pics
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 bob@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 <michaeljwouters@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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To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
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