Thinking outside the box a super reference
In message 59dc074a-3a09-6315-29d4-6877c3bf7510@rubidium.dyndns.org, Magnus Danielson write
s:
With respect to precision machining, that space has changed a lot
over the last five years, with precision CNC machines, factory
or home-built, dropping dramatically in price.
You need to tune it regardless.
First: Yes, but if you pick a sensible vibration mode for your
microwave resonance, that can be done with an screw-in endcap.
Second: No, I would actually not need to tune it.
Historically resonance cavities were used so that step/avalance
diode multipliers had enough power to excite them. Today we have
semiconductors which work at those frequencies.
Later people kept the resonance, because it works well with low
power budgets in telecoms/milspec applications.
But the resonanance leads to all sorts of trouble, including frequency
pulling, temperature sensitivities etc.
We're neither space nor power constrained, we'd probably be
perfectly happy if the end result is 4U and 100W, so resonance
is not mandatory.
Third: A lot of the "everybody knows" about which atoms can be
used for active vs. passive atomic standards comes from the
state of the art electronics about 30 years ago.
Using laser-pumping and modern semiconductors, it might actually
be possible to detect the 6.8GHz photons from the Rb.
They won't be coherent photons, like in a Hydrogen maser, but we
don't need them to be, in fact that just causes the same exact
problems as the tuned cavity anyway, as long as we can measure
the frequency well enough.
(No, I havn't done the math on this, my wife has banned me from
starting any new projects until our house is finished.)
--
Poul-Henning Kamp | UNIX since Zilog Zeus 3.20
phk@FreeBSD.ORG | TCP/IP since RFC 956
FreeBSD committer | BSD since 4.3-tahoe
Never attribute to malice what can adequately be explained by incompetence.
Hej Bruce,
Ah yes, that's it. Sorry for the bad wording.
Cheers,
Magnus
On 11/04/2016 11:41 PM, Bruce Griffiths wrote:
Hej Magnus
A quarter waveplate doesn't depolarise, it can however convert a linearly polarised beam to a circularly polarised one.If you really need to depolarise a laser beam, scattering from a colloidal suspension of Titanium dioxide is very effective.There are no macroscopic moving parts.Brownian motion of the colloidal partticels suffices.
Bruce
On Saturday, 5 November 2016 11:28 AM, Magnus Danielson <magnus@rubidium.dyndns.org> wrote:
Hi,
On 11/04/2016 10:27 PM, Poul-Henning Kamp wrote:
In message 2af27ebe-9200-c348-c89b-b98f9c973974@karlquist.com, "Richard (Rick) Karlquist" w
rites:
Also, one of the Rb isotopes is slightly radioactive.
35 years ago, the guy in the next cubicle got away with
storing it under his desk. He also happily smoked
cigarettes all day at his desk. Another ERA.
Rb87 has a halflife north of the age of the planet as far
as I recall, and the result is a beta which goes nowhere
far and Sr87 which is stable.
With a half-life of 49.2 Gigayears compared to universe life around 13.8
Gigayears and the beta-decay within both glas and metal enclosure, I'm
not overly concerned. For all practical purposes it is essentially stable.
He got a lot more ionizing radiation from his cigaretess than he
ever got from the Rb87.
Just for the heck of it, I'd go laser instead of the old UHF lamp.
The 780 nm laserdiodes isn't all that hard to get, in fact I've got some
lying around. Depolarizing needed with a quarter-wave needed not to get
a Stark-pull.
With respect to precision machining, that space has changed a lot
over the last five years, with precision CNC machines, factory
or home-built, dropping dramatically in price.
You need to tune it regardless.
Cheers,
Magnus
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Poul-Henning,
On 11/05/2016 12:04 AM, Poul-Henning Kamp wrote:
In message 59dc074a-3a09-6315-29d4-6877c3bf7510@rubidium.dyndns.org, Magnus Danielson write
s:
With respect to precision machining, that space has changed a lot
over the last five years, with precision CNC machines, factory
or home-built, dropping dramatically in price.
You need to tune it regardless.
First: Yes, but if you pick a sensible vibration mode for your
microwave resonance, that can be done with an screw-in endcap.
Indeed.
Second: No, I would actually not need to tune it.
Historically resonance cavities were used so that step/avalance
diode multipliers had enough power to excite them. Today we have
semiconductors which work at those frequencies.
Later people kept the resonance, because it works well with low
power budgets in telecoms/milspec applications.
But the resonanance leads to all sorts of trouble, including frequency
pulling, temperature sensitivities etc.
We're neither space nor power constrained, we'd probably be
perfectly happy if the end result is 4U and 100W, so resonance
is not mandatory.
Sure, but if you do have a cavity, as you was hinting at, tuning it is
still needed for the cavity pull effect.
Third: A lot of the "everybody knows" about which atoms can be
used for active vs. passive atomic standards comes from the
state of the art electronics about 30 years ago.
Sure, but some behaviors just remains there when still using such setups.
Using laser-pumping and modern semiconductors, it might actually
be possible to detect the 6.8GHz photons from the Rb.
They won't be coherent photons, like in a Hydrogen maser, but we
don't need them to be, in fact that just causes the same exact
problems as the tuned cavity anyway, as long as we can measure
the frequency well enough.
You can avoid the cavity using sidebands of the pumping laser and all
that, yes I know.
Active maser like the hydrogen would be possible naturally, but would
require the resonator.
A passive direct observation would also possible, but detection will be
harder and then you would run into S/N issues.
(No, I havn't done the math on this, my wife has banned me from
starting any new projects until our house is finished.)
Probably a wise thing.
Cheers,
Magnus
The N resonance discussedd in:http://walsworth.physics.harvard.edu/publications/2005_Smallwood_HUBAThesis.pdf
May be a better bet than traditional CPT.
Bruce
On Saturday, 5 November 2016 12:17 PM, Magnus Danielson <magnus@rubidium.dyndns.org> wrote:
Poul-Henning,
On 11/05/2016 12:04 AM, Poul-Henning Kamp wrote:
In message 59dc074a-3a09-6315-29d4-6877c3bf7510@rubidium.dyndns.org, Magnus Danielson write
s:
With respect to precision machining, that space has changed a lot
over the last five years, with precision CNC machines, factory
or home-built, dropping dramatically in price.
You need to tune it regardless.
First: Yes, but if you pick a sensible vibration mode for your
microwave resonance, that can be done with an screw-in endcap.
Indeed.
Second: No, I would actually not need to tune it.
Historically resonance cavities were used so that step/avalance
diode multipliers had enough power to excite them. Today we have
semiconductors which work at those frequencies.
Later people kept the resonance, because it works well with low
power budgets in telecoms/milspec applications.
But the resonanance leads to all sorts of trouble, including frequency
pulling, temperature sensitivities etc.
We're neither space nor power constrained, we'd probably be
perfectly happy if the end result is 4U and 100W, so resonance
is not mandatory.
Sure, but if you do have a cavity, as you was hinting at, tuning it is
still needed for the cavity pull effect.
Third: A lot of the "everybody knows" about which atoms can be
used for active vs. passive atomic standards comes from the
state of the art electronics about 30 years ago.
Sure, but some behaviors just remains there when still using such setups.
Using laser-pumping and modern semiconductors, it might actually
be possible to detect the 6.8GHz photons from the Rb.
They won't be coherent photons, like in a Hydrogen maser, but we
don't need them to be, in fact that just causes the same exact
problems as the tuned cavity anyway, as long as we can measure
the frequency well enough.
You can avoid the cavity using sidebands of the pumping laser and all
that, yes I know.
Active maser like the hydrogen would be possible naturally, but would
require the resonator.
A passive direct observation would also possible, but detection will be
harder and then you would run into S/N issues.
(No, I havn't done the math on this, my wife has banned me from
starting any new projects until our house is finished.)
Probably a wise thing.
Cheers,
Magnus
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On Fri, 04 Nov 2016 14:39:54 -0700, you wrote:
On Fri, Nov 4, 2016, at 02:27 PM, Poul-Henning Kamp wrote:
In message 2af27ebe-9200-c348-c89b-b98f9c973974@karlquist.com, "Richard
(Rick) Karlquist" w
rites:
Also, one of the Rb isotopes is slightly radioactive.
35 years ago, the guy in the next cubicle got away with
storing it under his desk. He also happily smoked
cigarettes all day at his desk. Another ERA.
Rb87 has a halflife north of the age of the planet as far
as I recall, and the result is a beta which goes nowhere
far and Sr87 which is stable.
87-Rb has a half life of something like 4.9e10 years you'll be waiting
a while for that strontium. /gp
Various online sources say that natural rubidium is radioactive enough
to fog photographic film in 1 to 2 months but that is also the case
with unprocessed uranium ore so I would not worry about it at all.
In message c57q1c5engv94amimot7pu3l8romu6g2p0@4ax.com, David writes:
Various online sources say that natural rubidium is radioactive enough
to fog photographic film in 1 to 2 months but that is also the case
with unprocessed uranium ore so I would not worry about it at all.
Yes, that sounds about right for an isotope with a 40 billion years
half-life.
1 to 2 months is a LOOOONG time for photographic film.
--
Poul-Henning Kamp | UNIX since Zilog Zeus 3.20
phk@FreeBSD.ORG | TCP/IP since RFC 956
FreeBSD committer | BSD since 4.3-tahoe
Never attribute to malice what can adequately be explained by incompetence.
On 11/4/2016 4:04 PM, Poul-Henning Kamp wrote:
Historically resonance cavities were used so that step/avalance
diode multipliers had enough power to excite them. Today we have
semiconductors which work at those frequencies.
A great deal of complexity in the 5061 went into
exciting an SRD at 90 MHz and getting a sufficient
line at 9180 MHz to put on a sideband at 9192.
I spent a lot of time trying to do this during the
5071 project and was never able to get anywhere
near the efficiency that the 5061 waveguide structure
was able to do. It was designed by a visiting Korean
professor, so he wasn't around to mentor me.
The 10816 also used an SRD, and it was also a
struggle, although I was able to make it work.
Fortunately, we were able to replace all this with a
DRO and PLL, and that was 25 years ago. At this time,
it is even more of a no brainer that you don't want
to knock yourself out trying to make an SRD multiplier
work. Also, these days, it is harder than ever to
purchase good SRD's.
Rick
On 11/4/2016 5:24 PM, Poul-Henning Kamp wrote:
Yes, that sounds about right for an isotope with a 40 billion years
half-life.
The problem with the half life number is that the cylinder
still was marked "radioactive" complex with the radiation
symbol. Radioactivity (for legal purposes) is a binary
property. We used to mark CBT's "cesium device, non radioactive"
because the work "cesium" means "cesium 137 nuclear fallout"
to many people.
Reminds me of an interesting Jack Kusters story.
There was some customer who was having problems with
his atomic clocks being noisy (I don't remember exactly
the story) but the bottom line was that they determined
it was because of helium contamination. Kusters was
called in to answer to the customer about this contamination
and how they were going to fix it. Kusters measured the
air in the customer's plant and found that in contained
helium. But the customer did not use helium at all in the
plant. Kusters pointed out that that could mean only one
thing: the plant had a radon problem, and radon breaks down
into helium. Kusters told the customer that if they
dropped the complaint, he wouldn't have to say anything
about radon to anyone. That was the last heard about the
helium problem.
Rick
Not to mention there is not so sensitive film, sensitive film and really sensitive film.
Good old orthographic film took minutes in bright light.
On Nov 4, 2016, at 20:24, Poul-Henning Kamp phk@phk.freebsd.dk wrote:
In message c57q1c5engv94amimot7pu3l8romu6g2p0@4ax.com, David writes:
Various online sources say that natural rubidium is radioactive enough
to fog photographic film in 1 to 2 months but that is also the case
with unprocessed uranium ore so I would not worry about it at all.
Yes, that sounds about right for an isotope with a 40 billion years
half-life.
1 to 2 months is a LOOOONG time for photographic film.
--
Poul-Henning Kamp | UNIX since Zilog Zeus 3.20
phk@FreeBSD.ORG | TCP/IP since RFC 956
FreeBSD committer | BSD since 4.3-tahoe
Never attribute to malice what can adequately be explained by incompetence.
time-nuts mailing list -- time-nuts@febo.com
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and follow the instructions there.
Rick on the pll DRO I agree with you for today.
So is it built for 9180 and then the 12.63 is mixed with it? Or is it
actually a direct PLL precisely at the frequency so not even the
synthesizer is used?
Regards
Paul
WB8TSL
On Fri, Nov 4, 2016 at 9:40 PM, bownes bownes@gmail.com wrote:
Not to mention there is not so sensitive film, sensitive film and really
sensitive film.
Good old orthographic film took minutes in bright light.
On Nov 4, 2016, at 20:24, Poul-Henning Kamp phk@phk.freebsd.dk wrote:
In message c57q1c5engv94amimot7pu3l8romu6g2p0@4ax.com, David writes:
Various online sources say that natural rubidium is radioactive enough
to fog photographic film in 1 to 2 months but that is also the case
with unprocessed uranium ore so I would not worry about it at all.
Yes, that sounds about right for an isotope with a 40 billion years
half-life.
1 to 2 months is a LOOOONG time for photographic film.
--
Poul-Henning Kamp | UNIX since Zilog Zeus 3.20
phk@FreeBSD.ORG | TCP/IP since RFC 956
FreeBSD committer | BSD since 4.3-tahoe
Never attribute to malice what can adequately be explained by
incompetence.
mailman/listinfo/time-nuts
and follow the instructions there.
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