Re: [time-nuts] hm H Maser
Hi
A cryo pump will get you into reliability issues if run 24/7. It also is doubtful
that you will be able to maintain the vacuum level over long periods.
Bob
On Jan 11, 2017, at 12:09 AM, Bruce Griffiths bruce.griffiths@xtra.co.nz wrote:
One could always use a cryo pump.
The following paper is a summary of the current state of the art for rubidium vapour frequency standards:http://www.euramet.org/Media/docs/Repository/A169/IND55/micalizio_02182015.pdf
Bruce
On Wednesday, 11 January 2017 5:15 PM, Ole Petter Ronningen <opronningen@gmail.com> wrote:
Add to this ion-pumps (in the case of EFOS type masers 2 every ~2 years),
plus substantial tooling (turbomolecular vacuum pump, anyone?) to service
the thing - unless you want the manufacturer to do so..
Ole
On Tue, Jan 10, 2017 at 11:12 PM, Dr. David Kirkby (Kirkby Microwave Ltd) <
drkirkby@kirkbymicrowave.co.uk> wrote:
On 10 January 2017 at 15:35, Ole Petter Rønningen <opronningen@gmail..com>
wrote:
... having said that, I for one think I'm with Bob on this one. The thing
about masers are that they are big. At least active masers. And they
require a substantial volume be kept at ultra high vacuum - which is not
trivial, especially not in a homeshop. The cavity needs to be kept at a
temperature stable to 0.001 degree C. With 4-5 magnetic shields. Add to
this costly pumps to keep the vacuum this low even if you succeed at
reaching that vacuum.. There's easily 1-2KUSD running cost per year just
to
keep the maser running.
Looking at the Microsemi MHM 2010 Active Hydogen Maser data sheet, the
maser has a peak power of 150 W and an operating power of 75 W. Based on a
power consumption of 75 W, that is 657 kW hr / year of energy. I pay around
£0.20 (GBP) per kW hr for electricity, so that's £131 (GBP) annually. I
believe electricity is cheaper in the USA than here in the UK, but
converting £131 (GBP) to USD, that's around $161/year in electricity.. So
running costs don't seem to be an issue.
But I must admit, the thought of spending a lot of time/money to build
something I could have bought for a lot less with higher performance is not
that attractive, although of course there would be a satisfaction from
building it yourself.
Dave
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On Tue, 10 Jan 2017 21:43:07 -0500, you wrote:
This does get back to state of the art Rb and what that means. In my suggested case thats measured in terms of ADEV for Tau = 1 to 1,000,000
seconds. If you wanted an Rb with (only) state of the art phase noise at 1 MHz offset
thats a different thing. State of the art for
power consumption and size is also not what Im suggesting in this case. Why the choice of spec?
this is TimeNuts.
Hi,
Some discussions on the performance that might be practically achieved
with different designs may be a useful start - as long as it's done in
the context of a practical unit that could actually get built, rather
than just a theoretical wish list.
It would also be good to have some idea of the cost of any special
parts like cells too. Without that info, it's hard to know how
practical particular designs would be.
Looking at export/technology controls might be useful early on too,
since we're going for high performance.
I've often wondered how a 21st century version of a 5065 would
perform, so it's great to see that I'm not completely alone in my
insanity!
Angus.
Angus
Read the paper I posted on the current state of the art.
ADEV ~ 2E-13/SQRT(Tau) is feasible with large cells and using a laser instead of rubidium lamp.In principle, one can use the same cell to lock the laser to the rubidium absorption line and lock the microwave signal.Suitable laser diodes are readily available.
Increasing the contrast of the signal used for locking reduces the noise significantly.One approach is to use an integrating sphere cell and use an optical fibre to bring the laser signal into the cell.Since random scattering in an integrating sphere depolarises the light and virtually eliminates any effect of spatial coherence a multimode fibre should suffice.Laser speckle can be reduced significantly by using a colloidal suspension of titanium dioxide if the colloidal suspension fills another integrating sphere or equivalent.I've tried the latter using plastic optical fibres to transport the laser light into and out of the colloid. Its extremely effective in eliminating speckle in an optical interferometer.
Bruce
On Thursday, 12 January 2017 12:19 PM, Angus <not.again@btinternet.com> wrote:
On Tue, 10 Jan 2017 21:43:07 -0500, you wrote:
This does get back to state of the art Rb and what that means. In my suggested case thats measured in terms of ADEV for Tau = 1 to 1,000,000
seconds. If you wanted an Rb with (only) state of the art phase noise at 1 MHz offset … thats a different thing. State of the art for
power consumption and size is also not what Im suggesting in this case. Why the choice of spec? … this is TimeNuts.
Hi,
Some discussions on the performance that might be practically achieved
with different designs may be a useful start - as long as it's done in
the context of a practical unit that could actually get built, rather
than just a theoretical wish list.
It would also be good to have some idea of the cost of any special
parts like cells too. Without that info, it's hard to know how
practical particular designs would be.
Looking at export/technology controls might be useful early on too,
since we're going for high performance.
I've often wondered how a 21st century version of a 5065 would
perform, so it's great to see that I'm not completely alone in my
insanity!
Angus.
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To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
Hi
On Jan 11, 2017, at 6:07 PM, Angus not.again@btinternet.com wrote:
On Tue, 10 Jan 2017 21:43:07 -0500, you wrote:
This does get back to state of the art Rb and what that means. In my suggested case thats measured in terms of ADEV for Tau = 1 to 1,000,000
seconds. If you wanted an Rb with (only) state of the art phase noise at 1 MHz offset
thats a different thing. State of the art for
power consumption and size is also not what Im suggesting in this case. Why the choice of spec?
this is TimeNuts.
Hi,
Some discussions on the performance that might be practically achieved
with different designs may be a useful start - as long as it's done in
the context of a practical unit that could actually get built, rather
than just a theoretical wish list.
The biggest issue with doing this is that if there is a magic formula that tells you
“these parts give you that ADEV” …. it’s in the same vault as the formula for Coke.
That sort of thing (if it even exists) would be the gold standard of corporate IP for
a company making atomic clocks.
About all you can really say is “they did this and the units the shipped did that”. There
are some obvious thing like “bigger cells work better”. Coming up with an equation that
correctly predicts a cell of this odd geometry functioning at these dimensions for 10,000
second ADEV ….not so much.
It would also be good to have some idea of the cost of any special
parts like cells too. Without that info, it's hard to know how
practical particular designs would be.
The most likely course would be to cut out a major chunk of cost and find somebody
who is willing to make up a couple hundred sets of cells. There has already been
a proposal to do this floated on the list. I don’t recall the exact numbers, but $2,000
is what comes to mind. Apologies if this is a bogus number.
Looking at export/technology controls might be useful early on too,
since we're going for high performance.
Indeed, if you get to crazy you could get in trouble. My guess is that a standard the
size of a 5065 or larger is unlikely to set off alarm bells.
I've often wondered how a 21st century version of a 5065 would
perform, so it's great to see that I'm not completely alone in my
insanity!
Which obviously is an itch many of us share. The gotcha of course is that each of
us has (likely incompatible) ideas about how to do it. We may even have
incompatible goals in terms of “what’s good”. Based on many decades of designing
things like this, feature creep and elastic goals will kill a project dead (usually after
a lot of money has been spent).
Lots of Fun
Bob
Angus.
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Hi
The obvious question would be: What does it cost to set up a line to make a proper
set of spherical Rb cells? Doing this as a glassblowing project is a dead end. You
need it properly tooled ….
Bob
On Jan 11, 2017, at 7:05 PM, Bruce Griffiths bruce.griffiths@xtra.co.nz wrote:
Angus
Read the paper I posted on the current state of the art.
ADEV ~ 2E-13/SQRT(Tau) is feasible with large cells and using a laser instead of rubidium lamp.In principle, one can use the same cell to lock the laser to the rubidium absorption line and lock the microwave signal.Suitable laser diodes are readily available.
Increasing the contrast of the signal used for locking reduces the noise significantly.One approach is to use an integrating sphere cell and use an optical fibre to bring the laser signal into the cell.Since random scattering in an integrating sphere depolarises the light and virtually eliminates any effect of spatial coherence a multimode fibre should suffice.Laser speckle can be reduced significantly by using a colloidal suspension of titanium dioxide if the colloidal suspension fills another integrating sphere or equivalent.I've tried the latter using plastic optical fibres to transport the laser light into and out of the colloid. Its extremely effective in eliminating speckle in an optical interferometer.
Bruce
On Thursday, 12 January 2017 12:19 PM, Angus <not.again@btinternet.com> wrote:
On Tue, 10 Jan 2017 21:43:07 -0500, you wrote:
This does get back to state of the art Rb and what that means. In my suggested case thats measured in terms of ADEV for Tau = 1 to 1,000,000
seconds. If you wanted an Rb with (only) state of the art phase noise at 1 MHz offset … thats a different thing. State of the art for
power consumption and size is also not what Im suggesting in this case. Why the choice of spec? … this is TimeNuts.
Hi,
Some discussions on the performance that might be practically achieved
with different designs may be a useful start - as long as it's done in
the context of a practical unit that could actually get built, rather
than just a theoretical wish list.
It would also be good to have some idea of the cost of any special
parts like cells too. Without that info, it's hard to know how
practical particular designs would be.
Looking at export/technology controls might be useful early on too,
since we're going for high performance.
I've often wondered how a 21st century version of a 5065 would
perform, so it's great to see that I'm not completely alone in my
insanity!
Angus.
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Hydrogen maser in radio astronomy to sync worldwide systems:
(Lifted from the Albany, NY astronomy group).
--
Gary Woods O- K2AHC Public keys at home.earthlink.net/~garygarlic, or get 0x1D64A93D via keyserver
fingerprint = E2 6F 50 93 7B C7 F3 CA 1F 8B 3C C0 B0 28 68 0B
An entire room kept near to absolute zero with a simple door access???Unlikely, likely the writer is unfamiliar with science/engineering.
Bruce
On Saturday, 14 January 2017 11:39 AM, Gary Woods <garygarlic@earthlink..net> wrote:
Hydrogen maser in radio astronomy to sync worldwide systems:
(Lifted from the Albany, NY astronomy group).
--
Gary Woods O- K2AHC Public keys at home.earthlink.net/~garygarlic, or get 0x1D64A93D via keyserver
fingerprint = E2 6F 50 93 7B C7 F3 CA 1F 8B 3C C0 B0 28 68 0B
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