subject:"\[time\-nuts\] Cheap Rubidium $heatpipe cooling for$"

Hi

I'm guessing that some kapton tape will get used at the junctions to take care 
of that issue.

Bob


On Dec 25, 2009, at 12:04 AM, Bruce Griffiths wrote:

 Another thing to watch out for is circulating currents due to thermal emfs 
 with the aluminium to steel contacts.
 Such thermoelectric currents will in turn generate a magnetic field.
 
 
 
 Bruce
 
 Bob Camp wrote:
 Hi
 
 The big hitters for heat outside the physics package seem to be the RF 
 excitation and the microwave generation stuff. The regulators will warm 
 things up if you run high voltage into them, but I would probably not do 
 that.
 
 I don't believe that putting multiple swimming pools into the basement, 
 mercury filled or otherwise was ever a real candidate for a solution. It is 
 kind of interesting to see just how big the jug of water would have to be.
 
 Right now my leading candidate is a multi layer aluminum / steel enclosure 
 with a point short between each of the layers to keep the heat rise under 
 control. Cool the baseplate with recirculating water and a cheap (  $50) 
 pump. Throw in a fan and radiator to cool the water to room temperature.  
 Servo the temperature with what ever at the point shorts. Monitor the 
 temperature as best you can.
 
 The main what ever still in there are TE coolers. A quick look suggests 
 that +12 heats and -12 cools. In between the two it's not clear that much 
 happens (maybe it does ...). Even if it does not, I haven't dug deep enough 
 to see if something like current drive takes care of the dead band issue.
 
 Some math. It's late, but I think this is about right:
 
 1) 4 layers
 2) Shorts at 2 C/W
 3) 10 W inside
 4)  80 C heat rise - not going to work
 
 If I stick with 4 layers, 10 W, and a 15 C rise then the shorts need to be ~ 
 0.38 C/W.  A 15C rise gets me to 40C which looks reasonable based on the app 
 notes I have read on the rubidiums.
 
 If the basement moves up 5 C then I'm cold pumping 1/3 of the 10W. Same 
 thing in reverse if the basement drops 5 C. Both are unlikely to happen as 
 long as there isn't a catastrophic failure of the HVAC.
 
 If I go to a air cooled baseplate heat sink, it's thermal resistance is 
 going to have to come out of the budget.  My *guess* is that's going to be 
 more involved than a simple pump and some plastic tubes.
 
 Bob
 
 On Dec 24, 2009, at 10:46 PM, Hal Murray wrote:
 
   
 li...@cq.nu said:
 
 The original intent was to simply take an existing cheap rubidium
 and do simple things to it. Tearing it into pieces and redesigning
 parts of it was not anything I originally contemplated. The tight
 integration of the physics package to the electronics would make this
 a fairly involved process.
   
 Sure, but if we are discussing digging a hole big enough for a ton of
 mercury, then taking apart a tightly integrated package seems worth
 considering.
 
 I expect the packaging might be reasonable for this purpose.  After all, the
 designers probably wanted to keep that heat away from the electronics.
 
 
 
 -- 
 These are my opinions, not necessarily my employer's.  I hate spam.
 
 
 
 
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Re: [time-nuts] Cheap Rubidium (heatpipe cooling for)

Hi

Cool link - 

Thanks!

One of next steps is digging into the TE parts. One tradeoff is weather heavy 
cooling of the water (5C)  makes sense or not. One cooler for four units versus 
a bit lower conductivity shunts inside the enclosures... 

Bob

On Dec 25, 2009, at 1:36 AM, J. Forster wrote:

 http://www.peltier-info.com/info.html
 
 -John
 
 ==
 
 
 
 Hi
 
 The big hitters for heat outside the physics package seem to be the RF
 excitation and the microwave generation stuff. The regulators will warm
 things up if you run high voltage into them, but I would probably not do
 that.
 
 I don't believe that putting multiple swimming pools into the basement,
 mercury filled or otherwise was ever a real candidate for a solution. It
 is kind of interesting to see just how big the jug of water would have
 to be.
 
 Right now my leading candidate is a multi layer aluminum / steel enclosure
 with a point short between each of the layers to keep the heat rise
 under control. Cool the baseplate with recirculating water and a cheap
 ( $50) pump. Throw in a fan and radiator to cool the water to room
 temperature.  Servo the temperature with what ever at the point shorts.
 Monitor the temperature as best you can.
 
 The main what ever still in there are TE coolers. A quick look suggests
 that +12 heats and -12 cools. In between the two it's not clear that much
 happens (maybe it does ...). Even if it does not, I haven't dug deep
 enough to see if something like current drive takes care of the dead band
 issue.
 
 Some math. It's late, but I think this is about right:
 
 1) 4 layers
 2) Shorts at 2 C/W
 3) 10 W inside
 4)  80 C heat rise - not going to work
 
 If I stick with 4 layers, 10 W, and a 15 C rise then the shorts need to be
 ~ 0.38 C/W.  A 15C rise gets me to 40C which looks reasonable based on the
 app notes I have read on the rubidiums.
 
 If the basement moves up 5 C then I'm cold pumping 1/3 of the 10W. Same
 thing in reverse if the basement drops 5 C. Both are unlikely to happen as
 long as there isn't a catastrophic failure of the HVAC.
 
 If I go to a air cooled baseplate heat sink, it's thermal resistance is
 going to have to come out of the budget.  My *guess* is that's going to be
 more involved than a simple pump and some plastic tubes.
 
 Bob
 
 On Dec 24, 2009, at 10:46 PM, Hal Murray wrote:
 
 
 li...@cq.nu said:
 The original intent was to simply take an existing cheap rubidium
 and do simple things to it. Tearing it into pieces and redesigning
 parts of it was not anything I originally contemplated. The tight
 integration of the physics package to the electronics would make this
 a fairly involved process.
 
 Sure, but if we are discussing digging a hole big enough for a ton of
 mercury, then taking apart a tightly integrated package seems worth
 considering.
 
 I expect the packaging might be reasonable for this purpose.  After all,
 the
 designers probably wanted to keep that heat away from the electronics.
 
 
 
 --
 These are my opinions, not necessarily my employer's.  I hate spam.
 
 
 
 
 ___
 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.
 
 
 
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 To unsubscribe, go to
 https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
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Re: [time-nuts] Cheap Rubidium (heatpipe cooling for)

2009-12-25 Thread Rex


Bob Camp wrote:
One tradeoff is weather heavy cooling of the water (5C)  makes sense or not. 
  


I think weather cooling is much too unstable and unpredictable. 
Especially with global warming. :-)




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Re: [time-nuts] Cheap Rubidium (heatpipe cooling for)

2009-12-25 Thread Joe Gwinn

At 12:45 AM + 12/25/09, time-nuts-requ...@febo.com wrote:

Date: Thu, 24 Dec 2009 17:14:38 -0700
From: Robert Darlington rdarling...@gmail.com
Subject: Re: [time-nuts] Cheap Rubidium (heatpipe cooling for)
To: Discussion of precise time and frequency measurement
time-nuts@febo.com

On Thu, Dec 24, 2009 at 1:32 PM, Bob Camp li...@cq.nu wrote:

 Hi

 A heat pipe might work if the fluid had a sufficiently low boiling point.

The working fluid in a heat pipe will boil at every temperature above its
melting point.

Well, I've been thinking about this, and I used the term heat pipe 
too loosely.  Both the one- and two-pipe systems mentioned here have 
no wicks, and so technically are two-phase thermosyphons, which 
depend on gravity to circulate vapor and condensate.  A true heat 
pipe has a wick, and will work in zero gravity.

One gets significant heat transfer by phase change so long as the 
vapor pressure in the heat input end is high enough to generate 
enough vapor to carry the thermal power flow, and this makes the pipe 
isothermal.  However the temperature (although constant along the 
pipe) varies with the thermal power flow (in thermal watts) being 
carried.

What I'm looking for is related but different:  A device where the 
heat transfer capacity varies sharply with temperature, so that there 
is a range of heat transfer rates over which the input-end 
temperature will be substantially constant.  This is why I envision 
the fluid boiling (versus evaporating), which is actually out of the 
operating regime of a true heat pipe.

I tend to use water because it's cheap, but have made them
with 3M engineered fluids, Fluorinert, and denatured alcohol.

Fluorinert.  I think that's what the expensive commercial CPU-cooling 
heatpipes use.

I've found
that ordinary solder works just fine.  A trick to make these things easy to
build is to use a ball valve at the top (I'm assuming there is a top and
we're going with gravity return because it's simple).  I've got a few that
are still under vacuum for several years now in this configuration.  My
giant heat pipe of doom is a 10 foot stick of 1/2 copper with a ball valve
at one end and an end cap at the other.  There is perhaps 100ml water in
there total, and no air.  You can either boil the liquid until it builds up
a nice head of steam, or go the easy way and pull a vacuum with a pump and
just close the valve.

I wouldn't have thought that an ordinary ball valve would be tight 
enough, allowing the water to escape and the air enter, slowly, 
although I suppose one can replace the water if it comes to that.

But I think people want to build this exactly once, so I followed 
refrigeration practice.  A properly made hermetically sealed 
refrigeration system keeps its working fluid essentially forever.  I 
suppose one can use a refrigeration fill valve, say from an 
automobile air conditioning system, but these all leak to some degree.

Is the ball valve anything special?

These things are incredible.  If you pack snow around
the end of this thing, the other end that is ten feet away gets cold almost
immediately.  They want to stay isothermal and the heat transfer is at the
speed of sound through the working fluid.  Delays are introduced because
you're dealing with a thermal mass of copper pipe that needs to change
temperature along with the working fluid so it's not quite instant, but
still about 10,000 times faster heat transfer than copper by itself.  They
are certainly handy for getting heat out of confined spaces.

What is the purpose of the heatpipe of doom?  Education?

-Bob

 The rubidium isn't terribly tolerant of high temperatures, and I'm going to
 pick up some heat rise as I put it inside some baffles / shields. You need
 to find something that fits a fairly narrow window.

 I suspect that a recirculating water loop is a more practical approach to
 carry away the heat. It's got a pump to move the water, but the rest of it

  is fairly simple.

 Bob

 On Dec 24, 2009, at 2:49 PM, Joe Gwinn wrote:

  A dodge occurs to me - a homebrew heat pipe: 
 http://en.wikipedia.org/wiki/Heat_pipe.

  Make the cold plate of copper, to which is soldered a meandering piece of
 copper tubing, which tubing is also soldered to a copper radiator plate that
 is above the coldplate, forming a closed loop with a fill tube attached by a
 T.  Braze all tubing connections, as for freon refrigeration systems.  (Soft
 solder is too porous to work for the joints, but is OK for attaching tubes

  to plates.)
[snip]  [This is really a kind of thermosyphon, as discussed above.]

  Anyway, a heat pipe system will stabilize the coldplate temperature
 fairly accurately despite variations in thermal load, has no moving or
 electrical parts, and may be sufficient by itself.  If not sufficient, it
 can be used as the outer stage in a two-stage ovening scheme.

  Joe Gwinn

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Re: [time-nuts] Cheap Rubidium (heatpipe cooling for)

2009-12-25 Thread Richard W. Solomon

Can you be a little more specific about the cooler ? Walgreens
search function is rather laborious and clumsy.

Tnx, Dick, W1KSZ

-Original Message-
From: J. Forster j...@quik.com
Sent: Dec 24, 2009 6:58 PM
To: Discussion of precise time and frequency measurement time-nuts@febo.com
Subject: Re: [time-nuts] Cheap Rubidium (heatpipe cooling for)

That's why I've been suggesting active control with TE devices.

You can buy a small TE cooler at Walgreens for about $20. It's big enough
for a 6-pack of Coke cans and already comes in an insulated box. Add a
simple temperature control in series w/ the DC supply and you should be
well on the way.

-John

=

 Hi

 The original intent was to simply take an existing cheap rubidium and do
 simple things to it. Tearing it into pieces and redesigning parts of it
 was not anything I originally contemplated. The tight integration of the
 physics package to the electronics would make this a fairly involved
 process.

 Bob

 On Dec 24, 2009, at 5:42 PM, Magnus Danielson wrote:

 Hal Murray wrote:
 A heat pipe might work if the fluid had a sufficiently low boiling
 point. The rubidium isn't terribly tolerant of high temperatures, and
 I'm going to pick up some heat rise as I put it inside some baffles /
 shields. You need to find something that fits a fairly narrow window.
 This is all backwards.
 The main reason the typical Rubidium box needs a serious heat sink is
 that there is an active heater inside it heating up the lamp to get it
 up to operating temperature.  That part of the system better be
 tolerant of high (enough) temperature.

 ... or a less heat-producing alternative could be used. The
 Rubidium-lamp produces two wavelengths of which one is filtered by a
 Rubidium-filter which leaves the final pumping wavelength. This is what
 a laser diode could supply instead.

 Maybe things would be a lot better/simpler if the heating/cooling we
 have been discussing were split into two sections.  One for the lamp
 assembly, and a second for the electronics.

 Most of the discussion has been on thermal isolation of the entier
 units. Not what needs generates temperature and what requires
 temperature stability etc.

 Anybody know what the thermal coefficient of the lamp is relative to
 the electronics?

 I am not sure I know what you mean by this...

 Cheers,
 Magnus

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Re: [time-nuts] Cheap Rubidium (heatpipe cooling for)

2009-12-25 Thread Bruce Griffiths


See:
http://www.walgreens.com/store/catalog/Accessories/Kool-Kaddy-12V-Cooler/ID=prod1833617navCount=0navAction=push-product 
http://www.walgreens.com/store/catalog/Accessories/Kool-Kaddy-12V-Cooler/ID=prod1833617navCount=0navAction=push-product


located using search term:
cooler

using the search term
thermoelectric
is even better

Bruce

Richard W. Solomon wrote:

Can you be a little more specific about the cooler ? Walgreens
search function is rather laborious and clumsy.

Tnx, Dick, W1KSZ


-Original Message-
   

From: J. Forsterj...@quik.com
Sent: Dec 24, 2009 6:58 PM
To: Discussion of precise time and frequency measurementtime-nuts@febo.com
Subject: Re: [time-nuts] Cheap Rubidium (heatpipe cooling for)

That's why I've been suggesting active control with TE devices.

You can buy a small TE cooler at Walgreens for about $20. It's big enough
for a 6-pack of Coke cans and already comes in an insulated box. Add a
simple temperature control in series w/ the DC supply and you should be
well on the way.

-John

=


 

Hi

The original intent was to simply take an existing cheap rubidium and do
simple things to it. Tearing it into pieces and redesigning parts of it
was not anything I originally contemplated. The tight integration of the
physics package to the electronics would make this a fairly involved
process.

Bob


On Dec 24, 2009, at 5:42 PM, Magnus Danielson wrote:

   

Hal Murray wrote:
 

A heat pipe might work if the fluid had a sufficiently low boiling
point. The rubidium isn't terribly tolerant of high temperatures, and
I'm going to pick up some heat rise as I put it inside some baffles /
shields. You need to find something that fits a fairly narrow window.
 

This is all backwards.
The main reason the typical Rubidium box needs a serious heat sink is
that there is an active heater inside it heating up the lamp to get it
up to operating temperature.  That part of the system better be
tolerant of high (enough) temperature.
   

... or a less heat-producing alternative could be used. The
Rubidium-lamp produces two wavelengths of which one is filtered by a
Rubidium-filter which leaves the final pumping wavelength. This is what
a laser diode could supply instead.

 

Maybe things would be a lot better/simpler if the heating/cooling we
have been discussing were split into two sections.  One for the lamp
assembly, and a second for the electronics.
   

Most of the discussion has been on thermal isolation of the entier
units. Not what needs generates temperature and what requires
temperature stability etc.

 

Anybody know what the thermal coefficient of the lamp is relative to
the electronics?
   

I am not sure I know what you mean by this...

Cheers,
Magnus

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Re: [time-nuts] Cheap Rubidium (heatpipe cooling for)

I got the kid a thermo electric wine fridge a while back. It took *days* to
pump a half case of wine down from 80F to 50F (yup F not C).

Some of these gizmos are better than others

Bob

On Dec 25, 2009, at 10:32 PM, Bruce Griffiths wrote:

See:
http://www.walgreens.com/store/catalog/Accessories/Kool-Kaddy-12V-Cooler/ID=prod1833617navCount=0navAction=push-product

http://www.walgreens.com/store/catalog/Accessories/Kool-Kaddy-12V-Cooler/ID=prod1833617navCount=0navAction=push-product

located using search term:
cooler

using the search term
thermoelectric
is even better

Bruce

Richard W. Solomon wrote:
Can you be a little more specific about the cooler ? Walgreens
search function is rather laborious and clumsy.

Tnx, Dick, W1KSZ

-Original Message-

From: J. Forsterj...@quik.com
Sent: Dec 24, 2009 6:58 PM
To: Discussion of precise time and frequency measurementtime-nuts@febo.com
Subject: Re: [time-nuts] Cheap Rubidium (heatpipe cooling for)

That's why I've been suggesting active control with TE devices.

You can buy a small TE cooler at Walgreens for about $20. It's big enough
for a 6-pack of Coke cans and already comes in an insulated box. Add a
simple temperature control in series w/ the DC supply and you should be
well on the way.

-John

The original intent was to simply take an existing cheap rubidium and do
simple things to it. Tearing it into pieces and redesigning parts of it
was not anything I originally contemplated. The tight integration of the
physics package to the electronics would make this a fairly involved
process.

Bob

On Dec 24, 2009, at 5:42 PM, Magnus Danielson wrote:

Hal Murray wrote:

A heat pipe might work if the fluid had a sufficiently low boiling
point. The rubidium isn't terribly tolerant of high temperatures, and
I'm going to pick up some heat rise as I put it inside some baffles /
shields. You need to find something that fits a fairly narrow window.

This is all backwards.
The main reason the typical Rubidium box needs a serious heat sink is
that there is an active heater inside it heating up the lamp to get it
up to operating temperature. That part of the system better be
tolerant of high (enough) temperature.

... or a less heat-producing alternative could be used. The
Rubidium-lamp produces two wavelengths of which one is filtered by a
Rubidium-filter which leaves the final pumping wavelength. This is what
a laser diode could supply instead.

Maybe things would be a lot better/simpler if the heating/cooling we
have been discussing were split into two sections. One for the lamp
assembly, and a second for the electronics.

Most of the discussion has been on thermal isolation of the entier
units. Not what needs generates temperature and what requires
temperature stability etc.

Anybody know what the thermal coefficient of the lamp is relative to
the electronics?

I am not sure I know what you mean by this...

Cheers,
Magnus

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Re: [time-nuts] Cheap Rubidium (heatpipe cooling for)

Hi

Actually the thing that got left out of the swimming pool discussion was indeed 
the weather. 

As the humidity (dew point) in the basement changes, the evaporation from the 
(open) pools changes. I suspect that does makes the pools even bigger. Not that 
I was putting them in anyway ...

Bob


On Dec 25, 2009, at 2:14 PM, Rex wrote:

 Bob Camp wrote:
 One tradeoff is weather heavy cooling of the water (5C)  makes sense or not. 
   
 
 I think weather cooling is much too unstable and unpredictable. Especially 
 with global warming. :-)
 
 
 
 ___
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 To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
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Re: [time-nuts] Cheap Rubidium (heatpipe cooling for)

2009-12-25 Thread J. Forster

I bought it at a physical store last summer. It was on a shelf for $20
with other picnic things. Chinese, of course. It takes a 6-pack of coke
and if it's cold outside (50F) cools enough to freeze after a day of
operation.

Outside it's anout 8 x 14 x 10 high (from memory). Black plastic. It
runs of 12 VDC at about 3 A. It includes a power supply (noisy switcher)
for line operation. There is a HEAT/OFF/COOL switch.

I looked a few weeks ago and Target and Best Buy both had similar units (a
bit bigger) for about $100.

Ask the Walgreens store manager.

FWIW,
-John




 Can you be a little more specific about the cooler ? Walgreens
 search function is rather laborious and clumsy.

 Tnx, Dick, W1KSZ


 -Original Message-
From: J. Forster j...@quik.com
Sent: Dec 24, 2009 6:58 PM
To: Discussion of precise time and frequency measurement
 time-nuts@febo.com
Subject: Re: [time-nuts] Cheap Rubidium (heatpipe cooling for)

That's why I've been suggesting active control with TE devices.

You can buy a small TE cooler at Walgreens for about $20. It's big enough
for a 6-pack of Coke cans and already comes in an insulated box. Add a
simple temperature control in series w/ the DC supply and you should be
well on the way.

-John

=


 Hi

 The original intent was to simply take an existing cheap rubidium and
 do
 simple things to it. Tearing it into pieces and redesigning parts of it
 was not anything I originally contemplated. The tight integration of
 the
 physics package to the electronics would make this a fairly involved
 process.

 Bob


 On Dec 24, 2009, at 5:42 PM, Magnus Danielson wrote:

 Hal Murray wrote:
 A heat pipe might work if the fluid had a sufficiently low boiling
 point. The rubidium isn't terribly tolerant of high temperatures,
 and
 I'm going to pick up some heat rise as I put it inside some baffles
 /
 shields. You need to find something that fits a fairly narrow
 window.
 This is all backwards.
 The main reason the typical Rubidium box needs a serious heat sink is
 that there is an active heater inside it heating up the lamp to get
 it
 up to operating temperature.  That part of the system better be
 tolerant of high (enough) temperature.

 ... or a less heat-producing alternative could be used. The
 Rubidium-lamp produces two wavelengths of which one is filtered by a
 Rubidium-filter which leaves the final pumping wavelength. This is
 what
 a laser diode could supply instead.

 Maybe things would be a lot better/simpler if the heating/cooling we
 have been discussing were split into two sections.  One for the lamp
 assembly, and a second for the electronics.

 Most of the discussion has been on thermal isolation of the entier
 units. Not what needs generates temperature and what requires
 temperature stability etc.

 Anybody know what the thermal coefficient of the lamp is relative to
 the electronics?

 I am not sure I know what you mean by this...

 Cheers,
 Magnus

 ___
 time-nuts mailing list -- time-nuts@febo.com
 To unsubscribe, go to
 https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
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Re: [time-nuts] Cheap Rubidium (heatpipe cooling for)

2009-12-25 Thread J. Forster

That's a significantly bigger one than I got.

-John

See:
http://www.walgreens.com/store/catalog/Accessories/Kool-Kaddy-12V-Cooler/ID=prod1833617navCount=0navAction=push-product
http://www.walgreens.com/store/catalog/Accessories/Kool-Kaddy-12V-Cooler/ID=prod1833617navCount=0navAction=push-product

located using search term:
cooler

using the search term
thermoelectric
is even better

Bruce

Richard W. Solomon wrote:
Can you be a little more specific about the cooler ? Walgreens
search function is rather laborious and clumsy.

Tnx, Dick, W1KSZ

-Original Message-

From: J. Forsterj...@quik.com
Sent: Dec 24, 2009 6:58 PM
To: Discussion of precise time and frequency
measurementtime-nuts@febo.com
Subject: Re: [time-nuts] Cheap Rubidium (heatpipe cooling for)

That's why I've been suggesting active control with TE devices.

You can buy a small TE cooler at Walgreens for about $20. It's big
enough
for a 6-pack of Coke cans and already comes in an insulated box. Add a
simple temperature control in series w/ the DC supply and you should be
well on the way.

-John

The original intent was to simply take an existing cheap rubidium
and do
simple things to it. Tearing it into pieces and redesigning parts of
it
was not anything I originally contemplated. The tight integration of
the
physics package to the electronics would make this a fairly involved
process.

Bob

On Dec 24, 2009, at 5:42 PM, Magnus Danielson wrote:

Hal Murray wrote:

A heat pipe might work if the fluid had a sufficiently low boiling
point. The rubidium isn't terribly tolerant of high temperatures,
and
I'm going to pick up some heat rise as I put it inside some baffles
/
shields. You need to find something that fits a fairly narrow
window.

This is all backwards.
The main reason the typical Rubidium box needs a serious heat sink
is
that there is an active heater inside it heating up the lamp to get
it
up to operating temperature. That part of the system better be
tolerant of high (enough) temperature.

Maybe things would be a lot better/simpler if the heating/cooling we
have been discussing were split into two sections. One for the lamp
assembly, and a second for the electronics.

Most of the discussion has been on thermal isolation of the entier
units. Not what needs generates temperature and what requires
temperature stability etc.

Anybody know what the thermal coefficient of the lamp is relative to
the electronics?

I am not sure I know what you mean by this...

Cheers,
Magnus

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Re: [time-nuts] Cheap Rubidium (heatpipe cooling for)

2009-12-25 Thread Bruce Griffiths

Try the cooler search term other models occur on the first 2-3 pages 
but none in the $20 range.


The 2.5A 12V models were relatively widespread and not very effective 
I've had one for several years.


A 70W Peltier heat pump from Melcor should be cheaper than $150 I have a 
couple of them.


However a very low thermal resistance heatsink is required not just a 
piece of finned (~ 1 fins abort 4 square) extrusion with a small fan 
as typically used in the cheap coolers.


The 70W module when clamped to a large but inadequate natural convection 
heatsink will cool down sufficiently to freeze ice from atmospheric 
water vapour for about 5 minutes or so until the heatsink warms up. It 
really needs a water cooled heatsink or similar.


Bruce

Richard W. Solomon wrote:

That's a tad more than the $20 John mentioned. I'd risk $20
but not $150 !!

73, Dick, W1KSZ


-Original Message-
   

From: Bruce Griffithsbruce.griffi...@xtra.co.nz
Sent: Dec 25, 2009 10:32 PM
To: Richard W. Solomonw1...@earthlink.net, Discussion of precise time and 
frequency measurementtime-nuts@febo.com
Subject: Re: [time-nuts] Cheap Rubidium (heatpipe cooling for)

See:
http://www.walgreens.com/store/catalog/Accessories/Kool-Kaddy-12V-Cooler/ID=prod1833617navCount=0navAction=push-product
http://www.walgreens.com/store/catalog/Accessories/Kool-Kaddy-12V-Cooler/ID=prod1833617navCount=0navAction=push-product

located using search term:
cooler

using the search term
thermoelectric
is even better

Bruce

Richard W. Solomon wrote:
 

Can you be a little more specific about the cooler ? Walgreens
search function is rather laborious and clumsy.

Tnx, Dick, W1KSZ


-Original Message-

   

From: J. Forsterj...@quik.com
Sent: Dec 24, 2009 6:58 PM
To: Discussion of precise time and frequency measurementtime-nuts@febo.com
Subject: Re: [time-nuts] Cheap Rubidium (heatpipe cooling for)

That's why I've been suggesting active control with TE devices.

You can buy a small TE cooler at Walgreens for about $20. It's big enough
for a 6-pack of Coke cans and already comes in an insulated box. Add a
simple temperature control in series w/ the DC supply and you should be
well on the way.

-John

=



 

Hi

The original intent was to simply take an existing cheap rubidium and do
simple things to it. Tearing it into pieces and redesigning parts of it
was not anything I originally contemplated. The tight integration of the
physics package to the electronics would make this a fairly involved
process.

Bob


On Dec 24, 2009, at 5:42 PM, Magnus Danielson wrote:


   

Hal Murray wrote:

 

A heat pipe might work if the fluid had a sufficiently low boiling
point. The rubidium isn't terribly tolerant of high temperatures, and
I'm going to pick up some heat rise as I put it inside some baffles /
shields. You need to find something that fits a fairly narrow window.

 

This is all backwards.
The main reason the typical Rubidium box needs a serious heat sink is
that there is an active heater inside it heating up the lamp to get it
up to operating temperature.  That part of the system better be
tolerant of high (enough) temperature.

   

... or a less heat-producing alternative could be used. The
Rubidium-lamp produces two wavelengths of which one is filtered by a
Rubidium-filter which leaves the final pumping wavelength. This is what
a laser diode could supply instead.


 

Maybe things would be a lot better/simpler if the heating/cooling we
have been discussing were split into two sections.  One for the lamp
assembly, and a second for the electronics.

   

Most of the discussion has been on thermal isolation of the entier
units. Not what needs generates temperature and what requires
temperature stability etc.


 

Anybody know what the thermal coefficient of the lamp is relative to
the electronics?

   

I am not sure I know what you mean by this...

Cheers,
Magnus

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Re: [time-nuts] Cheap Rubidium (heatpipe cooling for)

2009-12-25 Thread Hal Murray


mag...@rubidium.dyndns.org said:
 Anybody know what the thermal coefficient of the lamp
 is relative to the electronics?

 I am not sure I know what you mean by this... 

If I change the lamp (really the whole physics package) temperature by 1 C, 
how much does the frequency change?

If I change the temperature of the electronics by 1C, how much does the 
frequency change?

What is the ratio?  Which is more important?


-- 
These are my opinions, not necessarily my employer's.  I hate spam.




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Re: [time-nuts] Cheap Rubidium (heatpipe cooling for)

2009-12-24 Thread Joe Gwinn

A dodge occurs to me - a homebrew heat pipe: 
http://en.wikipedia.org/wiki/Heat_pipe.


Make the cold plate of copper, to which is soldered a meandering 
piece of copper tubing, which tubing is also soldered to a copper 
radiator plate that is above the coldplate, forming a closed loop 
with a fill tube attached by a T.  Braze all tubing connections, as 
for freon refrigeration systems.  (Soft solder is too porous to work 
for the joints, but is OK for attaching tubes to plates.)


Insulate the two tubes running between coldplate and radiator plate 
from one another.


Put enough working fluid into the system to fill the tubing that is 
soldered to the coldplate, but no more.  Warm the system up so the 
vapor drives all the air out, pinch the fill tube off and fold it 
back, and braze the end shut.   (It's not critical to get absolutely 
all the air out.)


Making the radiator plate be above the coldplate (the boiler) 
implements what amounts to an oldtime two-pipe water vapor heating 
plant.  Vapor goes up one pipe, condensed fluid returns via the 
other.  I lived in a house with such a system.  The difference 
between a vapor plant and a steam plant is pressure:  the vapor plant 
runs below atmospheric pressure, while the steam plant runs at or 
slightly above.


Make sure that things are arranged so the returning fluid does not 
pool anywhere but in the coldplate, or the heat pipe will bang like 
an old steam heating system.


There is a brazing filler metal intended for copper-to-copper joints 
that is widely used for freon systems: 
http://www.uniweld.com/catalog/alloys/silver_brazing_alloys/phos_copper.htm. 
The zero silver phos stuff is adequate, cheap and widely available. 
While copper-to-copper needs no flux, copper-to-brass does, so also 
get the flux.  Plumbing supply houses and welding equipment stores 
are likely sources.  You will also need a torch or pair of torches 
able to raise the tubing joints to an orange heat in a reasonable 
length of time.


Depending on the chosen working fluid, the cold plate temperature 
will not rise above the boiling point of the fluid unless the system 
is too small (in radiator heat removal capacity) to easily handle the 
10 or 20 thermal watts that are passing through.


What fluid to use?  Anything common and thermally stable that does 
not attack copper.  Alcohol (methyl or ethyl) and water are common 
choices, as are the various freons.  I bet acetone would also work. 
Anyway, one controls the coldplate temperature by a combination of 
choice of working fluid and internal pressure.



I have seen commercially made heat pipes for cooling Intel CPUs 
advertised, but I don't know that these units can be adapted.


Anyway, a heat pipe system will stabilize the coldplate temperature 
fairly accurately despite variations in thermal load, has no moving 
or electrical parts, and may be sufficient by itself.  If not 
sufficient, it can be used as the outer stage in a two-stage ovening 
scheme.



Joe Gwinn

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Re: [time-nuts] Cheap Rubidium (heatpipe cooling for)

2009-12-24 Thread Don Latham

Are we getting close to a Stirling engine running as a frig?
Don
Joe Gwinn
 A dodge occurs to me - a homebrew heat pipe:
 http://en.wikipedia.org/wiki/Heat_pipe.

 Make the cold plate of copper, to which is soldered a meandering
 piece of copper tubing, which tubing is also soldered to a copper
 radiator plate that is above the coldplate, forming a closed loop
 with a fill tube attached by a T.  Braze all tubing connections, as
 for freon refrigeration systems.  (Soft solder is too porous to work
 for the joints, but is OK for attaching tubes to plates.)

 Insulate the two tubes running between coldplate and radiator plate
 from one another.

 Put enough working fluid into the system to fill the tubing that is
 soldered to the coldplate, but no more.  Warm the system up so the
 vapor drives all the air out, pinch the fill tube off and fold it
 back, and braze the end shut.   (It's not critical to get absolutely
 all the air out.)

 Making the radiator plate be above the coldplate (the boiler)
 implements what amounts to an oldtime two-pipe water vapor heating
 plant.  Vapor goes up one pipe, condensed fluid returns via the
 other.  I lived in a house with such a system.  The difference
 between a vapor plant and a steam plant is pressure:  the vapor plant
 runs below atmospheric pressure, while the steam plant runs at or
 slightly above.

 Make sure that things are arranged so the returning fluid does not
 pool anywhere but in the coldplate, or the heat pipe will bang like
 an old steam heating system.

 There is a brazing filler metal intended for copper-to-copper joints
 that is widely used for freon systems:
 http://www.uniweld.com/catalog/alloys/silver_brazing_alloys/phos_copper.htm.
 The zero silver phos stuff is adequate, cheap and widely available.
 While copper-to-copper needs no flux, copper-to-brass does, so also
 get the flux.  Plumbing supply houses and welding equipment stores
 are likely sources.  You will also need a torch or pair of torches
 able to raise the tubing joints to an orange heat in a reasonable
 length of time.

 Depending on the chosen working fluid, the cold plate temperature
 will not rise above the boiling point of the fluid unless the system
 is too small (in radiator heat removal capacity) to easily handle the
 10 or 20 thermal watts that are passing through.

 What fluid to use?  Anything common and thermally stable that does
 not attack copper.  Alcohol (methyl or ethyl) and water are common
 choices, as are the various freons.  I bet acetone would also work.
 Anyway, one controls the coldplate temperature by a combination of
 choice of working fluid and internal pressure.


 I have seen commercially made heat pipes for cooling Intel CPUs
 advertised, but I don't know that these units can be adapted.

 Anyway, a heat pipe system will stabilize the coldplate temperature
 fairly accurately despite variations in thermal load, has no moving
 or electrical parts, and may be sufficient by itself.  If not
 sufficient, it can be used as the outer stage in a two-stage ovening
 scheme.


 Joe Gwinn

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-- 
Dr. Don Latham AJ7LL
Six Mile Systems LLP
17850 Six Mile Road
POB 134
Huson, MT, 59846
VOX 406-626-4304
www.lightningforensics.com
www.sixmilesystems.com


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Re: [time-nuts] Cheap Rubidium (heatpipe cooling for)

Hi

A heat pipe might work if the fluid had a sufficiently low boiling point. The 
rubidium isn't terribly tolerant of high temperatures, and I'm going to pick up 
some heat rise as I put it inside some baffles / shields. You need to find 
something that fits a fairly narrow window. 

I suspect that a recirculating water loop is a more practical approach to carry 
away the heat. It's got a pump to move the water, but the rest of it is fairly 
simple. 

Bob


On Dec 24, 2009, at 2:49 PM, Joe Gwinn wrote:

 A dodge occurs to me - a homebrew heat pipe: 
 http://en.wikipedia.org/wiki/Heat_pipe.
 
 Make the cold plate of copper, to which is soldered a meandering piece of 
 copper tubing, which tubing is also soldered to a copper radiator plate that 
 is above the coldplate, forming a closed loop with a fill tube attached by a 
 T.  Braze all tubing connections, as for freon refrigeration systems.  (Soft 
 solder is too porous to work for the joints, but is OK for attaching tubes to 
 plates.)
 
 Insulate the two tubes running between coldplate and radiator plate from one 
 another.
 
 Put enough working fluid into the system to fill the tubing that is soldered 
 to the coldplate, but no more.  Warm the system up so the vapor drives all 
 the air out, pinch the fill tube off and fold it back, and braze the end 
 shut.   (It's not critical to get absolutely all the air out.)
 
 Making the radiator plate be above the coldplate (the boiler) implements what 
 amounts to an oldtime two-pipe water vapor heating plant.  Vapor goes up one 
 pipe, condensed fluid returns via the other.  I lived in a house with such a 
 system.  The difference between a vapor plant and a steam plant is pressure:  
 the vapor plant runs below atmospheric pressure, while the steam plant runs 
 at or slightly above.
 
 Make sure that things are arranged so the returning fluid does not pool 
 anywhere but in the coldplate, or the heat pipe will bang like an old steam 
 heating system.
 
 There is a brazing filler metal intended for copper-to-copper joints that is 
 widely used for freon systems: 
 http://www.uniweld.com/catalog/alloys/silver_brazing_alloys/phos_copper.htm.
  The zero silver phos stuff is adequate, cheap and widely available. While 
 copper-to-copper needs no flux, copper-to-brass does, so also get the flux.  
 Plumbing supply houses and welding equipment stores are likely sources.  You 
 will also need a torch or pair of torches able to raise the tubing joints to 
 an orange heat in a reasonable length of time.
 
 Depending on the chosen working fluid, the cold plate temperature will not 
 rise above the boiling point of the fluid unless the system is too small (in 
 radiator heat removal capacity) to easily handle the 10 or 20 thermal watts 
 that are passing through.
 
 What fluid to use?  Anything common and thermally stable that does not attack 
 copper.  Alcohol (methyl or ethyl) and water are common choices, as are the 
 various freons.  I bet acetone would also work. Anyway, one controls the 
 coldplate temperature by a combination of choice of working fluid and 
 internal pressure.
 
 
 I have seen commercially made heat pipes for cooling Intel CPUs advertised, 
 but I don't know that these units can be adapted.
 
 Anyway, a heat pipe system will stabilize the coldplate temperature fairly 
 accurately despite variations in thermal load, has no moving or electrical 
 parts, and may be sufficient by itself.  If not sufficient, it can be used as 
 the outer stage in a two-stage ovening scheme.
 
 
 Joe Gwinn
 
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Re: [time-nuts] Cheap Rubidium (heatpipe cooling for)

Depending on the required flow rate you may be able to use a peristaltic 
pump.


Bruce

Bob Camp wrote:

Hi

A heat pipe might work if the fluid had a sufficiently low boiling point. The 
rubidium isn't terribly tolerant of high temperatures, and I'm going to pick up 
some heat rise as I put it inside some baffles / shields. You need to find 
something that fits a fairly narrow window.

I suspect that a recirculating water loop is a more practical approach to carry 
away the heat. It's got a pump to move the water, but the rest of it is fairly 
simple.

Bob


On Dec 24, 2009, at 2:49 PM, Joe Gwinn wrote:

   

A dodge occurs to me - a homebrew heat 
pipe:http://en.wikipedia.org/wiki/Heat_pipe.

Make the cold plate of copper, to which is soldered a meandering piece of 
copper tubing, which tubing is also soldered to a copper radiator plate that is 
above the coldplate, forming a closed loop with a fill tube attached by a T.  
Braze all tubing connections, as for freon refrigeration systems.  (Soft solder 
is too porous to work for the joints, but is OK for attaching tubes to plates.)

Insulate the two tubes running between coldplate and radiator plate from one 
another.

Put enough working fluid into the system to fill the tubing that is soldered to 
the coldplate, but no more.  Warm the system up so the vapor drives all the air 
out, pinch the fill tube off and fold it back, and braze the end shut.   (It's 
not critical to get absolutely all the air out.)

Making the radiator plate be above the coldplate (the boiler) implements what 
amounts to an oldtime two-pipe water vapor heating plant.  Vapor goes up one 
pipe, condensed fluid returns via the other.  I lived in a house with such a 
system.  The difference between a vapor plant and a steam plant is pressure:  
the vapor plant runs below atmospheric pressure, while the steam plant runs at 
or slightly above.

Make sure that things are arranged so the returning fluid does not pool 
anywhere but in the coldplate, or the heat pipe will bang like an old steam 
heating system.

There is a brazing filler metal intended for copper-to-copper joints that is widely 
used for freon 
systems:http://www.uniweld.com/catalog/alloys/silver_brazing_alloys/phos_copper.htm.
 The zero silver phos stuff is adequate, cheap and widely available. While 
copper-to-copper needs no flux, copper-to-brass does, so also get the flux.  Plumbing 
supply houses and welding equipment stores are likely sources.  You will also need a 
torch or pair of torches able to raise the tubing joints to an orange heat in a 
reasonable length of time.

Depending on the chosen working fluid, the cold plate temperature will not rise 
above the boiling point of the fluid unless the system is too small (in 
radiator heat removal capacity) to easily handle the 10 or 20 thermal watts 
that are passing through.

What fluid to use?  Anything common and thermally stable that does not attack 
copper.  Alcohol (methyl or ethyl) and water are common choices, as are the 
various freons.  I bet acetone would also work. Anyway, one controls the 
coldplate temperature by a combination of choice of working fluid and internal 
pressure.


I have seen commercially made heat pipes for cooling Intel CPUs advertised, but 
I don't know that these units can be adapted.

Anyway, a heat pipe system will stabilize the coldplate temperature fairly 
accurately despite variations in thermal load, has no moving or electrical 
parts, and may be sufficient by itself.  If not sufficient, it can be used as 
the outer stage in a two-stage ovening scheme.


Joe Gwinn

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Re: [time-nuts] Cheap Rubidium (heatpipe cooling for)

Hi

Exactly right. You don't need a multiple horsepower pump to make it happen. 
WIth some careful thought, you may be able to share one pump between the set of 
standards (back to correlation issues though ...) 

Bob


On Dec 24, 2009, at 3:41 PM, Bruce Griffiths wrote:

 Depending on the required flow rate you may be able to use a peristaltic pump.
 
 Bruce
 
 Bob Camp wrote:
 Hi
 
 A heat pipe might work if the fluid had a sufficiently low boiling point. 
 The rubidium isn't terribly tolerant of high temperatures, and I'm going to 
 pick up some heat rise as I put it inside some baffles / shields. You need 
 to find something that fits a fairly narrow window.
 
 I suspect that a recirculating water loop is a more practical approach to 
 carry away the heat. It's got a pump to move the water, but the rest of it 
 is fairly simple.
 
 Bob
 
 
 On Dec 24, 2009, at 2:49 PM, Joe Gwinn wrote:
 
   
 A dodge occurs to me - a homebrew heat 
 pipe:http://en.wikipedia.org/wiki/Heat_pipe.
 
 Make the cold plate of copper, to which is soldered a meandering piece of 
 copper tubing, which tubing is also soldered to a copper radiator plate 
 that is above the coldplate, forming a closed loop with a fill tube 
 attached by a T.  Braze all tubing connections, as for freon refrigeration 
 systems.  (Soft solder is too porous to work for the joints, but is OK for 
 attaching tubes to plates.)
 
 Insulate the two tubes running between coldplate and radiator plate from 
 one another.
 
 Put enough working fluid into the system to fill the tubing that is 
 soldered to the coldplate, but no more.  Warm the system up so the vapor 
 drives all the air out, pinch the fill tube off and fold it back, and braze 
 the end shut.   (It's not critical to get absolutely all the air out.)
 
 Making the radiator plate be above the coldplate (the boiler) implements 
 what amounts to an oldtime two-pipe water vapor heating plant.  Vapor goes 
 up one pipe, condensed fluid returns via the other.  I lived in a house 
 with such a system.  The difference between a vapor plant and a steam plant 
 is pressure:  the vapor plant runs below atmospheric pressure, while the 
 steam plant runs at or slightly above.
 
 Make sure that things are arranged so the returning fluid does not pool 
 anywhere but in the coldplate, or the heat pipe will bang like an old steam 
 heating system.
 
 There is a brazing filler metal intended for copper-to-copper joints that 
 is widely used for freon 
 systems:http://www.uniweld.com/catalog/alloys/silver_brazing_alloys/phos_copper.htm.
  The zero silver phos stuff is adequate, cheap and widely available. While 
 copper-to-copper needs no flux, copper-to-brass does, so also get the flux. 
  Plumbing supply houses and welding equipment stores are likely sources.  
 You will also need a torch or pair of torches able to raise the tubing 
 joints to an orange heat in a reasonable length of time.
 
 Depending on the chosen working fluid, the cold plate temperature will not 
 rise above the boiling point of the fluid unless the system is too small 
 (in radiator heat removal capacity) to easily handle the 10 or 20 thermal 
 watts that are passing through.
 
 What fluid to use?  Anything common and thermally stable that does not 
 attack copper.  Alcohol (methyl or ethyl) and water are common choices, as 
 are the various freons.  I bet acetone would also work. Anyway, one 
 controls the coldplate temperature by a combination of choice of working 
 fluid and internal pressure.
 
 
 I have seen commercially made heat pipes for cooling Intel CPUs advertised, 
 but I don't know that these units can be adapted.
 
 Anyway, a heat pipe system will stabilize the coldplate temperature fairly 
 accurately despite variations in thermal load, has no moving or electrical 
 parts, and may be sufficient by itself.  If not sufficient, it can be used 
 as the outer stage in a two-stage ovening scheme.
 
 
 Joe Gwinn
 
 ___
 time-nuts mailing list -- time-nuts@febo.com
 To unsubscribe, go to 
 https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
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Re: [time-nuts] Cheap Rubidium (heatpipe cooling for)

2009-12-24 Thread Hal Murray


 A heat pipe might work if the fluid had a sufficiently low boiling
 point. The rubidium isn't terribly tolerant of high temperatures, and
 I'm going to pick up some heat rise as I put it inside some baffles /
 shields. You need to find something that fits a fairly narrow window.

This is all backwards.

The main reason the typical Rubidium box needs a serious heat sink is that 
there is an active heater inside it heating up the lamp to get it up to 
operating temperature.  That part of the system better be tolerant of high 
(enough) temperature.

Maybe things would be a lot better/simpler if the heating/cooling we have 
been discussing were split into two sections.  One for the lamp assembly, and 
a second for the electronics.


Anybody know what the thermal coefficient of the lamp is relative to the 
electronics?


-- 
These are my opinions, not necessarily my employer's.  I hate spam.




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Re: [time-nuts] Cheap Rubidium (heatpipe cooling for)

Hi

I looked at it that way for quite a while. More or less: A rubidium is like an 
OCXO, and running it at the upper end of the specified range is just fine.

Then I cooked a few rubidiums 

The real answer appears to be that the rest of the circuitry in there drops 
MTBF quickly as it gets hotter. The cell runs just fine, but the circuits that 
drive it die. There are tables in the data sheets that pretty well document 
this. 

Since these gizmos already have been out in the field for a while, I need to 
get all the life I can out of them.

Bob


On Dec 24, 2009, at 4:59 PM, Hal Murray wrote:

 
 A heat pipe might work if the fluid had a sufficiently low boiling
 point. The rubidium isn't terribly tolerant of high temperatures, and
 I'm going to pick up some heat rise as I put it inside some baffles /
 shields. You need to find something that fits a fairly narrow window.
 
 This is all backwards.
 
 The main reason the typical Rubidium box needs a serious heat sink is that 
 there is an active heater inside it heating up the lamp to get it up to 
 operating temperature.  That part of the system better be tolerant of high 
 (enough) temperature.
 
 Maybe things would be a lot better/simpler if the heating/cooling we have 
 been discussing were split into two sections.  One for the lamp assembly, and 
 a second for the electronics.
 
 
 Anybody know what the thermal coefficient of the lamp is relative to the 
 electronics?
 
 
 -- 
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Re: [time-nuts] Cheap Rubidium (heatpipe cooling for)


Hal Murray wrote:

A heat pipe might work if the fluid had a sufficiently low boiling
point. The rubidium isn't terribly tolerant of high temperatures, and
I'm going to pick up some heat rise as I put it inside some baffles /
shields. You need to find something that fits a fairly narrow window.


This is all backwards.

The main reason the typical Rubidium box needs a serious heat sink is that 
there is an active heater inside it heating up the lamp to get it up to 
operating temperature.  That part of the system better be tolerant of high 
(enough) temperature.


... or a less heat-producing alternative could be used. The 
Rubidium-lamp produces two wavelengths of which one is filtered by a 
Rubidium-filter which leaves the final pumping wavelength. This is what 
a laser diode could supply instead.


Maybe things would be a lot better/simpler if the heating/cooling we have 
been discussing were split into two sections.  One for the lamp assembly, and 
a second for the electronics.


Most of the discussion has been on thermal isolation of the entier 
units. Not what needs generates temperature and what requires 
temperature stability etc.


Anybody know what the thermal coefficient of the lamp is relative to the 
electronics?


I am not sure I know what you mean by this...

Cheers,
Magnus

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Re: [time-nuts] Cheap Rubidium (heatpipe cooling for)


Magnus Danielson wrote:

Hal Murray wrote:

A heat pipe might work if the fluid had a sufficiently low boiling
point. The rubidium isn't terribly tolerant of high temperatures, and
I'm going to pick up some heat rise as I put it inside some baffles /
shields. You need to find something that fits a fairly narrow window.


This is all backwards.

The main reason the typical Rubidium box needs a serious heat sink is 
that there is an active heater inside it heating up the lamp to get 
it up to operating temperature.  That part of the system better be 
tolerant of high (enough) temperature.


... or a less heat-producing alternative could be used. The 
Rubidium-lamp produces two wavelengths of which one is filtered by a 
Rubidium-filter which leaves the final pumping wavelength. This is 
what a laser diode could supply instead.


Maybe things would be a lot better/simpler if the heating/cooling we 
have been discussing were split into two sections.  One for the lamp 
assembly, and a second for the electronics.


Most of the discussion has been on thermal isolation of the entier 
units. Not what needs generates temperature and what requires 
temperature stability etc.


Anybody know what the thermal coefficient of the lamp is relative to 
the electronics?


I am not sure I know what you mean by this...

Cheers,
Magnus
Probably the temperature fluctuations of the absorption cell is more 
significant than that of the lamp itself.

The effects to consider are:

1) The effect of temperature fluctuations of the electronics.
Probably dominated by the short term temperature fluctuations of the 
internal crystal oscillator.


2) The effect of temperature fluctuations of the Rubidium lamp and 
associated optical filters.


3) The effect of temperature fluctuations on the Rubidium absorption 
cell hyperfine transition frequency.




Bruce


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Re: [time-nuts] Cheap Rubidium (heatpipe cooling for)

Hi

The original intent was to simply take an existing cheap rubidium and do 
simple things to it. Tearing it into pieces and redesigning parts of it was not 
anything I originally contemplated. The tight integration of the physics 
package to the electronics would make this a fairly involved process. 

Bob


On Dec 24, 2009, at 5:42 PM, Magnus Danielson wrote:

 Hal Murray wrote:
 A heat pipe might work if the fluid had a sufficiently low boiling
 point. The rubidium isn't terribly tolerant of high temperatures, and
 I'm going to pick up some heat rise as I put it inside some baffles /
 shields. You need to find something that fits a fairly narrow window.
 This is all backwards.
 The main reason the typical Rubidium box needs a serious heat sink is that 
 there is an active heater inside it heating up the lamp to get it up to 
 operating temperature.  That part of the system better be tolerant of high 
 (enough) temperature.
 
 ... or a less heat-producing alternative could be used. The Rubidium-lamp 
 produces two wavelengths of which one is filtered by a Rubidium-filter which 
 leaves the final pumping wavelength. This is what a laser diode could supply 
 instead.
 
 Maybe things would be a lot better/simpler if the heating/cooling we have 
 been discussing were split into two sections.  One for the lamp assembly, 
 and a second for the electronics.
 
 Most of the discussion has been on thermal isolation of the entier units. Not 
 what needs generates temperature and what requires temperature stability etc.
 
 Anybody know what the thermal coefficient of the lamp is relative to the 
 electronics?
 
 I am not sure I know what you mean by this...
 
 Cheers,
 Magnus
 
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Re: [time-nuts] Cheap Rubidium (heatpipe cooling for)


Bruce Griffiths wrote:
Probably the temperature fluctuations of the absorption cell is more 
significant than that of the lamp itself.


The lamp itself shifts intensity sligthly, but the three most sensitive 
points to temperature and temperature shifts is the resonator cavity 
(pulls the frequency as it detunes), buffert gas shift change with 
temperature and this balance the wall-shift so shift in temperature 
change the buffer-gas/wall shift balance and shift in temperature will 
cause the OCXO to shift and that needs to be canceled in the loop.


The main effect of the lamp temperature is to shift S/N.

All according to my limited knowledge in the field.


The effects to consider are:

1) The effect of temperature fluctuations of the electronics.
Probably dominated by the short term temperature fluctuations of the 
internal crystal oscillator.


The magnetic field applied could also vary. To the best of my knowledge, 
I do not know of a way to servo the magnetic field in the fashion it is 
done for cesium beams. This servo is part of the modernisation that made 
cesiums much more stable.


2) The effect of temperature fluctuations of the Rubidium lamp and 
associated optical filters.


Mainly shift in intensity and also the temperature widening of the 
relevant wavelength. Likewise with the rubidium filter cell absorbing 
the unwanted wavelength.


3) The effect of temperature fluctuations on the Rubidium absorption 
cell hyperfine transition frequency.


Buffert-gas mix vs. wall-shift balance depend on temperature. At some 
temperature the buffert-gas completely cancels the wall-shift. We can 
expect the gas-mixture to shift over time and thus the 
shift-compensation for a certain temperature, so there is a wear 
mechanism in play.


4) The effect of temperature fluctionations on the Rubidium frequency 
resonator.


Resonator cavity frequency shifts with temperature as material expand 
(on rising temperature). The Q of the resonator plays a role in the 
amount of frequency pulling.


These effects is well covered in the literature.

Cheers,
Magnus

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Re: [time-nuts] Cheap Rubidium (heatpipe cooling for)

2009-12-24 Thread J. Forster

That's why I've been suggesting active control with TE devices.

You can buy a small TE cooler at Walgreens for about $20. It's big enough
for a 6-pack of Coke cans and already comes in an insulated box. Add a
simple temperature control in series w/ the DC supply and you should be
well on the way.

-John

=


 Hi

 The original intent was to simply take an existing cheap rubidium and do
 simple things to it. Tearing it into pieces and redesigning parts of it
 was not anything I originally contemplated. The tight integration of the
 physics package to the electronics would make this a fairly involved
 process.

 Bob


 On Dec 24, 2009, at 5:42 PM, Magnus Danielson wrote:

 Hal Murray wrote:
 A heat pipe might work if the fluid had a sufficiently low boiling
 point. The rubidium isn't terribly tolerant of high temperatures, and
 I'm going to pick up some heat rise as I put it inside some baffles /
 shields. You need to find something that fits a fairly narrow window.
 This is all backwards.
 The main reason the typical Rubidium box needs a serious heat sink is
 that there is an active heater inside it heating up the lamp to get it
 up to operating temperature.  That part of the system better be
 tolerant of high (enough) temperature.

 ... or a less heat-producing alternative could be used. The
 Rubidium-lamp produces two wavelengths of which one is filtered by a
 Rubidium-filter which leaves the final pumping wavelength. This is what
 a laser diode could supply instead.

 Maybe things would be a lot better/simpler if the heating/cooling we
 have been discussing were split into two sections.  One for the lamp
 assembly, and a second for the electronics.

 Most of the discussion has been on thermal isolation of the entier
 units. Not what needs generates temperature and what requires
 temperature stability etc.

 Anybody know what the thermal coefficient of the lamp is relative to
 the electronics?

 I am not sure I know what you mean by this...

 Cheers,
 Magnus

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Re: [time-nuts] Cheap Rubidium (heatpipe cooling for)

2009-12-24 Thread Robert Darlington

On Thu, Dec 24, 2009 at 1:32 PM, Bob Camp li...@cq.nu wrote:

 Hi

 A heat pipe might work if the fluid had a sufficiently low boiling point.


The working fluid in a heat pipe will boil at every temperature above its
melting point.  I tend to use water because it's cheap, but have made them
with 3M engineered fluids, Fluorinert, and denatured alcohol.  I've found
that ordinary solder works just fine.  A trick to make these things easy to
build is to use a ball valve at the top (I'm assuming there is a top and
we're going with gravity return because it's simple).  I've got a few that
are still under vacuum for several years now in this configuration.  My
giant heat pipe of doom is a 10 foot stick of 1/2 copper with a ball valve
at one end and an end cap at the other.  There is perhaps 100ml water in
there total, and no air.  You can either boil the liquid until it builds up
a nice head of steam, or go the easy way and pull a vacuum with a pump and
just close the valve.  These things are incredible.  If you pack snow around
the end of this thing, the other end that is ten feet away gets cold almost
immediately.  They want to stay isothermal and the heat transfer is at the
speed of sound through the working fluid.  Delays are introduced because
you're dealing with a thermal mass of copper pipe that needs to change
temperature along with the working fluid so it's not quite instant, but
still about 10,000 times faster heat transfer than copper by itself.  They
are certainly handy for getting heat out of confined spaces.

-Bob



 The rubidium isn't terribly tolerant of high temperatures, and I'm going to
 pick up some heat rise as I put it inside some baffles / shields. You need
 to find something that fits a fairly narrow window.

 I suspect that a recirculating water loop is a more practical approach to
 carry away the heat. It's got a pump to move the water, but the rest of it
 is fairly simple.

 Bob


 On Dec 24, 2009, at 2:49 PM, Joe Gwinn wrote:

  A dodge occurs to me - a homebrew heat pipe: 
 http://en.wikipedia.org/wiki/Heat_pipe.
 
  Make the cold plate of copper, to which is soldered a meandering piece of
 copper tubing, which tubing is also soldered to a copper radiator plate that
 is above the coldplate, forming a closed loop with a fill tube attached by a
 T.  Braze all tubing connections, as for freon refrigeration systems.  (Soft
 solder is too porous to work for the joints, but is OK for attaching tubes
 to plates.)
 
  Insulate the two tubes running between coldplate and radiator plate from
 one another.
 
  Put enough working fluid into the system to fill the tubing that is
 soldered to the coldplate, but no more.  Warm the system up so the vapor
 drives all the air out, pinch the fill tube off and fold it back, and braze
 the end shut.   (It's not critical to get absolutely all the air out.)
 
  Making the radiator plate be above the coldplate (the boiler) implements
 what amounts to an oldtime two-pipe water vapor heating plant.  Vapor goes
 up one pipe, condensed fluid returns via the other.  I lived in a house with
 such a system.  The difference between a vapor plant and a steam plant is
 pressure:  the vapor plant runs below atmospheric pressure, while the steam
 plant runs at or slightly above.
 
  Make sure that things are arranged so the returning fluid does not pool
 anywhere but in the coldplate, or the heat pipe will bang like an old steam
 heating system.
 
  There is a brazing filler metal intended for copper-to-copper joints that
 is widely used for freon systems: 
 http://www.uniweld.com/catalog/alloys/silver_brazing_alloys/phos_copper.htm.
 The zero silver phos stuff is adequate, cheap and widely available. While
 copper-to-copper needs no flux, copper-to-brass does, so also get the flux.
  Plumbing supply houses and welding equipment stores are likely sources.
  You will also need a torch or pair of torches able to raise the tubing
 joints to an orange heat in a reasonable length of time.
 
  Depending on the chosen working fluid, the cold plate temperature will
 not rise above the boiling point of the fluid unless the system is too small
 (in radiator heat removal capacity) to easily handle the 10 or 20 thermal
 watts that are passing through.
 
  What fluid to use?  Anything common and thermally stable that does not
 attack copper.  Alcohol (methyl or ethyl) and water are common choices, as
 are the various freons.  I bet acetone would also work. Anyway, one controls
 the coldplate temperature by a combination of choice of working fluid and
 internal pressure.
 
 
  I have seen commercially made heat pipes for cooling Intel CPUs
 advertised, but I don't know that these units can be adapted.
 
  Anyway, a heat pipe system will stabilize the coldplate temperature
 fairly accurately despite variations in thermal load, has no moving or
 electrical parts, and may be sufficient by itself.  If not sufficient, it
 can be used as the outer stage in a two-stage ovening scheme.

Re: [time-nuts] Cheap Rubidium (heatpipe cooling for)

Bob Camp wrote:

The original intent was to simply take an existing cheap rubidium and do simple things to it. Tearing it into pieces and redesigning parts of it was not anything I originally contemplated. The tight integration of the physics package to the electronics would make this a fairly involved process.

Well, the main point with that was that while passive temperature
stability craze have been raving high here, and into more and more
expensive and elaborate propositions, relative simple changes (not
without its challenges) would change the equation (amount of heat to
cool of) quite noticeably. If money was no object, building
no-compromise/prisoners temperature stabilization scehemes around used
commercial rubidiums should not be the optimum way to go. Building a
Rubidum or Cesium fointain would probably be way better use of the
money. Quite a different project thought.

Maybe we need to get back to doable levels, and also consider what
changes Rb frequency, why and what can we do to avoid it.

I have been dipping my nose into the literature, to refresh myself on
the complex interactions. Lamp intensity in itself is a fashinating
topic, while the filtering cells temperature to intensity dependence is
another little complex field of its own and that (as I suspected)
intensity too pulls the frequency. Oh, and after a quick glaze, I found
that the necessary side-peaks needed for servo of C-field exists for
Rb-87, so it can be done similar to that of Cesium.

Cheers,
Magnus

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Re: [time-nuts] Cheap Rubidium (heatpipe cooling for)

Hi

I certainly agree that, say potting the circuit board, would be a lot easier 
than some of the stuff we have been talking about. 

My main concern about tearing up the unit is impacting the magnetic shielding. 
I assume that the outer enclosure forms part of the magnetic shield (at least 
that's what the data sheets say ...).

Bob


On Dec 24, 2009, at 7:51 PM, Magnus Danielson wrote:

 Bob Camp wrote:
 Hi
 The original intent was to simply take an existing cheap rubidium and do 
 simple things to it. Tearing it into pieces and redesigning parts of it was 
 not anything I originally contemplated. The tight integration of the physics 
 package to the electronics would make this a fairly involved process. 
 
 Well, the main point with that was that while passive temperature stability 
 craze have been raving high here, and into more and more expensive and 
 elaborate propositions, relative simple changes (not without its challenges) 
 would change the equation (amount of heat to cool of) quite noticeably. If 
 money was no object, building no-compromise/prisoners temperature 
 stabilization scehemes around used commercial rubidiums should not be the 
 optimum way to go. Building a Rubidum or Cesium fointain would probably be 
 way better use of the money. Quite a different project thought.
 
 Maybe we need to get back to doable levels, and also consider what changes Rb 
 frequency, why and what can we do to avoid it.
 
 I have been dipping my nose into the literature, to refresh myself on the 
 complex interactions. Lamp intensity in itself is a fashinating topic, while 
 the filtering cells temperature to intensity dependence is another little 
 complex field of its own and that (as I suspected) intensity too pulls the 
 frequency. Oh, and after a quick glaze, I found that the necessary side-peaks 
 needed for servo of C-field exists for Rb-87, so it can be done similar to 
 that of Cesium.
 
 Cheers,
 Magnus
 
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Re: [time-nuts] Cheap Rubidium (heatpipe cooling for)


Bob Camp wrote:

Hi

I certainly agree that, say potting the circuit board, would be a lot easier than some of the stuff we have been talking about. 


I am not sure that it would significantly improve the case.

The physical package as a whole, needs temperature stabilization. 
Double-oven strategies etc. is among them. At the same time it is a heat 
source, so we need to cool a few wats off it. Except for possibly the 
resonant cavity, I don't think thermal gradients is as important as 
stable temperature, where as the crystal(s) of the electronics boards is 
another story. The electronics might enjoy a cooler and somewhat 
gradient free environment, but for longer taus most of the effects would 
be servoed in to the rubidium resonance anyway, so I suspect most of 
those long-term effects can be focused on the physical package.



My main concern about tearing up the unit is impacting the magnetic shielding. 
I assume that the outer enclosure forms part of the magnetic shield (at least 
that's what the data sheets say ...).


Good point.

Cheers,
Magnus

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Re: [time-nuts] Cheap Rubidium (heatpipe cooling for)

Hi

My main concern with gradients would be second order effects on the servo 
circuit. As you change the zero of the phase detector you get a net short term 
frequency shift. Gradients on the pc board - stress on smt parts - value 
changes - phase shift.

Bob

On Dec 24, 2009, at 8:09 PM, Magnus Danielson wrote:

 Bob Camp wrote:
 Hi
 I certainly agree that, say potting the circuit board, would be a lot easier 
 than some of the stuff we have been talking about. 
 
 I am not sure that it would significantly improve the case.
 
 The physical package as a whole, needs temperature stabilization. Double-oven 
 strategies etc. is among them. At the same time it is a heat source, so we 
 need to cool a few wats off it. Except for possibly the resonant cavity, I 
 don't think thermal gradients is as important as stable temperature, where as 
 the crystal(s) of the electronics boards is another story. The electronics 
 might enjoy a cooler and somewhat gradient free environment, but for longer 
 taus most of the effects would be servoed in to the rubidium resonance 
 anyway, so I suspect most of those long-term effects can be focused on the 
 physical package.
 
 My main concern about tearing up the unit is impacting the magnetic 
 shielding. I assume that the outer enclosure forms part of the magnetic 
 shield (at least that's what the data sheets say ...).
 
 Good point.
 
 Cheers,
 Magnus
 
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Re: [time-nuts] Cheap Rubidium (heatpipe cooling for)

Yes, dont start drilling or punching extra holes in the case as some 
have done, unless you are sure the case isn't mu metal or similar.


Optical interrogation of the resonance using lasers would make it much 
easier to separate the electronics from the absorption cell, it would 
also allow the rubidium lamp to be dispensed with.

However this method can be expensive and it has its own problems to solve.

Bruce

Bob Camp wrote:

Hi

I certainly agree that, say potting the circuit board, would be a lot easier 
than some of the stuff we have been talking about.

My main concern about tearing up the unit is impacting the magnetic shielding. 
I assume that the outer enclosure forms part of the magnetic shield (at least 
that's what the data sheets say ...).

Bob


On Dec 24, 2009, at 7:51 PM, Magnus Danielson wrote:

   

Bob Camp wrote:
 

Hi
The original intent was to simply take an existing cheap rubidium and do 
simple things to it. Tearing it into pieces and redesigning parts of it was not anything 
I originally contemplated. The tight integration of the physics package to the 
electronics would make this a fairly involved process.
   

Well, the main point with that was that while passive temperature stability 
craze have been raving high here, and into more and more expensive and 
elaborate propositions, relative simple changes (not without its challenges) 
would change the equation (amount of heat to cool of) quite noticeably. If 
money was no object, building no-compromise/prisoners temperature stabilization 
scehemes around used commercial rubidiums should not be the optimum way to go. 
Building a Rubidum or Cesium fointain would probably be way better use of the 
money. Quite a different project thought.

Maybe we need to get back to doable levels, and also consider what changes Rb 
frequency, why and what can we do to avoid it.

I have been dipping my nose into the literature, to refresh myself on the 
complex interactions. Lamp intensity in itself is a fashinating topic, while 
the filtering cells temperature to intensity dependence is another little 
complex field of its own and that (as I suspected) intensity too pulls the 
frequency. Oh, and after a quick glaze, I found that the necessary side-peaks 
needed for servo of C-field exists for Rb-87, so it can be done similar to that 
of Cesium.

Cheers,
Magnus

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Re: [time-nuts] Cheap Rubidium (heatpipe cooling for)

Hi

I'd check the case with a magnet, but I'm not real sure that it would not do 
something permanent.

Bob

On Dec 24, 2009, at 9:09 PM, Bruce Griffiths wrote:

 Yes, dont start drilling or punching extra holes in the case as some have 
 done, unless you are sure the case isn't mu metal or similar.
 
 Optical interrogation of the resonance using lasers would make it much easier 
 to separate the electronics from the absorption cell, it would also allow the 
 rubidium lamp to be dispensed with.
 However this method can be expensive and it has its own problems to solve.
 
 Bruce
 
 Bob Camp wrote:
 Hi
 
 I certainly agree that, say potting the circuit board, would be a lot easier 
 than some of the stuff we have been talking about.
 
 My main concern about tearing up the unit is impacting the magnetic 
 shielding. I assume that the outer enclosure forms part of the magnetic 
 shield (at least that's what the data sheets say ...).
 
 Bob
 
 
 On Dec 24, 2009, at 7:51 PM, Magnus Danielson wrote:
 
   
 Bob Camp wrote:
 
 Hi
 The original intent was to simply take an existing cheap rubidium and do 
 simple things to it. Tearing it into pieces and redesigning parts of it 
 was not anything I originally contemplated. The tight integration of the 
 physics package to the electronics would make this a fairly involved 
 process.
   
 Well, the main point with that was that while passive temperature stability 
 craze have been raving high here, and into more and more expensive and 
 elaborate propositions, relative simple changes (not without its 
 challenges) would change the equation (amount of heat to cool of) quite 
 noticeably. If money was no object, building no-compromise/prisoners 
 temperature stabilization scehemes around used commercial rubidiums should 
 not be the optimum way to go. Building a Rubidum or Cesium fointain would 
 probably be way better use of the money. Quite a different project thought.
 
 Maybe we need to get back to doable levels, and also consider what changes 
 Rb frequency, why and what can we do to avoid it.
 
 I have been dipping my nose into the literature, to refresh myself on the 
 complex interactions. Lamp intensity in itself is a fashinating topic, 
 while the filtering cells temperature to intensity dependence is another 
 little complex field of its own and that (as I suspected) intensity too 
 pulls the frequency. Oh, and after a quick glaze, I found that the 
 necessary side-peaks needed for servo of C-field exists for Rb-87, so it 
 can be done similar to that of Cesium.
 
 Cheers,
 Magnus
 
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Re: [time-nuts] Cheap Rubidium (heatpipe cooling for)


If you do that and it is mu metal then you'll have to demagnetise it.
However this is easier than having to anneal it.
If you have a magnetic probe you may be able to test its effectiveness 
in shielding against the earth's magnetic field.
This may be one way of checking if a mu metal case needs to be annealed 
as a result of rough handling.


If you have a dead rubidium then magnetising the case isn't an issue.

Bob Camp wrote:

Hi

I'd check the case with a magnet, but I'm not real sure that it would not do 
something permanent.

Bob

On Dec 24, 2009, at 9:09 PM, Bruce Griffiths wrote:

   

Yes, dont start drilling or punching extra holes in the case as some have done, 
unless you are sure the case isn't mu metal or similar.

Optical interrogation of the resonance using lasers would make it much easier 
to separate the electronics from the absorption cell, it would also allow the 
rubidium lamp to be dispensed with.
However this method can be expensive and it has its own problems to solve.

Bruce

Bob Camp wrote:
 

Hi

I certainly agree that, say potting the circuit board, would be a lot easier 
than some of the stuff we have been talking about.

My main concern about tearing up the unit is impacting the magnetic shielding. 
I assume that the outer enclosure forms part of the magnetic shield (at least 
that's what the data sheets say ...).

Bob


On Dec 24, 2009, at 7:51 PM, Magnus Danielson wrote:


   

Bob Camp wrote:

 

Hi
The original intent was to simply take an existing cheap rubidium and do 
simple things to it. Tearing it into pieces and redesigning parts of it was not anything 
I originally contemplated. The tight integration of the physics package to the 
electronics would make this a fairly involved process.

   

Well, the main point with that was that while passive temperature stability 
craze have been raving high here, and into more and more expensive and 
elaborate propositions, relative simple changes (not without its challenges) 
would change the equation (amount of heat to cool of) quite noticeably. If 
money was no object, building no-compromise/prisoners temperature stabilization 
scehemes around used commercial rubidiums should not be the optimum way to go. 
Building a Rubidum or Cesium fointain would probably be way better use of the 
money. Quite a different project thought.

Maybe we need to get back to doable levels, and also consider what changes Rb 
frequency, why and what can we do to avoid it.

I have been dipping my nose into the literature, to refresh myself on the 
complex interactions. Lamp intensity in itself is a fashinating topic, while 
the filtering cells temperature to intensity dependence is another little 
complex field of its own and that (as I suspected) intensity too pulls the 
frequency. Oh, and after a quick glaze, I found that the necessary side-peaks 
needed for servo of C-field exists for Rb-87, so it can be done similar to that 
of Cesium.

Cheers,
Magnus

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Re: [time-nuts] Cheap Rubidium (heatpipe cooling for)

Hi

I suspect that I will wind up with at least one dead rubidium in the course of 
all this ...

Bob


On Dec 24, 2009, at 10:19 PM, Bruce Griffiths wrote:

 If you do that and it is mu metal then you'll have to demagnetise it.
 However this is easier than having to anneal it.
 If you have a magnetic probe you may be able to test its effectiveness in 
 shielding against the earth's magnetic field.
 This may be one way of checking if a mu metal case needs to be annealed as a 
 result of rough handling.
 
 If you have a dead rubidium then magnetising the case isn't an issue.
 
 Bob Camp wrote:
 Hi
 
 I'd check the case with a magnet, but I'm not real sure that it would not do 
 something permanent.
 
 Bob
 
 On Dec 24, 2009, at 9:09 PM, Bruce Griffiths wrote:
 
   
 Yes, dont start drilling or punching extra holes in the case as some have 
 done, unless you are sure the case isn't mu metal or similar.
 
 Optical interrogation of the resonance using lasers would make it much 
 easier to separate the electronics from the absorption cell, it would also 
 allow the rubidium lamp to be dispensed with.
 However this method can be expensive and it has its own problems to solve.
 
 Bruce
 
 Bob Camp wrote:
 
 Hi
 
 I certainly agree that, say potting the circuit board, would be a lot 
 easier than some of the stuff we have been talking about.
 
 My main concern about tearing up the unit is impacting the magnetic 
 shielding. I assume that the outer enclosure forms part of the magnetic 
 shield (at least that's what the data sheets say ...).
 
 Bob
 
 
 On Dec 24, 2009, at 7:51 PM, Magnus Danielson wrote:
 
 
   
 Bob Camp wrote:
 
 
 Hi
 The original intent was to simply take an existing cheap rubidium and 
 do simple things to it. Tearing it into pieces and redesigning parts of 
 it was not anything I originally contemplated. The tight integration of 
 the physics package to the electronics would make this a fairly involved 
 process.
 
   
 Well, the main point with that was that while passive temperature 
 stability craze have been raving high here, and into more and more 
 expensive and elaborate propositions, relative simple changes (not 
 without its challenges) would change the equation (amount of heat to cool 
 of) quite noticeably. If money was no object, building 
 no-compromise/prisoners temperature stabilization scehemes around used 
 commercial rubidiums should not be the optimum way to go. Building a 
 Rubidum or Cesium fointain would probably be way better use of the money. 
 Quite a different project thought.
 
 Maybe we need to get back to doable levels, and also consider what 
 changes Rb frequency, why and what can we do to avoid it.
 
 I have been dipping my nose into the literature, to refresh myself on the 
 complex interactions. Lamp intensity in itself is a fashinating topic, 
 while the filtering cells temperature to intensity dependence is another 
 little complex field of its own and that (as I suspected) intensity too 
 pulls the frequency. Oh, and after a quick glaze, I found that the 
 necessary side-peaks needed for servo of C-field exists for Rb-87, so it 
 can be done similar to that of Cesium.
 
 Cheers,
 Magnus
 
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Re: [time-nuts] Cheap Rubidium (heatpipe cooling for)

2009-12-24 Thread Hal Murray


li...@cq.nu said:
 The original intent was to simply take an existing cheap rubidium
 and do simple things to it. Tearing it into pieces and redesigning
 parts of it was not anything I originally contemplated. The tight
 integration of the physics package to the electronics would make this
 a fairly involved process.  

Sure, but if we are discussing digging a hole big enough for a ton of 
mercury, then taking apart a tightly integrated package seems worth 
considering.

I expect the packaging might be reasonable for this purpose.  After all, the 
designers probably wanted to keep that heat away from the electronics.



-- 
These are my opinions, not necessarily my employer's.  I hate spam.




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Re: [time-nuts] Cheap Rubidium (heatpipe cooling for)

Hi

The big hitters for heat outside the physics package seem to be the RF 
excitation and the microwave generation stuff. The regulators will warm 
things up if you run high voltage into them, but I would probably not do that. 

I don't believe that putting multiple swimming pools into the basement, mercury 
filled or otherwise was ever a real candidate for a solution. It is kind of 
interesting to see just how big the jug of water would have to be. 

Right now my leading candidate is a multi layer aluminum / steel enclosure with 
a point short between each of the layers to keep the heat rise under control. 
Cool the baseplate with recirculating water and a cheap ( $50) pump. Throw 
in a fan and radiator to cool the water to room temperature.  Servo the 
temperature with what ever at the point shorts. Monitor the temperature as 
best you can.

The main what ever still in there are TE coolers. A quick look suggests that 
+12 heats and -12 cools. In between the two it's not clear that much happens 
(maybe it does ...). Even if it does not, I haven't dug deep enough to see if 
something like current drive takes care of the dead band issue. 

Some math. It's late, but I think this is about right:

1) 4 layers
2) Shorts at 2 C/W
3) 10 W inside
4)  80 C heat rise - not going to work

If I stick with 4 layers, 10 W, and a 15 C rise then the shorts need to be ~ 
0.38 C/W.  A 15C rise gets me to 40C which looks reasonable based on the app 
notes I have read on the rubidiums. 

If the basement moves up 5 C then I'm cold pumping 1/3 of the 10W. Same thing 
in reverse if the basement drops 5 C. Both are unlikely to happen as long as 
there isn't a catastrophic failure of the HVAC. 

If I go to a air cooled baseplate heat sink, it's thermal resistance is going 
to have to come out of the budget.  My *guess* is that's going to be more 
involved than a simple pump and some plastic tubes. 

Bob

On Dec 24, 2009, at 10:46 PM, Hal Murray wrote:

 
 li...@cq.nu said:
 The original intent was to simply take an existing cheap rubidium
 and do simple things to it. Tearing it into pieces and redesigning
 parts of it was not anything I originally contemplated. The tight
 integration of the physics package to the electronics would make this
 a fairly involved process.  
 
 Sure, but if we are discussing digging a hole big enough for a ton of 
 mercury, then taking apart a tightly integrated package seems worth 
 considering.
 
 I expect the packaging might be reasonable for this purpose.  After all, the 
 designers probably wanted to keep that heat away from the electronics.
 
 
 
 -- 
 These are my opinions, not necessarily my employer's.  I hate spam.
 
 
 
 
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Re: [time-nuts] Cheap Rubidium (heatpipe cooling for)