[time-nuts] Cheap Rubidium
Dick Moore
richiem at hughes.net
Thu Dec 24 22:10:32 UTC 2009
I like the idea of building a cold-storage plant with nested rooms, perhaps 20 or so 'til you end up with something about 1 cu. ft. to put the rubidium in, and renting out any unused space to frozen food folks to partially offset the costs. It wouldn't have to be as big as a football field, though that would be nice.....Some of the rooms could be made of mu-metal, but the re-annealing after the bending and forming can be a real hassle. And of course the large size makes it easier to use 3-axios orthogonal Helmholtz coils in a nested room while still allowing for a door for access, much like the Navy's demagnetizing coils for the Trident subs up here at Subase Bangor in Washington State.
After all, cost really is no object, right?
Best,
Dick Moore
On Dec 24, 2009, at 12:55 PM, time-nuts-request at febo.com wrote:
> Send time-nuts mailing list submissions to
> time-nuts at febo.com
>
> To subscribe or unsubscribe via the World Wide Web, visit
> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
> or, via email, send a message with subject or body 'help' to
> time-nuts-request at febo.com
>
> You can reach the person managing the list at
> time-nuts-owner at febo.com
>
> When replying, please edit your Subject line so it is more specific
> than "Re: Contents of time-nuts digest..."
>
>
> Today's Topics:
>
> 1. Re: Cheap Rubidium (Bob Camp)
> 2. Re: Cheap Rubidium (heatpipe cooling for) (Bruce Griffiths)
> 3. Re: Cheap Rubidium (Bruce Griffiths)
> 4. Re: Cheap Rubidium (Bob Camp)
> 5. Re: Cheap Rubidium (heatpipe cooling for) (Bob Camp)
> 6. Re: Cheap Rubidium (Bob Camp)
>
>
> ----------------------------------------------------------------------
>
> Message: 1
> Date: Thu, 24 Dec 2009 15:36:17 -0500
> From: Bob Camp <lists at cq.nu>
> Subject: Re: [time-nuts] Cheap Rubidium
> To: Discussion of precise time and frequency measurement
> <time-nuts at febo.com>
> Message-ID: <5ECF0D6A-EFA1-4244-BC09-7E0BAA640512 at cq.nu>
> Content-Type: text/plain; charset=us-ascii
>
> Hi
>
> Actually burying a recirculating loop might work pretty well. The gotcha is that going much deeper than 18" would require significant amounts of blasting powder. I suspect the neighbors *might* object ....
>
> Bob
>
>
> On Dec 24, 2009, at 3:32 PM, Don Latham wrote:
>
>> Actually, couldn't you just squeeze your fish before you eat it? Should
>> have a lot of mercury in notime, according to the scaremongers.
>> Also, consider a heatsink buried about 10-15 feet deep. The temperature at
>> that depth in the ground does not vary very much at all. The trick to all
>> of this is to have a heatsink/source at a constant temp somewhere...
>> Merry Christams to all the nuts!
>> Don
>>
>> Bruce Griffiths
>>> Magnus Danielson wrote:
>>>> Bruce,
>>>>
>>>> Bruce Griffiths wrote:
>>>>> At your location, at present, it wouldnt be a significant problem as
>>>>> long as the basement was unheated.
>>>>
>>>> Depends. But having 3 dm snow on the ground helps to keep the ground
>>>> around the house warmer, as it will insulate against the cold of the
>>>> open sky. -12.8 C is the lowest so far. Since winter is reoccuring, we
>>>> build the houses accordingly.
>>>>
>>>>> Also good ventilation would help, together with a thin layer of oil
>>>>> on top of the mercury.
>>>>
>>>> Mmm. Yes, didn't think about covering the baths with fluids.
>>>>
>>>>> The biggest obstacle would be the cost of the Mercury.
>>>>
>>>> Actually, it could be an obstcle just obtaining in those amounts it
>>>> here within EC, so it would involve some form of approval of some form
>>>> of excempt since it is mercury is a ROS element.
>>>>
>>>> Cheers,
>>>> Magnus
>>>>
>>>>
>>> Guidline price is around $US600/flask (1 flask = 34.5kg).
>>> Thus cost for 145 ton would be around $US2.5million.
>>>
>>> The Canadians have a liquid mercury mirror telescope about 6m in diameter.
>>> Whilst this doesn't use 145 tons of mercury the surface area would be of
>>> the same order.
>>>
>>> Bruce
>>>
>>>
>>> _______________________________________________
>>> time-nuts mailing list -- time-nuts at febo.com
>>> To unsubscribe, go to
>>> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
>>> and follow the instructions there.
>>>
>>
>>
>> --
>> 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
>>
>>
>> _______________________________________________
>> time-nuts mailing list -- time-nuts at febo.com
>> To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
>> and follow the instructions there.
>>
>
>
>
>
> ------------------------------
>
> Message: 2
> Date: Fri, 25 Dec 2009 09:41:31 +1300
> From: Bruce Griffiths <bruce.griffiths at xtra.co.nz>
> Subject: Re: [time-nuts] Cheap Rubidium (heatpipe cooling for)
> To: Discussion of precise time and frequency measurement
> <time-nuts at febo.com>
> Message-ID: <4B33D1FB.9040309 at xtra.co.nz>
> Content-Type: text/plain; charset=ISO-8859-1; format=flowed
>
> 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 at febo.com
>>> To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
>>> and follow the instructions there.
>>>
>>>
>>
>> _______________________________________________
>> time-nuts mailing list -- time-nuts at febo.com
>> To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
>> and follow the instructions there.
>>
>>
>
>
>
>
>
> ------------------------------
>
> Message: 3
> Date: Fri, 25 Dec 2009 09:50:30 +1300
> From: Bruce Griffiths <bruce.griffiths at xtra.co.nz>
> Subject: Re: [time-nuts] Cheap Rubidium
> To: Discussion of precise time and frequency measurement
> <time-nuts at febo.com>
> Message-ID: <4B33D416.5000001 at xtra.co.nz>
> Content-Type: text/plain; charset=ISO-8859-1; format=flowed
>
> One method of reducing the sensitivity to magnetic fields is to enclose
> the rubidium source in a series of nested magnetic shields (e.g. mu metal).
> The shield walls could form part of the good thermal conductor poor
> thermal conductor stack.
>
> One could also use something like a set of 3 orthogonal Helmholtz coils
> to null the magnetic field at the rubidium source.
> A servo loop using a magnetic field sensor could be employed.
>
> Bruce
>
> Bob Camp wrote:
>> Hi
>>
>> To tune the frequency of a rubidium, you make a very small change to the DC magnetic field around the cell. That's the way you put them on frequency. Anything that changes the local field also changes the frequency of the rubidium standard.
>>
>> The DC in the power leads is a constant current and therefore creates a non-changing field. That means no frequency change.
>>
>> The reason you change the current in the heater is to stabilize the rubidium. If while you are trying to stabilize it one way, you de-stabalize it another way, that may not be progress.
>>
>> I believe that putting a couple of watts of RF into the heater is not a very practical thing ....
>>
>> Bob
>>
>> On Dec 24, 2009, at 2:14 PM, WarrenS wrote:
>>
>>
>>> I Must not get it, Or I'm missing something.
>>> Some seem to be going on and on about a little added DC heater current that can be held to about 10% of what the unit draws
>>> Why does a little added DC heater current any more of a problem that what you do with the leads etc of the main power?
>>> (And with a few simple tricks you can also reduce the effect of the changing heater current so it has insignificant effect)
>>> Have to work a bit harder to say the same about putting AC or RF into the heater
>>>
>>> ws
>>>
>>> ***************
>>>
>>> Bob Camp wrote:
>>>
>>>> Hi
>>>>
>>>> Having a bunch of AC current gets me into another issue. I suspect it's going to couple into something somewhere and give me a spur on the system output.
>>>>
>>> Sure, but having a sufficiently high frequency makes it relatively easy
>>> to clean up, as well as it should be reduced by normal loop filtering
>>> and oscillator integration.
>>>
>>> Cheers,
>>> Magnus
>>> _______________________________________________
>>> time-nuts mailing list -- time-nuts at febo.com
>>> To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
>>> and follow the instructions there.
>>>
>>>
>>
>> _______________________________________________
>> time-nuts mailing list -- time-nuts at febo.com
>> To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
>> and follow the instructions there.
>>
>>
>
>
>
>
>
> ------------------------------
>
> Message: 4
> Date: Thu, 24 Dec 2009 15:50:39 -0500
> From: Bob Camp <lists at cq.nu>
> Subject: Re: [time-nuts] Cheap Rubidium
> To: Discussion of precise time and frequency measurement
> <time-nuts at febo.com>
> Message-ID: <C5979B3D-F15A-41EF-9E07-19C54803B45B at cq.nu>
> Content-Type: text/plain; charset=us-ascii
>
> Hi
>
> The gotcha with temperature compensation is that there are a lot of different time constants involved. Put another way, when the temperature does a step change, the "results" are still happening >2K seconds later, and they are related to the speed of the change. Simply coming up with a full set of coefficients is likely to be a mess. Once you do, you will find out if they are repeatable or not ...
>
> The computer water cool systems look like a fairly simple way to go. You could run a water loop and simply heat (or cool) the water well away from the enclosure. It's not going to be high speed control, but with big enough mass in the enclosure it probably does not have to be.
>
> I'm not really convinced that you buy enough with a platinum RTD over a good glass thermistor to make it worth the trouble. The TC of the thermistor is 10X that of the RTD and that helps in a fixed point system. A Hart RTD will hold < 0.001 C in a triple point cell for as long as the ice lasts. A good thermistor will do the same. The stability of either one is "good enough" in this application.
>
> Bob
>
>
>
>
> On Dec 24, 2009, at 1:56 PM, Bill Hawkins wrote:
>
>> Well, perhaps it is time to think outside of the sand box.
>>
>> We are trying to remove heat, not cool it to low temperatures. Who
>> else worries about heat from electronics? Gamers, who buy water-cooled
>> rigs for their over-cooked (clocked) computers. No magnetic fields
>> nearby, with enough tubing. Look around in a DIY computer store.
>> Now all you've got to do is control the temperature where the fan
>> and radiator are, and extreme insulate the tubing.
>>
>> Back into the box, microprocessors have been used to calculate
>> temperature compensation almost since they were introduced. If you
>> are measuring frequency with a counter, it does no harm to add or
>> drop a cycle to adjust the frequency.
>>
>> You'll need a high-stability temperature probe, such as platinum wire
>> from Rosemount (now part of Emerson), and equally stable conversion
>> electronics. The accuracy doesn't matter as long as the sensor doesn't
>> change with anything but sensed temperature. The micro is simply a
>> matter of programming (SMOP).
>>
>> Good luck finding a converted temperature reading that is stable to
>> 10E-13. But, hey, it's the magic season when the days start to grow
>> longer.
>>
>> Wish all problems were this easy. :-^
>>
>> Bill Hawkins
>>
>>
>> _______________________________________________
>> time-nuts mailing list -- time-nuts at febo.com
>> To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
>> and follow the instructions there.
>>
>
>
>
>
> ------------------------------
>
> Message: 5
> Date: Thu, 24 Dec 2009 15:53:18 -0500
> From: Bob Camp <lists at cq.nu>
> Subject: Re: [time-nuts] Cheap Rubidium (heatpipe cooling for)
> To: Discussion of precise time and frequency measurement
> <time-nuts at febo.com>
> Message-ID: <057A1D44-F7EC-44F4-8F09-36AB614E98E8 at cq.nu>
> Content-Type: text/plain; charset=us-ascii
>
> 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 at febo.com
>>>> To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
>>>> and follow the instructions there.
>>>>
>>>>
>>>
>>> _______________________________________________
>>> time-nuts mailing list -- time-nuts at febo.com
>>> To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
>>> and follow the instructions there.
>>>
>>>
>>
>>
>>
>> _______________________________________________
>> time-nuts mailing list -- time-nuts at febo.com
>> To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
>> and follow the instructions there.
>>
>
>
>
>
> ------------------------------
>
> Message: 6
> Date: Thu, 24 Dec 2009 15:55:23 -0500
> From: Bob Camp <lists at cq.nu>
> Subject: Re: [time-nuts] Cheap Rubidium
> To: Discussion of precise time and frequency measurement
> <time-nuts at febo.com>
> Message-ID: <8F61B9AF-818D-4D1C-B7A9-AC005D688E19 at cq.nu>
> Content-Type: text/plain; charset=us-ascii
>
> Hi
>
> Every time I've tried the coli thing, field uniformity has become an issue. I'm also not real sure just how stable multi axis mag sensors are.
>
> If I had a bunch of mu metal sitting in the basement I'd certainly use it in the setup. Last time I checked the stuff was not cheap ....
>
> Bob
>
>
> On Dec 24, 2009, at 3:50 PM, Bruce Griffiths wrote:
>
>> One method of reducing the sensitivity to magnetic fields is to enclose the rubidium source in a series of nested magnetic shields (e.g. mu metal).
>> The shield walls could form part of the good thermal conductor poor thermal conductor stack.
>>
>> One could also use something like a set of 3 orthogonal Helmholtz coils to null the magnetic field at the rubidium source.
>> A servo loop using a magnetic field sensor could be employed.
>>
>> Bruce
>>
>> Bob Camp wrote:
>>> Hi
>>>
>>> To tune the frequency of a rubidium, you make a very small change to the DC magnetic field around the cell. That's the way you put them on frequency. Anything that changes the local field also changes the frequency of the rubidium standard.
>>>
>>> The DC in the power leads is a constant current and therefore creates a non-changing field. That means no frequency change.
>>>
>>> The reason you change the current in the heater is to stabilize the rubidium. If while you are trying to stabilize it one way, you de-stabalize it another way, that may not be progress.
>>>
>>> I believe that putting a couple of watts of RF into the heater is not a very practical thing ....
>>>
>>> Bob
>>>
>>> On Dec 24, 2009, at 2:14 PM, WarrenS wrote:
>>>
>>>
>>>> I Must not get it, Or I'm missing something.
>>>> Some seem to be going on and on about a little added DC heater current that can be held to about 10% of what the unit draws
>>>> Why does a little added DC heater current any more of a problem that what you do with the leads etc of the main power?
>>>> (And with a few simple tricks you can also reduce the effect of the changing heater current so it has insignificant effect)
>>>> Have to work a bit harder to say the same about putting AC or RF into the heater
>>>>
>>>> ws
>>>>
>>>> ***************
>>>>
>>>> Bob Camp wrote:
>>>>
>>>>> Hi
>>>>>
>>>>> Having a bunch of AC current gets me into another issue. I suspect it's going to couple into something somewhere and give me a spur on the system output.
>>>>>
>>>> Sure, but having a sufficiently high frequency makes it relatively easy
>>>> to clean up, as well as it should be reduced by normal loop filtering
>>>> and oscillator integration.
>>>>
>>>> Cheers,
>>>> Magnus
>>>> _______________________________________________
>>>> time-nuts mailing list -- time-nuts at febo.com
>>>> To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
>>>> and follow the instructions there.
>>>>
>>>>
>>>
>>> _______________________________________________
>>> time-nuts mailing list -- time-nuts at febo.com
>>> To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
>>> and follow the instructions there.
>>>
>>>
>>
>>
>>
>> _______________________________________________
>> time-nuts mailing list -- time-nuts at febo.com
>> To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
>> and follow the instructions there.
>>
>
>
>
>
> ------------------------------
>
> _______________________________________________
> time-nuts mailing list
> time-nuts at febo.com
> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
>
> End of time-nuts Digest, Vol 65, Issue 89
> *****************************************
More information about the time-nuts
mailing list