Re: [time-nuts] What’s the BEST crystal?
On Sun, 1 Mar 2020 07:39:43 -0800 jimlux wrote: > How does a CSO compare with a Mercury Ion clock - the latter does fit in > a satellite and is intended to replace the USO kind of function. They use/used CSO's as local oscillators for the Hg ion clock. Their first papers ([1] and [2]) used to use a super conducting cavity Rb maser that generates 2.5GHz. In later papers, (e.g. [3] and [4]) they silently switched this to a CSO. The big problem with the Hg ion clock is the low photon efficiency it has. Ie, even though they have a lot of ions to probe, only a few react with the light comming in. Thus the SNR is very low. To get good performance they need to incrase the Ramsey interrogation time , which works well thanks due to the long life time of the hyperfine splitting in Hg and the low buffer gas pressure. With an VCO (ie OCXO) we are talking about ~10-20s interrogation time, with a CSO we are talking about 100s. Using this and a CSO as local oscillator, they even beat an active hydrogen maser with their best performing clock. As synthesizer for the 40GHz they are using a DRO for the space missions if I understood the previous papers correctly (easier space qualification, apparently) and an SRD based system for ground, which gives almost an order of magnitude better performance due to lower noise (c.f. Dick Effect) Attila Kinali [1] "Hg+ Trapped Ion Standard with the Superconducting Cavity Maser Oscillator", by Perstage, Tjoelker, Dick and Maleki, 1993 https://doi.org/10.1109/19.278549 [2] "A mercury ion frequency standard engineering prototype for the NASA deep space network", by Tjoelker, et al., 1996 https://doi.org/10.1109/FREQ.1996.560296 [3] "Mercury Atomic Frequency Standards for Space Based Navigation and Timekeeping", by Tjoelker et al. 2011 http://time.kinali.ch/ptti/2011papers/Paper37.pdf [4] "Mercury Ion Clock for a NASA Technology Demonstration Mission", by Tjoelker et al, 2016 https://doi.org/10.1109/TUFFC.2016.2543738 -- The bad part of Zurich is where the degenerates throw DARK chocolate at you. ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
Re: [time-nuts] What’s the BEST crystal?
Hello Jim >How does a CSO compare with a Mercury Ion clock - the latter does fit in >a satellite and is intended to replace the USO kind of function. The current CSOs can be surprisingly compact. I was visiting a university colleague who had recently bought one from Cryoclock for use in quantum computing experiments. The total package was about half a rack. One big improvement has been moving to a closed cycle cooling system. It’s difficult imagining it going into a spacecraft or satellite though. Cheers Michael On Mon, 2 Mar 2020 at 2:40 am, jimlux wrote: > On 2/29/20 2:47 PM, Attila Kinali wrote: > > On Sat, 29 Feb 2020 17:01:27 -0500 > > Bob kb8tq wrote: > > > >>> Isn't that where "whispering gallery" modes come into the picture ? > >> > >> …… and done with sapphire. > >> > >> This is the real answer to “why is nobody going to do this?”. You > already > >> have something ( the sapphire resonators ) that does better than > >> anything you could reasonably expect. > > > > It's the other way round. Yes, we have *a* solution for better phase > noise > > and stability, but not *the* solution. A CSO is a full size 19" rack > > filled with equipment that needs constant maintenance. Nothing you can > > put on a satellite, much less carry around. People wouldn't even put it > > in cellphone base station, although they would love to have the > additional > > frequency stability and phase noise performance to squeeze in some > > more customers into the limited frequency space. > > > How does a CSO compare with a Mercury Ion clock - the latter does fit in > a satellite and is intended to replace the USO kind of function. > > > > > It is actually very hard to beat crystal oscillators and vapor cell > > frequency standards in the stability/phase noise/size/power > consumption/cost > > trade-off. And until recently, quartz oscillators and vapor phase > > standards occupied seperate areas in this trade-off space. Until the > > CSAC came around and connected them. > > > > > > Attila Kinali > > > > > ___ > time-nuts mailing list -- time-nuts@lists.febo.com > To unsubscribe, go to > http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com > and follow the instructions there. > ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
Re: [time-nuts] What’s the BEST crystal?
On 2/29/20 2:47 PM, Attila Kinali wrote: On Sat, 29 Feb 2020 17:01:27 -0500 Bob kb8tq wrote: Isn't that where "whispering gallery" modes come into the picture ? …… and done with sapphire. This is the real answer to “why is nobody going to do this?”. You already have something ( the sapphire resonators ) that does better than anything you could reasonably expect. It's the other way round. Yes, we have *a* solution for better phase noise and stability, but not *the* solution. A CSO is a full size 19" rack filled with equipment that needs constant maintenance. Nothing you can put on a satellite, much less carry around. People wouldn't even put it in cellphone base station, although they would love to have the additional frequency stability and phase noise performance to squeeze in some more customers into the limited frequency space. How does a CSO compare with a Mercury Ion clock - the latter does fit in a satellite and is intended to replace the USO kind of function. It is actually very hard to beat crystal oscillators and vapor cell frequency standards in the stability/phase noise/size/power consumption/cost trade-off. And until recently, quartz oscillators and vapor phase standards occupied seperate areas in this trade-off space. Until the CSAC came around and connected them. Attila Kinali ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
Re: [time-nuts] What’s the BEST crystal?
In message <92c74f8b-f351-4a6c-916f-ec68cfd35...@n1k.org>, Bob kb8tq writes: >> Why would it be so expensive ? > >You would have to do a *lot* of things from scratch. First up, there is >no 'modern' cold weld package big enough to put the beast into. You would >have to tool that right up front. [...] Ahh, I misunderstood you then: I thought you meant it as a one-off research project. -- Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 p...@freebsd.org | TCP/IP since RFC 956 FreeBSD committer | BSD since 4.3-tahoe Never attribute to malice what can adequately be explained by incompetence. ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
Re: [time-nuts] What’s the BEST crystal?
On Sat, 29 Feb 2020 17:01:27 -0500 Bob kb8tq wrote: > > Isn't that where "whispering gallery" modes come into the picture ? > > …… and done with sapphire. > > This is the real answer to “why is nobody going to do this?”. You already > have something ( the sapphire resonators ) that does better than > anything you could reasonably expect. It's the other way round. Yes, we have *a* solution for better phase noise and stability, but not *the* solution. A CSO is a full size 19" rack filled with equipment that needs constant maintenance. Nothing you can put on a satellite, much less carry around. People wouldn't even put it in cellphone base station, although they would love to have the additional frequency stability and phase noise performance to squeeze in some more customers into the limited frequency space. It is actually very hard to beat crystal oscillators and vapor cell frequency standards in the stability/phase noise/size/power consumption/cost trade-off. And until recently, quartz oscillators and vapor phase standards occupied seperate areas in this trade-off space. Until the CSAC came around and connected them. Attila Kinali -- The bad part of Zurich is where the degenerates throw DARK chocolate at you. ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
Re: [time-nuts] What’s the BEST crystal?
Hi > On Feb 29, 2020, at 3:23 PM, Poul-Henning Kamp wrote: > > > In message <20200229210755.1abd900696f8aa85567d2...@kinali.ch>, Attila Kinali > writes: >> On Sat, 29 Feb 2020 13:44:59 -0500 > >> But, there is not much we can do about absorption/desorption. > > Actually, there are things you can do, but they are very > expensive. > > One of the early paths of experiments with optic fibers were > to replace the absorbed hydrogen with deuterium which is > slightly larger, in order to move the OH- absorption > peak away from the 1.3 micrometer band. (Bake at 1000°C > in a D2 atmosphere for a couple of hours). > > Stuffing bigger atoms into the gaps that way will reduce the > opportunities for other atoms to squeeze in. > > If you were *really* serious about it, you would start out growing > your quartz from monoisotopic silicon and oxygen, picking the smaller > silicon (28) and larger oxygen (18) in order to reduce the size > of the gaps to begin with. It will probably also do wonders for > your Q that all bonds are identical. > >> The diameter of the blank has to be scaled with its thickness, in >> order not to compromise the f*Q product. Which in turn makes it >> a bit problematic in terms of packaging, but nothing unsolvable. > > Isn't that where "whispering gallery" modes come into the picture ? …… and done with sapphire. This is the real answer to “why is nobody going to do this?”. You already have something ( the sapphire resonators ) that does better than anything you could reasonably expect. Bob > > -- > Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 > p...@freebsd.org | TCP/IP since RFC 956 > FreeBSD committer | BSD since 4.3-tahoe > Never attribute to malice what can adequately be explained by incompetence. > > ___ > time-nuts mailing list -- time-nuts@lists.febo.com > To unsubscribe, go to > http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com > and follow the instructions there. ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
Re: [time-nuts] What’s the BEST crystal?
Hi > On Feb 29, 2020, at 3:07 PM, Attila Kinali wrote: > > On Sat, 29 Feb 2020 13:44:59 -0500 > Bob kb8tq wrote: > >> One wonders what the result would be of doing a large blank (> 50mm) >> 2.5 MHz 5th OT using modern design, packaging and mounting techniques. > > If we use the venerable Sulzer as guide (see e.g. [1]) and going > by what the FE-405 achieves, I would say sub-1e-13 around 10-100s > should be possible. As far as I can tell, from the paper's I've > read, the major contributors to instability between 1s and 1000s > seem to be temperature and absorption/desorption of material on the blank. > We know how to do temperature control these days (see E1938 [2]). > But, there is not much we can do about absorption/desorption. > The best strategy is to polish the surface as much as possible > and use an as thick blank as possible. And then, backe the whole > thing in high vacuum for as long as possible at as high temperature > as possible (which isn't that high, due to twining). > > The diameter of the blank has to be scaled with its thickness, in > order not to compromise the f*Q product. Which in turn makes it > a bit problematic in terms of packaging, but nothing unsolvable. > > I am not sure, how much an advantage it is to go BVA. It helps in > terms of Q (seems to be 30-50% higher), but I'm not sure whether > the ab/desorption rate is much lower if there are no metal > electrodes on the crystal. The specs of the HSO-14 are awfully > close to the 8607, even though Rakkon places the electrodes > on the blank itself. But I have not seen any actual measurements > of an HS0-14 yet, so I don't know how it actually performs, > especially at tau >1000. > > BTW: this is another advantage of SC cut: an AT cut is ~1.6 MHz*mm > an SC cut is ~1.8 MHz*mm, ie you get about 10% more thicknes at the > same frequency for an SC cut than for an AT cut. > >> Given that it would take a rather large pile of nickels to >> find out (like > $50M worth), I very much doubt we ever will know the >> answer. > > Why would it cost so much? There are enough companies that make > crystal blanks for various purposes, getting one to make large > ones shouldn't be too difficult. And the FE-405 is very close > to what you are asking for, being a 5th OT 5MHz SC cut. The FE-405 crystal is in a package that is already a bit “tight” for a 3rd overtone at 5 MHz. You can *force* just about anything. The point is to make it at a thickness to diameter ratio that is more on the order of what is used at 10 MHz. That makes it a *very* large diameter blank (at least out of high performance quartz). Bob > > > Attila Kinali > > > [1] https://febo.com/for_sale/sulzer/index.html > > [2] "The Theory of Zero-Gradient Crystal Ovens", 1997 > by Karlquist, Cutler, Ingman, Johnson and Parisek > http://www.karlquist.com/oven.pdf > > -- > The bad part of Zurich is where the degenerates >throw DARK chocolate at you. > > ___ > time-nuts mailing list -- time-nuts@lists.febo.com > To unsubscribe, go to > http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com > and follow the instructions there. ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
Re: [time-nuts] What’s the BEST crystal?
In message <20200229210755.1abd900696f8aa85567d2...@kinali.ch>, Attila Kinali writes: >On Sat, 29 Feb 2020 13:44:59 -0500 >But, there is not much we can do about absorption/desorption. Actually, there are things you can do, but they are very expensive. One of the early paths of experiments with optic fibers were to replace the absorbed hydrogen with deuterium which is slightly larger, in order to move the OH- absorption peak away from the 1.3 micrometer band. (Bake at 1000°C in a D2 atmosphere for a couple of hours). Stuffing bigger atoms into the gaps that way will reduce the opportunities for other atoms to squeeze in. If you were *really* serious about it, you would start out growing your quartz from monoisotopic silicon and oxygen, picking the smaller silicon (28) and larger oxygen (18) in order to reduce the size of the gaps to begin with. It will probably also do wonders for your Q that all bonds are identical. >The diameter of the blank has to be scaled with its thickness, in >order not to compromise the f*Q product. Which in turn makes it >a bit problematic in terms of packaging, but nothing unsolvable. Isn't that where "whispering gallery" modes come into the picture ? -- Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 p...@freebsd.org | TCP/IP since RFC 956 FreeBSD committer | BSD since 4.3-tahoe Never attribute to malice what can adequately be explained by incompetence. ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
Re: [time-nuts] What’s the BEST crystal?
On Sat, 29 Feb 2020 13:44:59 -0500 Bob kb8tq wrote: > One wonders what the result would be of doing a large blank (> 50mm) > 2.5 MHz 5th OT using modern design, packaging and mounting techniques. If we use the venerable Sulzer as guide (see e.g. [1]) and going by what the FE-405 achieves, I would say sub-1e-13 around 10-100s should be possible. As far as I can tell, from the paper's I've read, the major contributors to instability between 1s and 1000s seem to be temperature and absorption/desorption of material on the blank. We know how to do temperature control these days (see E1938 [2]). But, there is not much we can do about absorption/desorption. The best strategy is to polish the surface as much as possible and use an as thick blank as possible. And then, backe the whole thing in high vacuum for as long as possible at as high temperature as possible (which isn't that high, due to twining). The diameter of the blank has to be scaled with its thickness, in order not to compromise the f*Q product. Which in turn makes it a bit problematic in terms of packaging, but nothing unsolvable. I am not sure, how much an advantage it is to go BVA. It helps in terms of Q (seems to be 30-50% higher), but I'm not sure whether the ab/desorption rate is much lower if there are no metal electrodes on the crystal. The specs of the HSO-14 are awfully close to the 8607, even though Rakkon places the electrodes on the blank itself. But I have not seen any actual measurements of an HS0-14 yet, so I don't know how it actually performs, especially at tau >1000. BTW: this is another advantage of SC cut: an AT cut is ~1.6 MHz*mm an SC cut is ~1.8 MHz*mm, ie you get about 10% more thicknes at the same frequency for an SC cut than for an AT cut. > Given that it would take a rather large pile of nickels to > find out (like > $50M worth), I very much doubt we ever will know the answer. Why would it cost so much? There are enough companies that make crystal blanks for various purposes, getting one to make large ones shouldn't be too difficult. And the FE-405 is very close to what you are asking for, being a 5th OT 5MHz SC cut. Attila Kinali [1] https://febo.com/for_sale/sulzer/index.html [2] "The Theory of Zero-Gradient Crystal Ovens", 1997 by Karlquist, Cutler, Ingman, Johnson and Parisek http://www.karlquist.com/oven.pdf -- The bad part of Zurich is where the degenerates throw DARK chocolate at you. ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
Re: [time-nuts] What’s the BEST crystal?
Hi > On Feb 29, 2020, at 2:44 PM, Poul-Henning Kamp wrote: > > > In message <2e09a559-b476-45c0-a476-7d5808a93...@n1k.org>, Bob kb8tq writes: > >> One wonders what the result would be of doing a large blank (> 50mm) 2.5 MHz >> 5th OT using modern >> design, packaging and mounting techniques. Given that it would take a rather >> large pile of nickels to >> find out (like > $50M worth), I very much doubt we ever will know the >> answer. > > Why would it be so expensive ? You would have to do a *lot* of things from scratch. First up, there is no “modern” cold weld package big enough to put the beast into. You would have to tool that right up front. Same issue ripples into the processing gear. A typical modern setup for normal packages is around $3M to develop and about $1.5M to duplicate. Best guess is that you would at least double (and more likely triple) those numbers for the much larger package. The blank, being larger than anything anybody uses today would need custom gear to cut / round / polish the part. Again, a lot of work from scratch. Probably not as exciting as the final plate / seal end, but still something that needs money and attention. It is unclear if anybody grows (or has the ability to grow) high quality quartz bars big enough to cut the blanks from. One would *guess* not since there is no demand for them. At the very least there would be some tooling and a custom run involved in sourcing the synthetic quartz. Sourcing seeds that are significantly larger than normal might be interesting as well. Simply doing the design of the resonator and proving that out is a multi pass process. Based on the way it typically seems to be done, you would run a couple hundred trials to get the right design worked out. Each of those would involve many dozens of finished crystals and some fairly involved analysis of those crystals. On top of all that, you have the inevitable management costs, overhead, and other nonsense that are all part of any modern undertaking. All that said, it’s just a guess. Bob > > -- > Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 > p...@freebsd.org | TCP/IP since RFC 956 > FreeBSD committer | BSD since 4.3-tahoe > Never attribute to malice what can adequately be explained by incompetence. ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
Re: [time-nuts] What’s the BEST crystal?
In message <2e09a559-b476-45c0-a476-7d5808a93...@n1k.org>, Bob kb8tq writes: >One wonders what the result would be of doing a large blank (> 50mm) 2.5 MHz >5th OT using modern >design, packaging and mounting techniques. Given that it would take a rather >large pile of nickels to >find out (like > $50M worth), I very much doubt we ever will know the answer. Why would it be so expensive ? -- Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 p...@freebsd.org | TCP/IP since RFC 956 FreeBSD committer | BSD since 4.3-tahoe Never attribute to malice what can adequately be explained by incompetence. ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
Re: [time-nuts] What’s the BEST crystal?
Hi More than the cut, the packaging, resonator design, mount design, and processing of the crystal (in no particular order ) are what really make this or that crystal suitable for use in a precision OCXO. You can indeed find AT cut OCXO’s that do pretty well once they warm up …. One wonders what the result would be of doing a large blank (> 50mm) 2.5 MHz 5th OT using modern design, packaging and mounting techniques. Given that it would take a rather large pile of nickels to find out (like > $50M worth), I very much doubt we ever will know the answer. Bob > On Feb 29, 2020, at 1:05 PM, John Moran, Scawby Design > wrote: > > Since the poor old SC cut crystal has been given such a kicking for its > inconvenient placement of spurious responses, is there a better, or BEST > crystal for putting in an oven and turning into a nice reference? > > John > > Cheers - John > > ___ > time-nuts mailing list -- time-nuts@lists.febo.com > To unsubscribe, go to > http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com > and follow the instructions there. ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
[time-nuts] What’s the BEST crystal?
Since the poor old SC cut crystal has been given such a kicking for its inconvenient placement of spurious responses, is there a better, or BEST crystal for putting in an oven and turning into a nice reference? John Cheers - John ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
