[time-nuts] vs Hg ion? Re: GPS clock stabilitiy, Rb vs Cs
On 5/5/13 1:48 AM, Magnus Danielson wrote: On 05/05/2013 10:05 AM, Attila Kinali wrote: On Sat, 4 May 2013 12:36:20 -0700 Tom Van Baak (lab)t...@leapsecond.com wrote: Rule of thumb: quartz is best short term, Rb or H-maser mid-term, and Cs by far the best long-term. Ah.. so it's a fundamental limitation. And i was looking for something GPS specific. Any references i could read on those limitations? A quick google did not produce any good results. There is a handful of references but picking up a book like Quantum Leap is a good start. Quartz is a bit of (syntetic) rock, cut at some angle(s), cleaned, mounted in some hermetic sealed chamber with residue dirt, and mounting snip For rubidium gas-cell, there is a bunch of systematics, including snip The caesium atomic beam does not have wall-shifts, but rather it has much lower systematics. One of the major onces being magnetic field. snip The above is a summary of things collected from a variety of sources, but I think this coarse walk-through of issues gives some insight as to what issues pops up where and the milage vary a lot within each group. Modern high-performance rubidium gas-cells outperform the early caesiums, high-performance crystals outperform several rubidiums. The HP5065A is an example of an old clock with really good performance, so modern is not everything, and the modern compact telecom rubidiums and for that mater CSAC is more space/power oriented than ultimate performance of the technology as such. I wonder where mercury ion fits in the scheme of things, since that's where we're spending some money for spacecraft applications right now. It's supposed to be orders of magnitude better than Rb. ___ 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.
Re: [time-nuts] vs Hg ion? Re: GPS clock stabilitiy, Rb vs Cs
Hi Mercury was tried very early on as a vapor standard. They had some significant problems with it in the 1950's. It's not surprising that after 60 years somebody might want to take another swing at it. Bob On May 5, 2013, at 9:59 AM, Jim Lux jim...@earthlink.net wrote: On 5/5/13 1:48 AM, Magnus Danielson wrote: On 05/05/2013 10:05 AM, Attila Kinali wrote: On Sat, 4 May 2013 12:36:20 -0700 Tom Van Baak (lab)t...@leapsecond.com wrote: Rule of thumb: quartz is best short term, Rb or H-maser mid-term, and Cs by far the best long-term. Ah.. so it's a fundamental limitation. And i was looking for something GPS specific. Any references i could read on those limitations? A quick google did not produce any good results. There is a handful of references but picking up a book like Quantum Leap is a good start. Quartz is a bit of (syntetic) rock, cut at some angle(s), cleaned, mounted in some hermetic sealed chamber with residue dirt, and mounting snip For rubidium gas-cell, there is a bunch of systematics, including snip The caesium atomic beam does not have wall-shifts, but rather it has much lower systematics. One of the major onces being magnetic field. snip The above is a summary of things collected from a variety of sources, but I think this coarse walk-through of issues gives some insight as to what issues pops up where and the milage vary a lot within each group. Modern high-performance rubidium gas-cells outperform the early caesiums, high-performance crystals outperform several rubidiums. The HP5065A is an example of an old clock with really good performance, so modern is not everything, and the modern compact telecom rubidiums and for that mater CSAC is more space/power oriented than ultimate performance of the technology as such. I wonder where mercury ion fits in the scheme of things, since that's where we're spending some money for spacecraft applications right now. It's supposed to be orders of magnitude better than Rb. ___ 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. ___ 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.
Re: [time-nuts] vs Hg ion? Re: GPS clock stabilitiy, Rb vs Cs
At HP in the 1990's, Len Cutler's group built some experimental mercury ion standards for USNO (IIRC). They were of the trapped ion type. BTW, it is important to understand that the architecture is the key factor, not the flavor of atom. When people say rubidium is inferior to cesium, they really mean a gas call is inferior to an atomic beam, etc. Rick Karlquist N6RK On 5/5/2013 8:20 AM, Bob Camp wrote: Hi Mercury was tried very early on as a vapor standard. They had some significant problems with it in the 1950's. It's not surprising that after 60 years somebody might want to take another swing at it. Bob On May 5, 2013, at 9:59 AM, Jim Lux jim...@earthlink.net wrote: On 5/5/13 1:48 AM, Magnus Danielson wrote: On 05/05/2013 10:05 AM, Attila Kinali wrote: On Sat, 4 May 2013 12:36:20 -0700 Tom Van Baak (lab)t...@leapsecond.com wrote: Rule of thumb: quartz is best short term, Rb or H-maser mid-term, and Cs by far the best long-term. Ah.. so it's a fundamental limitation. And i was looking for something GPS specific. Any references i could read on those limitations? A quick google did not produce any good results. There is a handful of references but picking up a book like Quantum Leap is a good start. Quartz is a bit of (syntetic) rock, cut at some angle(s), cleaned, mounted in some hermetic sealed chamber with residue dirt, and mounting snip For rubidium gas-cell, there is a bunch of systematics, including snip The caesium atomic beam does not have wall-shifts, but rather it has much lower systematics. One of the major onces being magnetic field. snip The above is a summary of things collected from a variety of sources, but I think this coarse walk-through of issues gives some insight as to what issues pops up where and the milage vary a lot within each group. Modern high-performance rubidium gas-cells outperform the early caesiums, high-performance crystals outperform several rubidiums. The HP5065A is an example of an old clock with really good performance, so modern is not everything, and the modern compact telecom rubidiums and for that mater CSAC is more space/power oriented than ultimate performance of the technology as such. I wonder where mercury ion fits in the scheme of things, since that's where we're spending some money for spacecraft applications right now. It's supposed to be orders of magnitude better than Rb. ___ 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. ___ 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. ___ 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.
Re: [time-nuts] vs Hg ion? Re: GPS clock stabilitiy, Rb vs Cs
On 5/5/13 8:42 AM, Richard (Rick) Karlquist wrote: At HP in the 1990's, Len Cutler's group built some experimental mercury ion standards for USNO (IIRC). They were of the trapped ion type. BTW, it is important to understand that the architecture is the key factor, not the flavor of atom. When people say rubidium is inferior to cesium, they really mean a gas call is inferior to an atomic beam, etc. OK, that's interesting.. So the Hg ion they're building for Deep Space Atomic Clock (DSAC) is a trapped ion type. The whole thing is, as I recall, 1 liter, 1 kilo, including both the physics package and the electronics. It's targeting USO type applications. ___ 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.
Re: [time-nuts] vs Hg ion? Re: GPS clock stabilitiy, Rb vs Cs
Hi Jim, On 05/05/2013 03:59 PM, Jim Lux wrote: On 5/5/13 1:48 AM, Magnus Danielson wrote: The above is a summary of things collected from a variety of sources, but I think this coarse walk-through of issues gives some insight as to what issues pops up where and the milage vary a lot within each group. Modern high-performance rubidium gas-cells outperform the early caesiums, high-performance crystals outperform several rubidiums. The HP5065A is an example of an old clock with really good performance, so modern is not everything, and the modern compact telecom rubidiums and for that mater CSAC is more space/power oriented than ultimate performance of the technology as such. I wonder where mercury ion fits in the scheme of things, since that's where we're spending some money for spacecraft applications right now. It's supposed to be orders of magnitude better than Rb. Mercury standards is of the ion trap variety. It has about 40,5 GHz of frequency, very high Q due to long unperturbed observation-time and also cool due to ion locking which reduces doppler shifts as well as thermal shift. If you also cool the ion trap physics to low temperature, the black body radiation shift can be reduced significantly. Ion traps can also be combined with laser cooling. Ion traps is the new and fancy stuff in a historical perspective. HP did an attempt to build a commercial device as I recall it. Would not mind having one. I think it is an interesting addition to the traditional mix. It achieves very high stability for the size. The CSAC is really a gas cell like rubidium, with similar issues. The ion trap takes a different route to the size issue. It has it's own set of challenges, but toss in a bit of engineering and they can be mastered. It has the potential to replace caesium beams in many applications. It would be interesting to see if your effort on space qualified ion traps spills over to the commercial market. If you get spare samples, I can give you an address to send them. ;-) Cheers, Magnus ___ 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.
Re: [time-nuts] vs Hg ion? Re: GPS clock stabilitiy, Rb vs Cs
On 05/05/2013 06:50 PM, Jim Lux wrote: On 5/5/13 8:42 AM, Richard (Rick) Karlquist wrote: At HP in the 1990's, Len Cutler's group built some experimental mercury ion standards for USNO (IIRC). They were of the trapped ion type. BTW, it is important to understand that the architecture is the key factor, not the flavor of atom. When people say rubidium is inferior to cesium, they really mean a gas call is inferior to an atomic beam, etc. OK, that's interesting.. So the Hg ion they're building for Deep Space Atomic Clock (DSAC) is a trapped ion type. The whole thing is, as I recall, 1 liter, 1 kilo, including both the physics package and the electronics. It's targeting USO type applications. They have been targeting this goal for a very long time. Several interesting papers is to be found at PTTI, NIST etc. Getting good performance with small volume and power is definitely interesting, and it does not have to be on the rice-grain level. Cheers, Magnus ___ 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.
Re: [time-nuts] vs Hg ion? Re: GPS clock stabilitiy, Rb vs Cs
On 5/5/13 10:05 AM, Magnus Danielson wrote: On 05/05/2013 06:50 PM, Jim Lux wrote: On 5/5/13 8:42 AM, Richard (Rick) Karlquist wrote: At HP in the 1990's, Len Cutler's group built some experimental mercury ion standards for USNO (IIRC). They were of the trapped ion type. BTW, it is important to understand that the architecture is the key factor, not the flavor of atom. When people say rubidium is inferior to cesium, they really mean a gas call is inferior to an atomic beam, etc. OK, that's interesting.. So the Hg ion they're building for Deep Space Atomic Clock (DSAC) is a trapped ion type. The whole thing is, as I recall, 1 liter, 1 kilo, including both the physics package and the electronics. It's targeting USO type applications. They have been targeting this goal for a very long time. Several interesting papers is to be found at PTTI, NIST etc. Yeah.. some years (6 or 7?) ago, John Prestage had a prototype of the physics package working on the bench. Getting from there to a repeatably manufacturable space flight qualified has been a few years. Not to mention making flight qualified electronics to go around it. I think the first flight will be next year or the year after as a hosted payload on something. ___ 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.
Re: [time-nuts] vs Hg ion? Re: GPS clock stabilitiy, Rb vs Cs
On 5/5/13 10:01 AM, Magnus Danielson wrote: Hi Jim, On 05/05/2013 03:59 PM, Jim Lux wrote: On 5/5/13 1:48 AM, Magnus Danielson wrote: The above is a summary of things collected from a variety of sources, but I think this coarse walk-through of issues gives some insight as to what issues pops up where and the milage vary a lot within each group. Modern high-performance rubidium gas-cells outperform the early caesiums, high-performance crystals outperform several rubidiums. The HP5065A is an example of an old clock with really good performance, so modern is not everything, and the modern compact telecom rubidiums and for that mater CSAC is more space/power oriented than ultimate performance of the technology as such. I wonder where mercury ion fits in the scheme of things, since that's where we're spending some money for spacecraft applications right now. It's supposed to be orders of magnitude better than Rb. It would be interesting to see if your effort on space qualified ion traps spills over to the commercial market. If you get spare samples, I can give you an address to send them. ;-) Hah.. getting just one made is a chore.. I've not worked on the project, but it's in the same general program as the stuff I do, so we all see each others' presentations at the semi-annual reviews. It took significantly more time than expected to get the physics package manufacturing worked out. Then there's whole thing of making 40 GHz electronics that are small, low power, radiation tolerant, etc.; I seem to recall that there's a tiny PMT in the system too, so that means HV, which is no easy feat either. ___ 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.
Re: [time-nuts] vs Hg ion? Re: GPS clock stabilitiy, Rb vs Cs
In message 51867df4.4010...@karlquist.com, Richard (Rick) Karlquist writes: BTW, it is important to understand that the architecture is the key factor, not the flavor of atom. Well, somewhat. Some flavours of atoms don't work with some architectures, so for most of the stuff in reach for us, the atoms do indeed equate an architecture. The exception seems to be fountains, which can run on pretty much any alkali atom you care to feed it, and some even able to use both Rb og Cs (Built to nail the Rb frequency firmly down, as I understand it). However, there seems to be actual differences between the flavours of atoms in fountains, and USNO have picked Rb over Cs because they get better results that way. -- 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@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] vs Hg ion? Re: GPS clock stabilitiy, Rb vs Cs
Hi Jim, On 05/05/2013 07:33 PM, Jim Lux wrote: On 5/5/13 10:05 AM, Magnus Danielson wrote: They have been targeting this goal for a very long time. Several interesting papers is to be found at PTTI, NIST etc. Yeah.. some years (6 or 7?) ago, John Prestage had a prototype of the physics package working on the bench. Getting from there to a repeatably manufacturable space flight qualified has been a few years. Not to mention making flight qualified electronics to go around it. I think the first flight will be next year or the year after as a hosted payload on something. Here is a starting-point: 33rd PTTI 2001: http://www.pttimeeting.org/archivemeetings/2001papers/paper4.pdf 38th PTTI 2006: http://trs-new.jpl.nasa.gov/dspace/bitstream/2014/40340/1/07-0487.pdf 39th PTTI 2007: http://www.pttimeeting.org/archivemeetings/2007papers/paper25.pdf NIST: http://tf.nist.gov/general/pdf/742.pdf JPL: http://trs-new.jpl.nasa.gov/dspace/bitstream/2014/40206/3/04-2783FN.pdf That was only a quick search, so it is easy to find those and more. Would be interesting to see how the lasers could be made affordable and compact. It's a bit difficult frequency/wavelength. Cheers, Magnus ___ 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.
Re: [time-nuts] vs Hg ion? Re: GPS clock stabilitiy, Rb vs Cs
On Sun, 05 May 2013 18:29:53 + Poul-Henning Kamp p...@phk.freebsd.dk wrote: In message 51867df4.4010...@karlquist.com, Richard (Rick) Karlquist writes: BTW, it is important to understand that the architecture is the key factor, not the flavor of atom. Well, somewhat. Some flavours of atoms don't work with some architectures, so for most of the stuff in reach for us, the atoms do indeed equate an architecture. The alkali atoms are pretty much interchangable. There have been masers from Rb as well as Cs, beam standards from Rb and H, and Rb fountains. I have not read of any H fountain yet, but i guess it's pretty difficult to build given that the laser light needed for cooling is in the 120nm range (UV) and lasers in that range are pretty difficult to build (there have been laser spectroscopy experiments using 120nm lasers nevertheless) and that H is very light, ie the fountain would get quite long. I also have never seen a H gas cell standard, probably for the same reason of needing UV light. Other classes are charged ions, these are mostly positive charged atoms where the outermost shell becomes an s orbital with a single electron. Prime examples are alkaline earth metals (Be, Mg, Ca, Sr,..), but also group 12 metals (Zn, Cd, Hg) and some lanthanide/actinide (e.g. Yb). AFAIK these are mostly interchangable as well. I do not know what the general property of laser cooled neutral atom frequency standards is. One property seldom explicitly mentioned is the nuclear spin. The alkali metal standards seem to depend on the spin being half-integral, while laser cooled ion standards seem to be possible with both integer (including 0) and half integer spins. Attila Kinali -- The people on 4chan are like brilliant psychologists who also happen to be insane and gross. -- unknown ___ 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.
Re: [time-nuts] vs Hg ion? Re: GPS clock stabilitiy, Rb vs Cs
In message 20130505205257.8497f166abb1e49186953...@kinali.ch, Attila Kinali w rites: I also have never seen a H gas cell standard, probably for the same reason of needing UV light. Hydrogen is very hard to contain. The way you *filter* hydrogen is to press it through a palladium film, and that doesn't take a particular high pressure. -- 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@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] vs Hg ion? Re: GPS clock stabilitiy, Rb vs Cs
Hi Poul-Henning, On 05/05/2013 08:29 PM, Poul-Henning Kamp wrote: In message51867df4.4010...@karlquist.com, Richard (Rick) Karlquist writes: BTW, it is important to understand that the architecture is the key factor, not the flavor of atom. Well, somewhat. Some flavours of atoms don't work with some architectures, so for most of the stuff in reach for us, the atoms do indeed equate an architecture. Well, the basic rule is that you want a single electron, preferably in the S state in the outermost shell. You can have that either as neutral atom or ionized. Depending on neutral or ionized you go into the classic or ion classes. This is why alkali atoms is so popular, as group 1 fits the description well in its neutral state. Another aspect is how you achieve the state imbalance which can be achieved either by state selection magnets or by pumping. Rubidium has been selected traditionally because of the suitable spectrum of Rb-85 and Rb-87 isotopes, and that these is relatively easy to come by (both exist in normal rubidium ore) allowing for simple filtering. Modern filtering and modern lasers allows a much freer selection. The exception seems to be fountains, which can run on pretty much any alkali atom you care to feed it, and some even able to use both Rb og Cs (Built to nail the Rb frequency firmly down, as I understand it). Beam devices has been built for much more than caesium. In the original conception caesium was fighting with thallium, with thallium actually being somewhat better, but was judged a bit impractical at the time. Rubidium was also built as research beam units, but it has higher sensitivity to magnetic field pulling, which used to be an issue, which now largely is gone with servo capability. The fountains is just an evolvement of the beam devices, but the beam falls backwards halfway through. In the fountain-context rubidium now has an edge over caesium. What make fountains feasible is the laser-cooling as it not only allows cooling, but also bouncing around the ball of atoms. However, there seems to be actual differences between the flavours of atoms in fountains, and USNO have picked Rb over Cs because they get better results that way. Indeed. Wasn't NPL in UK early out as well? In the end, the actual atom used for a particular device is a result of what makes practical engineering at the time and achieving the best performance. The optical clocks stretches the imagination even more than ion-traps ever did, but affordable ion-traps is still very interesting. Cheers, Magnus ___ 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.
Re: [time-nuts] vs Hg ion? Re: GPS clock stabilitiy, Rb vs Cs
On 05/05/2013 09:28 PM, Poul-Henning Kamp wrote: In message20130505205257.8497f166abb1e49186953...@kinali.ch, Attila Kinali w rites: I also have never seen a H gas cell standard, probably for the same reason of needing UV light. Hydrogen is very hard to contain. The way you *filter* hydrogen is to press it through a palladium film, and that doesn't take a particular high pressure. Another aspect is that D1 and D2 lines are essentially the same (121.5674 nm and 121.5668 nm) while for rubidium its 794.760 nm and 780.027 nm which is about 25000 times wider. This makes pumping state-selection hard for hydrogen but relatively easy with rubidium. So, for hydrogen you have to do state-selection through magnets, which is what is being used in hydrogen masers. There is so many practicalities that goes in to technical decisions. Cheers, Magnus ___ 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.
Re: [time-nuts] vs Hg ion? Re: GPS clock stabilitiy, Rb vs Cs
On 5/5/13 11:45 AM, Magnus Danielson wrote: Hi Jim, On 05/05/2013 07:33 PM, Jim Lux wrote: On 5/5/13 10:05 AM, Magnus Danielson wrote: They have been targeting this goal for a very long time. Several interesting papers is to be found at PTTI, NIST etc. Yeah.. some years (6 or 7?) ago, John Prestage had a prototype of the physics package working on the bench. Getting from there to a repeatably manufacturable space flight qualified has been a few years. Not to mention making flight qualified electronics to go around it. I think the first flight will be next year or the year after as a hosted payload on something. Here is a starting-point: JPL: http://trs-new.jpl.nasa.gov/dspace/bitstream/2014/40206/3/04-2783FN.pdf the last reference in that paper is from L.S. Cutler, et al. Is that the same Cutler at HP? ___ 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.
Re: [time-nuts] vs Hg ion? Re: GPS clock stabilitiy, Rb vs Cs
On 05/05/2013 11:14 PM, Jim Lux wrote: On 5/5/13 11:45 AM, Magnus Danielson wrote: Hi Jim, On 05/05/2013 07:33 PM, Jim Lux wrote: On 5/5/13 10:05 AM, Magnus Danielson wrote: They have been targeting this goal for a very long time. Several interesting papers is to be found at PTTI, NIST etc. Yeah.. some years (6 or 7?) ago, John Prestage had a prototype of the physics package working on the bench. Getting from there to a repeatably manufacturable space flight qualified has been a few years. Not to mention making flight qualified electronics to go around it. I think the first flight will be next year or the year after as a hosted payload on something. Here is a starting-point: JPL: http://trs-new.jpl.nasa.gov/dspace/bitstream/2014/40206/3/04-2783FN.pdf the last reference in that paper is from L.S. Cutler, et al. Is that the same Cutler at HP? Indeed it is. Guess who worked on the HP mercury ion clock? Cheers, Magnus ___ 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.
Re: [time-nuts] vs Hg ion? Re: GPS clock stabilitiy, Rb vs Cs
The idea of a Mercury Ion clocks started about 2000 and from about 2005 until recently has held the title of worlds most accurate clock. Approx 1 sec per 1.6 billion years the last I heard. At the heart is a single trapped mercury atom. Jim Bergquist at NIST was one of those that lead the development. This link has the basics: http://tf.nist.gov/general/pdf/1957.pdf. I want two. Thomas Knox 1-303-554-0307 Date: Sun, 5 May 2013 06:59:12 -0700 From: jim...@earthlink.net To: time-nuts@febo.com Subject: [time-nuts] vs Hg ion? Re: GPS clock stabilitiy, Rb vs Cs On 5/5/13 1:48 AM, Magnus Danielson wrote: On 05/05/2013 10:05 AM, Attila Kinali wrote: On Sat, 4 May 2013 12:36:20 -0700 Tom Van Baak (lab)t...@leapsecond.com wrote: Rule of thumb: quartz is best short term, Rb or H-maser mid-term, and Cs by far the best long-term. Ah.. so it's a fundamental limitation. And i was looking for something GPS specific. Any references i could read on those limitations? A quick google did not produce any good results. There is a handful of references but picking up a book like Quantum Leap is a good start. Quartz is a bit of (syntetic) rock, cut at some angle(s), cleaned, mounted in some hermetic sealed chamber with residue dirt, and mounting snip For rubidium gas-cell, there is a bunch of systematics, including snip The caesium atomic beam does not have wall-shifts, but rather it has much lower systematics. One of the major onces being magnetic field. snip The above is a summary of things collected from a variety of sources, but I think this coarse walk-through of issues gives some insight as to what issues pops up where and the milage vary a lot within each group. Modern high-performance rubidium gas-cells outperform the early caesiums, high-performance crystals outperform several rubidiums. The HP5065A is an example of an old clock with really good performance, so modern is not everything, and the modern compact telecom rubidiums and for that mater CSAC is more space/power oriented than ultimate performance of the technology as such. I wonder where mercury ion fits in the scheme of things, since that's where we're spending some money for spacecraft applications right now. It's supposed to be orders of magnitude better than Rb. ___ 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. ___ 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.
Re: [time-nuts] vs Hg ion? Re: GPS clock stabilitiy, Rb vs Cs
Hi Tom, On 05/05/2013 11:33 PM, Tom Knox wrote: The idea of a Mercury Ion clocks started about 2000 and from about 2005 until recently has held the title of worlds most accurate clock. Approx 1 sec per 1.6 billion years the last I heard. At the heart is a single trapped mercury atom. Jim Bergquist at NIST was one of those that lead the development. This link has the basics: http://tf.nist.gov/general/pdf/1957.pdf. I want two. The history is older than that. A quick review of the early history is available here: http://tf.nist.gov/general/pdf/910.pdf First detection of the transition was in 1973. Len Cutlers first article on the topic (as referenced in above article) was back in 1981. I have all the Hg-199 and Hg-202 I need for a few clocks, but in it's natural mixture. Don't feel like building a separation facility... Cheers, Magnus ___ 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.
Re: [time-nuts] vs Hg ion? Re: GPS clock stabilitiy, Rb vs Cs
On 5/5/13 2:49 PM, Magnus Danielson wrote: I have all the Hg-199 and Hg-202 I need for a few clocks, but in it's natural mixture. Don't feel like building a separation facility... Use the quadrupole system you're using as a trap as a mass-spec to do the separation. ___ 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.
Re: [time-nuts] vs Hg ion? Re: GPS clock stabilitiy, Rb vs Cs
Hi There were a number of trapped ion papers back in the 70's and 80's. The NIST effort to transition from Cs to an ion standard was well underway by the mid 1980's. Bob On May 5, 2013, at 5:49 PM, Magnus Danielson mag...@rubidium.dyndns.org wrote: Hi Tom, On 05/05/2013 11:33 PM, Tom Knox wrote: The idea of a Mercury Ion clocks started about 2000 and from about 2005 until recently has held the title of worlds most accurate clock. Approx 1 sec per 1.6 billion years the last I heard. At the heart is a single trapped mercury atom. Jim Bergquist at NIST was one of those that lead the development. This link has the basics: http://tf.nist.gov/general/pdf/1957.pdf. I want two. The history is older than that. A quick review of the early history is available here: http://tf.nist.gov/general/pdf/910.pdf First detection of the transition was in 1973. Len Cutlers first article on the topic (as referenced in above article) was back in 1981. I have all the Hg-199 and Hg-202 I need for a few clocks, but in it's natural mixture. Don't feel like building a separation facility... Cheers, Magnus ___ 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. ___ 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.
Re: [time-nuts] vs Hg ion? Re: GPS clock stabilitiy, Rb vs Cs
Hi The sawtooth issues of most GPS receivers are much greater than the position errors a short / long survey will produce. Unless you have a very fancy self correcting receiver or a driver that does sawtooth correction, don't' worry about it. Bob On May 5, 2013, at 5:33 PM, Tom Knox act...@hotmail.com wrote: The idea of a Mercury Ion clocks started about 2000 and from about 2005 until recently has held the title of worlds most accurate clock. Approx 1 sec per 1.6 billion years the last I heard. At the heart is a single trapped mercury atom. Jim Bergquist at NIST was one of those that lead the development. This link has the basics: http://tf.nist.gov/general/pdf/1957.pdf. I want two. Thomas Knox 1-303-554-0307 Date: Sun, 5 May 2013 06:59:12 -0700 From: jim...@earthlink.net To: time-nuts@febo.com Subject: [time-nuts] vs Hg ion? Re: GPS clock stabilitiy, Rb vs Cs On 5/5/13 1:48 AM, Magnus Danielson wrote: On 05/05/2013 10:05 AM, Attila Kinali wrote: On Sat, 4 May 2013 12:36:20 -0700 Tom Van Baak (lab)t...@leapsecond.com wrote: Rule of thumb: quartz is best short term, Rb or H-maser mid-term, and Cs by far the best long-term. Ah.. so it's a fundamental limitation. And i was looking for something GPS specific. Any references i could read on those limitations? A quick google did not produce any good results. There is a handful of references but picking up a book like Quantum Leap is a good start. Quartz is a bit of (syntetic) rock, cut at some angle(s), cleaned, mounted in some hermetic sealed chamber with residue dirt, and mounting snip For rubidium gas-cell, there is a bunch of systematics, including snip The caesium atomic beam does not have wall-shifts, but rather it has much lower systematics. One of the major onces being magnetic field. snip The above is a summary of things collected from a variety of sources, but I think this coarse walk-through of issues gives some insight as to what issues pops up where and the milage vary a lot within each group. Modern high-performance rubidium gas-cells outperform the early caesiums, high-performance crystals outperform several rubidiums. The HP5065A is an example of an old clock with really good performance, so modern is not everything, and the modern compact telecom rubidiums and for that mater CSAC is more space/power oriented than ultimate performance of the technology as such. I wonder where mercury ion fits in the scheme of things, since that's where we're spending some money for spacecraft applications right now. It's supposed to be orders of magnitude better than Rb. ___ 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. ___ 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. ___ 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.
