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?

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

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: jimlux@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)"<tvb@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.

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

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.

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 <magnus@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.

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 <actast@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: jimlux@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)"<tvb@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.

On 5/4/2013 2:40 PM, Attila Kinali wrote: > Can anyone shed some light on why the GPS Cs beams have a worse stability > than the Rb vapor clocks? I don't know, but it makes me wonder about things like 1) How sensitive is each to C-field tuning - i.e. for the same change in C-field, by how much does each type change in relative frequency? (or maybe it's exactly the same, I know nothing about the Zeeman effect) I'd think there would be orbital changes in frequency, after all, it's orbiting a big magnet. 2) How tight a lock can be obtained on each? i.e. might the physical realizations of Rb clocks have a higher Q-factor?

On 05/06/2013 02:29 AM, Mike S wrote: > On 5/4/2013 2:40 PM, Attila Kinali wrote: >> Can anyone shed some light on why the GPS Cs beams have a worse stability >> than the Rb vapor clocks? > > I don't know, but it makes me wonder about things like > > 1) How sensitive is each to C-field tuning - i.e. for the same change in > C-field, by how much does each type change in relative frequency? (or > maybe it's exactly the same, I know nothing about the Zeeman effect) I'd > think there would be orbital changes in frequency, after all, it's > orbiting a big magnet. Rubidium is more sensitive to C-field than Caesium. > 2) How tight a lock can be obtained on each? i.e. might the physical > realizations of Rb clocks have a higher Q-factor? The Q-value depends on the observation time, and for a Cs-beam this translates into beam-length assuming constant speed. Foutains has much better Q since they have longer observation time. H-masers started as a beam with a "bounce-box" to prolong the observation time. Cheers, Magnus

Hi Fountain's don't work very well in zero G….:) Bob On May 6, 2013, at 12:23 AM, Magnus Danielson <magnus@rubidium.dyndns.org> wrote: > On 05/06/2013 02:29 AM, Mike S wrote: >> On 5/4/2013 2:40 PM, Attila Kinali wrote: >>> Can anyone shed some light on why the GPS Cs beams have a worse stability >>> than the Rb vapor clocks? >> >> I don't know, but it makes me wonder about things like >> >> 1) How sensitive is each to C-field tuning - i.e. for the same change in >> C-field, by how much does each type change in relative frequency? (or >> maybe it's exactly the same, I know nothing about the Zeeman effect) I'd >> think there would be orbital changes in frequency, after all, it's >> orbiting a big magnet. > > Rubidium is more sensitive to C-field than Caesium. > >> 2) How tight a lock can be obtained on each? i.e. might the physical >> realizations of Rb clocks have a higher Q-factor? > > The Q-value depends on the observation time, and for a Cs-beam this translates into beam-length assuming constant speed. Foutains has much better Q since they have longer observation time. H-masers started as a beam with a "bounce-box" to prolong the observation time. > > 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.