Yuri, Sorry about that, but I guess the Trimble Thunderbolts are out of stock all ready.
Bill....WB6BNQ WB6BNQ wrote: > Hi Yuri, > > Unless you need the longer term stability of an undisciplined Rb source, I > think > you would be better served to get one of the “Timenuts group” Trimble > Thunderbolt > GPS units to use as a home standard. It is available via this page: > > http://www.tapr.org/kits_thunder.html > > and info about the unit is available at this URL: > > http://www.leapsecond.com/tbolt-faq.htm > > Add an external very high quality crystal oscillator locked to the Trimble and > you will have the same stability of a good Rb source. Most would use a high > quality Rb source, undisciplined, as a tool for comparing or generating > specifications of crystal oscillators. > > It seems that the Rb standards last longer turned off. My understanding > (subject > to disagreement) is the Rubidium in the lamp ends up coating the walls of the > lamp and reducing the transmission through the glass, i.e., the signal gets > more > and more noisy as time goes on. Also, it seems that the Rubidium may permeate > through the walls of the glass housing and thus reduce the amount of Rb over > time. I have not heard of anyone reversing the condition. Of course, other > things can go wrong with the Rb source besides the lamp. > > A very high quality crystal oscillator would most likely last longer with > fewer > problems. I have several +40 year old hp counters with decent oscillators > still > operating. > > Bill....WB6BNQ > > Yuri Ostry wrote: > > > Hello, > > > > Readed list archives and googled a lot, and seen two opposing points of > > view - one is that there is nothing to age in Rb lamp, another is that > > Rb lamp is degrading when in operation (without details, how and why). > > > > I'm planning to get some Efratom Rb oscillator to use it in a > > constantly running home lab frequency reference. Trying to understand > > for myself, is it worth to get spare unit (or even two) of the same > > model just to have replacement lamp on hand. > > > > One more question - does someone seen Rb standard that is > > malfunctioned due to degraded lamp, that, at same time, does have > > good vacuum. If so, which model, and how the failed lamp looks like? > > Was there any attempts to "rejuvenate" the lamp? (for example, heating > > to remove glass darkening, if any, or similar experiments). > > > > By the way, I'm very curious about physical process that may cause > > lamp degradation. > > > > Rubidium-87 that is included in the lamp (according to > > manuals) is a radionuclide, beta emitter. It decays very slowly (4.7 > > billion years half life) to stable Strontium-87, emitting 282.62keV > > electrons and (anti?)neutrino. I don't think that 87Rb decay may > > interfere with unit operation after tens of years, unless 87Sr is > > "poisonous" so much so it can interfere with lamp operation even in > > tiniest amounts. > > > > The only reference I located to date, is following article, that is > > not available to general public. It is hard to understand for me just > > from this abstract, does it specifically related to space environment > > factors, or it is something that may cause degradation of Rb clocks > > that is operated in average lab on Earth. ;) > > > > > A Mechanism of Rubidium Atomic Clock Degradation: Ring-Mode to > > > Red-Mode Transition in rf-Discharge Lamps > > > Camparo, J. Mackay, R. > > > Aerosp. Corp., El Segundo; > > > > > > > > > This paper appears in: Frequency Control Symposium, 2007 Joint with > > > the 21st European Frequency and Time Forum. IEEE International > > > Publication Date: May 29 2007-June 1 2007 > > > On page(s): 45-48 > > > Location: Geneva, > > > ISSN: 1075-6787 > > > ISBN: 978-1-4244-0647-0 > > > INSPEC Accession Number: 9805223 > > > Digital Object Identifier: 10.1109/FREQ.2007.4319027 > > > Current Version Published: 2007-10-01 > > > > > > > > > > > > > > > > > > Abstract > > > In the vapor-cell atomic clock, long-term stability can be > > > influenced by slow variations in the discharge lamp's output via the > > > light-shift effect. Additionally, over a multi-year mission lifetime > > > the lamp's aging can degrade its optical pumping efficiency. > > > Understanding the mechanism(s) that drives these changes is > > > particularly important for spacecraft devices, where the atomic > > > clocks are called upon to function continuously and reliably for > > > many years. Here, we consider the two well-known, but little > > > studied, modes associated with alkali rf-discharge lamp operation: > > > the ring mode and the red mode. Consistent with previous research, > > > we find that the ring mode is best for optical pumping, and that the > > > clock-signal amplitude degrades significantly when the lamp operates > > > in the red mode. Examining the emission spectrum as the lamp > > > transitions between these two modes, we show that the ring-mode to > > > red-mode transition is driven by radiation trapping within the lamp. > > > > -- > > Sincerely, > > Yuri UA3ATQ/KI7XJ mailto:[EMAIL PROTECTED] > > > > _______________________________________________ > > time-nuts mailing list -- [email protected] > > To unsubscribe, go to > > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > > and follow the instructions there. > > _______________________________________________ > time-nuts mailing list -- [email protected] > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
