Re: [time-nuts] Cs beam cavity: why is it U shaped?
On Tue, 1 May 2012 10:18:51 -0700 Tom Van Baak t...@leapsecond.com wrote: The U shape is called the Ramsey Cavity: http://www.nobelprize.org/nobel_prizes/physics/laureates/1989/ramsey-lecture.pdf Thanks a lot! That was exactly what i was looking for. It took me a while to read the paper though ^^' And the references will probably keep me busy for the next few weeks/months :-) Attila Kinali -- Why does it take years to find the answers to the questions one should have asked long ago? ___ 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] Cs beam cavity: why is it U shaped?
Moin, For some time now, i'm wondering why the microwave cavity of Cs beam standards is U shaped. Ie why does the Cs beam fly first trough the first subcavity, leaves it, flies a substantial length trough free space, passes the second subcavity and then goes to the detector. If the interaction time with the microwave field would be an issue, i would expect the beam to pass trough a longer stretch of the cavity, and not two time trough a short stretch that are widely spaced. Unfortunately, none of the papers i've read has shed any light on this, and google isn't helpfull either. Could anyone here enlighten me? Attila Kinali -- Why does it take years to find the answers to the questions one should have asked long ago? ___ 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] Cs beam cavity: why is it U shaped?
The U shape is called the Ramsey Cavity: http://www.nobelprize.org/nobel_prizes/physics/laureates/1989/ramsey-lecture.pdf /tvb - Original Message - From: Attila Kinali att...@kinali.ch To: time-nuts@febo.com Sent: Tuesday, May 01, 2012 9:47 AM Subject: [time-nuts] Cs beam cavity: why is it U shaped? Moin, For some time now, i'm wondering why the microwave cavity of Cs beam standards is U shaped. Ie why does the Cs beam fly first trough the first subcavity, leaves it, flies a substantial length trough free space, passes the second subcavity and then goes to the detector. If the interaction time with the microwave field would be an issue, i would expect the beam to pass trough a longer stretch of the cavity, and not two time trough a short stretch that are widely spaced. Unfortunately, none of the papers i've read has shed any light on this, and google isn't helpfull either. Could anyone here enlighten me? Attila Kinali -- Why does it take years to find the answers to the questions one should have asked long ago? ___ 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] Cs beam cavity: why is it U shaped?
Hi Attila, On 05/01/2012 06:47 PM, Attila Kinali wrote: Moin, For some time now, i'm wondering why the microwave cavity of Cs beam standards is U shaped. Ie why does the Cs beam fly first trough the first subcavity, leaves it, flies a substantial length trough free space, passes the second subcavity and then goes to the detector. If the interaction time with the microwave field would be an issue, i would expect the beam to pass trough a longer stretch of the cavity, and not two time trough a short stretch that are widely spaced. Unfortunately, none of the papers i've read has shed any light on this, and google isn't helpfull either. Could anyone here enlighten me? In combination with Tom's link to the Noble lecture, the U-shaped form is really a bent transmission line such that the same source provides the same signal. It's also important that the phase delay from the source to both branches be very closely matched. Miss-align them and you get a systematic frequency error as a result. Notice how the RF interaction has the RF field being oriented orthogonally to the direction of the beam. 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] Cs beam cavity: why is it U shaped?
The tube is like an interferometer. Think of two telescopes spaced apart x meters. It has the resolving power of an x meter diameter telescope. It doesn't have the light gathering power of an x meter telescope. There is sufficient RF power to flip the state of all the Cs atoms, so additional interaction time would not be helpful. Also, the accuracy of the standard depends on the phase error between the two ends. (The big machines send the beam through in both directions to cancel this out). There is no way to do this (AFAIK) if you had to excite the atoms over their entire flight. In the 5071 CBT, there are proprietary manufacturing techniques that reduce the random phase error to parts in 10^13 and the systematic phase error to parts in 10^14, or so I have been told. This cleverness is the kind of thing that gets noticed in Stockholm. Rick Karlquist, N6RK Attila Kinali wrote: Moin, For some time now, i'm wondering why the microwave cavity of Cs beam standards is U shaped. Ie why does the Cs beam fly first trough the first subcavity, leaves it, flies a substantial length trough free space, passes the second subcavity and then goes to the detector. If the interaction time with the microwave field would be an issue, i would expect the beam to pass trough a longer stretch of the cavity, and not two time trough a short stretch that are widely spaced. Unfortunately, none of the papers i've read has shed any light on this, and google isn't helpfull either. Could anyone here enlighten me? Attila Kinali -- Why does it take years to find the answers to the questions one should have asked long ago? ___ 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.
