Hej, On 09/28/2015 04:17 PM, Attila Kinali wrote:
On Sun, 27 Sep 2015 07:46:26 +0000 Poul-Henning Kamp <[email protected]> wrote:Discovery of the day: The voltage supplied to the Rb87 lamp changes the frequency on the order of 1.5e-11 per volt. I have no idea why... http://phk.freebsd.dk/hacks/HP5065A/index.htmlMy first guess would be "light shift" (aka "AC Stark effect"). Does the intensity of the lamp change as well? Also, it could be that the other spectral components of the lamp (due to Xe/Ne gas filling) get stronger modulation than the Rb D1 line. The only paper I know about that deals with the spectral modes of the Rb lamp is [1], but as it is quite current, it does not deal with much of the basics, but it might provide you with some references. There should be somewhere a mention how much the frequency shift of an Rb vapor cell due to light intensity change is, but i couldn't find a good number in a couple of minutes. If you need one, please let me know and I look a bit more carefull.
You really should check J. Vanier and C. Audoin "The Quantum Physics of Atomic Frequency Standards, Volume 2" Chapter 7 Rubidium Frequency Standards.
You will find that "Figure 7.3.6 Cell resonance frequency as a function of light intensity as measured by means of the current id at the photo detector" is an interesting plot showing linear slopes of different rates depending on which temperature the filter cell has.
Now, it is interesting to note that the temperature of the filter cell, the temperature of the lamp cell and the intensity of lamp plasma interacts here. For a optimum filter cell temperature, you can cancel the lamp intensity.
You will also find that "Figure 7.3.7 Cell resonance frequency as a function of the filter cell temperature" on the next page shows a parabolic shape.
Anyway, those plots give strong indication that measuring the light intensity from the detector and then servo the intensity can be a good strategy.
W.J. Riley "Rubidium Frequency Standard Primer" is a good read, but Vanier&Audoin is much more fundamental.
Cheers, Magnus _______________________________________________ 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.
