Hi Every time I've tried the coli thing, field uniformity has become an issue. I'm also not real sure just how stable multi axis mag sensors are.
If I had a bunch of mu metal sitting in the basement I'd certainly use it in the setup. Last time I checked the stuff was not cheap .... Bob On Dec 24, 2009, at 3:50 PM, Bruce Griffiths wrote: > One method of reducing the sensitivity to magnetic fields is to enclose the > rubidium source in a series of nested magnetic shields (e.g. mu metal). > The shield walls could form part of the good thermal conductor poor thermal > conductor stack. > > One could also use something like a set of 3 orthogonal Helmholtz coils to > null the magnetic field at the rubidium source. > A servo loop using a magnetic field sensor could be employed. > > Bruce > > Bob Camp wrote: >> Hi >> >> To tune the frequency of a rubidium, you make a very small change to the DC >> magnetic field around the cell. That's the way you put them on frequency. >> Anything that changes the local field also changes the frequency of the >> rubidium standard. >> >> The DC in the power leads is a constant current and therefore creates a >> non-changing field. That means no frequency change. >> >> The reason you change the current in the heater is to stabilize the >> rubidium. If while you are trying to stabilize it one way, you de-stabalize >> it another way, that may not be progress. >> >> I believe that putting a couple of watts of RF into the heater is not a very >> practical thing .... >> >> Bob >> >> On Dec 24, 2009, at 2:14 PM, WarrenS wrote: >> >> >>> I Must not get it, Or I'm missing something. >>> Some seem to be going on and on about a little added DC heater current that >>> can be held to about 10% of what the unit draws >>> Why does a little added DC heater current any more of a problem that what >>> you do with the leads etc of the main power? >>> (And with a few simple tricks you can also reduce the effect of the >>> changing heater current so it has insignificant effect) >>> Have to work a bit harder to say the same about putting AC or RF into the >>> heater >>> >>> ws >>> >>> *************** >>> >>> Bob Camp wrote: >>> >>>> Hi >>>> >>>> Having a bunch of AC current gets me into another issue. I suspect it's >>>> going to couple into something somewhere and give me a spur on the system >>>> output. >>>> >>> Sure, but having a sufficiently high frequency makes it relatively easy >>> to clean up, as well as it should be reduced by normal loop filtering >>> and oscillator integration. >>> >>> 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. >>> >>> >> >> _______________________________________________ >> 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.
