[time-nuts] Time Nuts at PTTI this past week

[Magnus Danielson]

From: "Bill Hawkins" <bill at iaxs.net>
Subject: Re: [time-nuts] Time Nuts at PTTI this past week
Date: Sat, 9 Dec 2006 10:11:05 -0600
Message-ID: <000c01c71bac$a1ef7c20$0900a8c0 at cyrus>

> Ah, yes, the C field. A change in magnetic field can change
> the clock frequency. Parts in 1e-14 are exceedingly small.

If you run a modern clock, it will adjust the C field for the propper feature
separation in the measurements. This way, vector sum of the C field applied and
the external magnetic sources as they affect the beam will be measured on its
feature effect and then the C field is steered to the "propper" separation.
As always, there is no perfect cancelation, but some of the external field
should be compensated. However, avoidance of strong fields and change of strong
fields is allways a good precaution.

> Is it necessary to correct for the Earth's magnetic field
> when the clock travels?
> 
> Bill Hawkins
> 
> Actually, that's a test that can be done at home with a
> couple of 2-3 foot diameter solenoid coils. Be tough to
> find an ammeter good to 1e-15, though.

The ampmeter does not have to have that accuraccy. For cesium, the frequency
shift is 42.745 GHz/T^2. A fairly normal ampmeter will suffice to predict the
shift. The actual added DC shift of the magnetic field you acheive on the beam
is a much larger error-factor than your amp-meter. But yes, you should
certainly be able to measure it at home.

I greatly enjoyed measuring the Rabi-Ramsey separations on my Cs beam by
inserting my own 12.6 MHz signal which I swept with my network analyzer. I then
modulated the detected level through a double-balanced mixer with 12.6 MHz
signal and tossed that in on the measurement port. Then I actually had built
myself a 9.192 GHz network analyzer. That was pretty fun. :)

Cheers,
Magnus