[time-nuts] Input voltage for Zeeman on 5061A

Tom Van Baak tvb at leapsecond.com
Sat Jan 22 16:33:40 EST 2005


> Lorentz, Zeeman did the work and Lorentz came up with the theory and 
> they shared the Nobel prize in 1902 (the second year of the Nobel 
> prize).  Their theory was based on a new particle called the 
> "electron".  By using the Zeeman effect they could compute some of it's 
> properties and confirm that it was the same particle that was used in 
> Cathode Ray Tubes.  But they did not understand the quantum mechanics 
> aspects relating to up and down electron spins that came later.  I think 
> to compute the Zeeman frequencies requires the use of quantum 
> mechanics.  What the Zeeman effect is correlating the magnetic field 
> strength and the splitting of a single spectral line allowing adjustment 
> or measuring the magnetic field.

Right, the HP diagrams at:

http://www.leapsecond.com/museum/hp5062c/theory.htm

show that at zero magnetic field the seven peaks
collapse into one. As you increase the field strength
the lines shift and split more and more. The frequency
domain plots you see of 7 Cs peaks are with a
magnetic field applied.

The magic that the lines split like that when exposed
to a magnetic field is called Zeeman splitting. (And if
there's a real physicist reading this please feel free to
correct the explanation.)

Effectively what you are doing with the Zeeman input
is calibrating the DC magnetic field within the
microwave cavity.

This is important for a primary standard because the
exact frequency of the center peak is a function of
magnetic field. Note also the HP 10638A degausser
for 5061B high-perf tubes.

It is not important if you simply tweak the C-field
until your standard is on-frequency as compared
with an accurate reference such as GPS.

Note that the second is defined as 9,192,631,770 Hz
in a *zero* magnetic field -- but because Cs beam
tubes need a non-zero magnetic field to operate the
actual frequency of the peak as passively probed is
not quite the xxx770 number.

But the synthesizer and C-field adjustment take care
of this so you don't have to worry. In two old service
manuals I found examples of the actual frequency of
the Cs peak: xxx771.39 in one and xxx774.3 in another
(the hp 5062c; an unusual tube).

> 
> Once I get my 4060 tweaked and know the C field based on GPS, then I'll 
> do some Zeeman experiments.
> 
> Tom:
> 
> I'm curious as to how close you get using the Zeeman method.  Do you 
> have any data showing Zeeman frequency vs. Source frequency for HP 
> and/or FTS tubes?

Let me dig that out for a 5061A. It's not an issue with the
5071A -- they don't even have a Zeeman input -- since they
digitally Zeeman calibrate themselves during warm-up.

/tvb





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