The Cesium clock returns (Patreon)

How can one have more fun than with one Cesium clock? With two Cesium clocks of course! 

In my HP Cesium clock explanation video, I left out the explanation of the C-field for a future day. Well the day has come. 

This C-field adjustment is used to extract even more precision from our Cesium clock by adjusting the Zeeman lines. The Zeeman effect is the sub-splitting of our hyperfine lines under a magnetic field (our C-field here), and is a very fine quantum process.

To do it, you first need an instrument that only works with the HP 5061 Cesium clock, the HP 10638 degausser. It's used to generate an alternating magnetic field with a perfect exponential decay, and get rid of any residual magnetic field in the cesium tube. Marcel found two of them on eBay. We started by checking the degaussers, and the procedure calls for a graph plotter. My HP 7132 was pressed into service.

After some adjustment, it works perfectly. We have pretty exponentials. Marcel is very proud.

Then we adjusted not just one, but two clocks. Because we can. And then you can compare one against the other. Because why not.

When you do it right, you can tickle the 10E-14 decimal. The Zeeman adjustment had been done at least once before on this clock, as the sticker attests. 

It's a complicated procedure which involves quantum physics and the spin number of the Cesium nucleus (which you'll be happy to know is 7/2) and Zeeman line resonances and plenty of degauss-and-repeat. We managed to get our resonance at 53,560 Hz, within 30 Hz of the ideal 53,530 Hz (less than +/- 70 Hz is the spec).

At the end of the procedure the two clocks were rock solid. We looked at the crossings of their two super magnified 5 MHz sine waves over 20 minutes and could not detect any movement. But at this point the stability of the scope itself starts to dominate. Maybe I should have used a modern one, but we were geeking out with period HP equipment.

Now one clock goes to Marcel and the other stays with me. If we did not turn them off we would stay locked in time for our lifetime...

Marc