The USNO Rubidium Fountain Project 

Work is underway on a new atomic fountain using Rubidium atoms. 

Design and modelling pictures of the new system.

New miniaturized optics table

Fabrication of some Rb fountain components.

The C-field solenoid being wound and in place.

The locking spectroscopy layout

The assembled tower

Tower assembly for trap and launch testing

How our rubidium fountain works (2.1 MB pdf file)
or a smaller 800 kB pdf file
Why Use Rubidium?

Since a goal of the fountain devices is to provide a stable reference rather than to define the second, we are not constrained to use Cesium. The cold-collision shift, which ends up being the largest contributor to frequency fluctuations in Cesium Fountains, is much smaller in Rubidium.

Since the Rb frequency is smaller than that of Cs, the wavelength is longer, and the entrance and exit holes to the microwave cavity can be larger without having leakage that would perturb the atoms in the drift region. This means the atom cloud can be physically larger, containing more atoms, and yields a larger fluorescence signal.

Rb also has a smaller nuclear spin, so there are fewer magnetic states. A larger fraction of the trapped atoms will start out in the m = 0 "clock state" that is less sensitive to magnetic fields.

These factors outweigh the disadvantage of having a smaller transition frequency.

Pictures of Individual Components. Click to enlarge

More information on general fountain design can be found on the Cesium Fountain page.

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last updated 3/28/06

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