Prof. Frank Moscatelli – Swarthmore College
“NIST F2 – The Cesium Fountain Atomic Clock”
The laser cooling and trapping of neutral atoms is a field with much ongoing activity worldwide. Many fundamental questions in physics have been impacted by this relatively new area of research. The 1997 Nobel Prize in Physics recognizes this fact. One of the practical applications to emerge is the use of ultra-cold atoms as new frequency standards and precise clocks. This talk will describe the development of such a clock at the National Institute of Standards and Technology (NIST) in Gaithersburg, MD – capable of achieving a short term stability of 2e-13. This is a factor of one hundred better than the current standard. It uses a cesium atomic fountain first proposed by Zacharias in 1953.
Cesium atoms from an atomic beam are slowed, cooled to ~1uK and trapped in a 1cm spherical volume to densities of roughly fifty million atoms per cc. They are then launched vertically using a moving optical molasses system. Their ballistic trajectory carries them up and then down through an RF microwave cavity where their ground state hyperfine structure is measured to one part in ten to the eleventh. Such frequency standards, employed as clocks, are planned for future space flight where they may be used in tests of fundamental theories such as general relativity.
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