ATOMIC clocks, currently the size of fridges, could shrink to the microscale thanks to a new way of measuring the second. The technique could also see aluminium displace caesium as the standard of time.
The world's most accurate atomic clocks are at the National Institute of Standards and Technology (NIST) at Boulder, Colorado. Known as fountain clocks, they send clouds of caesium atoms through a vacuum chamber in a magnetic field. Large atoms like caesium and aluminium have multiple energy levels that are so close together they appear indistinguishable. The magnetic field separates these levels into two "hyperfine" states.
http://www.newscientist.com/article/mg20126994.900-time-to-shrink-the-atomic-clock.html (http://www.newscientist.com/article/mg20126994.900-time-to-shrink-the-atomic-clock.html)
This article is messed up in the beginning. Cesium clocks have been smaller than a 8902A for a decade or more. I have not even seen a cesium clock as big as a fridge. What do they mean "Currently the size of fridges"? Makes one wonder if the the article has any validity. The NIST Fountain is the size of a fridge if that is what they mean, but "Atomic clocks" in general are not that big. Am I missing something here?
You are right that cesium clocks have been smaller than an HP 8902A for much longer than a decade, the HP 5060A was at least 30 years ago (anyone know?). I think the article without mentioning is implying the difference between a Primary Standard and a Commercial Lab Standard.
See Naval Observatory defintion:
Kinds of Cesium Clocks
Cesium clocks are of two general kinds: a "laboratory (or primary) standard" about as large as a railroad flatcar and a "commercial (or secondary) standard" about as large as a suitcase
from http://tycho.usno.navy.mil/cesium.html (http://tycho.usno.navy.mil/cesium.html)
Agilent called the 5071A a "primary frequency standard". Seems like I saw a TV several years ago with some footage from a Naval Observatory, they had about half a dozen of them in a rack.
The 5071A has since been sold off to some outfit called Symmetricom several years ago. Had mine since 94.
The 5061A was introduced in 1967 to replace the 5060A. 5060A dates back to 1964.