| Fountains of
Time
Tossing cold
atoms like confetti, atomic-fountain clocks launch a new era in
timekeeping
Atomic-fountain
clocks are about to take over—from a hot-atom technology that has
reigned for 50 years—as the world’s most accurate clocks.
References:
Santarelli, G.
... A. Clairon ... C. Salomon. 1999. Quantum projection noise in an
atomic fountain: A high stability cesium frequency standard. Physical
Review Letters 82(June 7):4619.
Further Readings:
1993. Starting up
an improved atomic clock. Science News 143(May 1):276.
Itano, W.M., and
N.F. Ramsey. 1993. Accurate measurement of time. Scientific American
269(July):56.
Peterson, I. 1989.
Atomic fountain springs from light touch. Science News 136(Aug.
19):117.
For information
about time scales, time-keeping history, and advanced clocks see the
U.S. Naval Observatory’s Time Service Master Clock Web page at http://tycho.usno.navy.mil/mc_to.html.
The National
Institute of Standards and Technology (NIST) Time and Frequency Division
in Boulder, Colo., offers an enlightening history of NIST timekeeping,
with links to images and additional information about particular types
of clocks, at http://www.bldrdoc.gov/timefreq.
Sources:
André Clairon
DANOF – Bâtiment B
Observatoire de Paris
61, Avenue de l’Observatoire
75014 Paris
France
Christopher R.
Ekstrom
United States Naval Observatory
3450 Massachusetts Avenue, N.W.
Washington, DC 20392
Steven Jefferts
National Institute of Standards and Technology
Atomic Standards Group
Time and Frequency Division
325 Broadway
Boulder, CO 80303
Judah Levine
National Institute of Standards and Technology
Network Synchronization Project
Time and Frequency Division
325 Broadway
Boulder, CO 80303
Thomas E. Parker
National Institute of Standards and Technology
Atomic Standards Group
Time and Frequency Division
325 Broadway
Boulder, CO 80303
Gérard Petit
Bureau International des Poids et Mesures
Pavilion de Breteuil
92312 Sèvres Cedex
France
Christophe
Salomon
Laboratoire Kastler Brossel
École Normale Supérieure
24 rue Lhomond
75005 Paris
France
Giorgio
Santarelli
DANOF – Bâtiment B
Observatoire de Paris
61, Avenue de l’Observatoire
75014 Paris
France
Donald B.
Sullivan
National Institute of Standards and Technology
Time and Frequency Division
325 Broadway
Boulder, CO 80303
From Science
News, Vol. 156, No. 6, August 7, 1999, p. 92. Copyright © 1999,
Science Service. |