The remaining beam is exposed to an RF field at or near the transition frequency. The accuracy of an atomic clock depends on two factors.
Quantum logic spectroscopy of a single Al ion became the most precise in 2008. In 2010 an improved setup using a Mg+ logic ion instead of Be was demonstrated Power consumption This section needs expansion. Ion traps have been used for numerous ions. 199Hg+ was an early candidate. The lifetime of a standard is an important practical issue.
Although the long-term stability of the active maser is not as good as that of a caesium beam, it remains one of the most stable sources available. The slow speed of the atoms also reduces black body temperature shifts. Retrieved 18 October 2015. ^ ESA. «Atomic clock ensemble in space (ACES)» (PDF). ERASMUS Centre — Directorate of Human Spaceflight and Operations.
Equality of the ET second with the (atomic clock) SI second has been verified to within 1 part in 1010. The SI second thus inherits the effect of decisions by the original designers of the ephemeris time scale, determining the length of the ET second. Weinheim: Wiley-VCH Verlag GmbH & Co. KGaA. p. 266. ISBN 978-3-527-40780-4. ^ «Global Positioning System». Gps.gov. Retrieved 22 June 2015. ^ 171Ytterbium BIPM document ^ «Blackbody Radiation Shift: Quantum Thermodynamics Will Redefine Clocks». Retrieved 5 December 2012. ^ Ost, Laura (22 January 2014). «JILA Strontium Atomic Clock Sets New Records in Both Precision and Stability». NIST Tech Beat.
New technologies, such as femtosecond frequency combs, optical lattices, and quantum information, have enabled prototypes of next-generation atomic clocks. Rev. A, vol. 80, no. 5, pp. 052703/1-11, 2009. D. C. Yost, Schibli, T. R. , Ye, J. , Tate, J. L. , Hostetter, J. , Gaarde, M. B. , and Schafer, K. J. , “Vacuum-ultraviolet frequency combs from below-threshold harmonics”, Nature Phys., vol. 5, pp. 815–820, 2009. Wall-shift can be reduced by wall coating and compensation by buffer gas. The wide range of clocks is supplied to many market areas, including offices, schools and colleges, banks, factories and warehouses, hospitals, sports halls and swimming pools.
The core of the atomic clock is a tunable microwave cavity containing a gas. In a hydrogen maser clock the gas emits microwaves (the gas mases) on a hyperfine transition, the field in the cavity oscillates, and the cavity is tuned for maximum microwave amplitude. Often, one standard is used to fix another. See also References ^ USNO Master Clock ^ McCarthy, Dennis; Seidelmann, P. Kenneth (2009). TIME from Earth Rotation to Atomic Physics. For example, some commercial applications use a rubidium standard periodically corrected by a global positioning system receiver (see GPS disciplined oscillator). This achieves excellent short-term accuracy, with long-term accuracy equal to (and traceable to) the U.S. national time standards.
Rubidium standard clocks are prized for their low cost, small size (commercial standards are as small as 17 cm3) and short-term stability. Modern clocks use magneto-optical traps to cool the atoms for improved precision. You can help by adding to it. (June 2008) The power consumption of atomic clocks varies with their size. This technology became available commercially in 2011. Ion trap experimental optical clocks are more precise than the current caesium standard. In March 2017, NASA plans to deploy the Deep Space Atomic Clock (DSAC), a miniaturized, ultra-precise mercury-ion atomic clock, into outer space.
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