Michael J. Delaney

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For the past 50 years, atomic standards based on the frequency of the cesium ground-state hyperfine transition have been the most accurate time pieces in the world. We now report a comparison between the cesium fountain standard NIST-F1, which has been evaluated with an inaccuracy of about 4 x 10(-16), and an optical frequency standard based on an(More)
We report tests of local position invariance and the variation of fundamental constants from measurements of the frequency ratio of the 282-nm 199Hg+ optical clock transition to the ground state hyperfine splitting in 133Cs. Analysis of the frequency ratio of the two clocks, extending over 6 yr at NIST, is used to place a limit on its fractional variation(More)
The paper summarizes the relative advantages and disadvantages of coherent population trapping (CPT) or intensity optical pumping (IOP) for the implementation of a passive atomic frequency standard using the isotope Rb. This paper outlines the basic principles common to both CPT and IOP when using laser optical pumping, and makes explicit their similarities(More)
We laser-cooled up to 106 9Be+ ions to ∼1 mK in a Penning-Malmberg trap and measured the ion temperature as a function of time after turning off the cooling laser. We observed a rapid heating of the ions when their temperature in a direction parallel to the magnetic field increased above 10 mK and show that this is due to the equilibration of a warm (few(More)
Traditionally a majority of the commercial satellite communications systems have been fixed repeaters at C-band and Ku-band. The satellite industry is presently undergoing significant changes in the types of systems that are being fielded. New low earth orbit and geo stationary mobile systems have large numbers of flexible beams at either L-band or S-band(More)
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