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Conference on Precision Electromagnetic Measurements

KRISS atomic fountain clock: Current status

Sang Eon Park, Long Zhe Li, Sang-Bum Lee, Dai-Hyuk Yu, Chang Yong Park, Won-Kyu Lee, Taeg Yong Kwon

Published Jul 1, 2012• 0 citations
Publisher

Abstract

We present a current status of a Rb/Cs double fountain clock developing at KRISS. Fountain clock has cooling laser beam with (111)-geometry so as to enlarge cooling beam diameter. Currently few 107Cs atoms are trapped and cooled in MOT. And we observed Ramsey fringes. The linewith of central Ramsey fringe was measured to be 1 Hz with the S/N of 600.

DOI
10.1109/cpem.2012.6251076

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Conference on Precision Electromagnetic Measurements•Jul 1, 2012•0 citations
We present a current status of a Rb/Cs double fountain clock developing at KRISS. Fountain clock has cooling laser beam with (111)-geometry so as to enlarge cooling beam diameter. Currently few 107Cs atoms are trapped and cooled in MOT. And we observed Ramsey fringes. The linewith of central Ramsey fringe was measured to be 1 Hz with the S/N of 600.
We report here on progress towards the realization of an atomic frequency standard using a fountain of laser cooled cesium atoms. We have recently observed Ramsey fringes on the 9.2 GHz clock transition and have begun preliminary work aimed at characterizing our fountain. This paper describes briefly the apparatus, discusses our current work and near-term directions. We conclude with a brief discussion of a laser system being built to realize two-dimensional Raman cooling or Raman velocity selection for cooling below the single photon recoil limit. This system will be used either in our fountain or in a cold-atom clock to be flown on the International Space Station.
This paper describes the current status of an ytterbium lattice clock under development at KRISS. After the success of 399 nm magneto-optical-trap (MOT) at a temperature 1 mK, we constructed the 2ndstage cooling laser system at a wavelength of 556 nm to cool atoms further down to several muK. We are also developing an ultra-narrow linewidth laser at a wavelength of 578 nm to probe the clock transition by doubling the frequency output of a commercial 1156 nm ECDL. Efforts to reduce the linewidth are under way.
Summary form only given. We have constructed a prototype of an /sup 87/Rb fountain clock. We collect 10/sup 10/ /sup 87/Rb atoms in a vapor cell magneto-optic trap (MOT). The laser system for trapping and cooling is entirely solid state--a grating stabilized laser injects a separate slave laser for each of the six beams of the MOT. We launch the atoms by frequency shifting the three downward propagating laser beams and then increasing the detuning and gradually reducing the intensity of the slave lasers to adiabatically cool the atoms to low temperatures in the fountain.
National Physical Laboratory India (NPLI) has been developing a cesium atomic fountain primary frequency standard. We have succeeded in trapping about 107Cs atoms, cool them to about 5 μK by both magneto-optical trap (MOT) and polarization gradient cooling (PGC) and launch them up by moving molasses method. We have demonstrated the fountain action by launching the atoms up to 72.9 cm up and detection of the return signal by measuring the fluorescence. Work is underway to interrogate the launched atoms with microwaves and observe Ramsey fringes.