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European Frequency and Time Forum

Preliminary Results of the Portable Cold 87Rb Atomic Clock in NIM

Fasong Zheng, Kun Liu, Weiliang Chen, Shaoyang Dai, Fang Fang

Published Jun 25, 2024• 1 citation
Publisher

Abstract

A portable cold87Rb atomic clock is under development at NIM. The clock uses87Rb atoms which are trapped and cooled in a small three-dimensional magneto-optical trap (3D-MOT) chamber. Within the 3D-MOT chamber, the free-falling atoms are prepared in$\vert F=2, m_{F}=0\rangle$clock state with optical pumping (OP) directly after post cooling by$2-2^{\prime}$OP light and repumping. Following optical state selection, the free-falling atoms enter a microwave cavity where they undergo microwave interrogation. Eventually, the number of atoms in two clock states are detected individually by the fluorescence detection method in the detection chamber. The preliminary results show that, the selected atom number has been improved about 3 times with the optical state selection compared to the microwave state selection method. And a Ramsey fringe has been obtained experimentally, and the contrast of the central Ramsey fringe exceeds 88% with a full width half maximum (FWHM) of less than 9 Hz.

DOI
10.1109/eftf61992.2024.10722244

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We present an atomic clock based on the interrogation of magnetically trapped (87)Rb atoms. Two photons, in the microwave and radiofrequency domain, excite the clock transition. At a magnetic field of 3.23 G the clock transition from |F = 1, m(F) = -1> to |F = 2, m(F) = 1> is 1st-order insensitive to magnetic field variations. Ramsey interrogation times longer than 2 s can be achieved, leading to a projected clock stability in the low 10(-13) at 1 s for a cloud of 10(5) atoms. We use an atom chip to cool and trap the atoms. A coplanar waveguide is integrated to the chip to carry the Ramsey interrogation signal, making the physics package as small as (5 cm)(3). We describe the experimental setup and show preliminary Ramsey fringes of line width 1.25 Hz.
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