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Joint Conference of the European Frequency and Time Forum and IEEE International Frequency Control Symposium (EFTF/IFCS)

Development of a compact cold atom clock

S. Trémine, Stéphane Guérandel, David Holleville, Andr  Clairon, N. Dimarcq

Published Apr 12, 2005• 14 citations
Publisher

Abstract

HORACE is a compact cold atom clock where the atoms are cooled inside the microwave interrogation cavity. About 10/sup 8/ atoms can be cooled at kinetic temperatures as low as 2.5 /spl mu/K. We report, for the first time, a Ramsey pattern observed with a 14 Hz linewidth and fringe contrast better than 80%. Since this clock is designed for space applications, some properties are extrapolated to micro-gravity operation.

DOI
10.1109/freq.2004.1418430

Related papers

Microwave interrogation in a compact atomic clock

S. Trémine, Stéphane Guérandel, David Holleville +2 more

HORACE is a compact cold atom clock where the atoms are cooled inside the microwave interrogation cavity. About 108 atoms can be cooled at kinetic temperatures as low as 2.5 μK. We report for the first time Ramsey pattern observed with a 14 Hz linewidth and fringe contrast better than 80%. Since this clock is designed for Space applications, some properties are extrapolated to micro-gravity operation.

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Joint Conference of the European Frequency and Time Forum and IEEE International Frequency Control Symposium (EFTF/IFCS)•Jan 22, 2003•3 citations

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We present a scheme for a compact rubidium cold-atom clock which performs diffuse light cooling, microwave interrogation, and detection of the clock signal in a cylindrical microwave cavity. The diffuse light is produced by laser light reflection at the inner surface of the microwave cavity. The pattern of the injected laser beams is specially designed to accumulate the majority of the cold atoms in the center of the microwave cavity. Microwave interrogation of the cold atoms in the cavity leads to Ramsey fringes, which have a linewidth of $24.5$ Hz with a contrast of $95.6%$ when the free evolution time is 20 ms. Recently, a frequency stability of $7.3\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}13}\phantom{\rule{0.28em}{0ex}}{\ensuremath{\tau}}^{\ensuremath{-}1/2}$ has been achieved. The scheme of this physical package can largely reduce the cold-atom clock complexity and increase clock performance.

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New design of the compact cold atoms clock HORACE

François-Xavier Esnault, Sean Perrin, S. Trémine +5 more

In the compact cold atoms clock HORACE caesium atoms are successively laser cooled, submitted to a Ramsey microwave interrogation scheme and then detected by linear absorption directly inside the microwave cavity. The whole physics package and optical bench have been entirely redesigned to optimize such an in-situ detection and to perform a normalization scheme. Main efforts have been concentrated on technical issues such as magnetic shielding, microwave cavity polishing and tuning, use of fast mechanical switches to realize the optical sequence.

•Jan 1, 2006•6 citations
HORACE is a compact cold atom clock where the atoms are cooled inside the microwave interrogation cavity. About 10/sup 8/ atoms can be cooled at kinetic temperatures as low as 2.5 /spl mu/K. We report, for the first time, a Ramsey pattern observed with a 14 Hz linewidth and fringe contrast better than 80%. Since this clock is designed for space applications, some properties are extrapolated to micro-gravity operation.
Our aim is to use cold atoms not for reducing instability or inaccuracy in the range of 10/sup -16/ or better, but to use them for reducing the size of atomic clocks. The key idea of HORACE is to fold in a microwave cavity every zone of the atomic resonator of a standard clock: zones of cooling and atomic preparation, zone of interrogation and zone of detection. Then the cell of HORACE has to be a microwave cavity as well as an optical cavity. Thus cooling of cesium atoms can only be obtained by isotropic cooling light generated inside it. In this paper, we first expose the main features of HORACE and two different configurations. Metrological aspects as well as the way the atoms would be efficiently cooled are then developed. A preliminary validation of HORACE is also demonstrated.
The HORACE device is a compact cold atom clock where about 10/sup 8/ cesium atoms are laser cooled at a few /spl mu/K, then interrogated and detected directly in a 20 cm/sup 3/ spherical microwave cavity. The optimization of the short term stability with the cooling and interrogation durations is presented, leading to an estimation of the Allan deviation of /spl sigma//sub y/(/spl tau/) -1 10/sup -13/ /spl tau/ /sup - 1/2 /on earth and /spl sigma//sub y/(/spl tau/) = 7 10/sup -14/ /spl tau//sup -frac12;/ in space. The quantum projection noise, the Dick effect and the detection laser noises are taken into account. The calculations are based on a preliminary model for the recapture of cold atoms, in reasonable agreement with measurements.
We present a scheme for a compact rubidium cold-atom clock which performs diffuse light cooling, microwave interrogation, and detection of the clock signal in a cylindrical microwave cavity. The diffuse light is produced by laser light reflection at the inner surface of the microwave cavity. The pattern of the injected laser beams is specially designed to accumulate the majority of the cold atoms in the center of the microwave cavity. Microwave interrogation of the cold atoms in the cavity leads to Ramsey fringes, which have a linewidth of 24.524.524.5 Hz with a contrast of 95.695.6%95.6 when the free evolution time is 20 ms. Recently, a frequency stability of $7.3\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}13}\phantom{\rule{0.28em}{0ex}}{\ensuremath{\tau}}^{\ensuremath{-}1/2}$ has been achieved. The scheme of this physical package can largely reduce the cold-atom clock complexity and increase clock performance.
In the compact cold atoms clock HORACE caesium atoms are successively laser cooled, submitted to a Ramsey microwave interrogation scheme and then detected by linear absorption directly inside the microwave cavity. The whole physics package and optical bench have been entirely redesigned to optimize such an in-situ detection and to perform a normalization scheme. Main efforts have been concentrated on technical issues such as magnetic shielding, microwave cavity polishing and tuning, use of fast mechanical switches to realize the optical sequence.