Compact, Continuous-Beam, Cold-Atom Clock for Satellite Applications

H. Wang, Walter F. Buell

Published Jun 30, 2002• 1 citation

Abstract

Highly stable atomic frequency standards are of increasing importance for a variety of space applications, ranging from communication to navigation and time transfer to tests of fundamental science. The requirements for an atomic clock vary significantly depending on the application, and for many space systems, compactness and robust design are at a premium, and stability dominates over absolute accuracy. We report on progress with our design for a compact laser-cooled Cs- beam atomic clock suitable for satellite applications such as GPS. The basic design features a continuous, cold atomic beam extracted from a magneto-optic trap (MOT). This cold atomic beam is then to be used in a laser-pumped Ramsey clock, with the clock signal derived from either a microwave C-field or, alternatively, by Raman resonance between the Ramsey fields. In order to reduce light shifts from the MOT light and improve signal-to-noise, the atomic beam will be optically deflected and transversely cooled upon extraction from the MOT. We estimate that the shot-noise-limited stability achievable with this physics package can be 2 to 3 orders of magnitude better than current Cs-beam clocks used in satellite applications. We present our experimental progress towards a working frequency standard, including characterization of our six-beam magneto-optic cold atom trap and production and characterization of a cold atomic beam.

Related papers

TOWARDS DEMONSTRATION OF A MOT-BASED CONTINUOUS COLD CS-BEAM ATOMIC CLOCK

H. Wang, James C. Camparo, Gebriel H. Iyanu

Laser-cooled low-velocity (v < 10 m/s) atomic beams have been considered to be feasible cold atom sources in developing compact and highly stable atomic clocks for satellite applications. A cold atomic beam can be realized by laser-accelerating an ensemble of ultracold (T < 1 mK) atoms from a laser-cooled magneto-optical trap (MOT). This technique has the unique advantage of generating a useful cold atomic beam just outside the volume of a MOT and, hence, can greatly reduce the size of the atomic clock physics package. In this paper, we present our design and experimental results towards demonstration of a MOT-based cold Cs beam atomic clock. We have generated a continuous cold Cs beam from a Cs MOT and have determined the typical longitudinal velocity of the Cs beam by Time of Flight (TOF) method to be 7 m/s with a velocity spread of 1 m/s. By adjusting the MOT parameters, the atomic beam velocity can be tuned continuously, with the velocity spread remaining to be 1 m/s. In order to separate the atomic beam from the MOT laser beam, we have used a one-dimensional optical molasses to efficiently deflect the cold Cs beam through an angle of 30 degrees. The 1-D optical molasses is set up in such a way that the molasses laser beams are perpendicular to the final atomic beam propagation path. Thus, the Cs-beam velocity components along the molasses axis are efficiently damped to nearly zero, while the Cs velocity component along the final atomic beam propagation path is unaffected. Our simulation indicates that a deflection efficiency of 100% is achievable for MOT-based cold atomic beams. Our cold Cs beam has an instantaneous atomic flux of 3.6 10 (exp 10) atoms/s when operated in pulsed mode and an estimated continuous beam flux of 2 10 (exp 8) atoms/s.

Nov 29, 20070 citations

Laser-cooled continuous Cs-beam master oscillator

H. Wang, Walter F. Buell, Gebriel H. Iyanu

In this paper, we present our design and prospects of a magneto-optical trap (MOT)-based cold Cs-beam atomic clock physics package and report the realization and characterization of a continuous, laser-cooled Cs atomic beam from a Cs MOT. We have determined the longitudinal velocity of the cold Cs beam by time of flight (TOF) method to be 7 m/s with a velocity spread of 1 m/s. By adjusting the MOT parameters, we are able to tune the Cs-beam velocity from 5 m/s to 8.5 m/s while the velocity spread remains to be 1 m/s. The Cs beam has an instantaneous atomic flux of 3.6 times 1010atoms/s when operated in pulsed mode and a continuous beam flux of 2 times 108atoms/s. Our theoretical simulation reveals that the MOT inhomogeneous magnetic field and the varying Doppler shift along the atomic beam propagation play an important role in determining the longitudinal velocity of the Cs atomic beam. With the cold Cs beam thus formed and a compact Ramsey cavity of 13 cm in length, we have estimated a short-term, shot-noise limited Allan standard deviation of 2.7 times 10-13pi-frac12(pi is the averaging time) for the atomic master oscillator under development

Joint Conference of the European Frequency and Time Forum and IEEE International Frequency Control Symposium (EFTF/IFCS)Jan 18, 20062 citations

Compact CW cold beam cesium atomic clock

Walter F. Buell, Bernardo Jaduszliwer

We present a novel cesium beam physics package, which uses optical techniques to combine the high signal-to-noise ratios achievable by optical pumping and beam brightening with the narrow linewidth allowed by a slow atomic beam. Our design can be realized in a compact, robust package suitable for space applications. Our approach differs from other laser-cooled clocks in that we use a cold-atom source that provides a continuous beam. We estimate the shot noise-limited stability that can be achieved with this physics package to be two to three orders of magnitude better than that of current compact cesium beam atomic clocks.

Joint Conference of the European Frequency and Time Forum and IEEE International Frequency Control Symposium (EFTF/IFCS)Jan 22, 20034 citations

MOT-based continuous cold Cs-beam atomic clock

Haijin Wang, Gebriel H. Iyanu

In this paper we report our design and experimental results towards demonstration of a magneto optical trap (MOT)-based cold Cs-beam atomic clock. We generated a continuous cold Cs beam from a Cs MOT by perturbing the MOT potential and measured the longitudinal velocity of the Cs beam to be 7 m/s. In order to separate the atomic beam from the MOT laser beam, we used a one-dimensional optical molasses to deflect the Cs beam through an angle of 30° before the atomic beam enters the microwave cavity. Our Cs beam has an instantaneous atomic flux of 3.6 × 1010atoms/s when operated in pulsed mode and a continuous flux of 2 × 108atoms/s. Under current experimental conditions, the observed cold Cs atomic beam parameters infer a short-term, shot-noise limited Allan standard deviation of 2.7 × 10-13τ-1/2(τ is the averaging time) for the cold Cs beam clock under development.

Joint Conference of the European Frequency and Time Forum and IEEE International Frequency Control Symposium (EFTF/IFCS)Jun 1, 20105 citations

Laser-pumped and laser-cooled atomic clocks for space applications

Walter F. Buell

Highly stable atomic frequency standards are of increasing importance for a variety of space applications, ranging from communication to navigation and time transfer to tests of fundamental science. We present a discussion of the improvements possible with laser pumping of vapor cell clocks, including applying coherent population trapping (CPT) techniques. We also present our progress toward a cold atom clock based on magneto-optically trapped atoms for space applications.

Laser and Particle BeamsDec 1, 19989 citations

Development of a MOT-based continuous cold Cs-beam atomic clock

H. Wang, Walter F. Buell

Summary form only given. We discuss our compact clock physics package and report the realization of a continuous, cold Cs atomic beam from a vapor-cell magneto-optical trap (MOT) of Cs atoms. Briefly, we generate the cold Cs beam by perturbing the trap potentials with a small opaque disk inserted in one of the MOT beams. Along the narrow dark column thus formed, Cs atoms are continuously accelerated out of the trap volume to form a Cs beam while the MOT remains in functioning of capturing and cooling Cs atoms from the Cs vapor. The fluorescence image of the Cs trap and the continuous Cs atomic beam are shown. Our MOT captures and confines 8 /spl times/ 10/sup 7/ Cs atoms at a loading rate of 2 /spl times/ 10/sup 8/ atoms/s and cools the atoms to a thermal temperature of 300 /spl mu/K. The longitudinal velocity of the cold Cs beam is measured by a time of flight (TOF) method. A single-shot laser-induced fluorescence signal recorded at a distance of 18 cm downstream from the MOT is shown. Under the nominal experimental conditions, the TOF measurement determines that our cold Cs atomic beam travels at 7 m/s and has a velocity spread of 0.9 m/s. With the cold Cs beam thus formed and a compact Ramsey cavity of 20 cm in length, we have estimated a short-term Allan deviation of 1.8 /spl times/ 10/sup -13/ /spl tau//sup -1/2/ (T is the averaging time) for the atomic clock under development.

Quantum Electronics and Laser Science ConferenceJun 25, 20031 citation