Experimental demonstration of intermodulation effects in a continuous cesium fountain microwave frequency standard

International audienceThe short-term stability of passive atomic frequency standards, particularly ones operated sequentially, is often limited by local oscillator noise via intermodulation effects. This article describes an experimental demonstration of the intermodulation effect on the frequency stability of a continuous atomic fountain standard usually imperceptible under normal operating conditions. To make the effect observable, we increase the phase instability of the microwave field interrogating the clock transition.We measure the frequency stability of the locked, commercial local oscillator, for both square-wave phase modulation and squarewave frequency modulation of the microwave field. The observed degradation of the stability depends on the modulation frequency in a way that agrees with our earlier theoretical predictions. Most significantly, no degradation is observed when the modulation frequency is made equal to the Ramsey linewidth. When no extra phase noise is added, the frequency instability, currently 2.0x10-13 at 1 s, is limited only by atomic shot-noise. This shows the potential to reduce it via the use of a higher atomic flux

Design Details of FOCS-2, an Improved Continuous Cesium Fountain Frequency Standard

International audienceWe report on the design, construction and current status of FOCS-2, the second continuous fountain microwave cesium frequency standard after FOCS-1. Both incorporate velocity-selective light traps driven by an electrostatic motor. FOCS-2 will take fuller advantage of the continuous fountain approach to gain in shot-noise-limited stability without loss of accuracy via the use of a higher flux. This is obtained via the implementation of a novel slow-atom pre-source and better collimation of the atomic beam. A detailed description of the apparatus is provided and compared with FOCS-1 to highlight improvements. In addition, we present results from related experiments on collimation in a 2D optical lattice. The goals for this new standard are a short-term stability of < 4x10-14 $\tau$-1/2 and a relative frequency uncertainty of < 1 x 10-15

Proposal for high-precision Atomic Parity Violation measurements using amplification of the asymmetry by stimulated emission in a transverse E and B field pump-probe experiment

Amplification by stimulated emission of radiation provides an intriguing means for increasing the sensitivity of Atomic Parity Violation (APV) measurements in a pump-probe configuration well adapted to the 6S-7S cesium transition. It takes advantage of the large number of atoms excited along the path of the pump beam. In the longitudinal E-field configuration currently exploited in an ongoing APV measurement, this number is limited only by the total voltage sustainable by the Cs vapor. In order to overcome this limit, we consider, both theoretically and experimentally, the possibility of performing the measurements in a transverse E-field configuration requiring a much lower voltage. We discuss the necessarily different nature of the observable and the magnetoelectric optical effects entering into play. They condition modifications of the experimental configuration with, in particular, the application of a transverse magnetic field. We suggest the possibility of rotating the transverse direction of the fields so as to suppress systematic effects. With a long interaction length, a precision reaching 0.1 percent in a quantum noise limited measurement can be expected, now limited only by the necessity of operating below the threshold of spontaneous superradiant emission of the excited medium. If we approached this limit, however, we could greatly amplify the asymmetry using triggered superradiance.Comment: Articl

Evaluation of Doppler Shifts to Improve the Accuracy of Primary Atomic Fountain Clocks

We demonstrate agreement between measurements and ab initio calculations of the frequency shifts caused by distributed cavity phase variations in the microwave cavity of a primary atomic fountain clock. Experimental verification of the finite element models of the cavities gives the first quantitative evaluation of this leading uncertainty and allows it to be reduced to delta nu / nu = 8.4\times10^-17. Applying these experimental techniques to clocks with improved microwave cavities will yield negligible distributed cavity phase uncertainties, less than \pm1\times10^-17.Comment: To appear in PR

Contributing to the International Atomic Time Using an Atomic Rb Fountain Clock

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Contributing to the International Atomic Time Using an Atomic Rb Fountain Clock

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Searching for a massive scalar dark matter using six years of clock data from SYRTE

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Searching for scalar Dark Matter using six years of LNE-SYRTE fountain clock comparison data

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Searching for a massive scalar dark matter using six years of clock data from SYRTE

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Advanced Timekeeping With Atomic Fountains

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