30 research outputs found
Proof-of-principle demonstration of vertical gravity gradient measurement using a single proof mass double-loop atom interferometer
We demonstrate a proof-of-principle of direct Earth gravity gradient
measurement with an atom interferometer-based gravity gradiomter using a single
proof mass of cold 87 rubidium atoms. The atomic gradiometer is implemented in
the so-called double-loop configuration, hence providing a direct gravity
gradient dependent phase shift insensitive do DC acceleration and constant
rotation rate. The atom interferometer (AI) can be either operated as a
gravimeter or a gradiomter by simply adding an extra Raman -pulse. We
demonstrate gravity gradient measurements first using a vibration isolation
platform and second without seismic isolation using the correlation between the
AI signal and the vibration signal measured by an auxilliary classical
accelerometer. The simplicity of the experimental setup (a single atomic source
and unique detection) and the immunity of the AI to rotation-induced contrast
loss, make it a good candidate for onboard gravity gradient measurements.Comment: 11 pages, 7 figure
New concepts of inertial measurements with multi-species atom interferometry
In the field of cold atom inertial sensors, we present and analyze innovative
configurations for improving their measurement range and sensitivity,
especially attracting for onboard applications. These configurations rely on
multi-species atom interferometry, involving the simultaneous manipulation of
different atomic species in a unique instrument to deduce inertial
measurements. Using a dual-species atom accelerometer manipulating
simultaneously both isotopes of rubidium, we report a preliminary experimental
realization of original concepts involving the implementation of two atom
interferometers first with different interrogation times and secondly in phase
quadrature. These results open the door to a new generation of atomic sensors
relying on high performance multi-species atom interferometric measurements
Local gravity measurement with the combination of atom interferometry and Bloch oscillations
We present a local measurement of gravity combining Bloch oscillations and
atom interferometry. With a falling distance of 0.8 mm, we achieve a
sensitivity of 2x10-7 g with an integration time of 300 s. No bias associated
with the Bloch oscillations has been measured. A contrast decay with Bloch
oscillations has been observed and attributed to the spatial quality of the
laser beams. A simple experimental configuration has been adopted where a
single retro-reflected laser beam is performing atoms launch, stimulated Raman
transitions and Bloch oscillations. The combination of Bloch oscillations and
atom interferometry can thus be realized with an apparatus no more complex than
a standard atomic gravimeter
Zero-velocity atom interferometry using a retroreflected frequency chirped laser
International audienceAtom interferometry using stimulated Raman transitions in a retroreflected configuration is the first choice in high-precision measurements because it provides low phase noise, a high-quality Raman wave front, and a simple experimental setup. However, it cannot be used for atoms at zero velocity because two pairs of Raman lasers are simultaneously resonant. Here we report a method which allows this degeneracy to be lifted by using a frequency chirp on the Raman lasers. Using this technique, we realize a Mach-Zehnder atom interferometer hybridized with a force balanced accelerometer which provides horizontal acceleration measurements with a short-term sensitivity of 3.2×10−5ms−2/Hz. This technique could be used for multiaxis inertial sensors, tiltmeters, or atom interferometry in a microgravity environment
Absolute airborne gravimetry with a cold atom sensor
Measuring gravity from an aircraft is essential in geodesy, geophysics and exploration. Today, only relative sensors are available for airborne gravimetry. This is a major drawback because of the calibration and drift estimation procedures which lead to important operational constraints and measurement errors. Here, we report an absolute airborne gravimeter based on atom interferometry. This instrument has been first tested on a motion simulator leading to gravity measurements noise of 0.3 mGal for 75 s filtering time constant. Then, we realized an airborne campaign across Iceland in April 2017. From a repeated line and crossing points, we obtain gravity measurements with an estimated error between 1.7 and 3.9 mGal. The airborne measurements have also been compared to upward continued ground gravity data and show differences with a standard deviation ranging from 3.3 to 6.2 mGal and a mean value ranging from-0.7 mGal to-1.9 mGal
Navigation à l'aide d'un gravimètre atomique
International audienceCold atom interferometer is a promising technology to obtain a highly sensitive and accurate absolute gravimeter. With the help of an anomalies gravity map, local measurements of gravity allow a terrain-based navigation. This paper follows the one we published in Fusion 2017. Based on an atomic gravimeter we present a method to map the gravity anomaly. We propose a modification of the Laplace-based particle filter so as to make it more robust. Some simulation results demonstrate a better robustness of the proposed filter.L'interférométrie à atomes froids est une technologie prometteuse pour obtenir un gravimètre absolu de grande sensibilité et précision. A partir d'une carte d'anomalies gravimétriques, la mesure locale de la gravité permet une navigation par corrélation de terrain. Ce papier fait suite à celui publié au congrès Fusion 2017. Nous présentons une méthode d'élaboration de cartes d’anomalies gravimétriques à partir du gravimètre atomique. Nous proposons une modification du filtre Particulaire de Laplace qui offre une meilleure robustesse. Des résultats de simulation montrent une meilleure robustesse de ce filtre
Phase shift in an atom interferometer induced by the additional laser lines of a Raman laser generated by modulation
The use of Raman laser generated by modulation for light-pulse atom
interferometer allows to have a laser system more compact and robust. However,
the additional laser frequencies generated can perturb the atom interferometer.
In this article, we present a precise calculation of the phase shift induced by
the additional laser frequencies. The model is validated by comparison with
experimental measurements on an atom gravimeter. The uncertainty of the phase
shift determination limits the accuracy of our compact gravimeter at 8.10^-8
m/s^2. We show that it is possible to reduce considerably this inaccuracy with
a better control of experimental parameters or with particular interferometer
configurations
I.C.E.: An Ultra-Cold Atom Source for Long-Baseline Interferometric Inertial Sensors in Reduced Gravity
The accuracy and precision of current atom-interferometric inertialsensors
rival state-of-the-art conventional devices using artifact-based test masses .
Atomic sensors are well suited for fundamental measurements of gravito-inertial
fields. The sensitivity required to test gravitational theories can be achieved
by extending the baseline of the interferometer. The I.C.E.
(Interf\'erom\'etrie Coh\'erente pour l'Espace) interferometer aims to achieve
long interrogation times in compact apparatus via reduced gravity. We have
tested a cold-atom source during airplane parabolic flights. We show that this
environment is compatible with free-fall interferometric measurements using up
to 4 second interrogation time. We present the next-generation apparatus using
degenerate gases for low release-velocity atomic sources in space-borne
experiments
Light-pulse atom interferometry in microgravity
We describe the operation of a light pulse interferometer using cold 87Rb
atoms in reduced gravity. Using a series of two Raman transitions induced by
light pulses, we have obtained Ramsey fringes in the low gravity environment
achieved during parabolic flights. With our compact apparatus, we have operated
in a regime which is not accessible on ground. In the much lower gravity
environment and lower vibration level of a satellite, our cold atom
interferometer could measure accelerations with a sensitivity orders of
magnitude better than the best ground based accelerometers and close to proven
spaced-based ones