Magnetic shielding of the cold atom space clock PHARAO

Moric, Igor; Laurent, Philippe; Chatard, Philippe; Thomin, S.; Christophe, Vincent; Grosjean, Olivier

doi:10.1016/j.actaastro.2014.06.007

Cited by 22 publications

(12 citation statements)

References 9 publications

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“…A homogeneous bias magnetic field of order 1 mG is applied along the tube using solenoid coils surrounding the microwave cavity and preparation regions. Three layers of magnetic shields improve the magnetic field homogeneity and attenuates by 18 000 external fields [27]. As this passive isolation is not sufficient in space, an active compensation system with a magnetic probe located inside the outmost magnetic shield and a servo-loop driving a current in a long solenoid provides a further attenuation by a factor 15 [28].…”

Section: Cesium Tubementioning

confidence: 99%

The ACES/PHARAO space mission

Laurent

Massonnet

Cacciapuoti

et al. 2015

Comptes Rendus. Physique

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Section: Cesium Tubementioning

confidence: 99%

The ACES/PHARAO space mission

Laurent

Massonnet

Cacciapuoti

et al. 2015

Comptes Rendus. Physique

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“…Elle est basée sur une sonde magnétique placée à l'extérieur du second blindage et sur un solénoïde qui entoure ce même blindage. Avec un asservissement proportionnel intégral, le gain supplémentaire en atténuation s'élève à 9 ; une valeur limitée par la dépendance en position de l'hystérésis du blindage extérieur [25] : l'évolution du champ magnétique à la position de la sonde n'est pas identique à celle vue par les atomes. L'atténuation maximale obtenue avec les blindages du Modèle d'Ingénierie MI est de 12 000.…”

Section: La Stabilité Du Champ Magnétiqueunclassified

“…Il sera possible de corriger cette variation en mesurant périodiquement la fréquence de la transition entre sous-états m F = 1. Pour le modèle de vol l'atténuation mesurée des blindages est de 17 000 [25] et un nouveau concept de compensation active a été développé [26]. Une atténuation totale de 400 000 est attendue.…”

Section: La Stabilité Du Champ Magnétiqueunclassified

PHARAO : le premier étalon primaire de fréquence, à atomes froids, spatial

Laurent¹,

Abgrall²,

Moric³

et al. 2014

R. franç. métrol.

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CNES, LKB and SYRTE are developing a primary frequency standard, called PHARAO, which is specially designed for space applications. The clock signal is referenced on the frequency measurement of the hyperfine transition performed on a cloud of cold cesium atoms (∼1 μK). The transition is induced by an external field feeding a Ramsey cavity. In microgravity the interaction time inside the cavity can be adjusted over two orders of magnitude by changing the atomic velocity (5 cm•s −1-5 m•s −1) in order to study the ultimate performances of the clock. An engineering model has been assembled to validate the architecture of the clock. This model has been fully tested on ground for operation faults. Of course the clock performances are reduced by the effect of the gravity on the moving atoms. The main results are a frequency stability of 3.3 × 10 −13 t −1/2. The main systematic effects have been analyzed and their frequency uncertainties contribution is 1.6 × 10 −15. The clock has been compared with the primary frequency standard, the mobile fountain of SYRTE. The mean frequency shift is lower than 2 × 10 −15. The mechanical and thermal space qualifications have been carried out by testing a representative mechanical model of the clock and by using refined calculations. The design of the clock has been improved and now the flight model is being assembled. The PHARAO clock is a key instrument of the European ESA space mission called ACES. This mission is dedicated to perform space-time measurements in order to test some fundamental physics aspects.

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“…Regions of space that require precisely controlled magnetic field environments are essential for a wide range of experiments, devices, and applications. These include quantum sensing of gravity and gravity gradients for geophysical survey and mapping [1][2][3][4]; atomic magnetometry [5][6][7] for applications including material characterization [8] and magnetoencephalography [9,10]; noise reduction in fundamental physics experiments [11,12] such as timing using high-precision atomic clocks [13,14], measuring the electric dipole moment of fundamental systems [15][16][17][18], and testing Lorentz invariance by observing the limits of spin precession [19][20][21]. Typically, these systems are enclosed within high-permeability materials, such as mumetal, to shield magnetically sensitive components from undesired magnetic fields.…”

Section: Introductionmentioning

confidence: 99%

Optimal Inverse Design of Magnetic Field Profiles in a Magnetically Shielded Cylinder

et al. 2020

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Magnetic shields that use both active and passive components to enable the generation of a tailored lowfield environment are required for many applications in science, engineering, and medical imaging. Until now, accurate field nulling, or field generation, has only been possible over a small fraction of the overall volume of the shield. This is due to the interaction between the active field-generating components and the surrounding high-permeability passive shielding material. In this paper, we formulate the interaction between an arbitrary static current flow on a cylinder and an exterior closed high-permeability cylinder. We modify the Green's function for the magnetic vector potential and match boundary conditions on the shield's interior surface to calculate the total magnetic field generated by the system. We cast this formulation into an inverse optimization problem to design active-passive magnetic field shaping systems that accurately generate any physical static magnetic field in the interior of a closed cylindrical passive shield. We illustrate this method by designing hybrid systems that generate a range of magnetic field profiles to high accuracy over large interior volumes, and simulate them in real-world shields whose passive components have finite permeability, thickness, and axial entry holes. Our optimization procedure can be adapted to design active-passive magnetic field shaping systems that accurately generate any physical user-specified static magnetic field in the interior of a closed cylindrical shield of any length, enabling the development and miniaturization of systems that require accurate magnetic shielding and control.

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Magnetic shielding of the cold atom space clock PHARAO

Cited by 22 publications

References 9 publications

The ACES/PHARAO space mission

The ACES/PHARAO space mission

PHARAO : le premier étalon primaire de fréquence, à atomes froids, spatial

Optimal Inverse Design of Magnetic Field Profiles in a Magnetically Shielded Cylinder

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