Commissariat a L'energie Atomique Et Aux Energies Alternatives

Safran

Agustin Palacios Laloy

Serge Gidon

Matthieu Le Prado

Gwenael Le Gal

Jean-Christophe Riou

William Fourcault

Gaëtan Lieb

François Beato

Francois Beato

Rafael Garces Malonda

A method is provided for determining a coupling between magnetometers of an array of N magnetometers, for example with optical pumping, where each magnetometer includes a field cancellation system capable of being activated to operate the magnetometer in zero field. This method includes a first phase during which one of the N magnetometers is a measuring magnetometer whose field cancellation system is activated and the other N-1 magnetometers have their field cancellation system deactivated. This first phase includes generation by the magnetometers, of a plurality of reference magnetic fields of known amplitudes and distinct directions, the measurement, by the measuring magnetometer, of the ambient magnetic field on a plurality of measurement axes, and determination of coupling coefficients between the measuring magnetometer and each of the N magnetometers from said measurement and said known amplitudes.

Array of magnetometers operating in zero field and associated method for calibrating inter-magnetometer couplings

A device for measuring the mass flow rate, including a flow pipe; a first set of actuators which are arranged in a first plane including a first transverse cross section of the pipe and perpendicular to the fluid flow path, these being configured to move selectively in the first plane; a control circuit configured to control a movement of the first and second actuators so that the cross-sectional area for flow through the pipe in the first plane remains constant; a measurement sensor measuring a force or a stress in a direction perpendicular to the flow path, in the vicinity of the actuators of the first set along the flow path; a computation device configured to calculate the mass flow rate passing through the flow pipe as a function of the force or stress measured by the sensor.

Mass flow rate measurement device

A magneto-optical sensor for sensing a current flowing through a conductor includes a light source capable of providing a linearly-polarised optical beam, and a polarisation analyser configured to perform a differential measurement of two polarisation components of the linearly-polarised optical beam having travelled along an optical path arranged between the light source and the polarisation analyser. The optical path forms a closed trajectory around the conductor. The sensor comprises a cell containing an atomic gas arranged along the optical path.

Current sensor based on the Faraday effect in an atomic gas

A parametric resonance magnetometer is provided comprising a cell filled with an atomic gas; an optical pumping source arranged to emit a light beam in a direction of the cell; a polarization device configured so that by the effect of the light beam, the atomic gas simultaneously acquires a state aligned according to an alignment direction and a state oriented according to an orientation direction; a parametric resonance excitation source configured to generate a radiofrequency magnetic field in the cell; and a device to detect parametric resonances and to measure an absorption of the light beam by the atomic gas. The parametric resonance excitation source is configured so that the radiofrequency magnetic field consists of two components orthogonal to one another, each oscillating at its natural oscillation frequency. The two components include a component longitudinal to the orientation direction and a component longitudinal to the alignment direction.

Elliptical polarisation magnetometer with two radiofrequency field components for parametric resonance detection in absorption

A three-axis vector optically pumped magnetometer includes a cell filled with an atomic gas subjected to an ambient magnetic field the projection of which on three rectangular coordinate axes defines three components thereof, and a photodetector arranged to receive a probe beam that passed through the cell. The photodetector includes a plurality of measurement units arranged in a plane transverse to a direction of propagation of the probe beam, the measurement units each providing a photodetection signal. The magnetometer further comprises a processing unit configured to determine, for each measurement unit and from the photodetection signal, a measurement associated with the measurement unit of each of the three components of the ambient magnetic field; calculate at least one difference between the measurements, associated with different measurement units, of a component of the magnetic field; and deliver a gradiometric measurement signal including the at least one difference calculated.

Three-axis optically pumped magnetometer for gradiometric measurement

An optical pumping magnetometer made with linearly polarised light. The magnetometer comprises a cell filled with an atomic gas and a detector configured to output a signal carrying information about an alignment state of atoms of the atomic gas in the cell. The magnetometer also comprises a collimator arranged to collimate a light beam before it illuminates the cell and a mirror arranged to reflect the collimated light beam after it has passed through the cell such that the collimated light beam makes a multipass through the cell and illuminates the same region of the cell several times.

Magnetometer with optical pumping of a sensitive element with linearly polarised light and multiple-pass in the sensitive element

A magnetometer is provided which measures an ambient magnetic field having a frequency range of interest. An optical pumping source emits in the direction of a cell filled with an atomic gas a light beam linearly polarised in a polarisation direction. A parametric resonance excitation circuit induces in the cell a radiofrequency magnetic field having two components orthogonal to the polarisation direction and each oscillating at its own oscillation frequency. A parametric resonance detection circuit performs synchronous detection at an inter-harmonic of oscillation frequencies of an electrical signal outputted by a photodetector arranged to receive the light beam having passed through the cell. A zero-field servo-control circuit generates from the synchronous detection a compensation magnetic field opposite to a component of the ambient magnetic field oriented in the polarisation direction. The servo-control circuit is configured so the compensation magnetic field has an attenuation within the frequency range of interest.

Zero field servo-controlled magnetometer with low frequency filtering of the compensation field

An optical-pumping magnetometer intended to measure an ambient magnetic field. It comprises: an arrangement for illuminating a cell filled with an atomic gas with a pump beam and an AC Stark effect beam propagating collinearly or almost collinearly in the cell, the pump beam being tuned to an atomic transition line, modulated by a first modulator by way of a first modulation frequency (f) and polarised linearly in a polarisation direction that can be turned by a polarisation rotator, the AC Stark effect beam being offset from the atomic transition line, modulated by a second modulator by way of a second modulation frequency (f) and polarised circularly, a first control circuit acting on the polarisation rotator in order to keep a constant angle (&#x3b2;) between the polarisation direction of the pump beam and the ambient magnetic field, a second control circuit acting on the first and second modulator in order to keep the first and second modulation frequency at the Larmor frequency of the atomic gas or at one of the harmonics thereof.

Isotropic and all-optical scalar magnetometer for measuring an ambient magnetic field

A vector magnetometer comprising a cell filled with an atomic gas subjected to an ambient magnetic field, an optical pumping source capable of emitting a pump beam tuned to a pumping wavelength towards the cell and a parametric resonance detection device receiving a probe beam that has passed through the cell, the probe beam being identical to or different from the pump beam. The magnetometer also comprises a polarisation device configured so as to simultaneously or alternately confer linear polarisation and circular polarisation to the pump beam emitted towards the cell. And the detection device comprises an optical set up configured to separate, from the probe beam that has passed through the cell, optical signals carrying respectively information about an alignment state of the atoms from information about an orientation state of the atoms.

Vector magnetometer with elliptical polarisation

The invention relates to the controlling of the wavelength of a laser () on an atomic transition. It in particular proposes a method comprising the steps consisting in: According to the invention, the supplying of energy to the atoms of the atomic vapour is modulated to carry out the alternating of a first phase and of a second phase, the first phase supplying more energy than the second phase.

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Grenoble, France

Agustin Palacios Laloy