Commissariat &#xc0; L'&#xc9;nergie Atomique Et Aux &#xc9;nergies Alternatives

Commissariat a L'energie Atomique Et Aux Energies

Institut Polytechnique De Grenoble

Matthieu Le Prado

Jean-Michel Leger

Sophie Morales

Mathieu Baicry

Umberto Rossini

Agustin Palacios Laloy

Etienne Labyt

Francois Bertrand

Jaroslaw Rutkowski

Saifeddine Aloui

Elisabeth Delevoye

William Fourcault

Augustin Palacios Laloy

Christine Lefrou

Laure-Line Rouve

François Bertrand

Laurence Clerc

Marie-Constance Corsi

The invention relates to a method of localisation of vector magnetometers arranged in a network, comprising the following steps: The invention also includes a magnetic field measurement instrument that includes a network of vector magnetometers and is capable of implementing the localisation method. Application to the imagery of biomagnetic fields, for example in magnetocardiography or in magnetoencephalography.

Vector magnetometers network and associated positioning method

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

The present description concerns a support helmet () for a medical imaging or treatment device, comprising a head cap () provided with a plurality of through openings (), each opening being adapted to receiving an elementary imaging or treatment module () assembled in the opening so as to slide along an axis substantially orthogonal to the head cap.

Support helmet for magnetoencephalography device

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 and isotropic measurement magnetometer. The magnetometer is all-optical in the sense that resonance between Zeeman sub-levels is induced by modulating the intensity or the frequency of the pump beam. Resonance is detected either using the pump beam itself or an unmodulated probe beam. The pump beam is linearly polarised and its polarisation direction is kept constant relative to the direction of the magnetic field to be measured, so that a measurement independent of the orientation of the field can be made.

All-optical and isotropic magnetometer

A magnetometer including a detector configured to measure the amplitude of an output signal at an oscillation frequency to deduce a component of a magnetic field to be measured starting from the value of a resonance gradient, including a main excitation source outputting a measurement signal oscillating at a main oscillation frequency and a secondary excitation source outputting a reference signal with known amplitude oscillating at a secondary oscillation frequency, the detector being configured to measure the output signal amplitude at a harmonic of the secondary oscillation frequency and to deduce said resonance gradient. The invention also applies to a network of magnetometers and a method of measuring a magnetic field without slaving and compensation of fluctuations of the resonance gradient.

Magnetometer without slaving and with compensation for fluctuations in the resonance gradient in weak field, magnetometers network and measurement method

A device for measuring an electric field in a conducting medium, including: two electrodes separated by a volume of an insulating material; a current measurement device; a voltage measurement device; and a switch enabling to alternately connect the current measurement device and the voltage measurement device between the electrodes.

Device for measuring an electric field in a conducting medium and method of calibrating such a device

A device for measuring an electric field in a conducting medium, including: an insulating enclosure; first, second, and third pairs of electrodes, the electrodes of a same pair being arranged on opposite external walls of the enclosure, and the electrodes of the first, second, and third pairs being centered on first, second, and third orthogonal axes; a first conductive coil; a first pair of switches enabling to alternately connect the first coil between the electrodes of the first, of the second, and of the third pair of electrodes; and a single magnetometer.

Device for measuring an electric field in a conducting medium

A device for measuring an electric field in a conducting medium comprises: two electrodes separated by a volume of an insulating medium; a device for measuring current coupled to said electrodes; and adjustment elements making it possible to vary a quantity on which the electrical conductivity of the field measuring device depends.

Calibration of a device for measuring an electric field in a conducting medium

The invention relates to a magnetic field measurement device, including a detector () configured to measure the amplitude of an output signal at a harmonic of an oscillation frequency of an excitation source, said amplitude being proportional to the magnetic field (B) to be measured, characterised in that it comprises an excitation circuit configured to associate with a principal excitation source (Bcos&#x3c9;t) oscillating at a principal oscillation frequency at least one secondary excitation source (Bcos(&#x3c9;/3t+&#x3a6;)) oscillating at a secondary oscillation frequency that is a fraction of the principal oscillation frequency, said fraction being odd if said harmonic is odd, and even if said harmonic is even.

Method and device for measuring a magnetic field by synchronised excitations

A magnetic resonance optical pumping isotropic magnetometer including a laser, a gas filled cell, a HF discharge circuit, RF magnetic field generating coils surrounding the cell, a first frequency regulating mechanism of an RF generator, a second polarization regulating mechanism of the laser beam, and a third regulating mechanism of the direction of the RF magnetic field. The direction of polarization of the laser beam at an inlet of the cell is orthogonally aligned with the magnetic field to be measured by virtue of a liquid crystal polarization rotator. The magnetometer is well-adapted to an integrated arrangement.

Isotropic and integrated optical pumping magnetometer

This method makes it possible to carry out the auto-calibration of the electromagnetic coils of an apparatus such as an atomic clock, a magnetometer or a gyroscope by injecting successive currents into the coils and measuring the magnetic fields induced in order to calculate the transfer coefficients (field/current) of each of the coils and the real angles that they form with very great precision.

Method of calibrating an atomic-functioning apparatus

This atomic clock comprises means for applying two mutually perpendicular oscillating magnetic fields (), governed by a control device () that makes them apply a static or nearly static magnetic field for compensating the ambient magnetic field in order to cancel sub-level energy variations of the matter, which disrupt the frequency of the returned photons and the reference provided by the clock. Traditional magnetic shielding may be omitted. Said device can also operate as a magnetometer.

Apparatus with ambient magnetic field correction

An atomic clock comprises helium 3 plasma as measurement medium, which is taken to the plasma state to exploit the metastable state of the material and the levels of the hyperfine structure, the lifetime of which is long and which thus enable an easier measurement than the excitations of gaseous atoms.

Atomic clock operating with helium 3

An atomic clock including a mechanism applying both a static magnetic field and two oscillating magnetic fields, all mutually perpendicular, in a magnetic shield. The amplitudes and frequencies of the oscillating magnetic fields may be chosen so as to annihilate energy variations between sub-transition levels of excited atoms and to reinforce a clock output signal, and with low sensitivity to defects in regulation.

Growing community of inventors

Saint-Marcellin, France

Matthieu Le Prado