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Antoine Weis

Publications and source records attributed to Antoine Weis.

11 recordsLinked to original sources
arXiv2024

Phase projection errors in rf-driven optically pumped magnetometers

We investigate the phase relationship between the oscillating (rf) excitation field and the detected (light) power modulation in scalar rf-driven optically pumped magnetometers (OPMs), in particular in the $M_x$ configuration. While the static dependence of the demodulation phase on the direction of the external static magnetic field vector can be largely mitigated by aligning the oscillating rf field along the light propagation direction, we demonstrate that a dynamic (transient) phase response arises under magnetic field tilts. We analytically solve the corresponding modified Bloch equation and confirm agreement with experimental observations obtained using an $M_x$ magnetometer incorporating a paraffin-coated Cs vapor cell. The results reveal fundamental limitations of $M_x$ magnetometers regarding response time and accuracy, in particular when employed with active electronic feedback, such as a phase-locked loop. Therefore, this work is highly relevant to important magnetometry applications where the direction of the quasi-static magnetic field of interest is unknown \textit{a priori} or varies over time, or in measurements requiring a large detection bandwidth. Such conditions are encountered in applications such as geomagnetic surveying, particularly with mobile platforms.

physics.atom-ph↗
arXiv2021

Search for topological defect dark matter with a global network of optical magnetometers

Ultralight bosons such as axion-like particles are viable candidates for dark matter. They can form stable, macroscopic field configurations in the form of topological defects that could concentrate the dark matter density into many distinct, compact spatial regions that are small compared to the galaxy but much larger than the Earth. Here, we report the results of a search for transient signals from axion-like particle domain walls with the Global Network of Optical Magnetometers for Exotic physics searches (GNOME). We search the data, consisting of correlated measurements from optical atomic magnetometers located in laboratories all over the world, for patterns of signals propagating through the network consistent with domain walls. The analysis of data from a continuous month-long operation of the GNOME finds no statistically significant signals, thus placing experimental constraints on such dark matter scenarios.

astro-ph.CO↗
arXiv2019

Analysis method for detecting topological defect dark matter with a global magnetometer network

The Global Network of Optical Magnetometers for Exotic physics searches (GNOME) is a network of time-synchronized, geographically separated, optically pumped atomic magnetometers that is being used to search for correlated transient signals heralding exotic physics. GNOME is sensitive to exotic couplings of atomic spins to certain classes of dark matter candidates, such as axions. This work presents a data analysis procedure to search for axion dark matter in the form of topological defects: specifically, walls separating domains of discrete degenerate vacua in the axion field. An axion domain wall crossing the Earth creates a distinctive signal pattern in the network that can be distinguished from random noise. The reliability of the analysis procedure and the sensitivity of the GNOME to domain-wall crossings is studied using simulated data.

astro-ph.IM↗
arXiv2017

Towards a mechanical MPI scanner based on atomic magnetometry

We report on our progress in the development of an atomic magnetometer (AM) based low-frequency magnetic particle imaging (MPI) scanner, expected to be free from Specific Absorption Rate (SAR) and Peripheral Nerve Stimulation (PNS) constraints. We address major challenges in coil and sensor design due to specific AM properties. Compared to our previous work we have changed the AM's mode of operation towards its implementation for detecting weak magnetic nanoparticles (MNP) response fields in the presence of nearby-located strong drive/selection fields. We demonstrate that a pump-probe AM scheme in a buffer gas filled alkali vapour cell can tolerate mT/m gradients while maintaining a sensitivity in the one-digit pT/Hz^(1/2) range over a bandwidth from DC to several kHz. We give a detailed description of the drive/selection coils' geometry and their hardware implementations that provides a field-free-line (FFL) operation, compatible with a best performance AM operation. We estimate the achievable field of view and spatial resolution of the scanner as well as its sensitivity, assuming mechanical scanning of a Resovist sample through the field-free point/line.

physics.ins-det↗
arXiv2016

MPS and ACS with an atomic magnetometer

We show that a single atomic magnetometer in a magnetically unshielded environment can be used to perform magnetic particle spectroscopy (MPS) and AC susceptometry (ACS) on liquid-suspended magnetic nanoparticles. We demonstrate methods allowing a simultaneous recording of M(H) and dM/dH(H) dependences of samples containing down to 1 $μ$g of iron. Our results pave the way towards an atomic magnetometer based MPI scanner.

physics.bio-ph↗
arXiv2014

Imaging magnetic scalar potentials by laser-induced fluorescence from bright and dark atoms

We present a spectroscopic method for mapping two-dimensional distributions of magnetic field strengths (magnetic scalar potential lines) using CCD recordings of the fluorescence patterns emitted by spin-polarized Cs vapor in a buffer gas exposed to inhomogeneous magnetic fields. The method relies on the position-selective destruction of spin polarization by magnetic resonances induced by multi-component oscillating magnetic fields, such that magnetic potential lines can directly be detected by the CCD camera. We also present a generic algebraic model allowing the calculation of the fluorescence patterns and find excellent agreement with the experimental observations for three distinct inhomogeneous field topologies. The spatial resolution obtained with these proof-of-principle experiments is on the order of 1 mm. A substantial increase of spatial and magnetic field resolution is expected by deploying the method in a magnetically shielded environment.

physics.atom-ph↗
arXiv2014

Measurement of the scalar third-order electric polarizability of the Cs ground state using CPT-spectroscopy in Ramsey geometry

The AC Stark shift induced by blackbody radiation is a major source of systematic uncertainty in present-day cesium microwave frequency standards. The shift is parametrized in terms of a third-order electric polarizability $α_0^{(3)}$ that can be inferred from the static electric field displacement of the clock transition resonance. In this paper, we report on an all-optical CPT pump-probe experiment measuring the differential polarizability $Δα_0^{(3)} = α_0^{(3)}(F{=}4) - α_0^{(3)}(F{=}3)$ on a thermal Cs atomic beam, from which we infer $ α_0^{(3)}(F{=}4) = 2.023(6)_{stat}(9)_{syst}~Hz/(kV/cm)^2$, which corresponds to a scalar Stark shift parameter $ k_{s} = -2.312(7)_{stat}(10)_{syst}~Hz/(kV/cm)^2$. The result agrees within two standard deviations with a recent measurement in an atomic fountain, and rules out another recent result obtained in a Cs vapor cell.

physics.atom-ph↗
arXiv2006

Experimental study of laser detected magnetic resonance based on atomic alignment

We present an experimental study of the spectra produced by optical/radio-frequency double resonance in which resonant linearly polarized laser light is used in the optical pumping and detection processes. We show that the experimental spectra obtained for cesium are in excellent agreement with a very general theoretical model developed in our group and we investigate the limitations of this model. Finally, the results are discussed in view of their use in the study of relaxation processes in aligned alkali vapors.

physics.atom-ph↗
arXiv2006

Theory of double resonance magnetometers based on atomic alignment

We present a theoretical study of the spectra produced by optical-radio-frequency double resonance devices, in which resonant linearly polarized light is used in the optical pumping and detection processes. We extend previous work by presenting algebraic results which are valid for atomic states with arbitrary angular momenta, arbitrary rf intensities, and arbitrary geometries. The only restriction made is the assumption of low light intensity. The results are discussed in view of their use in optical magnetometers.

physics.atom-ph↗
arXiv2004

Optimization and performance of an optical cardio-magnetometer

Cardiomagnetometry is a growing field of noninvasive medical diagnostics that has triggered a need for affordable high-sensitivity magnetometers. Optical pumping magnetometers are promising candidates satisfying that need since it was demonstrated that they can map the heart magnetic field. For the optimization of such devices theoretical limits on the performance as well as an experimental approach is presented. The promising result is a intrinsic magnetometric sensitivity of 63 fT / Hz^1/2 a measurement bandwidth of 140 Hz and a spatial resolution of 28 mm.

physics.med-ph↗