arXiv subjects

Ferruccio Renzoni

Publications and source records attributed to Ferruccio Renzoni.

At least 19 recordsLinked to original sources

arXiv2021

Electromagnetic induction imaging with a scanning radio-frequency atomic magnetometer

We demonstrate electromagnetic induction imaging with an unshielded, portable radio-frequency atomic magnetometer scanning over the target object. This configuration satisfies standard requirements in typical applications, from security screening to medical imaging. The ability to scan the magnetometer over the object relies on the miniaturization of the sensor head and on the active compensation of the ambient magnetic field. Additionally, a procedure is implemented to extract high-quality images from the recorded spatial dependent magnetic resonance. The procedure is shown to be effective in suppressing the detrimental effects of the spatial variation of the magnetic environment.

physics.atom-ph↗

arXiv2020

Sub-Sm$^{-1}$ electromagnetic induction imaging with an unshielded atomic magnetometer

Progress in electromagnetic induction imaging with atomic magnetometers has brought its domain to the edge of the regime useful for biomedical imaging. However, a demonstration of imaging below the required 1 Sm$^{-1}$ level is still missing. In this Letter, we use an $^{87}$Rb radio-frequency atomic magnetometer operating near room temperature in an unshielded environment to image calibrated solutions mimicking the electric conductivity of live tissues. By combining the recently introduced near-resonant imaging technique with a dual radio-frequency coil excitation scheme, we image 5 mL of solutions down to 0.9 Sm$^{-1}$. We measure a signal-to-noise ratio of 2.7 at 2 MHz for 0.9 Sm$^{-1}$, increased up to 7.2 with offline averaging. Our work is an improvement of 50 times on previous imaging results, and demonstrates the sensitivity and stability in unshielded environments required for imaging biological tissues, in particular for the human heart.

physics.ins-det↗

arXiv2019

Electromagnetic induction imaging with atomic magnetometers: unlocking the low-conductivity regime

Electromagnetic induction imaging with atomic magnetometers has disclosed unprecedented domains for imaging, from security screening to material characterization. However, applications to low-conductivity specimens -- most notably for biomedical imaging -- require sensitivity, stability, and tunability only speculated thus far. Here, we demonstrate contactless and non-invasive imaging down to 50 S/m using a 50 fT/Hz$^{-1/2}$ $^{87}$Rb radio-frequency atomic magnetometer operating in an unshielded environment and near room temperature. Two-dimensional images of test objects are obtained with a near-resonant imaging approach, which reduces the phase noise by a factor 172, with projected sensitivity of 1 S/m. Our results, an improvement of more than three orders of magnitude on previous imaging demonstrations, push electromagnetic imaging with atomic magnetometers to regions of interest for semiconductors, insulators, and biological tissues.

physics.atom-ph↗

arXiv2019

A Cold Atom Radio-Frequency Magnetometer

We propose and demonstrate a radio-frequency atomic magnetometer with sub-Doppler laser cooled rubidium-87. With a simple and compact design, our system demonstrates a sensitivity of $330~pT/\sqrt{Hz}$ in an unshielded environment, thus matching or surpassing previously reported cold atoms designs. By merging the multiple uses and robustness of radio-frequency atomic magnetometers with the detailed control of laser cooling, our cold atom radio-frequency magnetometer has the potential to move applications of atomic magnetometry to high spatial resolution. Direct impact in metrology for applied sciences, materials characterization, and nanotechnology can be anticipated.

physics.atom-ph↗

arXiv2018

Avoided crossing and sub-Fourier sensitivity in driven quantum systems

The response of a linear system to an external perturbation is governed by the Fourier limit, with the inverse of the interaction time constituting a lower limit for the system bandwidth. This does not hold for nonlinear systems, which can thus exhibit sub-Fourier behavior. The present work identifies a mechanism for sub-Fourier sensitivity in driven quantum systems, which relies on avoided crossing between Floquet states. Features up to three orders of magnitude finer than the Fourier limit are presented.

cond-mat.stat-mech↗

arXiv2018

A Facility for Production and Laser Cooling of Cesium Isotopes and Isomers

We report on the design, installation, and test of an experimental facility for the production of ultra-cold atomic isotopes and isomers of cesium. The setup covers a broad span of mass numbers and nuclear isomers, allowing one to directly compare chains of isotopes and isotope/isomer pairs. Cesium nuclei are produced by fission or fusion-evaporation reactions using primary proton beams from a 130 MeV cyclotron impinging upon a suitable target. The species of interest is ejected from the target in ionic form, electrostatically accelerated, mass separated, and routed to a science chamber. Here, ions are neutralized by implantation in a thin foil, and extracted by thermal diffusion. A neutral vapor at room temperature is thus formed and trapped in a magneto-optical trap. Real-time fluorescence imaging and destructive absorption imaging provide information on the number of trapped atoms, their density, and their temperature. Tests with a dedicated beam of $^{133}$Cs$^{+}$ ions at 30 keV energy confirm neutralization, evaporation, and laser cooling to 150 $μ$K, with an average atomic density of 10$^{10}$ cm$^{-3}$. Availability of cold and dense atomic samples of Cs isotopes and isomers opens new avenues for high-precision measurements of isotopic and isomeric shifts thereby gaining deeper insight into the nuclear structure, as well as for sensitive measurements of isotopes' concentration ratios in trace quantities. The facility also constitutes the core for future experiments of many-body physics with nuclear isomers.

physics.ins-det↗

arXiv2018

Sub-picotesla widely tunable atomic magnetometer operating at room-temperature in unshielded environments

We report on a single-channel rubidium radio-frequency atomic magnetometer operating in un-shielded environments and near room temperature with a measured sensitivity of 130 fT/\sqrt{Hz}. We demonstrate consistent, narrow-bandwidth operation across the kHz - MHz band, corresponding to three orders of magnitude of magnetic field amplitude. A compensation coil system controlled by a feedback loop actively and automatically stabilizes the magnetic field around the sensor. We measure a reduction of the 50 Hz noise contribution by an order of magnitude. The small effective sensor volume, 57 mm^3, increases the spatial resolution of the measurements. Low temperature operation, without any magnetic shielding, coupled with the broad tunability, and low beam power, dramatically extends the range of potential field applications for our device.

physics.atom-ph↗

arXiv2018

Non-destructive structural imaging of steelwork with atomic magnetometers

We demonstrate the imaging of ferromagnetic carbon steel samples and we detect the thinning of their profile with a sensitivity of 0.1 mm using a Cs radio-frequency atomic magnetometer. Images are obtained at room temperature, in magnetically unscreened environments. By using a dedicated arrangement of the setup and active compensation of background fields, the magnetic disturbance created by the samples' magnetization is compensated. Proof-of-concept demonstrations of non-destructive structural evaluation in the presence of concealing conductive barriers are also provided. The relevant impact for steelwork inspection and health and usage monitoring without disruption of operation is envisaged, with direct benefit for industry, from welding in construction to pipeline inspection and corrosion under insulation in the energy sector.

physics.ins-det↗

arXiv2018

Asymptotic theory of quasiperiodically driven quantum systems

The theoretical treatment of quasi-periodically driven quantum systems is complicated by the inapplicability of the Floquet theorem, which requires strict periodicity. In this work we consider a quantum system driven by a bi-harmonic driving and examine its asymptotic long-time limit, the limit in which features distinguishing systems with periodic and quasi-periodic driving occur. Also, in the classical case this limit is known to exhibit universal scaling, independent of the system details, with the system's reponse under quasi-periodic driving being described in terms of nearby periodically driven system results. We introduce a theoretical framework appropriate for the treatment of the quasi-periodically driven quantum system in the long-time limit, and derive an expression, based on Floquet states for a periodically driven system approximating the different steps of the time evolution, for the asymptotic scaling of relevant quantities for the system at hand. These expressions are tested numerically, finding excellent agreement for the finite-time average velocity in a prototypical quantum ratchet consisting of a space-symmetric potential and a time-asymmetric oscillating force.

cond-mat.stat-mech↗

arXiv2018

Active Underwater Detection with an Array of Atomic Magnetometers

We report on a 2x2 array of radio-frequency atomic magnetometers in magnetic induction tomography configuration. Active detection, localization, and real-time tracking of conductive, non-magnetic targets are demonstrated in air and saline water. Penetration in different media and detection are achieved thanks to the sensitivity and tunability of the sensors, and to the active nature of magnetic induction probing. We obtained a 100% success rate for automatic detection and 93% success rate for automatic localization in air and water, up to 190 mm away from the sensors' plane (100 mm underwater). We anticipate magnetic induction tomography with arrays of atomic magnetometers finding applications in civil engineering and maintenance, oil&gas industry, geological surveys, marine science, archeology, search and rescue, and security and surveillance.

physics.ins-det↗

arXiv2018

Machine learning based localization and classification with atomic magnetometers

We demonstrate identification of position, material, orientation and shape of objects imaged by an $^{85}$Rb atomic magnetometer performing electromagnetic induction imaging supported by machine learning. Machine learning maximizes the information extracted from the images created by the magnetometer, demonstrating the use of hidden data. Localization 2.6 times better than the spatial resolution of the imaging system and successful classification up to 97$\%$ are obtained. This circumvents the need of solving the inverse problem, and demonstrates the extension of machine learning to diffusive systems such as low-frequency electrodynamics in media. Automated collection of task-relevant information from quantum-based electromagnetic imaging will have a relevant impact from biomedicine to security.

physics.atom-ph↗

arXiv2017

Remote detection of rotating machinery with a portable atomic magnetometer

We demonstrate remote detection of rotating machinery, using an atomic magnetometer at room temperature and in an unshielded environment. The system relies on the coupling of the AC magnetic signature of the target with the spin-polarized, precessing atomic vapor of a radio-frequency optical atomic magnetometer. The AC magnetic signatures of rotating equipment or electric motors appear as sidebands in the power spectrum of the atomic sensor, which can be tuned to avoid noisy bands that would otherwise hamper detection. A portable apparatus is implemented and experimentally tested. Proof-of-concept investigations are performed with test targets mimicking possible applications, and the operational conditions for optimum detection are determined. Our instrument provides comparable or better performance than a commercial fluxgate and allows detection of rotating machinery behind a wall. These results demonstrate the potential for ultrasensitive devices for remote industrial and usage monitoring, security, and surveillance.

physics.ins-det↗

arXiv2016

Compact setup for the production of $^{87}$Rb $|F = 2, m_F = +2\rangle$ Bose-Einstein condensates in a hybrid trap

We present a compact experimental apparatus for Bose-Einstein condensation of $^{87}$Rb in the $|F = 2, m_F = +2\rangle$ state. A pre-cooled atomic beam of $^{87}$Rb is obtained by using an unbalanced magneto-optical trap, allowing controlled transfer of trapped atoms from the first vacuum chamber to the science chamber. Here, atoms are transferred to a hybrid trap, as produced by overlapping a magnetic quadrupole trap with a far-detuned optical trap with crossed beam configuration, where forced radiofrequency evaporation is realized. The final evaporation leading to Bose-Einstein condensation is then performed by exponentially lowering the optical trap depth. Control and stabilization systems of the optical trap beams are discussed in detail. The setup reliably produces a pure condensate in the $|F = 2, m_F = +2\rangle$ state in 50 s, which include 33 s loading of the science magneto-optical trap and 17 s forced evaporation.

physics.atom-ph↗

arXiv2016

Electromagnetic Imaging with Atomic Magnetometers: A Novel Approach to Security and Surveillance

We describe our research programme on the use of atomic magnetometers to detect conductive objects via electromagnetic induction. The extreme sensitivity of atomic magnetometers at low frequencies, up to seven orders of magnitude higher than a coil-based system, permits deep penetration through different media and barriers, and in various operative environments. This eliminates the limitations usually associated with electromagnetic detection.

physics.atom-ph↗

arXiv2016

Optical atomic magnetometry for magnetic induction tomography of the heart

We report on the use of radio-frequency optical atomic magnetometers for magnetic induction tomography measurements. We demonstrate the imaging of dummy targets of varying conductivities placed in the proximity of the sensor, in an unshielded environment at room-temperature and without background subtraction. The images produced by the system accurately reproduce the characteristics of the actual objects. Furthermore, we perform finite element simulations in order to assess the potential for measuring low-conductivity biological tissues with our system. Our results demonstrate the feasibility of an instrument based on optical atomic magnetometers for magnetic induction tomography imaging of biological samples, in particular for mapping anomalous conductivity in the heart.

physics.atom-ph↗

arXiv2016

Electromagnetic induction imaging with a radio-frequency atomic magnetometer

We report on a compact, tunable, and scalable to large arrays imaging device, based on a radio-frequency optically pumped atomic magnetometer operating in magnetic induction tomography modality. Imaging of conductive objects is performed at room temperature, in an unshielded environment and without background subtraction. Conductivity maps of target objects exhibit not only excellent performance in terms of shape reconstruction but also demonstrate detection of sub-millimetric cracks and penetration of conductive barriers. The results presented here demonstrate the potential of a future generation of imaging instruments, which combine magnetic induction tomography and the unmatched performance of atomic magnetometers.

physics.atom-ph↗

arXiv2015

Universal asymptotic behavior in nonlinear systems driven by a two-frequency forcing

We examine the time-dependent behavior of a nonlinear system driven by a two-frequency forcing. By using a non-perturbative approach, we are able to derive an asymptotic expression, valid in the long-time limit, for the time average of the output variable which describes the response of the system. We identify several universal features of the asymptotic response of the system, which are independent of the details of the model. In particular, we determine an asymptotic expression for the width of the resonance observed by keeping one frequency fixed, and varying the other one. We show that this width is smaller than the usually assumed Fourier width by a factor determined by the two driving frequencies, and independent of the model system parameters. Additional general features can also be identified depending on the specific symmetry properties of the system. Our results find direct application in the study of sub-Fourier signal processing with nonlinear systems.

cond-mat.stat-mech↗

arXiv2014

Magnetic induction tomography using an all-optical $^{87}$Rb atomic magnetometer

We demonstrate Magnetic Induction Tomography (MIT) with an all-optical atomic magnetometer. Our instrument creates a conductivity map of conductive objects. Both shape and size of the imaged samples compare very well with the actual shape and size. Given the potential of all-optical atomic magnetometers for miniaturization and extreme sensitivity, the proof-of-principle presented here opens up promising avenues in the development of instrumentation for magnetic induction tomography.

physics.atom-ph↗