Self-adaptive loop for external disturbance reduction in differential measurement set-up

We present a method developed to actively compensate common-mode magnetic disturbances on a multi-sensor device devoted to differential measurements. The system uses a field-programmable-gated-array card, and operates in conjunction with a high sensitivity magnetometer: compensating the common-mode of magnetic disturbances results in a relevant reduction of the difference-mode noise. The digital nature of the compensation system allows for using a numerical approach aimed at automatically adapting the feedback loop filter response. A common mode disturbance attenuation exceeding 50 dB is achieved, resulting in a final improvement of the differential noise floor by a factor of 10 over the whole spectral interval of interest.Comment: 7 pages, 8 figures, 26 ref

Multichannel optical atomic magnetometer operating in unshielded environment

A multi-channel atomic magnetometer operating in an unshielded environment is described and characterised. The magnetometer is based on D1 optical pumping and D2 polarimetry of Cs vapour contained in gas-buffered cells. Several technical implementations are described and discussed in detail. The demonstrated sensitivity of the setup is 100fT/Hz^1/2 when operating in the difference mode.Comment: 9 pages, 5 figures, appearing in Appl.Phys.

Restoring Narrow Linewidth to a Gradient-Broadened Magnetic Resonance by Inhomogeneous Dressing

We study the possibility of counteracting the line-broadening of atomic magnetic resonances due to inhomogeneities of the static magnetic field by means of spatially dependent magnetic dressing, driven by an alternating field that oscillates much faster than the Larmor precession frequency. We demonstrate that an intrinsic resonance linewidth of 25~Hz that has been broadened up to hundreds Hz by a magnetic field gradient, can be recovered by the application of an appropriate inhomogeneous dressing field. The findings of our experiments may have immediate and important implications, because they facilitate the use of atomic magnetometers as robust, high sensitivity detectors in ultra-low-field NMR imaging.Comment: 9 pages, 7 figures, 33 refs. This is the unedited versio

Magneto-optic spectroscopy with linearly polarized modulated light: Theory and experiment

We investigate the polarization modulation between two linear orthogonal states of the laser beam that synchronously pumps time-dependent atomic alignment in caesium atoms exposed to a static magnetic field. Because of the atomic alignment symmetry two independent groups of resonances can be distinguished in the transmitted light: when modulation frequency matches either the Larmor frequency or its second harmonics, ωL and 2ωL, respectively. We report on our experiments, and discuss a model that perfectly reproduces the observed spectra. We have observed that the amplitudes and linewidths of resonances at ωL and 2ωL show magnetic-field direction dependence. This peculiar behavior makes our approach interesting for future application to atomic magnetometry, in view of a dead-zone free high-sensitivity magnetometer

Palermo città tutto porto

il testo presenta il progetto per il nuovo porto di Palermo con un'intervista al presidente dell'Autorità portuale: quest'ultima sta svolgendo rapidamente un'azione di rinnovamento sia delle strutture del porto sia degli spazi pubblici posti a margine della città

Bright and dark Autler-Townes states in the atomic Rydberg multilevel spectroscopy

We investigated the Autler-Townes (AT) splitting produced by microwave (mw) transitions between atomic Rydberg states explored by optical spectroscopy from the ground electronic state. The laser-atom Hamiltonian describing the double irradiation of such a multilevel system is analysed on the basis of the Morris-Shore transformation. The application of this transformation to the mw-dressed atomic system allows the identification of bright, dark, and spectator states associated with different configurations of atomic states and mw polarisations. We derived synthetic spectra that show the main features of Rydberg spectroscopy. Complex AT spectra are obtained in a regime of strong mw dressing, where a hybridisation of the Rydberg fine structure states is produced by the driving

Microtesla NMR J-coupling spectroscopy with an unshielded atomic magnetometer

We present experimental data and theoretical interpretation of NMR spectra of remotely magnetized samples, detected in an unshielded environment by means of a differential atomic magnetometer. The measurements are performed in an ultra-low-field at an intermediate regime, where the J-coupling and the Zeeman energies have comparable values and produce rather complex line sets, which are satisfactorily interpreted.Comment: 8 pages, 8 figs, appearing in JMR (2016

Stray Magnetic Field Compensation with a Scalar Atomic Magnetometer

We describe a system for the compensation of time-dependent stray magnetic fields using a dual channel scalar magnetometer based on non-linear Faraday rotation in synchronously optically pumped Cs vapour. We detail the active control strategy, with an emphasis on the electronic circuitry, based on a simple phase-locked-loop integrated circuit. The performance and limits of the system developed are tested and discussed. The system was applied to significantly improve the detection of free induction decay signals from protons of remotely magnetized water precessing in an ultra-low magnetic field.Comment: 8 pages, 6 figures, 31 refs, v2 (with minor improvements) appearing in Rev.Sc.Instr. June 201