External Vibrational Noise Research Articles

Small-volume highly-sensitive all-optical gas sensor using non-resonant photoacoustic spectroscopy with dual silicon cantilever optical microphones

A small-volume highly-sensitive photoacoustic spectroscopy (PAS) methane detection system based on differential silicon cantilever optical microphones (SCOMs) is proposed and experimentally demonstrated. The system contains a compact non-resonant photoacoustic cell with a small volume of 1.2 mL and symmetrically-located dual SCOMs, as well as a distributed feedback laser at 1650.96 nm. The two identical SCOMs utilize the Fabry-Perot interferometric fiber-optic structure, with the differential Q-point demodulation algorithm to suppress the external vibration noise. Experimental results show that the SCOM has a high displacement sensitivity about 7.1 µm/Pa at 150 Hz and within 2.5 dB fluctuation between 5 Hz and 250 Hz. In the PAS gas sensing experiment, the normalized noise equivalent absorption coefficient of the PAS system is estimated to be 1.2 × 10−9 cm−1·W·Hz−1/2 and the minimum detection limit for methane is about 111.2 ppb with 1 s integration time. External disturbance is also applied to the dual SCOM system and results show excellent stability and noise resistance. The proposed PAS system exhibits superiorities of low gas consumption, high sensitivity and immunity to vibration and electromagnetic interference, which has an enormous potential in medicine, industry and environment.

A Novel $\phi$-OTDR System With a Phase Demodulation Module Based on Sagnac Balanced Interferometer

At present, a phase demodulation <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\phi$</tex-math></inline-formula> -OTDR-based on an unbalanced interferometer is widely used, but its demodulation module is easily affected by external vibration noise. To improve the reliability of a <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\phi$</tex-math></inline-formula> -OTDR, this paper proposed a phase demodulation method based on a balanced interferometer, which uses the Sagnac interferometer to obtain two Rayleigh scattering intensities and then recovers the phase information using an incoherent phase demodulation algorithm. The experimental results show that the proposed method can recover the disturbance signals on the sensing optical fiber well, even when the demodulation module is in serious external vibration noise including a vibration table shaking with different frequencies, opening and closing a door, and a car honking. These results indicate that the proposed method significantly reduces the influence of environmental vibration noise on the demodulation module, and offers a promising solution for the application of a <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\phi$</tex-math></inline-formula> -OTDR in a harsh environment.

Characterization of a double torsion pendulum used to detect spin-induced torque based on Beth's experiment.

We characterized a double torsion pendulum system, including measurements of the photon-spin-induced torque. Our experimental strategy was similar to that used in Beth's experiment, which was performed in 1936 to measure photon-spin-induced torque using forced oscillation caused by polarization modulation of light incident on a suspended object. Through simple passive isolation of the suspended object from external vibration noise, the achieved torque sensitivity was 2 × 10-17 N m in a measurement time of 104 s, which is close to the thermal noise limit and one order smaller than the minimum torque measured in Beth's experiment. The observed spin-induced torque exerted on the light-absorbing optics is consistent with the angular momentum transfer of ℏ per photon.

Direct detection of sub-GeV dark matter using a superfluid He4 target

A promising technology concept for sub-GeV dark matter detection is described, in which low-temperature microcalorimeters serve as the sensors and superfluid $^4$He serves as the target material. A superfluid helium target has several advantageous properties, including a light nuclear mass for better kinematic matching with light dark matter particles, copious production of scintillation light, extremely good intrinsic radiopurity, a high impedance to external vibration noise, and a unique mechanism for observing phonon-like modes via liberation of $^4$He atoms into a vacuum (`quantum evaporation'). In this concept, both scintillation photons and triplet excimers are detected using calorimeters, including calorimeters immersed in the superfluid. Kinetic excitations of the superfluid medium (rotons and phonons) are detected using quantum evaporation and subsequent atomic adsorption onto a microcalorimeter suspended in vacuum above the target helium. The energy of adsorption amplifies the phonon/roton signal before calorimetric sensing, producing a gain mechanism that can reduce the techonology's recoil energy threshold below the calorimeter energy threshold. We describe signal production and signal sensing probabilities, and estimate electron recoil discrimination. We then simulate radioactive backgrounds from gamma rays and neutrons. Dark matter - nucleon elastic scattering cross-section sensitivities are projected, demonstrating that even very small (sub-kg) target masses can probe wide regions of as-yet untested dark matter parameter space.

Modeling and experimental verification of a squeeze mode magnetorheological damper using a novel hysteresis model

The squeeze mode of the magnetorheological damper can be used to stabilize precision instruments (balances, optical devices, etc.) to eliminate interference from external vibrational noise, due to the small displacement and large damping offered by the magnetorheological fluid. The squeeze-strengthen effect observed experimentally in the magnetorheological fluid with squeeze mode can lead to the strain stiffening phenomenon, which is similar to that of the magnetorheological elastomer. In this study, a novel model is developed to characterize the dynamics of the squeeze mode magnetorheological damper considering the strain stiffening hysteresis behavior. An experimentally derived differential evolution algorithm is used to identify the model parameters. Simulation results show that the proposed model can accurately describe the dynamics of the squeeze mode magnetorheological damper including the strain stiffening phenomenon. Furthermore, the identified results obtained by the proposed model appear to be better than those obtained by the hyperbolic model.

A differential magnetoelectric heterostructure: Internal noise reduction and external noise cancellation

A differential heterostructure design which has a capability to reduce the internal noise and reject the external vibration noise for Metglas magnetostrictive foils/Pb(Zr, Ti)O3 piezofiber based-magnetoelectric (ME) laminated composite has been studied. The internal noise reduction is equivalent to that offered by sensor array stacks, and the external noise cancellation is based on a differential method (i.e., ME signal is in-phase but vibration noise is anti-phase). The ability of the structure to reduce the internal noise, and cancel the external vibration noise by a 10-fold attenuation factor, allows for practical applications of these sensors in real-world environments where contamination of magnetic signals by external vibrational noise increases the equivalent magnetic noise.

Vibrational noise rejection in multilayer structured magnetoelectric sensor

Giant ME effects in laminates have been investigated for highly sensitive low frequency magnetic field sensors. It has been shown in recent years that one of the biggest obstacles for magnetoelectric (ME) sensors achieving high sensitivity at low frequency is the vibrational noise introduced via piezoelectric effect.This work demonstrates a novel differential technique which has the ability to reject the vibrational noise in a multilayer structured ME sensor. It exhibits an excellent ME effect with a low equivalent magnetic noise floor of 32pT/Hz1/2 at 1Hz and 3pT/Hz1/2 at 10Hz, which was very close to the predicted value (27pT/Hz1/2 at 1Hz and 2.9pT/Hz1/2 at 10Hz). With respect to the ability to reject the vibrational noise, the external vibrational noise was incredibly attenuated by 91%. These unique properties of the multilayer structured sensor offer potential applications as a precise and sensitive magnetic field detector.

A review on equivalent magnetic noise of magnetoelectric laminate sensors

Since the turn of the millennium, multi-phase magnetoelectric (ME) composites have been subject to attention and development, and giant ME effects have been found in laminate composites of piezoelectric and magnetostrictive layers. From an application perspective, the practical usefulness of a magnetic sensor is determined not only by the output signal of the sensor in response to an incident magnetic field, but also by the equivalent magnetic noise generated in the absence of such an incident field. Here, a short review of developments in equivalent magnetic noise reduction for ME sensors is presented. This review focuses on internal noise, the analysis of the noise contributions and a summary of noise reduction strategies. Furthermore, external vibration noise is also discussed. The review concludes with an outlook on future possibilities and scientific challenges in the field of ME magnetic sensors.

Nonlinear Dynamics of an Ambient Noise Driven Array of Coupled Graphene Nanostructured Devices for Energy Harvesting

Nonlinearities have been shown to play an important role in increasing the extracted energy of energy harvesting devices at the macro and micro scales. Vibration-based energy harvesting on the nano scale has also received attention. In this paper, we characterize the nonlinear dynamical behavior of an array of three coupled strained nanostructured graphene for its potential use in energy harvesting applications. The array is formed by three compressed vibrating membrane graphene sheet subject to external vibrational noise excitation. We present the continuous time dynamical model of the system in the form of a double-well three degree of freedom system. Random vibrations are considered as the main ambient energy source for the system and its performances in terms of the probability density function, RMS or amplitude value of the position, FFT spectra and state plane trajectories are presented in the steady state non-equilibrium regime when the noise level is considered as a control parameter.

Differential-mode vibrational noise cancellation structure for Metglas/Pb(Zr,Ti)O3 fiber magnetoelectric laminates

A differential structure which has the ability to reject external vibrational noise for Metglas/Pb(Zr,Ti)O(3) (PZT) fiber-based magnetoelectric (ME) heterostructures has been studied. This type of ME structure functions better than conventional sensors as a magnetic sensor when used in an environment in which vibrational isolation is impractical. Sensors fabricated with this differential mode structure can attenuate external vibrational noise by about 10 to 20 dB at different frequencies, while simultaneously having a doubled ME voltage coefficient. Interestingly, in addition to offering a means of mitigating vibrational noise, this ME structure offers the potential to be a hybrid sensor, separating magnetic and acoustical signals.

Equivalent magnetic noise in magnetoelectric Metglas/Pb(Mg1/3Nb2/3)O3‐PbTiO3 laminate composites

AbstractWe have experimentally and theoretically investigated the equivalent magnetic noise in a magnetoelectric Metglas/ 0.7Pb(Mg1/3Nb2/3)O3‐0.3PbTiO3 laminate sensor unit by considering the constituent noise sources of dielectric loss (NDE) and DC leakage resistance (NR). In the low frequency range (f = 1 Hz), theory predicts that NR dominates the noise charge (1.6 times larger than NDE), with a 1 Hz noise of 9.1\;{\rm pt}/\sqrt {\rm Hz}. The experimental equivalent magnetic noise was 10.8\;{\rm pt}/\sqrt {\rm Hz}. This observed value is slightly higher than the predicted one, which might be due to an oversimplification of the theoretical model in terms of electrical charge amplifier and external vibration noise sources. (© 2011 WILEY‐VCH Verlag GmbH &amp; Co. KGaA, Weinheim)

Atom interferometer using a free oscillation of Bose-Einstein Condensate on an atom chip

We have demonstrated a novel atom interferometer which uses a free oscillation of 87Rb BEC atoms in a magnetic harmonic potential on an atom chip. This interferometer can effectively suppress the dephasing due to the trap potential by applying two Bragg laser pulses with an time interval T equal to the oscillation period of the axial mode of the magnetic trap. We observed a high contrast (∼30 %) interference fringe signal for T = 58 ms. When we increased the time interval T to 97 ms, an interference fringe was washed out by the random phase fluctuation. We attributed this phase fluctuation to the external vibrational noise from the floor.

Advances in Ripplon Surface Laser-Light Scattering Measurement for Highly Viscous Polymer-Solvent System

The surface properties of a polymer organic-solvent system was measured using a ripplon surface laser-light scattering (SLLS) technique. The power spectrum (PS) of a ripplon can be obtained by fast Fourier transform (FFT) analysis of the beat signal of scattered light using ripplon SLLS. However, the PS peak shifts to lower frequencies due to the low surface tension of typical organic solvents. This shift means that the PS can be easily affected by external vibrational noise. In addition, higher viscosities broaden the shape of the spectra so that the peak becomes less clear. It is therefore difficult to find a definite peak frequency and to determine its width at half maximum for analyzing surface properties. To address these issues, a new system for SLLS was developed and was used to demonstrate that the available viscosity measurement range can be extended to the higher values needed for organic-solvent systems.

Suppression of Dephasing due to a Trapping Potential and Atom-Atom Interactions in a Trapped-Condensate Interferometer

We propose and demonstrate a novel trapped-condensate interferometer using optical Bragg diffractions in a harmonic magnetic potential, which can realize a long coherence time with low dephasing. Dephasing of wave packets due to the magnetic potential is canceled by setting the interrogation time equal to the oscillation period of the harmonic potential. The harmonic potential also helps to suppress dephasing due to condensate atom-atom interactions. An interference signal with a fringe contrast of 30% is observed at an interrogation time of 58 ms. For a longer interrogation time about 100 ms, the spatial coherence of the condensate is still maintained with low dephasing, although the interference fringe is washed out by external vibrational noise.

Precision Measurements and Compensation for the Transverse Components of the Solenoids' Magnetic Field

A device developed at the Budker Institute of Nuclear Physics (BINP) to measure with a high precision the direction of the magnetic field lines in the vicinity of the solenoid axis is described. The transverse field components are automatically measured by a small (<15 cm3 in volume) compass-based sensor during its motion along the axis. The sensor's absolute sensitivity is ∼0.1–0.9 mG and is limited only by external vibration noise. The upper bound of this range (∼1 G) is governed by the current in the circuits producing the fields that compensate for the local misalignments of the field lines. The capabilities of the device are illustrated by the results from adjusting the solenoid fields in electron coolers recently built by the BINP. The procedures used to do this are described. The feasibility of obtaining the highest-quality field is shown. For one plant with a field intensity of ∼1 kG, the rms deviation of the field lines from the axis is <10−5 rad within a length of 3 m.