Electric Field Measurements Research Articles

Photodetector array for measuring the spatial–temporal distribution characteristics of electric field in oil–pressboard insulation based on the Kerr electro‐optic effect

AbstractAccurate measurement and effective analysis of the space electric field and charge characteristics within the oil–pressboard insulation structure of converter transformer are essential for achieving precise insulation structure design. Presently, most electric field measurement methods relying on the Kerr electro‐optical effect are limited to single‐point measurements. Given the complexity of converter transformer insulation structures, including their large scale and the use of various materials, existing technologies and findings struggle to provide comprehensive electric field observations within the oil–pressboard region. After leveraging the Kerr electro‐optic effect, a high‐precision 32‐unit photodetector array has been developed to achieve regional measurements of spatial‐temporal electric field in oil–pressboard insulation. The array boasts a measurement spatial resolution of 1.4 mm2 and a sensitivity of 0.15 kV/mm, ensuring measurement accuracy exceeding 96.50%. Through practical measurements of the spatial electric field distribution within the oil–pressboard insulation under direct current voltage, the non‐uniform distribution of the electric field is effectively captured in oil. Notably, the maximum deviation in field strength at different positions within the transformer oil can reach 18.5%. Moreover, as the applied voltage increases, the unevenness coefficient of the field strength gradually rises, peaking at 1.19, which signifies a progressive expansion in the area affected by electric field distortion. By conducting tests to assess the dispersion of volume resistivity in samples from various positions within large sheets of pressboard, the variation in volume resistivity of materials is posited as one of the contributing factors to the non‐uniform distribution of electric field within the oil. The detailed accomplishments aim to provide essential technical and theoretical support for optimising insulation structure design of converter transformers.

Theoretical study on Stark effect of Rydberg atom in super low frequency electric field measurement

AbstractSuper low frequency electric field measurements are crucial in analysing electromagnetic compatibility, assessing equipment status, and other related fields. Rydberg atom‐based super low frequency electric field measurements are performed by observing the Stark shift in the spectrum of the Rydberg state. In a specific range of field strength (E < Eavoid, where Eavoid is the threshold to avoid crossing electric fields), the Rydberg atomic spectrum experiences a quadratic frequency shift in relation to the field strength, with the coefficient being determined by the atomic polarisability α. The authors establish a dynamic equation for the interaction between the external electric field and the atomic system, and present the Stark structure diagram of the Caesium Rydberg atom. The mathematical formulae for α and Eavoid in different Rydberg states are also obtained: α = A × (n*)6 + B × (n*)7 and Eavoid = C/(n*)5 + D/(n*)7, where A(B) = 2.2503 × 10−9(7.49,948 × 10−11) and C(D) = 1.68,868 × 108(2.45,991 × 109). The error of α and Eavoid compared with the experimental values does not exceed 8% and is even lower in the low Rydberg states. Accurately calculating the values of α and Eavoid is crucial in incorporating the Rydberg atom quantum coherence effect into super low frequency electric field measurements in new power systems.

Enhancements of electric field and afterglow of non-equilibrium plasma by Pb(ZrxTi1−x)O3 ferroelectric electrode

Manipulating surface charge, electric field, and plasma afterglow in a non-equilibrium plasma is critical to control plasma-surface interaction for plasma catalysis and manufacturing. Here, we show enhancements of surface charge, electric field during breakdown, and afterglow by ferroelectric barrier discharge. The results show that the ferroelectrics manifest spontaneous electric polarization to increase the surface charge by two orders of magnitude compared to discharge with an alumina barrier. Time-resolved in-situ electric field measurements reveal that the fast polarization of ferroelectrics enhances the electric field during the breakdown in streamer discharge and doubles the electric field compared to the dielectric barrier discharge. Moreover, due to the existence of surface charge, the ferroelectric electrode extends the afterglow time and makes discharge sustained longer when alternating the external electric field polarity. The present results show that ferroelectric barrier discharge offers a promising technique to tune plasma properties for efficient plasma catalysis and electrified manufacturing.

Design and testing of a high-precision generating voltmeter for metal-enclosed megavolt level DC voltage source.

An extremely stable megavolt (MV) level DC voltage source is the key foundation for many scientific instruments, and the need for accurate measurement and long-term real-time monitoring of its output voltage is increasingly urgent. The utilization of conventional resistive voltage dividers for measurements introduces leakage currents, resulting in considerable measurement errors. The non-contact generating voltmeter (GVM) sensor based on electric field measurement has a simple structure and a low cost, making it expected to be an effective solution. Currently, most research on GVM sensors focuses on the measurement of weak electric fields at kV/m levels with significant interference. In this paper, an improved high-precision non-contact GVM sensor was designed. A DC voltage test platform was built, and the effects of the sampling resistor and motor rotation speed on the measurement results were discussed. The relative combined uncertainty of the improved GVM sensor reached 0.042%, which satisfied the urgent need for MV level DC voltage source measurement. The improved GVM sensor can provide an effective reference for measuring the output voltage of a metal-enclosed MV level DC voltage source or the potential of a suspended electrode.

Measurement of inhomogeneous electric field based on electric field-induced second-harmonic generation

The electric field-induced second-harmonic generation (E-FISH) method can offer high spatiotemporal resolution in electric field measurement, but faces challenge in reconstructing the inhomogeneous electric field along the probing laser. This paper presents an inversion method to reconstruct the electric field profile by using E-FISH signals measured from multiple points along the probing laser. The relationship between the condition number of the inversion coefficient matrix and the parameters of E-FISH measurement system is clarified. The inversion method is validated through experimental investigations conducted in three different electrode configurations, namely the plate-to-plate gap, the rod-to-rod gap, and the rod-plate gap. With the inhomogeneity coefficient varies from 1 to 10.7, the maximum deviation between the measured electric field and the finite element simulation is less than 6%. This method does not rely on priori assumptions and electrode configurations, and exhibits good robustness in resisting the effect of measurement noise on the inversion accuracy.

Влияние рельефа на атмосферное электрическое поле

Measurements of the fair-weather electric field in mountainous areas are affected by the terrain, and therefore need additional calibration to be included in the global field picture. To do this, it is proposed to solve the three-dimensional electric current continuity problem of the atmosphere in the region between the Earth's surface and the ionosphere. As an example, the neighborhood of Klyuchevskaya Sopka is considered. With an increase in the height of the plateaus, the fair-weather electric current density above them increases, and the electric field strength decreases. A one-dimensional model of atmosphere conductivity is not applicable for terrain with steep slopes. A comparison of the daily-seasonal diagrams constructed according to the data of the Carnegie Cruise VII and according to the Tomsk Observatory showed the similarity of variations of the fair-weather electric field strength in such different places on the Earth. The field over the sea is about half as small as over low-lying land at the same time.

Influence of relief on the atmospheric electric field

Measurements of the fair-weather electric field in mountainous areas are affected by the terrain, and therefore need additional calibration to be included in the global field picture. To do this, it is proposed to solve the three-dimensional electric current continuity problem of the atmosphere in the region between the Earth's surface and the ionosphere. As an example, the neighborhood of Klyuchevskaya Sopka is considered. With an increase in the height of the plateaus, the fair-weather electric current density above them increases, and the electric field strength decreases. A one-dimensional model of atmosphere conductivity is not applicable for terrain with steep slopes. A comparison of the daily-seasonal diagrams constructed according to the data of the Carnegie Cruise VII and according to the Tomsk Observatory showed the similarity of variations of the fair-weather electric field strength in such different places on the Earth. The field over the sea is about half as small as over low-lying land at the same time.

Influence of Double-Pulse Electrodeposition Parameters on the Performance of Ag/AgCl Electrochemical Electrode for Marine Electric Field.

This paper describes a Ag/AgCl electrochemical electrode for marine electric field measurements, which was prepared by depositing silver chloride on a silver foil substrate using double-pulse electrodeposition. The impact of positive direction peak current density and deposition time on electrode performance in the preparation of Ag/AgCl electrodes through double-pulse electrodeposition was investigated. Scanning electron microscopy and voltammetry have been used to study the properties of the prepared electrodes. This work reveals the correlation between the electrochemical behavior of electrodes and the physical properties of their surfaces, especially specific surface area and porosity. The study verified the characteristics of Ag/AgCl marine electric field electrodes obtained with different pulse parameters by analyzing the potential stability and noise level of the electrode in salt water. The study's results have positive significance for improving the accuracy of marine electric field measurements.

Local oscillator port integrated resonator for Rydberg atom-based electric field measurement enhancement

Rydberg atom-based superheterodyne with additional local oscillator (LO) signal is a novel approach to detect electric field with high measured sensitivity. However, the LO signal is often supplied to the atomic vapor cell by free-space illumination, which lacks mobility and integration for practical applications. Here, we present a LO port integrated split-ring resonator for realizing high sensitivity-enhanced electric field measurements. The LO signal is sent directly to the resonator through a parallel-plate waveguide, which is shown to achieve a sensitivity enhancement of 32 dB. The integrated resonator has an electrical size of 0.088λ and the feed port S11 reaches −38.2 dB.

Enhanced evanescent field via integration of a graphene oxide/poly(methyl methacrylate) hybrid film on coreless D-shaped fibers.

This study presents the implementation of an evanescent field (EF)-based sensing platform employing a hybrid film composed of graphene oxide (GO) and poly(methyl methacrylate) (PMMA), integrated onto coreless D-shaped fibers (cDsFs). The operational framework of the hybrid film-coated cDsFs (GoP-cDsFs) was comprehensively elucidated through theoretical and experimental analyses. To establish a baseline for comparison, the performance of the cDsFs with the sole inclusion of the PMMA film was investigated. Our investigations underscore the substantive role of graphene oxide in augmenting the evanescent field, thereby generating a synergistic effect that contributes to the overall enhancement of the evanescent field in the device. Consequently, the fabricated GoP-cDsF sensor manifests an outstanding sensitivity of -4.936 nm/°C, rendering it particularly well-suited for applications demanding high-sensitivity temperature sensing. Moreover, the unique attributes of the GoP-cDsF position it as a promising candidate for the measurement of both magnetic and electric fields, presenting an effective strategy for multifunctional sensing applications.

Abstract B032: Designing arrays for the mouse head to facilitate in vivo studies of Tumor Treating Fields (TTFields) treatment of glioblastoma

Abstract Background: Tumor Treating Fields (TTFields) therapy is a noninvasive, anticancer treatment delivered by two pairs of arrays placed on the skin surrounding the tumor location. Based on efficacy and safety data from phase 3 global clinical studies, TTFields therapy is FDA-approved and CE marked for treatment of glioblastoma (GBM), the most common malignant brain tumor. In vivo studies of TTFields in GBM models, which are mostly based on mice, are complicated by the relatively small size of the mouse head and corresponding limited surface area to apply the arrays. This challenge has thus far limited in vivo research on TTFields treatment in GBM. Materials and Methods: To identify a method for efficient delivery of TTFields to the mouse brain, we examined the ability of different array layouts to accommodate the geometries of the mouse head while minimally impacting head movement, taking into account that it may not be feasible to place two pairs of arrays on the head. The properties of different adhesive tapes, specifically their ability to attach to the skin, was also investigated. Finally, the ability of array layouts to deliver therapeutic intensities to the desired region was validated using simulations and direct electric field measurements. Results: Assessments showed an optimal layout consisted of arrays such that one of the pair was on the mouse head, and the other on the mouse torso; and the arrays for placement on the head divided into two smaller disks, A thin, transparent adhesive tape was identified that allowed the arrays to be securely attached to the skin, but was easily removed without leaving residues. Validation studies using simulations demonstrated that the array layout met the minimum treatment requirements (field intensity ≥1 V/cm RMS; current ≥50 mA), and facilitated TTFields usage for ≥75% of each day. Conclusions: These data show that TTFields treatment can be effectively delivered to the heads of mice by utilizing carefully designed arrays. Our newly developed mouse head arrays are a flexible construct, that adheres strongly to the skin, and enables efficient electric field delivery to the mouse brain. These improvements in the delivery of TTFields treatment to mice will facilitate research of TTFields as a therapy for GBM. Citation Format: Sewar Zbidat, Roni Blatt, Mariell Sellevoll, Martin Gabay, Inbar Schlachet, Shay Cahal, Shiri Davidi, Itai Tzchori, Amal El-Mabhouh, Adi Haber, Moshe Giladi, Yoram Palti. Designing arrays for the mouse head to facilitate in vivo studies of Tumor Treating Fields (TTFields) treatment of glioblastoma [abstract]. In: Proceedings of the AACR Special Conference on Brain Cancer; 2023 Oct 19-22; Minneapolis, Minnesota. Philadelphia (PA): AACR; Cancer Res 2024;84(5 Suppl_1):Abstract nr B032.

Motion Error Mechanism Analysis and Simulation Verification of Ocean Electric Field Sensor

The electric field measurement based on Unmanned Underwater Vehicle (UUV) can monitor and evaluate real-time electric field of underwater targets in motion, which has the ability to adapt to harsh marine environments. However, electric field sensors generate new errors during underwater motion, and there is still absence of studies on the error theory and simulation. To address this, the error generation mechanism of Ag/AgCl electrodes induced by the flow field was analyzed in this paper. A coupled mathematical model of flow-chemical-electric multi-physical field was established for the first time, and finite element simulation analysis was carried out. The results show that the change value of electrode surface potential under the influence of flow rate is basically in agreement with the empirical formulae. R-squared value of the two fits reaches up to 0.968, and RMSE value is less than 0.003, confirming the robustness of the model and simulations. The multi-physical field coupling model and simulation method proposed in this paper can provide theoretical and methodological support for the design of electric field sensors and motion error correction.

Polarization properties of E-FISH signals and optimization of simultaneous measurement of electric field vectors

Electric field measurements based on the electric field induced second harmonic (E-FISH) method have been employed in a wide range of studies. Most studies typically measure two components of the electric field separately. Although there have been proposals for the simultaneous measurement of electric field vectors, the imbalance of the two corresponding E-FISH signals has limited its application. Furthermore, the relationship between the polarization of the E-FISH signal and the direction of external electric field remains unclear. In this paper, the general expressions for the polarization and power of both components of E-FISH signals are derived, assuming arbitrary probe beam polarization and external electric field direction. The theoretical results indicate that the polarization of E-FISH signals varies along the interaction length. The final signal’s polarization is elliptically polarized for arbitrary electric field distribution and is correlated with the polarization of the probe beam, which deviates from what is commonly assumed to be consistent with the external electric field. If the polarization of the probe beam is not parallel to the axes, the power of each signal component is determined by both components of the external electric field, which lays the foundation for the simultaneous measurement of electric field vectors. This theoretical prediction is subsequently validated by experimental results. Finally, the power maps suggest that the optimal polarization angle of the probe beam is 45° or 135° to achieve a balanced signal power when measuring an unknown electric field vector. Both components of the electric field can be simultaneously obtained according to the theoretical relationship.

Solar Cycle Variation of Radiated Electric Field and Ionospheric Reflection Height Over NWC Transmitter During 2005–2009: DEMETER Spacecraft Observations and Simulations

AbstractBesides the significant effects of a variety of naturally occurring magnetospheric waves on the electron dynamics in the magnetosphere, the important contribution of ground‐based very‐low‐frequency (VLF) transmitter waves also has been gradually discovered. The VLF transmitter's wave penetrating into the topside ionosphere is its energy source injected into the magnetosphere and has been extensively investigated. In the VLF wave trans‐ionospheric propagation, the main energy attenuation occurs in the lower ionosphere which is controlled by solar short‐wave radiation. However, the investigation on the variation of the VLF transmitters' energy in the topside ionosphere and ionospheric reflection height with solar activity is lacking. We use 4 years electric field measurements performed by DEMETER satellite and full‐wave simulations to address these concerns. The results show the electric field radiated from NWC was relatively similar from May 1 to July 31 in 2006, 2008, and 2009 in daytime and nighttime, stronger than that in 2005, because the solar activity was similar and extremely low in these years compared with that in 2005. The nighttime and daytime ionospheric reflection heights are also relatively similar in these 3 years, with about 6 km higher than that in 2005. The difference in the simulated electric field based on the electron density profile from the IRI‐2016 model between 2005 and 2009 is lower compared with the observation results. However, considering 6 km added in ionospheric reflection height in 2009, the simulation results are much more consistent with the observation results both in daytime and nighttime.

Critical Evaluation of Polarizable and Nonpolarizable Force Fields for Proteins Using Experimentally Derived Nitrile Electric Fields.

Molecular dynamics (MD) simulations are frequently carried out for proteins to investigate the role of electrostatics in their biological function. The choice of force field (FF) can significantly alter the MD results, as the simulated local electrostatic interactions lack benchmarking in the absence of appropriate experimental methods. We recently reported that the transition dipole moment (TDM) of the popular nitrile vibrational probe varies linearly with the environmental electric field, overcoming well-known hydrogen bonding (H-bonding) issues for the nitrile frequency and, thus, enabling the unambiguous measurement of electric fields in proteins (J. Am. Chem. Soc. 2022, 144 (17), 7562-7567). Herein, we utilize this new strategy to enable comparisons of experimental and simulated electric fields in protein environments. Specifically, previously determined TDM electric fields exerted onto nitrile-containing o-cyanophenylalanine residues in photoactive yellow protein are compared with MD electric fields from the fixed-charge AMBER FF and the polarizable AMOEBA FF. We observe that the electric field distributions for H-bonding nitriles are substantially affected by the choice of FF. As such, AMBER underestimates electric fields for nitriles experiencing moderate field strengths; in contrast, AMOEBA robustly recapitulates the TDM electric fields. The FF dependence of the electric fields can be partly explained by the presence of additional negative charge density along the nitrile bond axis in AMOEBA, which is due to the inclusion of higher-order multipole parameters; this, in turn, begets more head-on nitrile H-bonds. We conclude by discussing the implications of the FF dependence for the simulation of nitriles and proteins in general.

Research on the brain phantom for transcranial electromagnetic neuromodulation

Transcranial magnetic stimulation (TMS), a widely used neuroregulatory technique, has been proven to be effective in treating neurological and psychiatric disorders. The therapeutic effect is closely related to the intracranial electric field caused by TMS, thus accurate measurement of the intracranial electric field generated by TMS is of great significance. However, direct intracranial measurement in human brain faces various technical, safety, ethical and other limitations. Therefore, we have constructed a brain phantom that can simulate the electrical conductivity and anatomical structure of the real brain, in order to replace the clinical trial to achieve intracranial electric field measurement. We selected and prepared suitable conductive materials based on the electrical conductivity of various layers of the real brain tissue, and performed image segmentation, three-dimensional reconstruction and three-dimensional printing processes on each layer of tissue based on magnetic resonance images. The production of each layer of tissue in the brain phantom was completed, and each layer of tissue was combined to form a complete brain phantom. The induced electric field generated by the TMS coil applied to the brain phantom was measured to further verify the conductivity of the brain phantom. Our study provides an effective experimental tool for studying the distribution of intracranial electric fields caused by TMS.

Low-noise co-arm differential sensor for an optical frequency comb sampling an E-field test system.

Optical frequency comb (OFC) technology can realize the rapid measurement of electric fields (E-fields) with large bandwidth. However, this technology suffers from the problem of high intensity noise, resulting in low sensitivity and a blind frequency region. In order to solve the above problems, a dual-path optical E-field sensor with a common reference arm based on a lithium niobate optical waveguide is proposed. The introduction of the reference arm improves the balance of optical paths and the degree of integration. A segmented electrode is also designed to ensure the generation of reverse electrical signals on two Mach-Zehnder interferometers (MZIs). After exiting from the differential photodetector (PD), the intensity noise can be removed, and the sensitivity of the sensor can be improved. After testing, the maximum intensity noise reduction is about 37 dB, the average noise reduction is about 22.3 dB, and the blind frequency region can be eliminated with the co-arm differential optical E-field (CDOE) sensor in the process of measuring the signal. This sensor can be used in the 1 MHz-12 GHz bandwidth with a sensitivity better than 10 mV/m·√Hz.

Investigation of structural, optical, electrical and magnetic properties of magnetoelectric composite of NiFe2O4 and YMnO3

Magnetoelectric composites of Nickel Ferrite and Yttrium Manganite (xNiFe2O4 – (1-x) YMnO3, x = 0.25 and 0.50) were prepared using solid state reaction method. Their structural, optical, magnetic and electric behavior was studied by X-ray diffraction (XRD), UV–Vis spectroscopy, vibrating sample magnetometer (VSM), dielectric and polarization versus electric field (P-E) measurement at room temperature. Coexistence of the both ferrite and ferroelectric phases in the composites was confirmed by X-ray diffraction. Structural analysis had shown that lattice strain corresponding to nickel ferrite (NFO) phase was increased while for Yttrium Manganite (YMO) it was not much affected after formation of composites. The values of direct band gap for the composite came out to be larger than that for YMnO3 (1.43 eV) and smaller than that for NiFe2O4 (1.74 eV). Existence of ferromagnetic ordering in the composites was confirmed by VSM. Value of saturation magnetization was found to be highest in nickel ferrite (46 emu/g) and it was decreased with increase in concentration of ferroelectric phase in the composites. The sample with 75% YMO has shown highest dielectric constant (∼700) among all the four samples. P-E loops were not saturated and polarization current was found mainly due to conduction of charge carriers.

Application of the Z-transform on the deconvolution of lightning electric field waveforms obtained from single-station measurements

Fast electric field measurement systems used in the field of atmospheric electricity often have decay time constants of the order of 1 ms, which means that slower processes – such as long continuing currents – are not visible in the raw electric field records. This paper presents a practical approach to compensate for the time decay caused by the system response and regain the original lightning electric field waveforms. To accomplish this task, the transfer function of the measurement system is modeled in the Z-domain. Then, from the inverse Z-transform of the transfer function, the compensated electric field is obtained in discrete time domain. Based on data obtained at Nova Gameleira campus of CEFET-MG (Belo Horizonte, Brazil), we present and discuss results of typical electric field waveforms that include some slower lightning processes, which are not readily observable in the raw data.

Electric field measurements in preclinical MRI at 11.7 T and 7 T for experimental SAR comparison

SAR assessment is a major concern in MRI. The energy absorbed by tissues increases quadratically with the static magnetic field; therefore, ultra-high field (≥7 T) systems require careful dosimetry to exploit their potential. The objectives are to validate the use of electric-field probe for SAR assessment for high-field MRI, and to study the advantages and drawbacks of E-field measurements.The experiments were performed at 7 and 11.7 T on preclinical systems in a phantom with calibrated dielectric properties. Absolute values of the E-field were measured according to position inside a birdcage coil and electrical conductivity, local temperature increase were simultaneously evaluated with operating RF frequency, as well as the re-positioning precision through five repetitive measurements. Results yielded a 14.8 ± 0.36 W/kg SAR near the coil’s capacitors compared to 6.8 ± 0.17 W/kg estimated at the center of the coil. The temperature rise was nevertheless higher in the center likely due to heat transfer effects. The SAR measured in similar conditions was 5.2 times higher at 11.7 T than at 7 T. The probes induced no visible artefact, and the test to estimate the reproducibility of positioning the sensors granted a low 2.3 % coefficient of variation. Measuring both the cause (E-field) and the effect (temperature rise) yielded different information, both useful in the context of EM simulation validation.