Minimum Electric Field Research Articles

Rydberg atom-based microwave electrometry using polarization spectroscopy

Abstract In this study, we investigated Rydberg atom-based microwave electrometry using polarization spectroscopy in a room-temperature vapor cell. By measuring Autler-Townes splitting in the electromagnetically induced transparency (EIT) spectrum, we determined that the minimum measurable microwave electric field is approximately five times lower than conventional EIT techniques. The results are well reproduced by a full optical Bloch equation model, which takes into account all the hyperfine levels involved. Subsequently, the EIT setup was used to characterize a custom microwave cylindrical lens, which increases the field at the focus by a factor of three, decreasing the minimum measurable microwave electric field by the same amount. Our results indicate that the combination of polarization spectroscopy and a microwave lens may enhance microwave electrometry, and may allow its use as a secondary standard.

High sensitivity measurement of ULF, VLF, and LF fields with a Rydberg-atom sensor.

Fields with frequencies below megahertz are challenging for Rydberg-atom-based measurements, due to the low-frequency electric field screening effect caused by the alkali-metal atoms adsorbed on the inner surface of the container. In this paper, we investigate electric field measurements in the ultralow frequency (ULF), very low frequency (VLF), and low frequency (LF) bands in a Cs vapor cell with built-in parallel electrodes. With optimization of the applied DC field, we achieve high-sensitive detection of the electric field at frequencies of 1 kHz, 10 kHz, and 100 kHz based on the Rydberg-atom sensor, with the minimum electric field strength down to 18.0 μV/cm, 6.9 μV/cm, and 3.0 μV/cm, respectively. The corresponding sensitivity is 5.7 μV/cm/Hz1/2, 2.2 μV/cm/Hz1/2, and 0.95 μV/cm/Hz1/2 for the ULF, VLF, and LF fields, which is better than a 1-cm dipole antenna. Besides, the linear dynamic range of the Rydberg-atom sensor is over 50 dB. This work presents the potential to enable more applications that utilize atomic sensing technology in the ULF, VLF, and LF fields.

Exploring the onset field strength of nanoscale electrospray: A detailed investigation

Electrospray, essential in nanoparticle synthesis, biomedical diagnostics, and drug delivery, relies on onset field strength, the minimum electric field needed for liquid ejection. Nanoscale electrospray, with nanometer-sized nozzles, offers precise control and efficiency. This study uses molecular dynamics simulations to examine factors affecting onset field strength, such as pore geometry, solution environment, and surface properties. Findings show that surface properties can alter onset field strength by up to 50%, with enhanced hydrophilicity and negative surface charges reducing the required field strength. These insights are crucial for optimizing nanoscale electrospray in various applications.

Length of Critical Streamers

The concept of equipotential length of positive quasi-stationary streamers is introduced as a criterion for assessing their degree of isolation. The equipotential length of positive critical streamers (streamers moving in the minimum electric field sufficient for the unrestricted propagation of a positive streamer) in the normal atmosphere is defined, both for individual streamers and those forming a thin bundle of streamers. The dependence of the equipotential length of positive quasi-stationary streamers on external field, velocity, radius, and electron concentration in the streamer head is investigated. A criterion is proposed for analytical models of quasi-stationary streamers, providing an additional independent equation to the system of equations describing the dynamics of quasi-stationary streamers, valid only for critical streamers. The insignificance of the influence of electrodes located at a distance greater than its equipotential length from the streamer head on the quasi-stationary streamer is proven, confirming the adequacy of using the equipotential length to assess the isolation of positive streamers.

Phase-field theory study on the modulation mechanism of oxygen vacancy concentration on charged domain wall in ferroelectric thin films

This study analyzes the regulatory mechanism of oxygen vacancy concentration on tail-to-tail charged domain walls (T–T CDWs), along with the writing time, conduction current magnitude, and retention performance of through-type T–T CDWs. The research results show that the highest density and length of T–T CDWs are achieved when the oxygen vacancy concentration is 1 × 1020 cm−3. Moreover, the successful writing of through-type T–T CDWs is limited to a certain electric field range, which is controlled by oxygen vacancy concentration. An increase in the oxygen vacancy concentration leads to a decrease in the maximum and minimum threshold electric fields required for writing through-type charged domain walls. The writing time and conductivity of through-type T–T CDWs determine the information writing speed and signal strength of domain wall memories, and the oxygen vacancy concentration also plays a regulatory role in both aspects. When the oxygen vacancy concentration is 1 × 1020 cm−3, the through-type T–T CDW exhibits the fastest writing speed, requiring only 8 ns. The magnitude of the conduction current of through-type T–T CDWs is directly proportional to the oxygen vacancy concentration. The through-type T–T CDWs formed by the aggregation of oxygen vacancies exhibit excellent retention performance, making them highly promising for applications in ferroelectric domain wall memories. Our research demonstrates that oxygen vacancies have a significant regulatory effect on the morphology and current response of charged domain walls, opening up new avenues for the study of domain wall memories.

Acousto-optic-based time domain electric field sensor for magnetic resonance imaging applications.

An acousto-optic (AO)-based electric field sensor is presented for time domain measurement under magnetic resonance imaging (MRI). A fully MR-compatible sensor is designed and fabricated using a phase-shifted fiber Bragg grating mechanically coupled to a piezoelectric transducer. Mechanical resonance of the piezoelectric transducer is matched to the operating frequencies of commonly used MRI systems to increase the sensitivity of the sensor. Sensitivity of the sensor is measured as 1.27 mV/V/m, with a minimum detectable electric field of 4.4 mV/m/√/Hz. Directivity of the sensor is measured with a 18 dB orthogonal component rejection. The dynamic range of the sensor is calculated as 117 dB/Hz, which allows the measurement of electric fields up to 3.2 kV/m. In MRI studies, the AO sensor was able detect local hot spots around a reference implant accurately with high signal-to-noise ratio. AO sensor exhibited similar or better performance when compared with commercially available MRI compatible electric field sensors. Furthermore, the small size of the sensor with the flexible fiber optic link could allow in situ measurements of electric fields during critical interventional procedures such as pacemaker lead or deep brain stimulator placement as an MRI dosimeter during diagnostic scans.

Optimization design of insulation structure of multiwinding high-frequency transformer based on response surface method

PurposeThe purpose of this paper is to study the insulation structure optimization method of multiwinding high-frequency transformer (HFT).Design/methodology/approachThis paper takes 100 kW, 10 kHz multiwinding HFT as the research object. First, the distribution of electric field strength within the core window of multiwinding HFT with different winding configurations is simulated by the electrostatic field finite element method. The symmetrical hybrid winding structure with minimum electric field strength is selected as the insulation design. To reduce the electric field strength at the end region of the winding, the electrostatic ring and angle ring are designed based on the response surface method.FindingsThe optimal results show that the maximum electric field strength can be reduced by 15.4%, and the low voltage stress can be achieved.Originality/valueThe above research provides guidance and basis for the optimal design of insulation structure of multiwinding HFT.

Seasonal dependence of the equatorial electrojets generated by thunderstorms

A model for the distribution of the ionospheric potential which drives the ionospheric currents closing the electric currents from/to the atmosphere is constructed. It is a part of the global electric circuit (GEC). Only the internal electric fields and currents generated by thunderstorms are studied, and without any magnetospheric or ionospheric generators. The atmospheric conductivity profiles with altitude are empirically determined, and the topography of the Earth’s surface is taken into account. A two-dimensional approximation of the ionospheric conductor is based on high conductivity along the geomagnetic field. The model of the global distribution of thunderstorms obtained from the ground-based World Wide Lightning Location Network is used as a proxy for the electric currents to the ionosphere from the atmosphere above thunderstorm regions. The global distributions of the electric potential in the ionosphere are calculated for twelve months during a year with low solar activity. The designed models contain the equatorial electrojets. There are day-time electrojets, the strengths of which are up to 200 A, and night-time ones (which are up to only half this value), while the total current of the GEC is taken equal between 1.5 and 2.5 kA in our model to satisfy the Carnegie data for the simulated dates and UT. The results are presented as diagrams of the currents in the electrojets depending on the geomagnetic longitude and month for 04 and 18 UT. These times are chosen to be the times of minimum and maximum fair weather electric field in accordance with the Carnegie results. The diagrams could help us to choose optimal conditions for measurements of the magnetic perturbations observed on the ground or by satellites to find the electrojets of the GEC which are obtained in our simulations.

Experimental study of electron cyclotron heating assisted start-up on J-TEXT

Second harmonic X-mode (X2 mode) electron cyclotron heating (ECH) assisted start-up has been studied experimentally on the J-TEXT device to determine the minimum ECH power requirements to assist breakdown and develop a better physical description of the process. Results indicate that the minimum toroidal electric field for a successful start-up on J-TEXT changed from to , and that injecting of X2-mode ECH power can ensure robust breakdown. The critical ECH power for successful start-up was determined to be approximately . At lower powers ECH was observed to cause ionization, but this did not necessarily result in successful start-up. The effects of varying ECH power, pulse-width and toroidal magnetic field on start-up were also investigated. Higher ECH power leads to quicker, stronger ionization and CIII emission, and is beneficial for burn-through. Higher pre-plasma density caused by high ECH power can decrease the required toroidal electric field for ohmic breakdown, while the enhanced CIII emission may not be good for start-up. The characteristics of the pre-plasma formed by ECH prior to application of the loop voltage were also studied. The toroidal magnetic field affects the initial location where pre-plasma forms and this also affected the subsequent tokamak start-up. The analysis of spatial density showed that the pre-plasma can radially develop at a velocity of . Furthermore, it was found that injecting ECH power at the appropriate time with a low power of can achieve similar pre-ionization results to the high-power case. The transition from ECH plasma to ohmic plasma suggests that the ECH assisted start-up modified the process of purely ohmic breakdown.

Terahertz Receiver based on Room-Temperature Rydberg-Atoms

Realization of practical terahertz wireless communications still faces many challenges. The receiver with high sensitivity is important for THz wireless communications. Here we demonstrate a terahertz receiver based on the cesium Rydberg atoms in a room-temperature vapor cell. The minimum detectable THz electric field is calibrated. With this receiver, the phase-sensitive conversion of amplitude-modulated or frequency-modulated terahertz waves into optical signals is performed. The results show that the atomic receiver has many advantages due to its quantum properties. Particularly, the long distance THz wireless communications is achievable using this receiver. Furthermore, the atomic receiver can be used in the THz wireless-to-optical link.

Impact of molecular architectures on mesogen reorientation relaxation and post-relaxation stress of liquid crystal elastomers under electric fields

Applying electric fields to liquid crystal elastomers (LCEs) has attracted attention as a fast and energy-efficient actuation method for soft robotics. It is helpful to predict the minimum electric field strength that can drive the mesogen reorientation and the time required for the reorientation of LCEs with specific molecular architecture to optimize LCE electrical actuation. In this study, molecular dynamics (MD) simulations of main- and side-chain LCE systems under an applied electric field were performed, and the relaxations of stress and orientational order were observed. The minimum electric field strength that can drive the reorientation for each LCE molecular system was estimated. The time required for reorientation follows a power law of the electric field strength, and the reorientation time for side-chain LCEs is much shorter than that for main-chain LCEs. The behavior of the relaxation value of stress with respect to the electric field strength differed markedly between the main- and side-chain LCEs. These results suggest that designing LCEs at the molecular architecture level and using different LCE molecules in different actuation sites are essential to more precise soft robotics.

The Impact of Scalp's Temperature on the Choice of the Best Layout for TTFields Treatment

Background and ObjectivesTumor Treating Fields (TTFields) is an FDA-approved technique used in the treatment of glioblastoma. It consists in applying an electric field (EF) with a frequency of 200 kHz using two pairs of transducer arrays. During treatment planning, the NovoTAL system is used to strategically place the arrays on the head in regions that maximize the EF at the tumor. Current should be injected at least 18 hours/day and induce a minimum EF of 1 V/cm at the tumor. To avoid any thermal harm to the patient, the temperature of the scalp is kept around 39.5°C by changing the injected current. The goal of this study was to investigate how accounting for the temperature of the scalp during treatment planning might affect the choice of the best layout suggested by NovoTAL. Furthermore, we also studied the sensitivity of the results to the metric used to evaluate the layouts. MethodsWe used a realistic head model with a virtual glioblastoma in our studies. Through the NovoTAL system we obtained five realistic array layouts and we predicted the best one for our model based on the approach currently implemented in this system. We then repeated the same type of analysis, but also accounting for the temperature during planning. In both cases we ranked the layouts based on three different criteria: the LMiPD and the LAPD (local minimum and local average power densities, respectively) in the tumor and the SAR (specific absorption rate) in the head ResultsAccounting for the temperature does not significantly affect the choice of the best layout provided that the arrays are at least 1 cm apart from each other. Otherwise, a common temperature hotspot occurs in the scalp between the closest transducers of the adjacent arrays, which limits how much current can be injected and consequently treatment effectiveness. Also, the choice of the best layout depends on the criterion used. ConclusionsAccounting for the temperature might led to significant variations in the current injected. The LMiPD might be used as a first criterion to choose the best treatment layout, followed by the LAPD and then the SAR.

Protein Dielectrophoresis with Gradient Array of Conductive Electrodes Sheds New Light on Empirical Theory.

Dielectrophoresis (DEP) is a versatile tool for the precise microscale manipulation of a broad range of substances. To unleash the full potential of DEP for the manipulation of complex molecular-sized particulates such as proteins requires the development of appropriate theoretical models and their comprehensive experimental verification. Here, we construct an original DEP platform and test the Hölzel-Pethig empirical model for protein DEP. Three different proteins are studied: lysozyme, BSA, and lactoferrin. Their molecular Clausius-Mossotti function is obtained by detecting their trapping event via the measurement of the fluorescence intensity to identify the minimum electric field gradient required to overcome dispersive forces. We observe a significant discrepancy with published theoretical data and, after a very careful analysis to rule out experimental errors, conclude that more sophisticated theoretical models are required for the response of molecular entities in DEP fields. The developed experimental platform, which includes arrays of sawtooth metal electrode pairs with varying gaps and produces variations of the electric field gradient, provides a versatile tool that can broaden the utilization of DEP for molecular entities.

Improving the spectral resolution and measurement range of quantum microwave electrometry by cold Rydberg atoms

We theoretically and experimentally studied quantum microwave electrometry in a cold atomic system using Rydberg electromagnetic induction transparency (EIT) and Autler–Townes splitting (EIT-AT splitting). In cold atoms, a spectral linewidth of ∼500 kHz for EIT was achieved owing to a significant reduction in residual Doppler width, i.e. by at least an order of magnitude, compared to that in vapor cells at room temperature. Therefore, the minimum microwave electric field intensity (E MW) that can be measured is 430 µV cm−1, which is one order higher sensitivity in the EIT-AT regime than that in vapor cells at room temperature. Unlike microwave electrometry in atomic vapor cells, EIT-AT splitting cannot be observed if E MW is so large that the EIT-AT splitting interval exceeds the absorption peak width of the cold atom while scanning the frequency of the probe laser (ω p ). Moreover, EIT-AT splitting can be observed if exceeds the natural linewidth of the intermediate states while scanning the coupling laser (ω c ) and maintains a high spectral resolution with a high signal-to-noise ratio. While scanning ω c , the upper microwave electric field intensity is limited by the scanning range of our setup. Using our system, we measure the maximum field to be 21.6 mV cm−1, nearly three times higher than that of 6.8 mV cm−1 while scanning ω p . The results indicate that the linear range of E MW measured using EIT-AT splitting considerably improves in cold Rydberg atoms.

Optimal Design of Corona Ring for 132 kV Insulator at High Voltage Transmission Lines Based on Optimisation Techniques

The installation of a corona ring on an insulator string on a transmission line is one of the solutions to reduce the electric field stress surrounding the energised end of the insulator string. However, installing a corona ring with an optimum design to reduce the electric field magnitude on an insulator string is a challenging task. Therefore, in this work, a method to achieve the optimum design of a corona ring for 132 kV composite non-ceramic insulator string was proposed using two optimisation methods: the Imperialist Competitive Algorithm (ICA) and Grey Wolf Optimisation (GWO). A composite non-ceramic insulator string geometry with and without a corona ring was modelled in finite element analysis and used to obtain the electric field distribution in the model geometry. The electric field distribution was evaluated using a variation in the corona ring’s dimensions, i.e., the ring diameter, the ring tube diameter and the vertical position of the ring along the insulator string. From the results achieved, a comparison of the minimum electric field magnitude along the insulator string with a corona ring design shows that the minimum electric field magnitude is found to be lower using optimisation techniques compared to without using optimisation techniques by between 3.724% and 3.827%. Hence, this indicates the capability and effectiveness of the proposed methods in achieving the optimum design of a corona ring on an insulator string.

On Calculating the Phase-to-Phase CFO of Overhead Transmission Lines Based on the Spatial Minimum Electric Field

A spatial approach for calculating phase-to-phase switching impulse critical flashover voltage of overhead transmission lines is implemented using the Fourier enhanced charge simulation method (FEnCSM). Cathode-directed leader and streamer characteristics are used in an engineering model of pre-breakdown conditions. Rather than identifying breakdown based on complete bridging of the air gap, the proposed method identifies breakdown based on the ability of the leader-streamer system to survive the region of minimum electric field between phase conductors. Use of the minimum field as a basis for identifying breakdown allows anode-directed negative streamers to be reasonably neglected. Combined with FEnCSM, the proposed approach enables explicit representation of phase bundle subconductors and avoids the electrode-specific geometric constants or gap factors common in existing methods. Results obtained with the method compare well to four independent sets of experimental data for phase-to-phase flashover from the literature. The method was developed to facilitate ongoing research into practical use of the electric field as a basis for unifying electrical studies in the design of overhead transmission lines, including HSIL and other novel configurations.

Highly Sensitive Measurement of a Megahertz rf Electric Field with a Rydberg-Atom Sensor

Rydberg atoms have great potential in electric field measurement and have an advantage with a large frequency bandwidth from the kHz to the THz scale. However, the sensitivity for measuring a weak MHz electric field signal is limited by the spectroscopic resolution, because the weak electric field induces only a small perturbation of the population and energy level shift of the Rydberg atoms. Here, we report highly sensitive measurement of a weak MHz electric field using electromagnetically induced transparency with Rydberg atoms in a thermal atomic system. Using the heterodyne method on a 30-MHz electric field, we successfully measure the minimum electric field strength to be \textcolor{black}{37.3 $\mathrm{\mu V/cm}$} with a sensitivity up to $-65$ dBm/Hz and a linear dynamic range over 65 dB. Additionally, we measure an amplitude-modulated signal and demodulate the signal with a fidelity over 98\%. This work extends the sensitivity of atomic sensors for measuring MHz electric fields, which advances atomic electric field-sensing technology.

Electric-Field-Induced Coherent Anti-Stokes Raman Scattering of Hydrogen Molecules in Visible Region for Sensitive Field Measurement.

Nonintrusive optical measuring of electric fields in space is crucial for various sciences and technologies. In this study, a simple and highly sensitive optical electric field measurement is demonstrated in high-pressure hydrogen by performing electric-field-induced coherent anti-Stokes Raman scattering (E-CARS) in the visible region. The minimum detectable electric field is 0.5 V/mm at atmospheric pressure. This method does not require excited or atomic species and shows a considerably higher sensitivity than those demonstrated by the commonly applied E-CARS method in the infrared region and electric-field-induced second-harmonic generation. This method can be applied to various Raman-active molecules.

Negative Streamer Propagation in Nitrogen

For the development of negative streamer, a one dimension simulation is presented when a negative electric field is applied at atmospheric pressure to a 4 mm gap in nitrogen. At applied electric fields of 55, 60, 65 and 70 kV/cm, streamer parameters were studied at various time intervals. The aim of this paper is to determine the minimum electric field that must be applied for stable propagation of negative streamer discharge in nitrogen gas. As functions of position and time, the calculations provide detailed electron and ion density predictions, electric fields and density of space charges. The time interval was with a nanosecond resolution. Using 8000 element mesh to resolve the characteristics of the streamer, spatial resolution over the separation of electrodes 4 mm was obtained. The results were obtained by solving the equation of continuity for electrons and ions and the Poisson equation solution.

Terahertz electrometry via infrared spectroscopy of atomic vapor

In recent years, the characterization of radiation falling within the so-called “terahertz (THz) gap” has become an ever more prominent issue due to the increasing use of THz systems in applications such as nondestructive testing, security screening, telecommunications, and medical diagnostics. THz detection technologies have advanced rapidly, yet traceable calibration of THz radiation remains challenging. In this paper, we demonstrate a system of electrometry in which a THz signal can be characterized using laser spectroscopy of highly excited (Rydberg) atomic states. We report on proof-of-principle measurements that reveal a minimum detectable THz electric field amplitude of 1.07 ± 0.06 V / m at 1.06 THz (3 ms detection), corresponding to a THz power at the atomic cell of approximately 3.4 nW. Due to the relative simplicity and cryogen-free nature of this system, it has the potential to provide a route to a SI traceable “atomic candle” for THz calibration across the THz frequency range, and provide an alternative to calorimetric methods.