Optimal Electric Field Research Articles

Study of the optimal configuration for a Gas Electron Multiplier aimed at plasma impurity radiation monitoring

For the purpose of monitoring the level of plasma impurity (especially tungsten) and its distribution reconstruction at tokamaks (ITER in particular), a Soft X-Ray (SXR) tomographic diagnostics based on Gas Electron Multiplier (GEM) detectors with energy discrimination has been extensively considered for a while. Coupled with advanced electronics, GEM detectors offer excellent time and space resolution, as well as a charge spectrum from which the SXR photon spectrum can be deconvolved. In addition, they are less subjected to a neutron damage as compared to standard semiconductor diodes. This contribution highlights the latest studies supporting the development of such diagnostics focusing on laboratory tests to examine: (a) the impact of GEM holes geometry on the properties and distribution of the electron avalanche; (b) the effect of the high rate photon flux on GEM foil performance; and (c) the optimal electric field distribution.

Non-Markovianity in the optimal control of an open quantum system described by hierarchical equations of motion

Optimal control theory is implemented with fully converged hierarchical equations of motion (HEOM) describing the time evolution of an open system density matrix strongly coupled to the bath in a spin-boson model. The populations of the two-level sub-system are taken as control objectives; namely, their revivals or exchange when switching off the field. We, in parallel, analyze how the optimal electric field consequently modifies the information back flow from the environment through different non-Markovian witnesses. Although the control field has a dipole interaction with the central sub-system only, its indirect influence on the bath collective mode dynamics is probed through HEOM auxiliary matrices, revealing a strong correlation between control and dissipation during a non-Markovian process. A heterojunction is taken as an illustrative example for modeling in a realistic way the two-level sub-system parameters and its spectral density function leading to a non-perturbative strong coupling regime with the bath. Although, due to strong system-bath couplings, control performances remain rather modest, the most important result is a noticeable increase of the non-Markovian bath response induced by the optimally driven processes.

Parametric optimization of electric field strength for cancer electrochemotherapy on a chip-based model.

Electrochemotherapy (ECT), as one of the very few available treatments for cutaneous and subcutaneous tumors when surgery and radiotherapy are no longer available, requires applying a proper electric field to the tumor to realize electroporation-mediated cytotoxic drug delivery. It is impossible to exhaust all possible electrical parameters on patients to realize the optimal tradeoff between tumor suppression and adverse effects. To address this issue, this study provides a feasible solution by developing a four-leaf micro-electrode chip (F-MEC) in which the electric field was specially designed by linear distribution to cover all possible electric field strengths for ECT.Methods: We developed a F-MEC that provides a linearly varied electric field and a capacity for in situ observation of cell status. By culturing tumor cells on the F-MEC surface and in situ monitoring the cell responses to ECT drugs, the optimal electric field strength for any given cell type could be rapidly and accurately calculated in a few, or even only one, simple assay.Results: Using this chip, we monitored MCF-7 and A315 cell responses to ECT and determined the optimum ECT voltage. More importantly, we successfully verified that the in vitro determined voltage coincided with the optimal value for in vivo ECT in mice.Conclusion: In this proof-of-concept study, the in vivo tumor suppression assays proved that the optimal parameters acquired from in vitro F-MEC assay could be used for in vivo ECT.

3-D Edge Termination Design and ${R}_{ \mathrm{\scriptscriptstyle ON},\text {sp}}$ -BV Model of A 700-V Triple RESURF LDMOS With N-Type Top Layer

3-D edge termination design and analytic model for specific on-resistance ( ${R}_{ \mathrm{\scriptscriptstyle ON},\text {sp}})$ versus breakdown voltage (BV) of a 700-V triple reduced surface field lateral double-diffused MOSFET (LDMOS) with n-type top layer are presented in this paper. To eliminate the premature avalanche breakdown induced by the electric field crowding and the local charge imbalance in the transition region of the source-centered edge termination structure, 3-D numerical simulations and experiments are performed to investigate two crucial parameters ${L}_{1}$ and ${L}_{2}$ in the layout of the transition region. It is observed that optimal electric field distribution is obtained and breakdown positions are transferred to the active region at ${L}_{1} = 30~\mu \text{m}$ and ${L}_{2} = 1~\mu \text{m}$ . On the other hand, an analytic model is developed to describe the relation between ${R}_{ \mathrm{\scriptscriptstyle ON},\text {sp}}$ and BV, which is obtained as ${R}_{ \mathrm{\scriptscriptstyle ON},\text {sp}} = 5.93 \times 10^{-6} \times 22({T}/298)^{1.7} \times \text {BV}^{2}$ and theoretically verifies that the fabricated device has achieved optimized ${R}_{ \mathrm{\scriptscriptstyle ON},\text {sp}}$ and BV. Compared with our previous paper, the LDMOS experimentally demonstrated improved performance with ${R}_{ \mathrm{\scriptscriptstyle ON},\text {sp}}$ of 86.49 $\text{m}\Omega ~\cdot $ cm2 and BV of 805 V, which is leading performance for the 700-V applications in published data.

Inhomogeneous electric-field–induced negative/positive electrocaloric effects in ferroelectric nanoparticles

The electrocaloric effect in PbTiO3 ferroelectric nanoparticles has been studied using Landau-Ginzburg-Devonshire theory to determine the optimal electric field to induce large adiabatic temperature changes. The calculation results show that a large positive or negative adiabatic temperature change could be induced using an inhomogeneous electric field. The electrically induced negative adiabatic temperature change becomes positive as the strength of the electric field is increased. This transformation of the adiabatic temperature change is attributed to domain switching owing to the applied electric field. These results may provide an explanation for transformations from a negative to a positive electrocaloric effect in ferroelectrics.

Research on electrostatic coalescence of water-in-crude-oil emulsions under high frequency/high voltage AC electric field based on electro-rheological method

The viscosity–temperature characteristics and phase inversion point as well as the chord lengths distribution of dispersed droplets have been investigated. The relative viscosity reduction is then effectively taken as the evaluation means to investigate the effects of shear rate, electric field strength, frequency, voltage waveform, and initial water cut on the electrocoalescence efficiency experimentally systematically. It is determined that the phase inversion point is located between 35%–45%. The chord lengths of dispersed droplets are concentrated in range of 10–150μm and the average value is 61.3μm for the water-in-crude-oil emulsions sample. We found that the coalescence efficiency can be improved by increasing shear rate to some extent while keeping other parameters unchanged, but decreased instead with the shear rate exceeding 50s−1, which suggests that only the appropriate flow shear condition can help to promote the electrostatic coalescence. Meanwhile, the present work has demonstrated that there exists optimum electric field strength(8kV/cm) and frequency(2kHz) for the given water-in-crude-oil emulsions, and the ranking of three voltage waveforms in decreasing order of coalescence efficiency is AC square, triangular and sinusoidal waveform. In addition, with the three kinds of voltage waveforms, the coalescence efficiency are all significantly improved as the water cut increases from 10% up to 40%, which demonstrates the good performance of high frequency/high voltage electric field for treating crude oil emulsions with high water cut.

Product-driven process synthesis: Extraction of polyphenols from tea

In this contribution, the Product-Driven Process Synthesis methodology is used as a well-defined structured approach for the conceptual design of an extraction process for polyphenols from fresh tea leaves. A detailed specification of the starting material (fresh tea leaves) and product (polyphenols) leads to a subsequent definition of fundamental tasks to convert our raw material into the desired product. Among the different mechanisms and techniques that could be used to perform the tasks under mild conditions, pulsed electric field has been selected as non-invasive and non-thermal method for cell wall disruption. To define the operating window for pulsed electric field method an experimental design has been defined and executed (varying several settings of the pulsed electric field). From the collected data, the analysis of variance has been used to determine which variables are significant i.e. electric field strength, pulse duration and number of pulses. Box-Behnken design has been used as part of statistical analysis to find optimal pulsed electric field settings to maximize the extraction yield of polyphenols (extraction yield). With the outcome of optimization of pulsed electric field settings maximum value of 32% of extraction yield was achieved. This is better as compared to a conventional process where extraction is done by hot (boiling) water or solvents while not destroying valuable components in raw material itself.

Simulation study of a novel 3D SPAD pixel in an advanced FD-SOI technology

In this paper, a novel SPAD architecture implemented in a Fully-Depleted Silicon-On-Insulator (SOI) CMOS technology is presented. Thanks to its intrinsic vertical 3D structure, the proposed solution is expected to allow further scaling of the pixel size while ensuring high fill factors. Moreover the pixel and the detector electronics can benefit of the well-known advantages brought by SOI technology with respect to bulk CMOS, such as higher speed and lower power consumption. TCAD simulations based on realistic process parameters and dedicated post-processing analysis are carried out in order to optimize and validate the avalanche diode architecture for an optimal electric field distribution in the device but also to extract the main parameters of the SPAD, such as the breakdown voltage, the avalanche triggering probability, the dark count rate and the photon detection probability. A comparison between the efficiency in back-side and front-side approaches is carried out with a particular focus on time-of-flight applications.

Axon Outgrowth of Rat Embryonic Hippocampal Neurons in the Presence of an Electric Field

Application of an electric field (EF) has long been used to induce axon outgrowth following nerve injuries. The response of mammalian neurons (e.g., axon length, axon guidance) from the central nervous system (CNS) to an EF, however, remains unclear, whereas those from amphibian or avian neuron models have been well characterized. Thus, to determine an optimal EF for axon outgrowth of mammalian CNS neurons, we applied a wide range of EF to rat hippocampal neurons. Our results showed that EF with either a high magnitude (100 mV/mm or higher) or long exposure time (10 h or longer) with low magnitude (10-30 mV/mm) caused a neurite collapse and cell death. We also investigated whether neuronal response to an EF is altered depending on the growth stage of neuron cultures by applying 30 mV/mm to cells from 1 to 11 days in vitro (DIV). Neurons showed the turnover of axon outgrowth pattern when electrically stimulated between 4-5 DIV at which point neurons have both axonal and dendritic formation. The findings of this study suggest that the developmental stage of neurons is an important factor to consider when using EF as a potential method for axon regeneration in mammalian CNS neurons.

3D design and electric simulation of a silicon drift detector using a spiral biasing adapter

The detector system of combining a spiral biasing adapter (SBA) with a silicon drift detector (SBA-SDD) is largely different from the traditional silicon drift detector (SDD), including the spiral SDD. It has a spiral biasing adapter of the same design as a traditional spiral SDD and an SDD with concentric rings having the same radius. Compared with the traditional spiral SDD, the SBA-SDD separates the spiral's functions of biasing adapter and the p–n junction definition. In this paper, the SBA-SDD is simulated using a Sentaurus TCAD tool, which is a full 3D device simulation tool. The simulated electric characteristics include electric potential, electric field, electron concentration, and single event effect. Because of the special design of the SBA-SDD, the SBA can generate an optimum drift electric field in the SDD, comparable with the conventional spiral SDD, while the SDD can be designed with concentric rings to reduce surface area. Also the current and heat generated in the SBA are separated from the SDD. To study the single event response, we simulated the induced current caused by incident heavy ions (20 and 50μm penetration length) with different linear energy transfer (LET). The SBA-SDD can be used just like a conventional SDD, such as X-ray detector for energy spectroscopy and imaging, etc.

Effects of high-frequency and high-voltage pulsed electric field parameters on water chain formation

Separation methods utilizing high-frequency and high-voltage pulsed DC electric fields have been used extensively in the oil and petroleum industries, where the occurrence of water-in-oil dispersions is highly unwelcome because of physical constraints and the high maintenance costs required to treat these dispersions. This paper reports the results of studies of the effects of applied electric field parameters, including electric field strength, frequency, and duty ratio, on water chain formation in water-in-oil emulsions. The investigations were performed in a rectangular Perspex® cell. The results of the studies show that dipole–dipole forces dominate the process of water chain formation. At low electric field strength, frequency, or duty ratio, dipole–dipole forces are negligible; therefore, the process of water chain formation and aqueous drop coalescence are inconspicuous. However, at high electric field strength, frequency, or duty ratio, significant dipole–dipole forces give rise to water chain formation and aqueous drop coalescence. At extremely high electric field strength, frequency, or duty ratio, aqueous drops are excessively polarized and disintegrate, inhibiting the processes of water chain formation and aqueous drop coalescence. The optimum electric field parameters for separation of water-in-oil dispersions are as follows: electric field strength, 3.80 kV cm−1; frequency, 4.0 kHz; and duty ratio, 0.65.

Development of a <sup>1</sup>H-<sup>13</sup>C Dual-Optimized NMR Probe Based on Double-Tuned High Temperature Superconducting Resonators

Nuclear magnetic resonance (NMR) spectroscopy is a very powerful technique to study molecular structure and dynamics because of the rich chemical information it can extract. However, low inherent sensitivity is the Achilles' heel of NMR. The use of high temperature superconducting (HTS) resonators as pick-up coils in NMR probes can significantly improve the detection sensitivity of NMR and expand the use of NMR for dilute and mass-limited samples. In previously proposed HTS-based probes, the resonators for the various channels are nested orthogonally around the sample region. With this configuration, optimal sensitivity can be achieved only by the single innermost channel, which has its coils closest to the sample. We report here a new configuration in which the NMR probe has been simultaneously optimized for detection sensitivity of two channels, namely, hydrogen and carbon. The probe employs novel double-tuned HTS resonators that generate strong, uniform, and mutually orthogonal magnetic fields at the hydrogen and carbon NMR frequencies. The resonator is designed for optimal magnetic field homogeneity and minimal electric field in the sample region. Design considerations for the resonators and probe performance in NMR tests are presented.

Review of the Dynamics of Coalescence and Demulsification by High-Voltage Pulsed Electric Fields

The coalescence of droplets in oil can be implemented rapidly by high-voltage pulse electric field, which is an effective demulsification dehydration technological method. At present, it is widely believed that the main reason of pulse electric field promoting droplets coalescence is the dipole coalescence and oscillation coalescence in pulse electric field, and the optimal coalescence pulse electric field parameters exist. Around the above content, the dynamics of high-voltage pulse electric field promoting the coalescence of emulsified droplets is studied by researchers domestically and abroad. By review, the progress of high-voltage pulse electric field demulsification technology can get a better understanding, which has an effect of throwing a sprat to catch a whale on promoting the industrial application.

Effect of an electric field on nucleation and growth of crystals

The effect of the electric field strength on nucleation and growth of the crystals of ammonium halides and alkali metal sulfates has been studied. The optimal electric field strength for NH4Cl and NH4Br crystals was found to be 15 kV/cm, and for NH4I, it equaled 10 kV/cm. No effect of the electric field strength on the crystal growth was found for alkali metal sulfates. This difference is analyzed in terms of the crystal growth thermodynamics. In case, when the electric field is small and the Gibbs energy is of a significant value, the influence of the electric field at the crystal growth is negligible. A method to estimate the critical radius of homogeneous nucleation of the crystal is suggested.

SPPO pore-filled composite membranes with electrically aligned ion channels via a lab-scale continuous caster for fuel cells: An optimal DC electric field strength-IEC relationship

In this paper, novel composite membranes with electrically aligned ion channels in the thickness direction are presented for fuel cell applications; a fabrication method in the scale-up system and continuous mode is also suggested. The sulfonated poly(2,6-dimethyl-1,4-phenlyene oxide) (SPPO) polymer filled porous polyethylene (ρPE) films were prepared using a lab-scale continuous caster and simultaneously a direct-current (DC) electric field was applied for the alignment of ion channels in SPPO. Importantly, the proton conductivity of aligned-composite membranes with various ion exchange capacities was enhanced by three to five times than the non-aligned SPPO composite membranes. Finally, the optimized aligned composite membranes with the highest transport number were only applied for the fuel cell test. The optimized aligned composite membrane revealed the highest maximum power density than other fabricated composite membranes and Nafion® 115. Especially, the normalized maximum power density for unit conductivity value was introduced to confirm the effects of alignment of ion channels in a practical electrochemical system. The normalized maximum power density for unit conductivity value for the optimized aligned composite membrane was also stood 43% higher than that of Nafion® 212. According to all properties in this study, understanding the technique of alignment the ion channel in composite membranes offers a great possibility for improving the performance of the ion exchange membrane.

The influence and optimisation of electrical parameters for enhanced coalescence under pulsed DC electric field in a cylindrical electrostatic coalescer

A pulsed DC electric field is usually used to enhance drop–drop and drop–interface coalescence in a water-in-oil (W/O) emulsion. The effect and optimisation of electrical parameters are important when designing an electrostatic coalescer. In this work, experiments were performed with a small-scale electrostatic coalescer and image processing technology using water in crude oil emulsions to investigate the influence of electric field intensity, frequency, duty ratio and rise time. The comparison between experimental data and predicted data based on the two-layer capacitor model of a cylindrical electro-coalescer was also obtained to validate whether the two-layer capacitor model is applicable for a concentric cylindrical electrostatic coalescer. Optimum electric field strength exists for different water content emulsions (525.6kVm−1 for water content of 10% and 338.1kVm−1 for 30%), which suggests that it is higher for lower water content emulsion. There are two optimum frequencies in the low and high frequency ranges. For water content of 10%, the optimum frequency is approximately 20Hz, while for 30%, it is 10Hz in the low frequency range. The coalescence effect is also high when the frequency is 2000Hz. The droplet diameter is largest when the duty ratio is 50% for different electric field strengths, frequencies and water contents. The effect of rise time for pulsed DC is negative and the longer the rise time is, the worse the electrostatic coalescence effect is. The optimum frequency and duty ratio are obtained by using a theoretical formula and an empirical formula. The optimum frequency is nearly the same for the low frequency range especially for emulsions with a water content of 10%, but coalescence effects will increase at high frequency, which is different from the theoretical predicted value, indicating that the theory is applicable in the low frequency range for the concentric cylindrical coalescer. The predicted duty ratio is close to 0.5 and is nearly the same as the experimental results. In the electrostatic coalescer, the waveform of pulsed DC will be distorted to a triangle wave at high frequency. The high-frequency pulsed DC electric field is therefore not suitable for use in an electrostatic coalescer with an insulated electrode.

The coil orientation dependency of the electric field induced by TMS for M1 and other brain areas.

BackgroundThe effectiveness of transcranial magnetic stimulation (TMS) depends highly on the coil orientation relative to the subject’s head. This implies that the direction of the induced electric field has a large effect on the efficiency of TMS. To improve future protocols, knowledge about the relationship between the coil orientation and the direction of the induced electric field on the one hand, and the head and brain anatomy on the other hand, seems crucial. Therefore, the induced electric field in the cortex as a function of the coil orientation has been examined in this study.MethodsThe effect of changing the coil orientation on the induced electric field was evaluated for fourteen cortical targets. We used a finite element model to calculate the induced electric fields for thirty-six coil orientations (10 degrees resolution) per target location. The effects on the electric field due to coil rotation, in combination with target site anatomy, have been quantified.ResultsThe results confirm that the electric field perpendicular to the anterior sulcal wall of the central sulcus is highly susceptible to coil orientation changes and has to be maximized for an optimal stimulation effect of the motor cortex. In order to obtain maximum stimulation effect in areas other than the motor cortex, the electric field perpendicular to the cortical surface in those areas has to be maximized as well. Small orientation changes (10 degrees) do not alter the induced electric field drastically.ConclusionsThe results suggest that for all cortical targets, maximizing the strength of the electric field perpendicular to the targeted cortical surface area (and inward directed) optimizes the effect of TMS. Orienting the TMS coil based on anatomical information (anatomical magnetic resonance imaging data) about the targeted brain area can improve future results. The standard coil orientations, used in cognitive and clinical neuroscience, induce (near) optimal electric fields in the subject-specific head model in most cases.Electronic supplementary materialThe online version of this article (doi:10.1186/s12984-015-0036-2) contains supplementary material, which is available to authorized users.

Design, fabrication and characterization of dielectrophoretic microelectrode array for particle capture

Purpose – The purpose of this study is to design and characterize the dielectrophoretic (DEP) microelectrodes with various array structure arrangements in order to produce optimum non-uniform electric field for particle capture. The DEP-electrodes with 2D electrode structure was fabricated and characterized to see the effect of electrode structure configuration on the capture capability of the cells suspending in the solution. Design/methodology/approach – The presented microelectrode array structures are made of planar conductive metal structure having same size and geometry. Dielectrophoretic force (FDEP) generated in the fluidic medium is initially simulated using COMSOL Multi-physics performed on two microelectrodes poles, which is then continued on three-pole microelectrodes. The proposed design is fabricated using standard MEMS fabrication process. Furthermore, the effect of different sinusoidal signals of 5, 10 and 15 volt peak to peak voltage (Vpp) at fixed frequency of 1.5 MHz on capturing efficiency of microelectrodes were also investigated using graphite metalloids particles as the suspended particles in the medium. The graphite particles that are captured at the microelectrode edges are characterized over a given time period. Findings – Based on analysis, the capturing efficiency of microelectrodes at the microelectrode edges is increased as voltage input increases, confirming its dependency to the FDEP strength and direction of non-uniform electric field. This dependency to field consequently increases the surface area of the accumulated graphite. It is also showed that the minimum ratio of the surface accumulated area of captured graphite is 1, 2.75 and 9 μm2 for 5, 10 and 15 Vpp, respectively. The simulation result also indicates a significant improvement on the performance of microelectrodes by implementing third pole in the design. The third pole effect the particles in the medium by creating stronger non-uniform electric field as well as more selective force toward the microelectrodes’ edges. Originality/value – The microelectrode array arrangement is found as a reliable method to increase the strength and selectivity of non-uniform electric field distribution that affect FDEP. The presented findings are verified through experimental test and simulation results.

Enhancing the dielectric property of 0.69PZT-0.31PZNN thick films by optimizing the poling condition

We investigated how the applied electric-field’s magnitude and the poling time affected, respectively, the dielectric property and the microstructure of piezoelectric lead zirconate titanate/lead zirconate nickel niobate (PZT-PZNN) thick films in order to apply the films to piezoelectric energy harvesters. Several 300-µm-thick, 10 × 10-mm2 PZT-PZNN squares were tape cast, laminated, sintered, and poled under 2-, 4-, 6-, 10-, 14-, and 15-kV/mm electric fields for 30 min. The 10-kV/mm electric field produced the highest d 33 × g 33 without mechanically damaging the sample. Further, samples were sintered at 950, 1000, and 1020 °C and subsequently poled at 10 kV/mm (previously determined as the magnitude of the optimal poling electric field) for 15, 30, 60, 120, and 240 min to investigate how the poling time affected the piezoelectric ceramic’s microstructure. The optimal poling time for all the sintered samples was 60 min. Further, the piezoelectric ceramics composed of small grains and poled longer than 60 min showed higher dielectric constants. However, those composed of large grains and poled for times shorter than 60 min showed higher dielectric constants because the element mobility of the piezoelectric ceramics increased with increasing poling time.

Effect of interaction between AC electric field and phonon oscillation of metal cluster on tip-growth of carbon nanotube

The paper reports effect of interaction between AC electric field and metal cluster sitting at tip end of the carbon nanotube (CNT) on CNT tip-growth in CVD theoretically. For this purpose, a theoretical model based on phonon oscillations of the metal catalyst and influence of AC electric field on these oscillations is presented. Results show that there is an optimum AC electric field which optimizes growth of ultra-long CNTs. Then it is demonstrated that, in comparison with CNTs in the absence of field, CNTs under optimum electric field grow more. In addition, relation between optimum temperature and amplitude of AC electric field is investigated and it is shown that increasing electric field leads to higher optimum temperature. Finally, Investigation of effect of catalyst type on optimum electric field demonstrates the optimum field for various catalysts is different due to their different characteristics including van der Waals interaction with carbon, atomic mass and number of free charge carriers per each atom. All results are discussed and interpreted.