Electric Field Uniformity Research Articles

A novel nanoscale FD-SOI MOSFET with energy barrier and heat-sink engineering for enhanced electric field uniformity

This paper aims to present a novel method to mitigate the undesirable issues associated with short-channel-effects (SCEs) and the critical lattice temperature of a fully depleted silicon-on-insulator (FD-SOI) MOSFET in the nanoscale regime. The proposed approach is based on simultaneously merging the energy barrier and heat-sink engineering simultaneously. Hafnium oxide as a high-k dielectric inside the channel region around the drain region is embedded to redistribute the band energy resulting in the enhancement of the energy barrier. This reformation of the band profile reduces variations in the channel depletion charge volume percentage caused by the drain voltage, thereby mitigating short-channel effects (SCEs). In order to promote effective thermal conduction, a portion of the buried oxide is replaced by doped P-type silicon which acts as an effective heat-sink. The devices under the investigation have been simulated using SILVACO software, considering the comprehensive physical models. Drain-Induced Barrier Lowering (DIBL), leakage current, Ion to Ioff ratio, subthreshold swing, hot carrier effect and lattice temperature as the essential parameters have been successfully improved for the proposed device in comparison to the conventional device.

The effect of electric field uniformity on electrospun jet evolution and fiber morphology

Electric field distribution has a considerable impact on jet motion and resultant fibers’ diameter and morphology in electrospinning process. This study aims to explore the effect of electric field uniformity on jet evolution and fiber morphology by using auxiliary electrodes. Four disc auxiliary electrodes with different external diameters were designed. A high-speed photography equipment was employed to capture the jet motion. The morphology the fibers obtained from different locations of the jet were observed by the SEM to investigate jets evolution under different electric fields. The three-dimensional electric field were calculated by the ANSYS Maxwell software to simulate and quantify the electric field distribution throughout the electrospinning process. The results show that the larger diameter of the auxiliary electrode creates more uniform electric field distribution, smaller jet straight lengths, larger whipping amplitude, and lower the jet velocity. These factors result in finer and more uniform fibers. It was found that the morphology of fiber surface, beads shape and size also influenced by the uniformity of electric field distribution. This research indicates that a controllable uniform electric field was essential in preparing high-performance fibers.

Effects of energy input modes on energy efficiency and berry quality in continuous microwave drying

To elucidate the effects of energy input modes on energy efficiency and berry quality in continuous microwave drying, four energy input modes with variational working ways of magnetrons were investigated by using numerical simulation and bench experiments in a continuous microwave dryer. Energy efficiency was divided into absorption and conversion efficiency to study the change rule of drying process, and the retention rate of anthocyanins of berry’s representative nutrition ingredient was studied considering both of the temperature and its uniformity. Results indicate that the energy input modes affect the absorption efficiency by changing the distribution uniformity of electric field of material layer, and the conversion efficiency by altering the matching degree between the energy allocation and drying characteristics of berry, which are both determined by the ways of working magnetrons of different energy input modes. The conversion efficiency has a greater influence on the final energy efficiency, so the energy input mode should be paid attention to the provision of microwave energy by selecting proper way of working magnetrons according to the drying characteristics. The effect of temperature uniformity on anthocyanin degradation is more obvious with average temperature increasing gradually, where better uniformity of electric field strength should be provided to guarantee the quality of dried berry by adjusting the energy input mode. The research results provide significant insights to optimize the energy input mode of taking into account both the energy efficiency and dried quality of material.

The mechanism of tuning filler orientation degree in composites based on AC electric field assist: from microscopic dynamical model to macroscopic electrical properties

Using the AC electric field to induce the orientation of nonlinear conductive fillers in composites is an effective solution for alleviating electric field distortion in power modules. However, the mechanism by which the electric field affects the filler dynamic characteristics and the composites’ electrical properties remains unclear. In this paper, the correlation between the microscopic dynamic processes of fillers and the macroscopic current amplitude was analyzed. The results show that the current increases rapidly (0 ∼ 173 s) and then slowly (173 ∼ 869 s) at 600 V mm−1, influenced by the rotation and attraction processes of the fillers. This demonstrates that the orientation stops at about 869 s and the filler orientation state is a key factor in determining the dielectric properties. Secondly, the global orientation evaluation index D for the filler network was proposed, which can also derive the minimum time and energy loss required for preparation. Finally, the impact of different filler orientations on the composites’ conductivity was investigated. In the low electric field stress region, with the average carrier jump distance decreasing from 150.23 to 109.71 nm as the D increases from −0.93 to −0.05. On this basis, materials with nonlinear conductivity gradient distribution can be easily prepared. Before optimization, the electric field stress of the power module at the triple point was 35.79 kV. This composite can reduce the value to 15.42 kV, a decrease of 56.9%, while maintaining good electric field uniformity.

Implementation of the frozen-spin technique for the search for a muon electric dipole moment

Applying the frozen-spin technique in a compact 3 T solenoid will enable a search for the muon electric dipole moment (EDM) with unprecedented sensitivity, improving upon the current direct limit by approximately a factor of 1000. After injection of a selected muon, a pulsed magnetic field will reduce its longitudinal momentum sufficiently to be confined within a static weakly-focusing magnetic field and maintain a closed circular orbit. A precisely tuned radial electric field will cancel the spin precession induced by the muon's anomalous magnetic moment, a = (g - 2)/2, relative to the orientation of the momentum. In this configuration, the EDM becomes the only remaining inherent source of relative precession. Asymmetry in the direction and energy of positrons emitted from muon decay provides an experimental signature of such precession.In the first of two phases, 28 MeV/c muons from the πE1 beamline at PSI will be used to demonstrate the systems necessary for injecting and trapping muons, tuning fields to the frozen-spin condition and reconstructing positron trajectories. Designs for the coils producing the pulsed magnetic field and the electrodes applying the frozen-spin electric field are currently being evaluated with simulations and prototypes. These systems must be designed in parallel, especially due to the impact of eddy-currents induced in the electrodes by the pulsed magnetic field. The electrode design must minimise eddy-currents to preserve the field strength of the pulsed field responsible for muon trapping, while maintaining the electric field uniformity necessary to achieve the sensitivity goal. This article summarises some of the efforts underway to address these design challenges.

A phase-locked transit time oscillator operated with low external guiding magnetic field

A phase-locked coaxial transit time oscillator is designed for microwave sources with a small volume and low magnetic field in high-power microwave coherent combining. The oscillator achieves controlled output phase through pre-modulation of electron beams. To improve the phase-locked performance with low magnetic fields, a reentrant input cavity is used to ensure the stability and uniformity of the electric field. Electric field uniformity of the buncher and extractor is also improved. To reduce the device volume, a reflector with pre-modulation function is used to reduce the axial size of the device. Particle-in-cell simulation shows that 5 kW input power is sufficient to lock-in a 610 MW output microwave, with a conversion efficiency of 40.6% at 0.66 T. The input power ratio reaches −50.8 dB. Simulation results demonstrate that the device can still achieve phase locking with a magnetic field as low as 0.5 T.

Two-Stage Electric Field Optimization Method for High-Voltage Power Module Using Dielectrically Graded Insulation Micro-Region

Dielectrically graded insulation (DGI) with spatially inhomogeneous dielectric parameter distribution can provide extraordinary insulation performance for high-voltage power equipment. The most crucial objective in the application of DGI is to identify the optimal distribution of dielectric parameters. However, the calculation efficiency and electric field optimization results of the existing methods are poor under complex insulation structures. Also, the dielectric loss of DGI calculated by these methods is relatively large. In this work, an efficient DGI parameter optimization method was developed. Firstly, a variable density topology optimization model was proposed to improve the electric field uniformity of the power module and suppress the electric field stress at the triple point. Secondly, the influence of different model parameters on the mitigation degree of the electric field was studied to obtain the optimal parameters. Finally, to reduce the dielectric loss of the insulation, the DGI micro-region was constructed by narrowing the optimized region. Numerical results indicate that the model only needs 23 iterations to obtain the optimal result. After optimization, the electric field stress at the triple point is reduced by 71.7%. DGI micro-regions reduce dielectric loss by 85.1% compared to global DGI. This study shows that the proposed method is anticipated to provide a new route for the preparation and application of DGI.

Heterogeneous mesoscopic structure modulation enhancing dielectric strength of polypropylene insulation

This paper focuses on the heterogeneous mesoscopic structure modulation enhancing dielectric strength of polypropylene insulation. α-nucleating agents are used to modulate the heterogeneous mesoscopic structure of polypropylene, and Voronoi Network models with similar structures are established to simulate the electric field distribution at the mesoscopic scale. The experimental results show that the addition of an α-nucleating agent effectively diminishes the spherocrystal size and increases its density. The high continuity and wide range electric field distortion caused by the too-large spherocrystal size and too-loose arrangement is thus suppressed. The improvement of electric field uniformity effectively inhibits the frequency and intensity of partial discharge. Compared with pure polypropylene, the partial discharge in polypropylene composite with α-nucleating agents at 0.1 wt% decreased by 2414 times, and its maximum amplitude decreased by 58.3%. The increase in the spherocrystal density also enhances its blocking effect on the electrical tree growth, and the length and width of it are reduced by 88.6% and 89.1%, respectively. The dispersive development of the electrical tree reduces the incidence of penetration channels along the electric field direction. The breakdown strength is therefore increased by approximately 20%. The simulation results demonstrate that the dielectric property difference between the crystal and amorphous regions within polypropylene at the mesoscopic scale is the main reason that triggers the electric field distortion at its interface and further leads to insulating degradation or even failure. In this study, heterogeneous mesoscopic structure modulation is proved to be an efficient means to enhance the dielectric strength of polypropylene insulation.

Study of a planar cascaded GEM TEPC with sealed chamber for the radiation detection in microdosimetry

In the field of radiation detection in microdosimetry, the Tissue Equivalent Proportional Counters (TEPCs) are the key detector options in determining the radiation quality. In this paper, two different structures of TEPCs were introduced, and their electric field uniformity and angular dependence were disscussed. A planar cascaded GEM TEPC with sealed chamber was developed in the laboratory and the general materials used in the detector were tested for outgassing characteristics. The experimental results showed that the polyether ether ketone (PEEK) had the lowest outgassing rate among all tested materials and were selected as the main assembly materials of the TEPC detector. The 241Am was used as the built-in radioactive source for detector calibration, and the detector gain characteristics were studied. The long-term operating stability was tested at working pressure of 54.72 kPa, with a gain consistency of better than 97.8% over 7 days (168 hours) and relative gain variation less than 1% over 4 days (96 hours).

The effect of nozzle spacing on the electric field and fiber size distribution in a multi‐nozzle electrospinning system

AbstractThe present study investigates the characteristics of nanofiber uniformity in a multi‐nozzle electrospinning system widely used to prepare nanofiber matrix. The effect of nozzle spacing on the electric field and nanofiber diameter uniformity is analyzed using a four‐nozzle electrospinning system. The electric field distribution at the nozzle tip at different nozzle spacings is simulated numerically using COMSOL Multiphysics 5.6. Simulation results find that as nozzle spacings increase from 1 to 5 cm, the average electric field intensity at 1 mm from the tip of four nozzles increases from 32.46 to 40.08 kV/cm. Variations of electric field intensity at a given spacing decrease from 11% to 3.2% for spacings of 1 to 5 cm. Corresponding experiments are conducted with a gelatin solution. As the nozzle spacing increases, the four nozzles produce nanofibers with diameters of 88–508 nm, 112–498 nm, and 90–418 nm. Nanofiber diameter uniformity increases, and the average diameter decreases from 268 to 222 nm. In addition, the effect that changes in voltages and nozzle‐to‐collector distances have on fiber diameter is also studied. The experiments show that nanofiber diameter decreased as voltage increased and increased as nozzle‐to‐collector distance increased.

Analysis of Influencing Factors on Electric Field Distribution of 500 kV Porcelain Insulators

With the upsurge of the digital twin power grid, it is very necessary to carry out a three-dimensional model and simulation analysis of the power grid system. Insulators are one of the important components in the power system, and the appropriate simplification of the simulation model is of great significance. In this paper, the finite element software is used to calculate the three-dimensional model, and the influence of the length of the conductor, the tower, the yoke plate, the grading ring, and the arrangement of the insulators on the axial electric field distribution (EFD) is analyzed. The results show that: the length of the conductor will affect the uniformity of the axial electric field; compared with the grading ring, the yoke plate will cause serious distortion of the electric field intensity curve; the integrity of the tower has different effects; the arrangement of the insulators will affect the magnitude of the electric field and even the shape of the curve. Therefore, in the simulation analysis of the axial electric field, the above factors should be considered when simplifying the insulator model, which will promote the development of relevant digital twin technology.

An Investigation into the Effects of Electric Field Uniformity on Electrospun TPU Fiber Nano-Scale Morphology.

ANSYS Maxwell was used to replicate the conditions of two potential electrospinning configurations: a needle-plate and a parallel-plate configuration. Simulations showed that the electric field generated within the parallel-plate configuration was much more uniform than that within the needle-plate configuration. Both configurations were assembled and used electrospin fibers at three different spinning distances (10 cm, 12 cm, and 15 cm), at a consistent electric field strength of 1.7 kV/cm. Scanning electron microscopy was used to compare the morphologies of the fibers produced in both configurations in order to confirm whether a more uniform electric field yielded thinner fibers. The results show that the needle-plate configuration produced finer fibers than the parallel-plate configuration at all three spinning distances. However, there was no difference in the fiber diameters produced at the 12 and 15 cm spinning distances within the needle-plate configuration, implying thinning may only occur up to a certain distance in this configuration.

Effect of stimulation frequency on hippocampal electric field induced by deep-brain magnetic stimulation

Deep-brain Magnetic Stimulation (DMS) is a noninvasive brain modulation method that improves hippocampal neural activity. The frequency of DMS has a significant effect on the hippocampal induced electric field. In this paper, we investigate the relationship between stimulation frequency and DMS-induced hippocampal electric field. The frequency sensitivity and distribution uniformity of the hippocampal electric field are calculated to quantify this relationship. The results show that the DMS-induced hippocampal electric field has a frequency-dependent property. The frequency sensitivity of the DMS-induced hippocampal electric field in the high frequency band is lower than that in the low frequency band, which corresponds to the low-pass filtering property of the neuron membrane. The frequency sensitivity of DMS-induced hippocampal electric field is highest in the range of 30–40 Hz. The uniformity of the hippocampal electric field induced by a single coil also reaches the highest in the range of 30–40 Hz, while uniformity of the hippocampal electric field induced by multiple-coil increases with increasing frequency. The frequency-dependent property of the DMS-induced hippocampal electric field is positively correlated with the quantity and size of coils, while negatively correlated with the spacing of the coils. This study is of great help in the selection of DMS frequencies and the design of coils.

New trapezoid-shaped Frisch-grid ionization chamber for low-energy particle measurements

A new trapezoid-shaped Frisch-grid ionization chamber (TFG-IC) has been built as a part of a varDelta {E}-E telescope system for the detection and identification of charged particles at energies down to a few MeV. To study the effect of the drift electric field uniformity, two types of sealed windows, namely a pair of SSA (split-strip aluminized mylar film) and a pair of DSA (double-sided aluminized mylar film) sealed windows have been investigated. The detector’s performances were studied using a standard ^{241}Am source at different gas pressures, and the total energy-deposit resolution achieved is about 1.1%(FWHM). The varDelta {E}-E telescope, which was composed of TFG-IC and a DSSSD (double-sided silicon strip detector), has been tested using a three-component alpha source and the ^{241}Am source under laboratory conditions. The results show that the energy resolution with the SSA sealed windows which provide uniform drift electric field has a smaller fluctuation than that with the DSA ones; the fluctuations are about 1% and 4% for the former and the latter, respectively. Simulations using the COMSOL software also confirmed the electric-field distortion at the edge of the detector with the DSA windows. A correlation curve between energy resolution and energy deposit of charged particles at various gas pressures and for two gas species is derived for TFG-IC with the SSA sealed windows using the measurement with the ^{241}Am source. Incorporating the above results, we performed Monte Carlo simulations to evaluate the particle-identification capability of the telescope. The results show that the telescope can be extended to the identification of low-energy particles.

Synergistic improved electrical resistivity-temperature characteristics and DC breakdown strength in insulating XLPE composites by incorporating positive temperature coefficient particles

Weakening the electrical resistivity-temperature dependence of cross-linked polyethene (XLPE) is an effective way to enhance the electric field uniformity of high-voltage direct current (HVDC) cables. Therefore, an attempt is made to suppress the negative temperature coefficient (NTC) of electrical resistivity by incorporating BaTiO3-based ceramic fillers with positive temperature coefficient (PTC) electrical resistivity into XLPE. Morphology characterization indicated that PTC particles were well dispersed in the XLPE matrix. The measurements of electrical resistivity and DC breakdown strength are carried out from 30 °C to 90 °C. The electrical resistivity and DC breakdown strength of the sample at high temperatures were significantly improved with the introduction of PTC particles, which is attributed to the deep traps near the Curie temperature region. The high doping content has a better suppression of the NTC effect. The activation energy (0.63 eV) and NTC strength (1.74) of the sample with the addition of 10 wt% of PTC are considerably reduced compared with XLPE. The content of PTC particles was positively correlated to the enhancement of electrical resistivity and DC breakdown strength. The optimum content for DC breakdown strength is about 5 wt%. The low electrical resistivity-temperature dependence of insulation performance shows a potential to obtain temperature-stable HVDC cable insulation.

Circular Geometry in Molecular Stream Separation to Facilitate Nonorthogonal Field-to-Flow Orientation.

Molecular stream separation (MSS) is a promising complement for continuous-flow synthesis. MSS is driven by forces exerted on molecules by a field applied at an angle to the stream-carrying flow. MSS has only been performed with a 90° field-to-flow angle because of a rectangular geometry of canonic MSS; the second-order rotational symmetry of a rectangle prevents any other angle. Here, we propose a noncanonic circular geometry for MSS, which better aligns with the polar nature of MSS and allows changing the field-to-flow. We conducted in silico and experimental studies of circular geometry for continuous-flow electrophoresis (CFE, an MSS method). We proved two advantages of circular CFE over its rectangular counterpart. First, circular CFE can support better flow and electric-field uniformity than rectangular CFE. Second, the nonorthogonal field-to-flow orientation, achievable in circular CFE, can result in a higher stream resolution than the orthogonal one. Considering that circular CFE devices are not more complex in fabrication than rectangular ones, we foresee that circular CFE will serve as a new standard and a testbed for the investigation and creation of new CFE modalities.

Investigation of the Electric Field Uniformity in the ReD Detector

Investigation of the Electric Field Uniformity in the ReD Detector

A novel all-metal metamaterial for constructing relativistic slow wave structure

In recent vacuum electronic devices, metamaterials have shown an obvious advantage of miniaturization. Due to increasing miniaturization demand, research of metamaterials in high-power microwave (HPM) field is now also a hotspot. For better applications of metamaterials, there are still two issues to be solved, the low space limit current of the structure and the low uniformity of the working electric field. To solve these problems, we construct a novel all-metal metamaterial structure by applying a 45° rotational arrangement in space and a four-support rod structure. This new metamaterial structure has a great uniformity of the axis electric field, and its electric field fluctuation is reduced from 8.6% to 2.8%. Based on this metamaterial structure, we proposed a novel relativistic slow wave structure, and its working mode has a negative dispersion characteristic. Using the method of expanding the electron beam channel, the space limit current of the relativistic slow wave structure is greatly improved to 12.3 kA, and the particle simulation method is used to prove the increase in the space limit current. In addition, it is found that this slow wave structure has higher coupling impedance, which provides a better working environment for an annular relativistic electron beam. Therefore, this metamaterial structure has great potential in the HPM field.

Design and Simulation of High-Aspect-Ratio Sheet Beam EIK at 0.22 THz

To improve the output performance of 0.22 THz extended-interaction klystrons (EIKs), we utilized a 20:1-aspect-ratio sheet beam to drive the circuit. The applicable high-frequency structure is discussed to obtain effective characteristic impedance, which is conducive to stronger beam-wave interaction. In addition, the loaded waveguide and the tuning scheme in the input cavity are proposed to provide good electric field uniformity over the whole beamwidth. Moreover, the nonuniform period output circuit based on the phase dynamic synchronization technology is optimized to further enhance power. Meanwhile, considering the feasibility of cathode performance, the beam current density in the tunnel is limited to 330 A/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> . The designed four-cavity interaction circuit is comprised of two 9-gap idler cavities and 11-gap input and output cavities. With the operating parameters of 16.2 kV beam voltage and 0.66 A beam current, the particle-in-cell (PIC) simulation predicts a stable output power of 700 W with a 39 mW input excitation. The corresponding gain and 3 dB bandwidth are 42.5 dB and 500 MHz, respectively. An asymmetric single-stage depressed collector is also designed to recover the spent beam energy from the interaction circuit. The collector efficiency is 81.1% with zero electron reflux rate while taking secondary electrons into consideration, and the overall tube efficiency is 26.9%.

Study of a 0.34-THz Ladder-Type Extended Interaction Klystron With Narrow Coupling Cavities

A narrow coupling ladder-type extended interaction klystron (EIK) operating at 0.34 THz is proposed and analyzed. Compared with the traditional THz EIKs, the narrow coupling EIK can offer higher power capability and increased efficiency because such arrangement has higher characteristic impedance and a more uniform electric field in the beam tunnel. This article studies the electric field distribution of the narrow coupling circuits and traditional circuits. Moreover, the coefficient of variation is introduced to quantify the uniformity of the axial electric field in the beam tunnel. The operating stability is also ensured by adjusting the period length and number of cells. The 3-D particle-in-cell (PIC) simulation predicts the ideal EIK, driven by a 0.15-A, 17.5-kV electron beam confined in a 0.22-mm diameter beam tunnel, and generates an output power of 41 W. The corresponding gain, electronic efficiency, and 3-dB bandwidth are 28.03 dB, 1.56%, and 600 MHz, respectively. Finally, in order to verify the feasibility of the designed structure, we perform a sensitivity study on the EIK design for an eight-micron fabrication tolerance assuming normal distributions for all critical dimensions per each cell with PIC simulations.