Customized modulation on plasma uniformity by non-uniform magnetic field in capacitively coupled plasma

A two-dimensional fluid model based on COMSOL Multiphysics is developed to investigate the modulation of static magnetic field on plasma homogeneity in a capacitively coupled plasma(CCP)chamber. To generate a static magnetic field, direct current is applied to a circular coil located at the top of the chamber. By adjusting the magnetic field's configuration, which is done by altering the coil current and position, both the plasma uniformity and density can be significantly modulated. In the absence of the magnetic field, the plasma density exhibits an inhomogeneous distribution characterized by higher values at the plasma edge and lower values at the center. The introduction of a magnetic field generated by coils results in a significant increase in electron density near the coils. Furthermore, an increase in the sets of coils improves the uniformity of the plasma. By flexibly adjusting the positions of the coils and the applied current,a substantial enhancement in overall uniformity can be achieved. These findings demonstrate the feasibility of using this method for achieving uniform plasma densities in industrial applications.

Input signal design to estimate interwell connectivities in mature fields from the capacitance-resistance model

Interwell connectivities are fundamental parameters required to manage waterfloods in oil reservoirs. Data-driven models, such as the capacitance-resistance model （CRM）, are fast tools to estimate these parameters from time-correlations of input （injection rates） and output （production rates） signals. Noise and structure of the input time-series impose limits on the information that can be extracted from a given data-set. This work uses the CRM to study general prescriptions for the design of input signals that enhance the information content of injection/production data in the estimation of well-to-well interactions. Numerical schemes and general features of the optimal input signal strategy are derived for this problem.

Silicon Solar Cell Space Charge Region and Capacitance Behavior under Electric Field

This paper investigates theoretically the behavior of the space charge region of a silicon solar cell and its associated capacitance under the effect of an external electric field. The purpose of this work is to show that under illumination the solar cell’s space charge region width varies with both operating point and the external induced electric field and how the solar cell capacitance varies with the space charge region width. Based on a 1D modelling of the quasi-neutral p-base, the space charge region width is determined and the associated capacitance is calculated taking into account the external electric field and the junction dynamic velocity. Based on the above calculations and simulations conducted with Mathcad, we confirmed the linear dependence of the inverse capacitance with space charge region width for thin space charge region and we exhibit an exponential dependence for large space charge region.

Polycrystalline Silicon Solar Cell p-n Junction Capacitance Behavior Modelling under an Integrated External Electrical Field Source in Solar Cell System

The state of the p-n junction is very important to explain the performances of a solar cell. Some works give the influence of the electric field on the junction capacitance. However, these works do not relate the quality of the p-n junction under the electic field. The present manuscript is about a theoretical modelling of the p-n junction capacitance behavior of the polycrystalline silicon solar cell under an integration of the external electrical field source. An external electrical source is integrated in a solar cell system. The electronic carriers charge generated in the solar cell crossed mainly the junction with the great strength external electrical field. In open circuit, this crossing of the electronic charge carriers causes the thermal heating of the p-n junction by Joule effect. The p-n junction capacitance plotted versus the junction dynamic velocity and the photo-voltage for different external electrical fields. The electric field causes the decrease of the photo-voltage mainly the open-circuit photo-voltage. The decrease of the photo-voltage translates the narrowing of the Space Charge Region (SCR). The average value of the external electric field used in this study is not sufficient to cause the breakdown of the p-n junction of the solar cell system under integration of the external electrical field production source. The increase of the electrical field causes rather the narrowing of the SCR. That can provide an improvement of the solar cell’s electrical outputs.

Influences of fringing capacitance on threshold voltage and subthreshold swing of a GeOI metal-oxide-semiconductor field-effect transistor

Models of threshold voltage and subthreshold swing, including the fringing-capacitance effects between the gate electrode and the surface of the source/drain region, are proposed. The validity of the proposed models is confirmed by the good agreement between the simulated results and the experimental data. Based on the models, some factors impacting the threshold voltage and subthreshold swing of a GeOI metal-oxide-semiconductor field-effect transistor（MOSFET） are discussed in detail and it is found that there is an optimum thickness of gate oxide for definite dielectric constant of gate oxide to obtain the minimum subthreshold swing. As a result, it is shown that the fringing-capacitance effect of a shortchannel GeOI MOSFET cannot be ignored in calculating the threshold voltage and subthreshold swing.

The Finite Element Analysis for Parallel-wire Capacitance Probe in Small Diameter Two-phase Flow Pipe

This paper presents a novel capacitance probe, i.e., paraUel-wire capacitance probe （PWCP）, for two-phase flow measurement. Using finite element method （FEM）, the sensitivity field of the PWCP is investigated and the optimum sensor geometry is determiend in term of the characterisitc parameters. Then, the response of PWCP for the oil-water stratified flow is calculated, and it is found the PWCP has better linearity and sensitivity to the variation of water-layer thickness, and is almost independant of the angle between the oil-water interface and the sensor electrode. Finally, the static experiment for oil-water stratified flow is carried out and the calibration method of liquid holdup is presented.

Capacitance Evaluation on Non-parallel Thick-Plate Capacitors by Means of Finite Element Analysis

In this work we show the influence of the edge-effect on the electric field distribution and, hence, on the inner and outer capacitance in an inclined-plate capacitor system surrounded by an insulating medium taking into account the thickness of the conducting plates for a complete set of dimensions and insulating characteristics. Where available, we compare our results with previously published works. Finally, using statistical tools, we obtain approximate expression for computing the relationship between capacitance and insulation material characteristics, insulation gap, plate dimensions and angle.

Mapping wind by the first-order Bragg scattering of broad-beam high-frequency radar

Mapping wind with high-frequency(HF)radar is still a challenge.The existing second-order spectrum based wind speed extraction method has the problems of short detection distances and low angular resolution for broadbeam HF radar.To solve these problems,we turn to the first-order Bragg spectrum power and propose a space recursion method to map surface wind.One month of radar and buoy data are processed to build a wind spreading function model and a first-order spectrum power model describing the relationship between the maximum of first-order spectrum power and wind speed in different sea states.Based on the theoretical propagation attenuation model,the propagation attenuation is calculated approximately by the wind speed in the previous range cell to compensate for the first-order spectrum in the current range-azimuth cell.By using the compensated first-order spectrum,the final wind speed is extracted in each cell.The first-order spectrum and wind spreading function models are tested using one month of buoy data,which illustrates the applicability of the two models.The final wind vector map demonstrates the potential of the method.

Active and Capacitive Conductance of the Diode in a Strong Microwave Field

It is shown that the mean value of the capacitive current arising in the p-n-junction in a microwave field is zero, and the average value of the active current independently of the current value is different from zero and is equal to the current generated by the diode.

Synthesis and characterization of Fe_3O_4 magnetic nanoparticles and their heating effects under radiofrequency capacitive field

Fe3O4 magnetic nanoparticles with diameters varying from 10 to 426 nm were synthesized and characterized.Heating effects of Fe3O4 magnetic nanoparticles under radiofrequency capacitive field(RCF) with frequency of 27.12 MHz and power of 60-150 W were investigated.When the power of RCF is lower than 90 W,temperatures of Fe3O4 magnetic nanoparticles(75-150 mg/mL) can be raised and maximal temperatures are all lower than 50 ℃.When the power of RCF is 90-150 W,temperatures of Fe3O4 magnetic nanoparticles can be quickly raised and are all obviously higher than those of normal saline and distilled water under the same conditions.Temperature of Fe3O4 magnetic nanoparticles can even reach 70.2 ℃ under 150 W RCF.Heating effects of Fe3O4 magnetic nanoparticles are related to RCF power,particle size and particle concentration.

Simulation study on electron heating characteristics in magnetic enhancement capacitively coupled plasmas with a longitudinal magnetic field

The electron heating characteristics of magnetic enhancement capacitively coupled argon plasmas in presence of both longitudinal and transverse uniform magnetic field have been explored through both theoretical and numerical calculations.It is found that the longitudinal magnetic field can affect the heating by changing the level of the pressure heating along the longitudinal direction and that of the Ohmic heating along the direction which is perpendicular to both driving electric field and the applied transverse magnetic field,and a continuously increased longitudinal magnetic field can induce pressure heating to become dominant.Moreover,the electron temperature as well as proportion of some low energy electrons will increase if a small longitudinal magnetic field is introduced,which is attributed to the increased average electron energy.We believe that the research will provide guidance for optimizing the magnetic field configuration of some discharge systems having both transverse and longitudinal magnetic field.

Analytical capacitance model for 14 nm Fin FET considering dual-k spacer

The conformal mapping of an electric field has been employed to develop an accurate parasitic capacitance model for nanoscale fin field-effect transistor（Fin FET） device. Firstly, the structure of the dual-layer spacers and the gate parasitic capacitors are thoroughly analyzed. Then, the Cartesian coordinate is transferred into the elliptic coordinate and the equivalent fringe capacitance model can be built-up by some arithmetical operations. In order to validate our proposed model, the comparison of statistical analysis between the proposed calculation and the 3D-TCAD simulation has been carried out, and several different material combinations of the dual-k structure have been considered. The results show that the proposed analytical model can accurately calculate the fringe capacitance of the Fin FET device with dual-k spacers.

FEM Edge Effect and Capacitance Evaluation on Cylindrical Capacitors

The purpose of this paper is to show the influence of the edge-effect on the electric field distribution, and hence on the inner capacitance and outer capacitance of a cylindrical capacitor surrounded by an insulating medium. To generalize the results, a two-dimensional axisymmetric finite element model of a cylindrical capacitor has been generated and the problem has been resolved taking into account the distance between the conductors for a complete set of dimensions. The available obtained results have been compared with previous published works. Finally, using statistical tools, the mathematical expression for computing the relationship between capacitance and insulation gap and cylindrical plates dimensions has been obtained.

Bifacial Silicon Solar Cell Steady Photoconductivity under Constant Magnetic Field and Junction Recombination Velocity Effects

The paper reported a theoretical study on the photoconductivity of a bifacial silicon solar cell under polychromatic illumination and a constant magnetic field effect. By use of the continuity equation in the base of the solar cell maintained in a constant temperature at 300 K, an expression of the excess minority carriers’ density was determined according to the applied magnetic field, the base depth and the junction recombination velocity. From the expression of the minority carriers’ density, the photoconductivity of the solar cell was deduced and which allowed us to predict some recombination phenomena, the use of such solar cell in optoelectronics. The profile of the photoconductivity also permitted us to utilize a linear model in order to determine an electrical capacitance that varied with magnetic field.

Development of mean-field electrical double layer theory

In order to understand the electric interfacial behavior, mean field based electric double layer （EDL） theory has been continuously developed over the past 150 years. In this article, we briefly review the development of the EDL model, from the dimensionless Gouy-Chapman model to the symmetric Bikerman-Freise model, and finally toward size-asymmetric mean field theory models. We provide the general derivations within the framework of Helmholtz free energy of the lattice- gas model, and it can be seen that the above-mentioned models are consistent in the sense that the interconversi0n among them can be achieved by reducing the basic assumptions.

Research Progress of Electromagnetic Field and Electromagnetic Compatibility of UHVDC Converter Valves

特高压直流换流阀的电磁场和电磁兼容性是其研制过程中的关键问题,国内外学者对此进行了系统研究。中国电力科学研究院成功研制出中国首个具有完全自主知识产权的800 kV/4 750 A特高压直流（ultra high voltage directcurrent,UHVDC）换流阀。针对电磁场和电磁兼容问题,利用三维电场边界元法实现换流阀寄生参数的提取,通过理论计算、数值仿真及试验测试等多种手段,对瞬态电磁干扰等问题提出了解决方案,为换流阀的研制和工程应用提供了必要的技术支撑。总结了上述领域的研究成果,对未来特高压直流换流阀电磁兼容领域的研究课题与解决方案提出了一些建议和设想。

Electrical properties and electrical field in depletion layer for CZT crystals

Current—voltage (I—V) and capacitance—voltage (C—V) characteristics of Au/p-CZT contacts with different surface treatments on cadmium zinc telluride (CZT) wafer’s surface were measured with Agilent 4339B high resistance meter and Agilent 4294A precision impedance analyzer, respectively. The Schottky barrier height was 0.85±0.05, 0.96±0.05 eV for non-passivated and passivated CZT crystals by I—V measurement. By C—V measurement, the Schottky barrier height was 1.39±0.05, 1.51±0.05 eV for non-passivated and passivated CZT crystals. The results show that the passivation treatment can increase the barrier height of the Au/p-CZT contact and decrease the leakage current. The main reason is that the higher barrier height of Au/p-CZT contacts can decrease the possibility for electrons to pass through the native TeO2 film. Most of the applied voltage appears on the depleted layer and there is only a negligible voltage drops across the nearly undepleted region. Furthermore, the electric field in the depleted layer is not uniform and can be calculated by the depletion approximation. The maximum electric field of CZT crystals is Em1=133 V/cm at x=0 for non-passivated CZT crystal and Em2=55 V/cm for passivated CZT crystal, respectively.

A New Type of Capacitive Machine

The paper proposes a new type of the synchronous capacitive machine operated on a principle of the electric field effect. The proposed machine has smaller size and lighter weight than the standard electromagnetic synchronous machines with the same rated parameters. Another important advantage is a simple structure of the machine, which simplifies the production process and reduces the costs of the motor. The paper also presents extensive simulation results of the proposed capacitive machine. The simulation results show that the proposed machine is able to reach the same power output as the electromagnetic machines.

Explanation of Capacitive Performance of the Plasma in Damavand Tokamak

In this work capacity of tokamak plasma is calculated using modeling of tokamak configuration as toroidal and coaxial capacitor. This value is very important and plays an important role in time- varying regimes in tokamak. For exact simulation of plasma behavior, this amount will be added to circuit equations and transport codes. Since capacitive properties of tokamak cause production of a radial electric field, it deserves our special attention.

Isotope effects of plasma chemical carbon oxidation in a magnetic field

The influence of different factors on the plasma chemical reactions is widely studied today. However, insufficient consideration is given to the research of paramagnetic phenomena which takes place in plasma systems. The results of modeling the process of redistribution carbon isotopes between different phases while oxidizing it in high-frequency low-temperature plasma in an external magnetic field are shown in the article. The equilibrium concentrations of components involved in the oxidation process in a plasma system are defined. A principle possibility of isotope-selective plasma chemical reactions in a magnetic field was experimentally determined. The increase of concentration of 13C in the gas phase up to 1.3 times relative to natural abundance was obtained. It was found that the content of the carbon heavy isotope in the gas phase depends on the magnetic field action area. The best results were achieved with the combination of magnetic field impact area and the priority area of the appearance of plasma chemical reactions products.