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Uniform field coil design based on the target-field method in miniature atomic sensors
摘要： This paper presents the design of a uniform ?eld coil based on the target-?eld method, which offers an innovative in miniature atomic sensors. A selected uniform ?eld cubical target region is located inside a cylinder with the surface comprised of coil windings. Firstly, the current density was de?ned with unknown coef?cients, and then a straightforward approach was used to obtain these coef?cients via solving a matrix constructed by selecting ?eld points in the target region. Subsequently, using the stream-function, the winding patterns of the coils are generated. Compared to the traditional coil design method, this method effectively solves the inconsistency between the uniform ?eld areas and the sensor structures, by prede?ning the size of the coil surface before calculating the current distribution. It also avoids the cumbersome calculation process caused by the multi-order Taylor expansion based on the traditional method. Furthermore, a current density formula was expanded by trigonometric series, which is particularly suitable for a cylindrical coil system with the uniform internal ?eld. The theoretical accuracy can be greatly improved by choosing an optimal order of the trigonometric series. To prove its performance, a contrast with a Lee-Whiting coil is proposed. In addition, the utilized coil was manufactured by Flexible Printed Circuit technology and magnetic ?eld uniformities were veri?ed by an actual test using a ?uxgate magnetometer.
关键词： miniature atomic sensors,The target-?eld method,current density,uniform ?eld coil
更新于2025-09-10 09:29:36
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High-performance black phosphorus field-effect transistors with long-term air-stability
摘要： Two-dimensional layered materials (2DLMs) are of considerable interest for high-performance electronic devices for their unique electronic properties and atomically thin geometry. However, the atomically thin geometry makes their electronic properties highly susceptible to the environment changes. In particular, some 2DLMs (e.g., black phosphorus (BP) and SnSe2) are unstable and could rapidly degrade over time when exposed to ambient conditions. Therefore, the development of proper passivation schemes that can preserve the intrinsic properties and enhance their lifetime represents a key challenge for these atomically thin electronic materials. Herein we introduce a simple, non-disruptive and scalable van der Waals passivation approach by using organic thin films to simultaneously improve the performance and air stability of BP field-effect transistors (FETs). We show that dioctylbenzothienobenzothiophene (C8-BTBT) thin films can be readily deposited on BP via van der Waals epitaxy approach to protect BP against oxidation in ambient conditions over 20 days. Importantly, the non-covalent van der Waals interface between C8-BTBT and BP effectively preserves the intrinsic properties of BP, allowing us to demonstrate high-performance BP FETs with a record-high current density of 920 μA/um, hole drift velocity over 1 ⅹ 107 cm/s, and on/off ratio of 104~107 at room temperature. This approach is generally applicable to other unstable two-dimensional (2D) materials, defining a unique pathway to modulate their electronic properties and realize high-performance devices through hybrid heterojunctions.
关键词： black phosphorus,saturation velocity,saturation current density,two-dimensional materials,passivation,field effect transistors
更新于2025-09-10 09:29:36
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Improvement of Superconducting Properties by Optimized Post-Heat Treatment for Nb3Al Wires Fabricated by RHQ
摘要： With extremely high critical current density (Jc) and excellent strain tolerance, Nb3Al superconductor is considered as an alternative to Nb3Sn for application of high-filed magnets. However, complexity in the phase formation of Nb3Al hinders the Nb3Al superconducting wires to satisfy the requirement of engineering applications at present. Here, we have reported the improved performance of simple-structured 18-filamnet jelly-roll Nb3Al precursor long wires fabricated with rapid heating and quenching (RHQ) process. After processed with RHQ heat-treatment under various heating conditions, the Nb3Al wire were post-heat treated at a temperature between 700 oC to 1100 oC. The phase formation and the superconducting properties of the wires were investigated. It has been found that even if the RHQ process deviates from the optimum processing state, the superconducting properties of the wire can be improved by appropriately selecting post-heat treatment conditions.
关键词： critical current density,Nb3Al wires,rapid heating and quenching process,superconductivity
更新于2025-09-10 09:29:36
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Gauge invariance and origin independence of electronic charge density and current density induced by optical fields
摘要： Expressions for the first-order polarization charge density ρ(1) and current density J(1) induced in a molecule by a monochromatic plane wave, obtained by time-dependent quantum mechanical perturbation theory, have been investigated to assess their gauge invariance and independence of the coordinate system in passive and active translations. The conditions arrived at show that, within the (long wavelengths) dipole approximation, only the electric contributions to these densities are needed to rationalize the phenomenology. To the next higher quadrupole approximation, assuming that the magnetic field and the electric field gradient are uniform over the molecular dimensions, corresponding contributions to ρ(1) and J(1) are considered. It has been found that total densities are independent of the origin, whereas the contributions from electric and magnetic fields are not separately invariant. A magnetic contribution to J(1), which is by itself origin independent, can be defined by means of an approach based on continuous translation of the origin of the coordinate system.
关键词： time-dependent perturbation theory,origin independence,quadrupole approximation,current density,optical fields,gauge invariance,dipole approximation,electronic charge density
更新于2025-09-09 09:28:46
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[Advances in Intelligent Systems and Computing] Modelling and Simulation in Science, Technology and Engineering Mathematics Volume 749 (Proceedings of the International Conference on Modelling and Simulation (MS-17)) || Computation of Current Density in Double Well Resonant Tunneling Diode Using Self-consistency Technique
摘要： Double well resonant tunneling diode is analytically simulated for different constituent layer widths, and also for different operating temperatures. Peak current densities are obtained at particular bias values, which speak for eigenstates alignment between adjacent quantum wells. Self-consistency technique is incorporated for simulation purpose which provides accurate result regarding the position of the peaks, optimum structural parameters in order to obtain that magnitude, and the junction temperature to obtain measurable current at the applied bias range. It may also be noted that current increases with increase in temperature. Two different dimension set are used for simulation in order to reveal the external influence on electrical properties of the device. Different dimensions of contact regions also help to analyze fluctuations in peak current profile. Thus the device can be operated at those biasing points, where peaks are appeared.
关键词： Resonant tunneling diode,Self-consistency technique,Quantum transport,Current density,Semiconductor heterostructures
更新于2025-09-09 09:28:46
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Light Entrapping, Modeling & Effect of Passivation on Amorphous Silicon Based PV Cell
摘要： This research paper present efforts to enhance the performance of amorphous silicon p-i-n type solar cell using sidewall passivation. For sidewall passivation, MEMS insulation material Al2O3 was used. The main objective of this paper is to observe the effect of sidewall passivation in amorphous silicon solar cell and increase the conversion efficiency of the solar cell. Passivation of Al2O3 is found effective to subdue reverse leakage. It increases the electric potential generated in the designed solar cell. It also increases the current density generated in the solar cell by suppressing the leakage. Enhancement in J-V curve was observed after adding sidewall passivation. The short circuit current density (Jsc) increased from 14.7 mA/cm2 to 18.5 mA/cm2, open circuit voltage (Voc) improved from 0.87 V to 0.89 V, and the fill factor also slightly increased. Due to the sidewall of passivation of Al2O3, conversion efficiency of amorphous silicon solar cell increased by 29.07%. At the end, this research was a success to improve the efficiency of the amorphous silicon solar cell by adding sidewall passivation.
关键词： Aluminum Oxide,Electric Potential,Passivation,COMSOL Multiphysics,Amorphous Silicon,Current Density
更新于2025-09-09 09:28:46
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Transport Critical Current Density of Bi1.6Pb0.4Sr2Ca2Cu3O10)/Ag Superconductor Tapes with Addition of 50 and 70 nm MgO
摘要： added size 50 average particle and 70 nm were MgO nanoparticles with into Bi1.6Pb0.4Sr2Ca2Cu3O10(MgO)x/Ag superconductor tapes and sintered at 845 oC for 50 and 100 h. The effect of sintering time on the transport critical current density (Jc) was investigated. Jc of the tapes were measured in zero-field between 30 and 77 K and under magnetic fields at 77 K. The phase and microstructure of the tapes were examined by X-ray diffraction method and scanning electron microscopy, respectively. All tapes showed plate-like grains and a larger plate-like grain was observed in the tapes sintered for 100 h. Jc of the MgO added tapes was higher than those of the non-added tapes. Jc of the non-added tape sintered for 100 h was 10820 A/cm2 at 30 K and 1262 A/cm2 at 77 K. Jc of the tapes sintered for 100 h was higher than the tapes sintered for 50 h. The 50 nm MgO added tapes showed a higher Jc than the 70 nm MgO added tapes. Jc for the 100 h sintered MgO (50 nm) added tape was 22710 and 3070 A/cm2 at 30 and 77 K, respectively which are higher than that of the 100 h sintered MgO (70 nm) added tape. The improved Jc was attributed to the increase in flux pinning potential and improvement in the microstructure due to the addition of nano-sized MgO. This work showed the importance of the size of the added nanoparticles to the transport current properties of these superconductors.
关键词： flux pinning,transport critical current density,nano MgO,size effect
更新于2025-09-04 15:30:14
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[IEEE 2018 IEEE International Conference on Computational Electromagnetics (ICCEM) - Chengdu (2018.3.26-2018.3.28)] 2018 IEEE International Conference on Computational Electromagnetics (ICCEM) - Resonance Frequency Inversion of Cold Unmagnetized Plasma Based on CDLT-FDTD and PSO Methods
摘要： Current density Laplace finite-difference time-domain (CDLT-FDTD) method conjunction with particle swarm optimization (PSO) method is introduced to reconstruct the resonance frequency of cold unmagnetized plasma medium. During the inversion, the resonance frequency of the plasma is reconstructed by Fourier series expansion method and the traditional direct method, respectively. The simulation results show that the Fourier series expansion method has better reconstruction accuracy than the traditional direct method, and the number of unknowns is only 1/3 of that of the traditional direct method.
关键词： finite-difference time-domain method,Fourier series expansion,particle swarm optimization,Current density Laplace transform
更新于2025-09-04 15:30:14
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An Automated System for Measuring the Current Density of a Pulse–Periodic Electron Beam with a Large Cross Section
摘要： In an electron source with a mesh plasma cathode on the basis of a low-pressure arc discharge, studies of the spatiotemporal stability of a pulse–periodic beam with a large cross section (750 × 150 mm2), which was extracted into the atmosphere through an output foil window, were performed. The automated system that was used in the studies allowed real-time measurements with the ability to visualize the data on a computer. This system provides an accuracy of measurements of no worse than ±2%; it differs from the known analogues in the compactness, reliability, and simplicity of its design and allows studies of the current-density distribution over the beam cross section in a wide range of beam parameters, such as the beam energy, beam current, and beam-current pulse duration. A satisfactory coincidence of the previously obtained data and the present experimental data is shown with the possibility of substantially increasing the accuracy of setting up a scientific experiment and, consequently, the speed of debugging and the reproducibility of the technological process.
关键词： automated system,pulse–periodic beam,low-pressure arc discharge,electron source,mesh plasma cathode,current-density distribution
更新于2025-09-04 15:30:14