Electric field intensity measurement by using doublet electromagnetically induced transparency of cold Rb Rydberg atoms

We demonstrate a simple method to measure electric field intensity by using doublet electromagnetically induced transparency(EIT) spectra of cold Rb Rydberg atoms, where the frequency of the coupling laser does not need to be locked. Based on the Stark splitting of the Rb Rydberg state, 10D_(3/2), under electric fields and the corresponding calculated polarizabilities, the real electric field intensity is calculated using the difference in radio-frequency diffraction between two acousto-optic modulators, which acts as a frequency criterion that allows us to measure the electrical field without locking the coupling laser. The value measured by this simple method shows a good agreement with our previous work [Opt.Express 29 1558(2021)] where the frequency of the coupling laser needs to be locked with an additional EIT spectrum based on atom vapor and a proportional–integral–differential feedback circuit. Our presented method can also be extended to the measurement of electric field based on hot Rydberg atom vapor, which has application in industry.

Non-Kramers doublet ground state in a quaternary cubic compound PrRu_(2)In_(2)Zn_(18) investigated by ultrasonic measurements

We performed ultrasonic measurements on a quaternary cubic compound PrRu_(2)In_(2)Zn_(18) to explore the ground state properties derived from non-Kramers Γ_(3) doublet of Pr^(3+).PrRu_(2)In_(2)Zn_(18) is a quaternary derivative of the ternary compound PrRu_(2)Zn_(20) that exhibits a structural phase transition at T_S=138 K.In PrRu_(2)In_(2)Zn_(18),the Zn atoms at the 16c site in PrRu_(2)Zn_(20) are selectively replaced by In atoms.A monotonic increase was observed in the temperature dependence of elastic constants C_L=(C_(11)+2C_(12)+4C_(44))/3 and C_(T)=(C_(11)-C_(12)+C_(44))/3 in the temperature range around T_(S) to which an elastic softening was observed in(C_(11)-C_(12))/2 for PrRu_(2)Zn_(20).The disappearance of the softening indicates that the structural transition in PrRu_(2)Zn_(20) is suppressed by the substitution of Zn ions by In ones with a larger ionic radius.Alternatively,the C_(T) of PrRu_(2)In_(2)Zn_(18) exhibits a precursor Curie-type elastic softening toward low temperatures being responsible for the non-Kramers Γ_(3) ground state.We discuss the ground state and the evolution of the elastic properties of the different single-crystal samples of PrRu_(2)In_(2)Zn_(18) grown under different conditions.

Three-Dimensional Analytical Modeling of Axial-Flux Permanent Magnet Drivers

In this paper, the axial-flux permanent magnet driver is modeledand analyzed in a simple and novel way under three-dimensional cylindricalcoordinates. The inherent three-dimensional characteristics of the deviceare comprehensively considered, and the governing equations are solved bysimplifying the boundary conditions. The axial magnetization of the sectorshapedpermanent magnets is accurately described in an algebraic form bythe parameters, which makes the physical meaning more explicit than thepurely mathematical expression in general series forms. The parameters of theBessel function are determined simply and the magnetic field distribution ofpermanent magnets and the air-gap is solved. Furthermore, the field solutionsare completely analytical, which provides convenience and satisfactoryaccuracy for modeling a series of electromagnetic performance parameters,such as the axial electromagnetic force density, axial electromagnetic force,and electromagnetic torque. The correctness and accuracy of the analyticalmodels are fully verified by three-dimensional finite element simulations and a15 kW prototype and the results of calculations, simulations, and experimentsunder three methods are highly consistent. The influence of several designparameters on magnetic field distribution and performance is studied and discussed.The results indicate that the modeling method proposed in this papercan calculate the magnetic field distribution and performance accurately andrapidly, which affords an important reference for the design and optimizationof axial-flux permanent magnet drivers.

EXPERIMENTAL INVESTIGATION FOR THE EFFECT OF ROTATION ON THREE-DIMENSIONAL FLOW FIELD IN FILM-COOLED TURBINE

An experimental investigation of three-dimensional flow field in a film-cooled turbine model is carried out by using particle image velocimeter （PIV） in a low-speed wind tunnel. The effects of different blowing ratios （M=1.5, 2） on the flow field are studied. The experimental results reveal the classical phenomena of the formation of kidney vortex pair and secondary flow in wake region behind the jet hole. And the changes of the kidney vortex pair and the wake at different locations away from the hole on the suction and pressure sides are also studied. Compared with the flow field in stationary cascade, there are centrifugal force and Coriolis force existing in the flow field of rotating turbine, and these forces bring the radial velocity in the jet flow. The effect of rotatien on the flow field of the pressure side is more distinct than that on the suction side from the measured flow fields in Y-Z plane and radial velocity contours. The increase of blowing ratio makes the kidney vortex pair and the secondary flow in the wake region stronger and makes the range of the wake region enlarged.

Estimation of the Lyman-α signal of the EFILE diagnostic under static or radiofrequency electric field in vacuum

The electric field induced Lyman-a emission diagnostic aims to provide a non intrusive and precise measurement of the electric field in plasma, using a beam of hydrogen atoms prepared in the metastable 2s state. The metastable particles are obtained by means of a proton beam extracted from a hydrogen plasma source, and neutralised by interaction with vaporised caesium. When a 2s atom enters a region where an electric field is present, it undergoes a transition to the 2p state （Stark mixing）. It then quickly decays to the ground level, emitting Lyman-a radiation, which is collected by a photomultiplier. The 2s → 2p transition rate is proportional to the square of the magnitude of the electric field, and depends on the field oscillation frequency （with peaks around l GHz）. By measuring the intensity of the Lyman-a radiation emitted by the beam it is possible to determine the magnitude of the field in a defined region. In this work, an analysis of the behaviour of the diagnostic under static or radiofrequency electric field is presented. Electric field simulations obtained with a finite element solver of Maxwell equations, combined with theoretical calculations of the Stark mixing transition rate, are used to develop a model for the interpretation of photomultiplier data. This method shows good agreement with experimental results for the static field case, and allows to measure the field magnitude for the oscillating case.

VFT PHASE VOLTAGE MEASUREMENT IN THREE-PHASE ENCLOSED GIS

The measuring of VFT phase voltage in three-phase enclosed GIS is more complex and difficult than in single-phase ones. There are 3 capacitive sensors in the measuring system, the outputs of which are with a linear relation to the three phase voltages. This linear relation is presented with a factorial matrix. Because each capacitive sensor is coupled with the electric field of three phases (A, B, and C), the electric coupling coefficients are introduced. In order to determine the matrix of electric coupling coefficients, the numerical calculation method can be used. From the discussion on two types of three-phase enclosed GIS bus, i.e. standard arrangement and biased arrangement, the dominant electric coupling coefficients are named, which can be simply and approximately calculated by an analytic expression. Finally, as an example, the waveforms of VFT phase voltage generated on a three-phase enclosed GIS bus model are displayed. When a capacitive sensor is located at the ’shortest point’ of phase A (or B, or C), the VFT phase voltage V A (or V B, or V C) can almost be measured by that capacitive sensor alone.

Energy and flux measurements of laser-induced silver plasma ions by using Faraday cup

Silver(Ag)plasma has been generated by employing Nd:YAG laser(532 nm,6 ns)laser irradiation.The energy and flux of ions have been evaluated by using Faraday cup(FC)using time of flight(TOF)measurements.The dual peak signals of fast and slow Ag plasma ions have been identified.Both energy and flux of fast and slow ions tend to increase with increasing irradiance from 7 GW cm-2 to 17.9 GW cm-2 at all distances of FC from the target surface.Similarly a decreasing trend of energies and flux of ions has been observed with increasing distance of FC from the target.The maximum value of flux of the fast component is21.2×10^(10) cm^(-2),whereas for slow ions the maximum energy and flux values are 8.8 keV,8.2×10^(10) cm^(-2) respectively.For the analysis of plume expansion dynamics,the angular distribution of ion flux measurement has also been performed.The overall analysis of both spatial and angular distributions of Ag ions revealed that the maximum flux of Ag plasma ions has been observed at an optimal angle of~15°.In order to confirm the ion acceleration by ambipolar field,the self-generated electric field(SGEF)measurements have also been performed by electric probe;these SGEF measurements tend to increase by increasing laser irradiance.The maximum value of 232 V m^(-1) has been obtained at a maximum laser irradiance of 17.9 GW cm^(-2).

基于场致二次谐波的大气压脉冲流注放电时变非均匀电场测量研究

诊断大气压脉冲流注放电空间电场是实现流注放电精准调控和揭示等离子体不稳定性机制的重要基础。基于场致二次谐波的空间电场测量方法具有非侵入式、时空分辨率高等优点。然而,流注放电时变非均匀电场对二次谐波信号产生过程的影响规律尚不完善,真实电场标定系数随流注放电不同阶段的变化规律尚不清晰。该文首先计算二次谐波信号产生规律和电场空间分布的影响;然后,基于等离子体流体模拟,分析二次谐波信号对流注放电不同阶段时变非均匀电场的敏感程度;最后,基于纳秒脉冲激光场致二次谐波电场测量平台,实验获得了重频脉冲作用下组合电极结构产生的单根负流注轴向电场演变规律,分析脉冲重复频率对空间电场的影响机制,并针对流注放电时变非均匀电场特点提出电场致二次谐波测量优化若干建议。

静电放电模拟器近区辐射电场的测量研究

静电放电(ESD)是电磁兼容领域的关键测试项目。为在近区获得更多可供参考的ESD辐射电场实测数据,建立了ESD辐射电场测量系统,测量并研究了四个厂家的主流ESD模拟器在接触放电模式下产生的辐射电场。实验结果表明,不同试验等级ESD辐射电场波形参数与IEC 61000-4-2:2008中的参考值一致,测量结果准确;在严格控制实验条件的情况下,电场峰值和上升时间的重复性可以得到保证,且电场峰值的重复性优于上升时间的重复性;不同型号的ESD模拟器在电流波形都符合IEC 61000-4-2:2008限值的情况下,辐射电场的波形存在更大差异,早日实现ESD辐射电场的准确、可靠测量并规范其测量方法及其限值十分必要。

Impact Factors in Calibration and Application of Field Mill for Measurement of DC Electric Field with Space Charges

The DC electric field is sometimes accompanied by space charges caused by the partial discharge in the air,which impacts DC electric field measurements.This paper describes the impact factors in the calibration and application of the field mill for measuring the DC electric field with space charges.First,the influence of the space charges on calibration results is evaluated and discussed.Then,both the impact of the height of the meter probe above the ground and the touch resistance between the ground and the meter on the measurement results are investigated.Correct calibration and application methods are presented.The results are expected to be of use to engineers for conducting accurate measurements of the DC electric field with space charges.

Visualized measurement of the electric field in large aperture LiNbO_3 crystal by digital holographic interferometry

The electric field distribution in Li Nb O3 crystal under different electrode shape is presented by using the digital holographic interferometry. Three configurations of phase modulator including the rectangular electrode type,single-triangle electrode type, and dual-triangle electrode type are performed in this experiment. The nonuniform electric field distribution in these phase modulators are observed and the electric field increases with voltage increasing. The digital holographic interferometry with high electro-optic effect improves the measurement precision. The digital holographic interferometry provides an effective way for studying the electric field distribution. Such in situ quantitative analysis of electric field distribution is a key to optimizing electrode shape.

Electric field simulation and measurement of a pulse line ion accelerator

An oil dielectric helical pulse line to demonstrate the principles of a Pulse Line Ion Accelerator （PLIA） has been designed and fabricated. The simulation of the axial electric field of an accelerator with CST code has been completed and the simulation results show complete agreement with the theoretical calculations. To fully understand the real value of the electric field excited from the helical line in PLIA, an optical electric integrated electric field measurement system was adopted. The measurement result shows that the real magnitude of axial electric field is smaller than that calculated, probably due to the actual pitch of the resister column which is much less than that of helix.

基于多物理场复合的新型无创脑深部精准刺激方法探究

现有的无创电磁刺激技术,以临床应用最广的经颅磁刺激(TMS)为代表,尚无法突破聚焦性和刺激深度的技术瓶颈,实现对深部功能核团的直接精准刺激。本研究基于磁声耦合理论,结合TMS技术中的交变磁场,提出一种新的基于多物理场复合的无创脑深部精准刺激方法(MI-TMAS),以期实现对脑深部的直接精准聚焦刺激。基于磁声耦合理论和磁感应理论对MI-TMAS中的刺激物理场进行仿真研究,并搭建了MI-TMAS系统及多物理场测试平台,对刺激物理场分布并进行实测。结合仿真和实测结果,对MI-TMAS复合刺激电场的聚焦性和电场强度进行探究。结果显示,该方法能够在脑深部靶区产生聚焦声场、磁声耦合电场、磁感应电场等3个复合刺激物理场,可以在刺激深度50 mm处形成聚焦尺寸约6.2 mm(-3 dB)的复合刺激电场,其在脑深部电场的聚焦性明显优于TMS,且刺激电场强度大于稳恒磁场下的TMAS。本研究为MI-TMAS方法应用于在体神经调控提供了理论以及技术基础。

原子热运动对电场量子测量的影响及修正方法

基于里德堡原子电磁诱导透明(EIT)效应的电场量子测量方法,能够突破传统基于电学原理、光学原理测量法在测量精度和灵敏度上的极限,并且具有自校准性。采用热里德堡原子进行测量具有工程应用的便捷性,但是原子热运动形成的多普勒效应会导致EIT谱峰发生频移和形变,混淆电场对原子的相干效应,从而影响电场测量精度。基于激光、电场与原子的作用机理,以及原子热力学,该文提出通过调整探测光和耦合光频率,修正原子热运动对电场量子测量影响的方法。首先,假设里德堡原子静止不动,建立和求解密度矩阵方程,描述双光子阶梯型三能级系统的EIT光谱;然后,引入温度与原子运动数学关系,将温度造成的原子热运动多普勒影响量化为探测光和耦合光频率失谐量,通过修正探测光和耦合光的频率来抵消该影响。仿真实验表明,该文提出的修正方法效果良好,该研究有利于推进基于里德堡原子电场量子测量的实用化进程。

微型宽频交流电场传感器设计及其电场无失真测量评价

电场信息是新型电力系统状态智能感知、信息深度融合的基础。电场测量需兼顾无失真、微型宽频、强稳定性、易集成等众多性能需求。针对新型电力系统数字化发展需求,对地线侵入造成的电场测量误差来源进行分析,提出了微型宽频交流电场传感器设计方案和电场无失真测量方法,开展了无失真电场传感器设计,并与微机电系统(microelectro mechanical systems,MEMS)和光学电场传感器进行了无失真测量效果对比。结果表明MEMS电场传感器向上偏移间隙中心2 cm时电场测量误差为13.2%,光学电场传感器的电场测量误差在3%左右。无失真电场传感器的测量误差均在2%左右,且不随传感器的偏移距离而增大或减小,实现了地线干扰的隔离效果,且电场无失真程度优于光学电场传感器。

基于电场传感器阵列的输电线路电压非接触式测量方法

电压作为表征线路运行状态的重要参量,实现其灵活准确的测量对保证电力系统稳定运行至关重要。传统的接触式电压测量方法,因电压互感器体积较大、会产生电磁谐振和高频振荡、额外测量需断电安装等问题,对于海量化测量并不便利。相比较而言,非接触式测量不接触导线,更加安全和便捷,将成为未来电压测量的发展方向。文中提出了基于电场传感器阵列的输电线路电压非接触式测量方法,该方法为了解决导线位置信息未知的问题,设计了与导线方向垂直排列的电场传感器阵列;求解了含导线未知信息量的方程组;构建了比例系数矩阵,反推出导线电压瞬时值;分析了电场传感器对测量的影响;最后,进行了10 kV电压等级电压瞬时值仿真验证,结果显示最大测量误差为2.219%。

基于电场耦合原理的SiC

功率器件作为电能变换的核心,准确测量其开关电压可以优化器件的开关行为,评估器件的开关损耗,为功率转换系统的设计提供重要指导。以SiC MOSFET为代表的宽禁带半导体器件具有高速开关特性,传统商用电压探头难以同时满足低侵扰、强抗扰、高带宽与小体积的测量要求,因此提出了一种基于电场耦合原理的同轴圆柱型电压探头。通过感应电极包围引出端的结构降低侵入电容,应用屏蔽覆铜、过孔阵列与屏蔽铜管的强抗扰结构实现对环境噪声的抑制。利用有限元仿真指导了探头参数选取的方案,验证了屏蔽层对噪声的抑制能力,详细分析了同轴探头有效降低侵入性的机理。所设计的同轴探头带宽为280 MHz,量程为-750 V~+750 V,侵入电容约为0.92 pF。最后通过双脉冲实验证明,同轴探头可以准确测量ns级的开关时间,满足SiC MOSFET开关电压的测量需求。

输电线路矢量电场测供一体传感器及电压反演方法

通过传感器测量电场信号并经过反演运算还原场源导体的电压值,是监测输电线路运行的可靠方法。本文提出测量矢量电场并反演计算输电线路各相电压的方法,设计球形矢量电场测量传感器,实现通过单传感器测量单点电场得到输电线路三相电压。由于电场测点包含丰富的电场能量,设计电场取能电路,实现检测装置的测供一体化。球形矢量传感器、电场取能装置的实验测试结果表明,球形矢量传感器相位偏移约1.3°,响应速度较快;反演结果线性度较好且能够实现10MHz宽频测量;取能模块在相同的实验测点加压10kV即可达到可观的mW级输出功率。

高压电能计量现场校准装置及其不确定度分析

随着新建产能增加和新技术的不断应用,油田用电量逐渐增大,对高压电能计量设备进行科学的评价,可以对设备运行情况提供可靠的数据支持,以节省和减少油田的能源消耗,进而为设备维护更新、技术改造、新建项目等提供决策支持。高压电能计量现场校准装置,采用高压三相标准功率源和多功能标准表、V/V转换器、I/V转换器组合的方式对高压电能计量设备进行整体校准,对装置进行不确定度分析,使装置在现场校准的过程中能够保持稳定的性能指标。

基于变容二极管的直流电压非接触测量方法研究

为解决接触式测量技术对原电路的侵入性和安全性问题,根据变容二极管PN结反向偏压下的电容特性,提出了一种基于变容二极管的非接触式直流电压测量方法。该方法通过电场耦合效应感应待测直流电压,通过正弦信号激励和相关测量技术实现变容二极管的电容测量。利用LTspice软件对设计的测量电路进行仿真,并搭建实验测量系统。仿真和实验结果表明:该测量系统可以实现非接触式的直流电压测量,在变容二极管的工作电压范围内,相对测量误差≤2.50%。文中提出的测量方法,摒弃了传统直流电压非接触测量方式中的机械运动部件,具有较好的应用前景。