Comparison of pulse-modulated and continuous operation modes of a radio-frequency inductive ion source

The paper describes an experimental study of the characteristics of a pulse-modulated radiofrequency(RF)discharge sustained at low pressures,typical of the operating modes of RF gridded ion sources.The motivation for the study is the question of whether the RF pulsemodulated mode can increase the efficiency of the ion source.The ion current values extracted from an RF inductive ion source operating in continuous and pulse-modulated modes were compared.The experimental data were also compared with the parameter calculations based on a0D numerical model of the discharge.The measurements showed that the pulse-modulated operation mode of the RF ion source had a noticeable advantage when the power of the RF generator was 140 W or lower.However,as the generator power increased,the advantage was lost because the pulse-modulated operation mode,having a higher RF power instant value,entered the region of existence sooner than the continuous mode,where the ion production cost begins to grow with RF power.

Compressing ultrafast electron pulse by radio frequency cavity

An ultrafast electron diffraction technique with both high temporal and spatial resolution has been shown to be a powerful tool to observe the material transient structural change on an atomic scale.The space charge forces in a multi-electron bunch will greatly broaden the electron pulse width,and therefore limit the temporal resolution of the high brightness electron pulse.Here in this work,we design an ultrafast electron diffraction system,and utilize a radio frequency cavity to realize the ultrafast electron pulse compression.We experimentally demonstrate that the stretched electron pulse width of14.98 ps with an electron energy of 40 keV and the electron number of 1.0 ×10;can be maximally compressed to about0.61 ps for single-pulse measurement and 2.48 ps for multi-pulse measurement by using a 3.2-GHz radiofrequency cavity.We also theoretically and experimentally analyze the parameters influencing the electron pulse compression efficiency for single-and multi-pulse measurements by considering radiofrequency field time jitter,electron pulse time jitter and their relative time jitter.We suggest that increasing the electron energy or shortening the distance between the compression cavity and the streak cavity can further improve the electron pulse compression efficiency.These experimental and theoretical results are very helpful for designing the ultrafast electron diffraction experiment equipment and compressing the ultrafast electron pulse width in a future study.

Radio-frequency compressed electron pulse-width characterization by cross-correlation between electron bunches and laser-induced plasma

A method is proposed to determine the temporal width of high-brightness radio-frequency compressed electron pulses based on cross-correlation technique involving electron bunches and laser-induced plasma. The temporal evolution of 2-dimensional transverse profile of ultrafast electron bunches repelled by the formed transient electric field of laser-induced plasma on a silver needle is investigated, and the pulse-width can be obtained by analyzing these time-dependent images.This approach can characterize radio-frequency compressed ultrafast electron bunches with picosecond or sub-picosecond timescale and up to 105 electron numbers.

Investigation of high sensitivity radio-frequency readout circuit based on AlGaN/GaN high electron mobility transistor

An Al Ga N/Ga N high electron mobility transistor（HEMT） device is prepared by using a semiconductor nanofabrication process. A reflective radio-frequency（RF） readout circuit is designed and the HEMT device is assembled in an RF circuit through a coplanar waveguide transmission line. A gate capacitor of the HEMT and a surface-mounted inductor on the transmission line are formed to generate LC resonance. By tuning the gate voltage V g, the variations of gate capacitance and conductance of the HEMT are reflected sensitively from the resonance frequency and the magnitude of the RF reflection signal. The aim of the designed RF readout setup is to develop a highly sensitive HEMT-based detector.

Application of Radio Frequency Identification (RFID) in Dairy Information Management

As a kind of brand-new technology, radio frequency identification management, data control and acquisition. This paper introduced food safety system construction, analyzed the advantages and problems in dairy modem suggestions for solution according to the practical situation. （RFID） plays an important role in dairy information tracing and culture function extension of managing breeding technology, and finally put forward some

A Simple Model for the Calculation of Plasma Impedance in Atmospheric Radio Frequency Discharges

In atmospheric radio-frequency （rf） discharges, the plasma parameters, such as electron density, sheath thickness and sheath voltage, are not easy to be probed experimentally, while the electrical characteristics, such as impedance, resistance and reactance, are relatively convenient to be measured. In this paper we presented a simple theoretical model derived from the fluid description of generated plasmas without considering the circuit model, to investigate the relationship between the plasma impedance and plasma parameters. By introducing a relaxation frequency, the plasma impedance could be predicted by formulas presented in this study, and the mean electron density and sheath thickness can also be calculated from the measured or simulated impedance and reactance, respectively.

Effect of driving frequency on electron heating in capacitively coupled RF argon glow discharges at low pressure

A one-dimensional（1D） fluid model on capacitively coupled radio frequency（RF） argon glow discharge between parallel-plates electrodes at low pressure is established to test the effect of the driving frequency on electron heating. The model is solved numerically by a finite difference method. The numerical results show that the discharge process may be divided into three stages： the growing rapidly stage, the growing slowly stage, and the steady stage. In the steady stage,the maximal electron density increases as the driving frequency increases. The results show that the discharge region has three parts： the powered electrode sheath region, the bulk plasma region and the grounded electrode sheath region. In the growing rapidly stage（at 18 μs）, the results of the cycle-averaged electric field, electron temperature, electron density, and electric potentials for the driving frequencies of 3.39, 6.78, 13.56, and 27.12 MHz are compared, respectively. Furthermore,the results of cycle-averaged electron pressure cooling, electron ohmic heating, electron heating, and electron energy loss for the driving frequencies of 3.39, 6.78, 13.56, and 27.12 MHz are discussed, respectively. It is also found that the effect of the cycle-averaged electron pressure cooling on the electrons is to ＂cool＂ the electrons; the effect of the electron ohmic heating on the electrons is always to ＂heat＂ the electrons; the effect of the cycle-averaged electron ohmic heating on the electrons is stronger than the effect of the cycle-averaged electron pressure cooling on the electrons in the discharge region except in the regions near the electrodes. Therefore, the effect of the cycle-averaged electron heating on the electrons is to ＂heat＂ the electrons in the discharge region except in the regions near the electrodes. However, in the regions near the electrodes, the effect of the cycle-averaged electron heating on the electron is to ＂cool＂ the electrons. Finally, the space distributions of the electron pressure cooling the electron ohmic heating and the electron heating at 1/4 T, 2/4 T, 3/4 T, and 4/4 T in one RF-cycle are presented and compared.

Theoretical Study on the Characteristics of Atmospheric Radio Frequency Discharges by Altering Electrode Gap

In this paper, we present a theoretical study on the discharge characteristics of radio-frequency discharges at atmospheric pressure driven by a higher frequency of 40.68 MHz while the electrode gap is altered. Based on the analytical equations and simulation data from a one-dimensional fluid model, an optimal gap between electrodes, at which the largest electron density is obtained, can be observed under a constant power condition; however, as the electrode gap increases the time-averaged electron temperature decreases, and the underpinning physics is also discussed based on the simulation results. This study indicates that at a constant power by choosing an appropriate electrode spacing, the rf discharge can be effectively optimized at atmospheric pressure.

Graphene-based ambipolar electronics for radio frequency applications

Graphene is considered as a promising material to construct field-effect transistors (FETs) for high frequency electronic applications due to its unique structure and properties,mainly including extremely high carrier mobility and saturation velocity,the ultimate thinnest body and stability.Through continuously scaling down the gate length and optimizing the structure,the cut-off frequency of graphene FET (GFET) was rapidly increased and up to about 300 GHz,and further improvements are also expected.Because of the lack of an intrinsic band gap,the GFETs present typical ambipolar transfer characteristic without off state,which means GFETs are suitable for analog electronics rather than digital applications.Taking advantage of the ambipolar characteristic,GFET is demonstrated as an excellent building block for ambipolar electronic circuits,and has been used in applications such as highperformance frequency doublers,radio frequency mixers,digital modulators,and phase detectors.

基于RFID的成箱服装信息检测系统可靠性设计

目的解决目前服装企业存在的服装量大、品种多、整箱货运盘货难度大等问题。方法将RFID技术与服装信息管理相结合,设计整箱服装信息自动化采集系统,通过对系统RFID阅读器天线数量及位置进行优化设计,同时改进RFID标签多叉树防碰撞算法,以提高服装信息检测系统识别的可靠性。结果通过计算分析,构建了阅读器“M”形四天线空间分布全覆盖检测模型,同时配合服装检测系统的识别软件完成了批量服装电子标签可靠性检测,对最大服装包装箱的检测准确率达到了100%。在系统的检测速度为60 m/min时,每分钟的理论识别量可达到2600件。结论有效提高了服装信息检测系统的可靠性和采集效率。

基于磁控溅射和电子束蒸发合成Mn-Co-Ni-O薄膜

锰钴镍氧(Mn-Co-Ni-O,MCNO)薄膜因为具有优异的负温度系数特性在近年来受到广泛关注,现采用射频磁控溅射和电子束蒸发相结合的方式,在单抛蓝宝石(Al2O3)衬底上制备MCNO薄膜,并采用一系列表征探讨了后道退火(Post Annealing,PA)温度对所制薄膜的微观结构和光学性质的影响。结果表明,随着PA温度的提高,MCNO膜的晶粒尺寸和间隔均呈现增大趋势。X射线光电子能谱结果表明,Mn3+/Mn4+的比例随着温度的升高而增大。电学和光学特性研究表明,在PA温度为850℃,条件为空气退火1 h得到的MCNO薄膜在温度范围为220~300 K范围内符合VRH模型,TCR系数良好,激活能为0.32 eV,薄膜在红外可见波段具有较高吸收率。

大面积单激励器射频离子源等离子体均匀性分析

为了提高等离子体分布均匀度,基于有限元分析法与实验相结合的方法,从射频离子源驱动器尺寸和引出区尺寸2个方面对单驱动射频离子源放电室进行设计。模拟研究结果表明,电子均匀度的增长幅度随驱动器尺寸的大小变化比较缓慢。根据不同驱动器尺寸电子密度分布研究结果,在引出区尺寸为320 mm时,电子均匀度能够满足90%的要求。根据实验研究结果表明,在引出区尺寸为320 mm时电子分布均匀且均匀度>90%,并与模拟结果相吻合。因此,为使得等离子体分布均匀度能够达到要求,离子源放电室底部引出面附近引出区尺寸应该设计为320 mm。

一般条件下的电子自旋共振(ESR)理论

文中从数学的角度分析了dμz/dt=0在电子自旋共振(ESR)中的物理含义,把ESR理论由直流磁场推广到了交流磁场,而直流磁场下的ESR理论只是当交流磁场的频率为0时的一种特殊情况,从而建立了一般条件下的ESR理论和一般条件下实现ESR的方法。该理论的建立使得采用ESR原理研制的分析仪器省去了耗能大、重量重、造价高的直流磁场,仅采用原有的调制磁场便可实现ESR,从而大大降低了该分析仪器的体积、重量、耗能和成本,具有一定的理论研究和推广应用价值。

基于物联网技术的医院楼宇智能控制系统

当前系统控制效果差,智能化程度低,为此设计基于物联网技术的医院楼宇智能控制系统。物联网模块包括射频识别、网络传感器等单元,选择两种总线进行数据通信,以ARM构架为基础设计控制器芯片,通过对继电反馈PID控制算法实施PID参数求解,实现各种系统运行调度控制,通过智能策略模块,设置各种系统设备的开关状态,并采用在某大型医院作为测试对象,结果表明,所设计系统能够实现送排风系统、电梯系统、消防系统的全面智能控制,可以有效节省医院建筑电力消耗,具有较高的实际应用价值。

国外机载投掷式有源诱饵发展现状及趋势

近年来光电技术迅速发展,推动电子战发展到了新阶段。新型空-空导弹的广泛应用对战斗机的生存能力带来极大的挑战,机载投掷式有源射频诱饵是一种一次性使用的雷达诱饵,可以模拟己方战机的飞行特性和雷达特征,用于欺骗敌方的雷达检测设备,提高己方的生存概率。与小型空射诱饵(MALD)相比具有体积小、重量轻及成本低等优势受到各国的广泛关注。介绍了国外公开报道的几种机载投掷式有源诱饵基本概况及应用,并对投掷式有源诱饵未来发展趋势进行了展望。

冷链云互联低温保障系统研究及其应用

介绍了一种集仓储技术、运输技术、管理技术于一体的冷链业务管控方案,设计了其系统功能模型和关键流程;对冷链的数据交互、货物流通管理、运输行为和设施设备管控等环节进行了优化;通过云服务器完成数据交互,实现了冷链各环节的智能化协作,提升了低温运输的品质和安全保障,助力冷链产业智能化发展。

Regulation and Control of Electromagnetic Field in Radio-Frequency Circuits and Systems

Since the first demonstrations of radio-frequency(RF)circuits,the physics of the electromagnetic(EM)field and its regulation and control with codesigned circuits,have become essential competencies of RF circuit designers.Leveraging advanced regulation or control methods,numerous high-performance circuits have been developed at RF and millimeter-wave(mm-wave)frequencies.Three main methods of electromagnetic regulation have been widely utilized,namely,the separation of electric and magnetic coupling paths,the manipulation of electromagnetic energy through the coupling of multiple tanks or multiple resonators,and the regulation of electromagnetic fields in air cavities or meta-substrates.The separated coupling paths of electric and magnetic fields provide guidance for designing a high-performance filter topology with a quasielliptical response through additional zeros.The manipulation of the EM field through electrical and magnetic intercouplings of multitanks or multiresonators,such as are used in oscillators,power amplifiers(PAs),etc.,results in remarkable power efficiency,size reduction,and wide bandwidth.The regulation of electromagnetism through an air cavity,patterned substrate,or metasubstrate reduces dielectric losses and size,especially when using a substrate integrated suspended line(SISL)platform.Many excellent circuits have been reported based on SISL with low loss,high integration,and self-packaging.Here,we present state-of-the-art cases that demonstrate the benefits of EM field regulation and control.

Spatial distribution of electron characteristic in argon rf glow discharges

The spatial distributions of the electron density and the mean electron energy of argon radio frequency （rf） glow discharge plasma in a plasma-enhanced chemical vapour deposition （PECVD） system have been investigated using an established movable Langmuir probe. The results indicate that in the axial direction the electron density tends to peak at midway between the two electrodes while the axial variation trend of mean electron energy is different from that of the electron density, the mean electron energy is high near the electrodes. And the mean electron energy near the cathode is much higher than that near the anode. This article focuses on the radial distribution of electron density and mean electron energy. A proposed theoretical model distribution agrees well with the experimental one： the electron density and the mean electron energy both increase from the centre of the glow to the edge of electrodes. This is useful for better understanding the discharge mechanism and searching for a better deposition condition to improve thin film quality.

The influence of magnetic field on the beam quality of relativistic electron beam long-range propagation in near-Earth environment

In recent years,it has been proposed to use satellite-mounted radio-frequency(RF)accelerators to produce high-current relativistic electron beams to complete debris removal tasks.However,when simulating the long-range propagation(km-range)process of the electron beam,it is difficult to directly use the particle-in-cell method to simultaneously consider the space charge effect of beam and the influence of the geomagnetic field.Owing to these limitations,in this paper,we proposed a simplified method.The ps-range electronic micropulses emitted by the RF accelerator were transmitted and fused to form a ns-range electron beam;then,combined with the improved moving window technology,the model was constructed to simulate the long-range propagation process of the relativistic electron beam in near-Earth environment.Finally,by setting the direction of movement of the beam to be parallel,perpendicular and at an inclination of 3°to the magnetic field,we analyzed and compared the effects of the applied magnetic fields in different directions on the quality of the beam during long-range propagation.The simulation results showed that the parallel state of the beam motion and magnetic fields should be achieved as much as possible to ensure the feasibility of the space debris removal.

An Indirect Method for Measuring Electron Density of Atmospheric Pressure Plasma Jets

An indirect method for measuring the electron density of radio frequency atmospheric pressure plasma jets （RF-APPJ） based on the discharge voltage and current waveforms is presented. An equivalent circuit of the plasma discharge is assumed by taking into account the electrode capacitance, serial resistance and inductance of the bulk plasma, as well as the sheath impedance. Based on the circuit model, the electron density can be obtained according to Ohm＇s law. By using this method, the effects of the electrode shape and discharge gap on the electron density are discussed.