High current dosimetry techniques

A review of techniques for electrical measurement of high current ion beams is presented. A computer analysis of the secondary-particle current-collection schemes is made for dosimetry-cup configurations commonly used on ion implanters with electrostatic scanning. The design of a dosimetry cup for a high current implanter with mechanical scanning is discussed. Also beam monitoring techniques for uniformity measurements are reviewed.     

工业辐照加速器扫描磁铁电源的研制

 分析了工业辐照加速器扫描磁铁的三角波励磁电流的选取。介绍了一种输出电流峰 峰值20 A、扫描频率为20～50 Hz的连续三角波的工业辐照加速器扫描磁铁电源。阐述了三角波调制器的原理、三角波线性度、基于单片机的控制系统以及其在工业辐照环境下采取的抗干扰措施。理论和应用均表明该设计具有很好的辐照均匀度。     

The optimization of electrostatic energy selection systems for low energy electrons

Design criteria are presented which allow electrostatic energy selection systems to be optimized to give the highest currents for electron beams having a low mean energy (? 500 eV) and a small energy spread (? 30 meV). Limitations in various parts of the system are discussed and a relationship between the current delivered by the system and the energy spread is presented. Different types and sizes for the energy selectors in these systems are considered and the best results are obtained with hemispherical deflectors. The advantage of using, within reasonable limits, a large selector with small image sizes is also demonstrated.     

DG型电子加速器自校正扫描系统的研制

为了提高DG型电子加速器束流扫描均匀度、解决束流中心偏移、提升束流引出效率,开发了一种既可实现X,Y两相互垂直方向均匀扫描又可以实现束流中心自动对中调节的扫描系统。介绍了扫描磁铁及其电源参数的选取依据,阐述了将扫描磁铁和束流校正线圈进行整体式设计的扫描系统扫描电流成形方式及自动对中电路信号调制过程,包括为提高加速器运行安全性而设计的连锁保护信号。产业化现场使用事实已证明,该系统设计完全达到了设计要求,具有优良的扫描均匀度和长时间工作稳定可靠性。     

A hybrid aerodynamic and electrostatic atomization system for enhanced uniformity of thin film

Droplet deposition processes by the mechanisms of either aerodynamics or electrostatic spray have been widely studied in various applications such as aerosol generators, thin film coatings, and nanoparticle formations. Among the current state-of-art methodologies, air spray deposition can produce small-sized droplets without fine control on their sizes and uniformity in deposited thin films. Conventional electrospray depositions, on the other hand, can fabricate thin films with good uniform with a relatively slow deposition speed. In this paper, a hybrid mechanism by means of aerodynamic and electrostatic deposition is investigated and demonstrated to allow high throughput and improved uniformity for thin film depositions. It utilizes both the electrostatic force and aerodynamic force to atomize the liquid and control the droplet spraying process with good stability/repeatability. A uniform thin TiO₂ film has been deposited as the demonstration example using this method. The velocities and trajectories of droplets during the deposition process have been characterized under different experimental parameters by using the technique of particle image velocimetry (PIV). This hybrid thin film fabrication method could be applicable in several industrial processes for better uniformity in making transparent electrodes, solar cells, displays, and automobiles.     

扫描探针针尖与试样间的静电力分析与建模

针对主体为圆锥、尖端为球冠的扫描探针针尖物理模型,提出了针尖与试样之间等效电场分布假设,基于该假设导出了二者之间静电力的解析模型,分析了针尖结构参数与静电力间的关系.模拟计算结果和数值计算结果一致,并与相关的实验结果吻合,证实了电场分布假设的合理性.     

辐照直线加速器电子束扫描控制

 在工业辐照电子直线加速器的扫描线圈内通以准三角波电流能使电子束在扫描方向分布均匀。系统的扫描电流周期和调制器的主脉冲同步, 可消除扫描均匀性中出现的拍频现象。根据速调管调制器主振脉冲频率、扫描宽度和电子束的束斑大小可以定出辐照床的最高运动速度以实现高效率的辐照。     

A full 3D numerical model of the industrial electrostatic coating process for moving targets

In this paper, a full three dimensional FLUENT numerical model of the electrostatic coating process as used in the automotive industry is presented and selected parametric studies on the numerical model have been conducted. The model incorporates a moving mesh capability in order to simulate movements of the target. The target follows piecewise linear motion and the entire area of the target has been coated in multiple passes. All the dominant mechanical and electrical phenomena were taken into account and cases with both neutral and charged particles were examined. It was confirmed that the transfer efficiency increases when the electrical forces are present in the model and that the coating uniformity improves with the movement of the target. The deposition pattern corresponds to the motion of the target and gradually builds up in a cumulative manner. Due to the aggregation effect associated with the target movement, the deposition uniformity is dramatically improved.     

High throughput ion implantation systems in western electric

Within Western Electric, a number of high throughput systems have been developed to meet the differing needs of high voltage and low voltage ion implantation applications. The PR-500 is a general purpose 500 kV machine which provides typical target currents of 0.5 ma of the common dopants and throughputs of 100 75-mm wafers/hour. The PR-200 is a 200 kV machine with typical target currents of 2.5 ma P, As, and Sb, and 1.0 ma B, and wafer throughputs of 150/hour. The PR-30 is a 30 kV single-species machine which can perform predeposition implants at rates of up to 450 wafers/hour. Typical PR-30 target currents are 5 ma P, As, and Sb. and 1.5 ma B. Each of these systems makes use of a common family of high current ion sources, and a rotating disk mechanical scanning system which permits a minimum implant time for 1 % uniformity of two seconds per wafer.     

Computer controlled techniques for high emission density mapping of thermionic cathodes

Some of the techniques commonly used (e.g. SLEEP and thermionic emission microscope) for measuring emission or work function uniformity of thermionic cathode surfaces require the use of very low or near zero current densities, thus the cathode is characterized at current densities and temperatures much lower than that of a normally operating cathode. The system reported on here uses a high voltage pulse technique and is capable of measuring emission densities in the range 1 to 80 A/cm² at normal cathode operating temperatures. The cathode surface is scanned with an anode having a 0.025 mm aperture whose position is controlled by computer operated stepping motors. The current through the aperture to a collector electrode is measured using a sample-and-hold amplifier. Pulsing and sampling are computer synchronized with the scanning, and data for each pulse are accumulated and can be processed and displayed in several ways using the computer, including a detailed “three-dimensional” map of either the electron emission density or work function variations. The entire surface of the cathode or any portion of it can be mapped in steps as small as 0.001 mm (1μm), but typically steps of 5–100 μm were used. Measurements are presented illustrating the uniformity or nonuniformity of the electron emission densities and work functions for type-B and type-M cathodes.     

一种新型谐振式微机电系统扫描镜及其利萨如图形显示

研制了一种基于微光机电系统(MOEMS)技术的新型谐振式扫描镜,该扫描镜采用绝缘体上硅(SOI)加工工艺,静电梳齿驱动,利用工艺中残余应力的释放产生垂直梳齿偏差,作为启动电极。针对该器件的机电性能,设计并搭建了一套光学系统测试其性能。结果表明,该器件具有加工工艺简单、低成本、低电压和大的扫描角度等优点。此外,将所制造的两个扫描镜进行合理组合,搭建了利萨如图形的显示装置,显示图案与Matlab软件仿真结果基本一致。     

First Russian standards in nanotechnology

The problem of ensuring uniformity of measurements in nanotechnology is discussed. A functional block diagram is developed for length unit size transfer from the primary length standard (meter) to the nanometric range. The first six Russian national standards are presented, which ensure this transfer using scanning electron and atomic force microscopes.     

Multiscale molecular dynamics using the matched interface and boundary method

The Poisson-Boltzmann (PB) equation is an established multiscale model for electrostatic analysis of biomolecules and other dielectric systems. PB based molecular dynamics (MD) approach has a potential to tackle large biological systems. Obstacles that hinder the current development of PB based MD methods are concerns in accuracy, stability, efficiency and reliability. The presence of complex solvent-solute interface, geometric singularities and charge singularities leads to challenges in the numerical solution of the PB equation and electrostatic force evaluation in PB based MD methods. Recently, the matched interface and boundary (MIB) method has been utilized to develop the first second order accurate PB solver that is numerically stable in dealing with discontinuous dielectric coefficients, complex geometric singularities and singular source charges. The present work develops the PB based MD approach using the MIB method. New formulation of electrostatic forces is derived to allow the use of sharp molecular surfaces. Accurate reaction field forces are obtained by directly differentiating the electrostatic potential. Dielectric boundary forces are evaluated at the solvent-solute interface using an accurate Cartesian-grid surface integration method. The electrostatic forces located at reentrant surfaces are appropriately assigned to related atoms. Extensive numerical tests are carried out to validate the accuracy and stability of the present electrostatic force calculation. The new PB based MD method is implemented in conjunction with the AMBER package. MIB based MD simulations of biomolecules are demonstrated via a few example systems.     

Elektrische Charakterisierung von Hochfrequenz-Niederdruck-Gasentladungen

In recent years there has emerged significant interest in low pressure radio frequency (rf) glow discharges which are used widely particulary in IC fabrication. Various parameters of the rf glow discharge have been found to be useful for its electrical characterization; however, there is no uniformity and agreement. Extensive experimental investigations on various discharge systems have shown, that the self-bias on the rf driven electrode, the complex conductivity and the breakdown characteristic are preferable parameters of rf discharges. Advantageously the self-bias and the complex conductivity should be presented in dependence on the pressure and the applied rf voltage. The discharge current cannot be measured quite accurately due to currents via leaky capacitors and the deviations from a sinusoidal form of the current due to nonlinearities.     

Experimental study of V–I characteristics of wire–plate electrostatic precipitators under clean air conditions

In this paper a laboratory-scale model for prediction of the voltage–current characteristics of wire–plate electrostatic precipitators under clean air conditions is presented and experimentally validated. The model investigates the effect of electrode configurations, wire diameter, spacing between wire electrodes, number of discharge wires and distance between collecting plates that on voltage–current characteristic of wire–plate electrostatic precipitators. Also, this paper presents a simulation model, based on the Finite Difference Method (FDM), to simulate electric conditions of wire–plate electrostatic precipitators under clean air conditions. The experimental results of some models are compared with those obtained from the simulation models.     

Competitive technologies of third generation infrared photon detectors

Hitherto, two families of multielement infrared (IR) detectors are used for principal military and civilian infrared applications; one is used for scanning systems (first generation) and the other is used for staring systems (second generation). Third generation systems are being developed nowadays. In the common understanding, third generation IR systems provide enhanced capabilities like larger number of pixels, higher frame rates, better thermal resolution as well as multicolour functionality and other on-chip functions. In the paper, issues associated with the development and exploitation of materials used in fabrication of third generation infrared photon detectors are discussed. In this class of detectors two main competitors, HgCdTe photodiodes and quantum well IR photoconductors (QWIPs) are considered. The performance figures of merit of state-of-the-art HgCdTe and QWIP focal plane arrays (FPAs) are similar because the main limitations come from the readout circuits. However, the metallurgical issues of the epitaxial layers such as uniformity and number of defected elements are the serious problems in the case of long wavelength infrared (LWIR) and very LWIR (VLWIR) HgCdTe FPAs. It is predicted that superlattice based InAs/GaInSb system grown on GaSb substrate seems to be an attractive to HgCdTe with good spatial uniformity and an ability to span cutoff wavelength from 3 to 25 μm.     

The energetic balance of the two different electrostatic processes: Electrostatic liquid spraying and electrostatic induction for electrical field measuring

In the specialized literature, two previous studies [S. Zhao, G.S.P. Castle, K. Adamiac, The effect of space charge on the performance of an electrostatic induction charging spray nozzle, J. Electrostat., 63 (2005) 261–272; S. Zhao, G.S.P. Castle, K. Adamiac, Comparison of conduction and induction charging in liquid spraying, J. Electrostat., 63 (6–10) (2005) 871–876] aim to clarify, by theoretical and experimental means, the following aspects concerning the charge through conduction and induction: charging mechanism, distribution of electrical field, conversion of energy and effect of spatial charge. This paper presents the energetic balance of the two systems, namely induction and conduction charge systems, with the purpose of establishing the quantitative energetic aspects of the phenomena that take place and, most of all, establishing the contribution to the energetic value of the drops that end up on the target and come from the high voltage source supplying power to the system and from the air flow that contributes to spraying and transporting particles to the target. At the same time, the energetic balance of a device which uses electrostatic induction for measuring electrical field intensity and high voltage is presented for exemplification. The device scheme, the way of functioning, the equivalent electrical schemes and the expression of the electrical current generated by the device as a consequence of the electrostatic induction are presented, and it is demonstrated that the electrical energy of the generated current does not result from the energy stored in the electrical field which is being measured, respectively of the one generating the electrostatic induction, but from the mechanical energy, by conversion, consumed by the motor which sets in motion the mobile part of this device.     

Computer analysis of the source image structure in 3D electron-optic systems: II. A stationary electromagnetic system

Computer analysis of the image of an arbitrary (point or extended) source obtained in 3D electron-optic systems is performed. The systems involve magnetostatic and electrostatic fields, which, respectively, focus and deflect the electron beams. Two approaches to image scanning are considered where the scan potentials are applied in two (symmetric and asymmetric) modes. It is shown that the spread function of the source, which characterizes the imaging quality of the system most fully, may serve as a primary computational criterion.     

Setup of a photomultiplier tube test bench for LHAASO-KM2A

To fulfill the requirements for testing the photomultiplier tubes(PMTs) of the electromagnetic detector at the Large High Altitude Air Shower Observatory(LHAASO),a multi-functional PMT test bench with a two-dimensional scanning system has been developed.With this 2D scanning system,16 PMTs can be scanned simultaneously for characteristics tests,including uniformity,cathode transit time difference,single photo-electron spectrum,gain vs.high voltage,linear behavior and dark noise.The programmable hardware and intelligent software of the test bench make it convenient to use and provide reliable results.The test methods are described in detail and primary results are presented.     

静电放电火花产生的电磁场树枝模型

 静电放电火花产生的电磁脉冲会对电子系统的正常工作造成严重的干扰，甚至造成系统的损伤。利用时域有限差分法建立了静电放电火花产生的电磁场的数值模型，模型中充分考虑了放电电极上的静电荷对电场的影响。把由此模型放电计算的电磁场值与由此解析方法得到的场值进行了比较，结果吻合良好。由此可以用此模型来研究静电放电火花产生的电磁场与电子系统的能量耦合问题。