Effect of low-voltage spark discharge parameters on the spectral line intensities of sulfur and halogens

The influence of various circuit parameters on the spectral line intensities of sulfur and the halogens when excited in a low-voltage spark discharge have been investigated. The intensities were maximum for a discharge current of 6–8 A and a 1.0–1.5 mm spark gap. In ac spark discharges the maximum intensities occurred with capacitances of 20–50F and an inductance of 15H for primary circuit resistance of 200 ohm, and with 50–100F and 30–60H for 400 ohm. The intensities attained with dc sparks were higher than those with ac sparks. The intensity increased if the specimen served as the cathode and, in this case, occurred with capacitances of 100–800F and inductances of 30–60H for an ignition frequency of 12 sec^–1.     

Computational procedure to evaluate physical parameters from electron spin-echo decay functions

Analysis of the decay behavior of two-pulse and three-pulse electron spin-echo patterns gives information on the physical properties of the spin system such as the spin concentration and the spin reorientation rates. A computer-simulation approach is developed to study the effects of the spin concentration and of the spin-flip rate on the decay. The analysis is extended to two limiting models that describe different dynamic processes affecting the spectral diffusion of the spin system. The instantaneous diffusion mechanism is also taken into account. On the basis of the combined analysis of two-pulse and three-pulse simulated decay patterns the possibility of distinguishing the different dynamic models is investigated as well as the degree of accuracy in the determination of the physical quantities. A general finding is that the possibility of distinguishing the different dynamic models and the degree of accuracy depend both on the ratio between the interpulse times and the spin-flip time and on the relative weights of the spectral diffusion and instantaneous diffusion mechanisms.     

Growth and properties of Ti-Cu films with respect to plasma parameters in dual-magnetron sputtering discharges

Properties of different methods of magnetron sputtering (dc-MS, dual-MS and dual-HiPIMS) are studied and compared with respect to intermetallic Ti-Cu film formation. The quality and features of thin films are strongly influenced by the energy of incoming particles. The ion velocity distribution functions (IVDFs) were measured by time-resolved retarding field analyzer (RFA) in the substrate position. Thin films were characterized by X-ray photoelectron spectroscopy (XPS), X-ray diffractometry (XRD) and X-ray reflectometry (XR). Properties and crystallography of Ti-Cu films are discussed as a function of ion energy which is affected by the mode of sputtering. It was found that IVDFs measured in pulsed discharges exhibit double-peak distribution. The IVDFs reach the maximum at ion energies about  ~8 eV. The ion saturated current is highest in dual-HiPIMS discharge (~5 μA/cm²) and is mostly represented by Cu⁺ and Ar⁺ ions. The mode of sputtering influences chemical composition and film formation. The copper forms polycrystalline fcc-phase while much smaller Ti particles enwraps the copper crystallites or are part of a solid solution.     

Prospects of developing multibeam systems for low-voltage electron lithography

The prospects of developing tiny multibeam systems for electron lithography have been considered. Designs of tiny basic elements of electron-optical systems, including a magnetic lens with an open magnetic circuit and a lens with aligned axially symmetric fields (whose magnetic circuit simultaneously plays the role of electrodes of an electrostatic lens), are represented, as well as their analysis. The results of the investigation of high-speed one-turn deflection systems without or with a core and the analysis of a stigmator are reported. Radically new approaches to design of tiny electron-optical systems have been considered, which make it possible to increase the efficiency of electron beam formation and pass to micro-and nanotechnological design of vacuum microsystems.     

Effects of ultrasound on electrode damage and spectrum intensity for a low-voltage discharge

Journal of Applied Spectroscopy -     

电子枪功率与束宽对金属原子蒸气特性的影响

在原子法激光同位素分离工程中,电子枪加热金属铀产生的原子蒸气的密度、速度以及温度等宏观量分布特性是非常重要的参数.为了分析电子枪功率和束宽对原子蒸气密度、速度、温度、质量通量和速度分布等物理特性的影响,采用直接MonteCarlo方法用柱坐标模拟了铀原子平面蒸发动力学过程.在电子枪加热方式下,蒸发源温度场不均匀,而且温度场随电子枪功率和束宽变化.着重研究这种变化对蒸气各种物理特性的影响.模拟结果表明,电子枪功率越高,蒸气径向宏观漂移速度越大,蒸发量越大;电子束束宽越窄,蒸发量越大. 关键词： 金属蒸发 原子法激光同位素分离 直接MonteCarlo 电子枪     

Synthesis of electrodes for relativistic electron streams

The condition for geometrical similarity of trajectories given by Dryden has been modified to be relativistically correct, thus allowing the complete Dryden-Harker procedure to be used to design electrodes for relativistic electron streams of limited velocity spread. The magnetic field in the cathode region has been modelled by an analytic expression, to allow converging field to be simulated while similarity of the magnetic force is retained. Examples are given of the use of the revised method for design of high-voltage and external electron guns for gyrotrons.     

Annealing effect of platinum-based electrodes on physical properties of PZT thin films

This study examined the crystal structure and surface morphology, including the Ti segregation mechanism on the surface due to the inter-diffusion between Pt, Ti and TiO_x as a glue layer, according to the annealing temperature and growth orientation of a Pt film. In addition, the fatigue mechanism of ferroelectric PZT thin films deposited on a Pt-based electrode was also investigated. The nano-structure, orientation mapping, and micro-morphologies of the triangular Pt hillocks were investigated by scanning electron microscopy with an electron backscatter diffraction (EBSD) function. The D–E hysteresis loop of the ferroelectric films was measured using a Sawyer–Tower circuit at 1 kHz to obtain the remanent polarization and coercive field.     

Optimization of acoustic parameters for ultrasonic separation of emulsions with different physical properties

Ultrasound is an emerging and promising method for demulsification, which is highly affected by acoustic parameters and emulsion properties. Herein, a series of microscopic and dehydration experiments are carried out to investigate the parameter optimization of ultrasonic separation. The results show that the optimal acoustic parameters highly depend on the emulsion properties. For low frequency ultrasonic standing waves (USWs), mechanical vibrations not only facilitate droplet collision and coalescence, but also disperse the surfactant absorbed on the interface to decrease the interfacial strength. Therefore, low frequency ultrasound is suitable for separating emulsions with high viscosity and high interfacial strength. Increasing the energy density to produce moderate cavitation can increase demulsification efficiency. However, excessive cavitation results in secondary emulsification. In high frequency USWs, the droplets migrate directionally and form bandings, thereby promoting droplet coalescence. Therefore, high frequency ultrasound is favorable for separating emulsions with low dispersed phase content and small droplet size. Increasing the energy density can accelerate the aggregation of droplets, however, excessive energy density causes acoustic streaming that disturbs the aggregated droplets, resulting in reduced demulsification efficiency. This work presents rules for acoustic parameter optimization, further advancing industrial applications of ultrasonic separation.     

高功率脉冲非平衡磁控溅射放电特性和参数研究

用线圈电流控制非平衡磁场,用汤森放电击穿形成深度自触发放电,用磁阱捕获放电形成的二次电子和导致漂移电流,形成了高功率非平衡磁控溅射放电。采用偏压为-100V相对磁控靶放置的圆形平面电极收集饱和离子电流;在距离磁控靶14cm的位置由Langmuir探针测量浮置电位;示波器测量磁控靶的脉冲电压、电流、浮置电位和饱和离子电流信号。装置的放电脉冲功率达到0.9MW,脉冲频率最大值为40Hz左右,空间电荷限制条件是控制电子电流和离子电流的主要机制。     

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用线圈电流控制非平衡磁场,用汤森放电击穿形成深度自触发放电,用磁阱捕获放电形成的二次电子和导致漂移电流,形成了高功率非平衡磁控溅射放电。采用偏压为-100V相对磁控靶放置的圆形平面电极收集饱和离子电流;在距离磁控靶14cm的位置由Langmuir探针测量浮置电位;示波器测量磁控靶的脉冲电压、电流、浮置电位和饱和离子电流信号。装置的放电脉冲功率达到0.9MW,脉冲频率最大值为40Hz左右,空间电荷限制条件是控制电子电流和离子电流的主要机制。     

Simple model for electron inelastic mean free paths: Application to condensed organic materials

A simple, ‘one-mode’ approximation for the wavevector- and frequency-dependent energy-loss function is employed to derive an expression for the electron inverse mean free path, λ_v^?1, including the effect of exchange between the incident electron and the electrons in the medium. Relation to optical data is made by averaging λ_v^?1, over the optical oscillator strength distribution, which is proportional to ωIm[— 1/?(ω)]. For materials for which the optical oscillator strength distribution may be approximated by a single, Drude-type function, especially organic materials, the general results may be cast in a particularly simple form. Using a few constants derived from optical data for a given material, electron mean free paths in that material can be predicted for electron energies ? 150 eV. An approximate expression is also deduced for estimating electron mean free paths in materials for which no optical data are available. Mean free paths determined using this approximate expression agree well with those obtained in our earlier ‘universalcurve’ predictions. For polyethylene, the excellent agreement between results from the model presented here and those from a more detailed insulator model gives additional support for this simple theoretical approach. Agreement between theoretical predictions and experimental measurements of electron mean free paths in organic compounds, which in some cases is quite good, is on the whole less than satisfactory.     

TEA CO2激光器几种放电电极的比较

 从均匀场电极理论出发，计算并讨论了近似Rogowski电极、Chang电极(含紧凑式Chang电极)和Ernst电极的形状、理论电场分布和实际电场分布。对实验室所用的几种电极进行了脉冲放电实验，从而获得了TEA CO₂激光器的放电参数与输出特性，并对这些结果进行了比较和分析。计算表明，在基本参数相同的情况下，Ernst电极具有最紧凑的外形和最佳的均匀电场分布。实验表明，采用近似Rogowski电极的TEA CO₂激光器具有最大放电辉光范围和44 kV的最小放电击穿电压；采用Ernst电极的TEA CO₂激光器具有25 J的最高单脉冲能量和最大17.2%的斜率效率。最后提出了TEA CO₂激光器主电极的选择建议。