射频激励的铜和金离子激光器中等离子体特性的实验研究

通过对射频 (RF)放电电压电流以及其相位角的精确测定 ,结合射频放电的物理模型与等效电路 ,对金属铜和金电极He气中的射频放电进行实验研究 ,得出射频放电溅射型铜和金离子等离子体电阻、容抗、鞘层厚度与电流密度的关系 ;在Goydak模型的基础上计算出电子密度 ,得出电子密度与气体压强、放电电流密度之间的实验曲线 ,并对两电极进行了比较。     

用于离子激光器的容性耦合射频放电理论研究

为了对高电流下的容性耦合射频(CCRF)放电有清晰的了解,我们建立了CCRF放电的自洽模型,研究了CCRF放电的放电特性和从低电流向高电流模式的转变规律.利用两电子组模型,结合流体模型自洽地研究了射频放电中放电参量与射频电压之间的变化关系.研究表明,在不考虑电极的γ过程时,射频放电的参量基本上随射频电压线性变化,没有出现转变迹像,而当考虑电极的γ过程后,射频放电明显出现两个不同的运行区域,对应于射频放电的低电流α区和高电流γ区.当射频放电出现转变后,传导电流密度和等离子体密度大幅度升高,鞘层电场增强,鞘层宽度明显减小,等离子体电场也减小.在γ放电下,快电子的电离速率分布主要在放电中心区且比较均匀,说明快电子在电极鞘层间形成了振荡,因此放电类似于空心阴极放电.(PC11)     

微波共振探针在测量等离子体密度中的应用

本文介绍了一种可以测量局部等离子体电子密度的微波共振探针法，并给出了它的测量原理、设计方法和实验结果。实验结果表明：由于微波共振探针不受鞘层的影响，因此它比通常的朗谬静电探针对等离子体密度的测量要精确得多。微波共振探针的空间分辨率与它的几何尺寸有关。     

用光电流效应测量CO_2正柱放电中径向电子密度的分布

利用光电流效应测量了CO_2正柱放电中径向电子密度分布,发现随气压升高和电流增大,电子密度分布向管轴收缩。     

空心阴极激光器放电特性的研究

本文对开槽式Ｃｕ空心阴极激光器的放电特性进行了研究，主要内容包括放电器的伏安特性和等离子体参量。本文采用双探针法测量电子温度与电子密度，在我们的实验条件下，测得空心阴极放电中电子温度为２￣３ｅＶ，电子密度为１０＾１２￣１０＾１３ｃｍ＾－３的数量级范围内，显然它们都高于正常辉光放电正柱区中这些参量的数值。     

影响ESD荷电器件模型放电电流的关键参数研究

静电放电峰值电流是基于荷电器件放电模型的放电测试装置中波形验证的关键指标.针对影响放电峰值电流的几个因素:测试探针长度、直径、形状和充电盘绝缘介电层的厚度,研究了这些参数变化对放电峰值电流的影响规律.根据研究结果可调整相应参数,保证荷电器件放电模型的测试装置符合测试标准.基于LRC放电电路的等效模型,实验结果给出了到满意的定量或定性解释.     

实验室研究等离子体鞘套测量方法和干预技术

航天飞行器再入大气层时,由于激波加热和热化学防护材料的烧蚀等原因,会在飞行器表面形成致密的等离子体鞘套,从而造成无线电通信信号中断。因此,减轻和消除黑障对飞行器测控安全至关重要。为了解决该难题,本文针对性地发展了适用于等离子体鞘套测量的探针设备和主动干预的技术,并利用实验室等离子体进行了验证。首先,提出了一种静电-微波复合探针,基于探针和飞行器表面曲面共形的优势,可以实时、有效地探测黑障高温流场中的电子密度;进一步,发展了亲电子物质释放实验主动干预方法,地面模拟实验表明该方法可以有效地降低流场等离子体中的电子密度。     

真空电子技术

046 94050162直流空心阴极放电中鞘层区电子的输运过程/魏合林,刘祖黎(华中理工大学)//物理学报一1994.43(6)一刃50~957 用蒙特一卡洛方法对空心阴极放电中鞘层区电子的输运过程进行了研究.研究了电子平均能量、电子密度和电离系数在径向的分布。图8参11(文) 介绍了SLAC后处理程序的基本结构与功能、并给出了用该软件绘制的部分电子注分析结果。图,参9(许)0463 94050163带电粒子束的自动聚焦技术/汪荣军,应根裕‘清华大学)//微细加工技术一1994,(2)一卜8 现代聚焦电子束、聚焦离子束装置大都采用白动聚焦、白动消象散技术,文章对目前常用…     

一种用于小型激光器的新颖放电结构的放电性质研究

依据微空心阴极自持的辉光放电结构,设计了一款新颖的微小放电结构.用空气进行了有关的放电实验,稳定的直流辉光放电,放电气压最大能够达到66.7 kPa.放电的伏安特性具有正的斜坡,放电能够稳定地运行,而不需要个体镇流电阻.在气压为40 kPa和放电电流为60 mA时,放电等离子体中的电流密度估计为0.048 A/cm2,功率密度估计为52.8 W/cm3,电子密度估计为2.7×1013 cm-3.实验结果表明:这种高气压、大体积、高电子密度的放电等离子体能够用作小型激光器的工作介质.     

等离子体鞘套中的电波传播特性研究

采用压力权函数修正的迎风型矢通量分裂格式（AUSMPW+）,求解纳维-斯托克斯（Navier-Stokes）方程组,得出不同飞行速度下等离子鞘套内的电子密度分布。基于改进的文策尔-克拉莫斯-布里渊（WKB）方法分析了电磁信号经过等离子鞘套的幅频特性,同时还给出了电磁波在鞘套中传输的相频曲线、群时延特性曲线。计算结果表明：随着飞行器速度增大,鞘套内电子密度增加,电波衰减明显增大,且电磁波在等离子鞘套中传输的相频特性受等离子体频率以及碰撞频率影响,在等离子体频率附近群时延最大。     

Effect of a magnetic field on the structure of a high-current electron beam with a compensated charge

A mathematical model of a high-current electron beam with a compensated charge is developed. The effect of the 3D axially symmetric magnetic field induced by the beam current is taken into account. The model is based on the method of current tubes, which makes it possible to calculate electron trajectories in the presence of an external axially symmetric magnetic field. It is demonstrated that, in the presence of an external axially symmetric magnetic field, the beam rotates around its axis and the azimuthal current is induced. The shapes of electron trajectories are strongly affected by the magnetic field of the azimuthal current. The electron trajectories are calculated for various beam currents and external magnetic fields. It is shown that a significant nonlinearity leads to crossing of the trajectories of the initially laminar beam, sheath formation after passing the crossover, and collisionless thermalization of the beam. The boundary of the region inside which the beam can stably overcome the first crossover is determined.     

The admittance of the infinite cylindrical antenna immersed in a lossy, compressible plasma

Some numerical results obtained from an analysis of the admittance of an infinite cylindrical antenna excited at a circumferential gap of finite thickness and immersed in a lossy, compressible (warm) plasma are given. The linearized hydrodynamic equations are used for the electrons (ion motion is neglected). A free-space layer, or vacuum sheath, is used to approximate the ion sheath which forms about an object at floating potential in a nonzero temperature plasma. Values for the antenna admittance are obtained by a direct numerical integration of the Fourier integral for the current, and are presented as a function of frequency for plasma parameter values typical of theEregion of the ionosphere. The admittance exhibits a maximum below the plasma frequency unless the electron temperature and sheath thickness are both zero; however, above the plasma frequency, the sheath and electron temperature have relatively little effect on the antenna admittance. The nonzero plasma temperature considerably enhances the antenna conductance below the plasma frequency compared with the zero-temperature case while at the same time reducing the dependence of the conductance on the electron collision frequency. A susceptance zero the location of which is not sensitive to the vacuum sheath thickness occurs near the plasma frequency.     

Langmuir-probe measurement of ionisation density on a plasma jet

The current to a negative probe in an argon plasma jet shows a strong dependence on probe bias and is up to an order of magnitude less than the usual convection/diffusion saturation current. The current is also in surprisingly good agreement with the calculated sheath/convection current. The results are attributed to electron?ion recombination in the vicinity of the probe.     

Recombination effects with high-pressure Langmuir probes

With increasing ion density, the ion current collected by a negatively biased electric probe is eventually dominated by ions produced by reactive processes in the vicinity of the probe. Here, we derive an expression for the probe current to a cylindrical probe when all the ions collected to the probe are assumed to be generated within the sheath which surrounds the probe. Measurements of probe current in a seeded atmospheric-pressure flame are in good agreement with the theory. The significance of reaction processes is reinforced by the fact that the maximum probe current is found to be approximately three times the total current that the flame would produce with frozen chemistry, i.e. the saturation current.     

Scattering by an infinite cylinder coated with an inhomogeneous and anisotropic plasma sheath

The problem of the interaction of an incidentHwave with an infinite conducting cylinder coated with an inhomogeneous and anisotropic plasma sheath is treated analytically. Numerical results for the farfield pattern of the scattered field as well as the backscattering cross sections are presented for various interesting ranges of the parameters involved. Detailed discussion of the effects of the impressed static magnetic field, the sheath thickness, and the density and profile of the plasma sheath on the scattered wave is also presented. A parabolic electron density profile is assumed.     

Correlation between cold deformation and microcrack formation in BSCCO-2223 powder in tube superconductor

This paper describes the result of a cold rolling deformation path on the microstructure and the longitudinal and transverse critical currents of monofilamentary BSCCO-2223 tape produced via the oxide powder in tube (OPIT) process. The fully reacted BSCCO-2223 powder used in this experiment highlights the deformation mechanisms effect on the microstructure of the core, and hence the effect on the longitudinal and transverse critical currents. Tapes with different sheath properties are produced by controlling the hardness of the pure silver sheath either by annealing at 500 °C between rolling stages or by allowing the sheath to work harden throughout the deformation path. The results show that the ultimate core density depends on the hardness of the sheath and that the maximum core density is reached whilst the tape is still relatively thick. Microscopy shows that continued rolling after the core has reached its maximum density results in the production of transverse cracks in the core. The critical current measurements show that these cracks severely limit the potential longitudinal critical current of the superconductor. A softer sheath allowed a greater reduction in thickness before transverse microcracking became severe, whilst a harder sheath enabled a higher core density to be reached. This technique of controlling sheath hardness suggests possible improvements in the deformation processing of OPIT produced superconducting BSCCO-2223 tapes.     

基于二维PIC-DSMC的微间隙气体放电等离子体演化过程研究

准确的理解微间隙气体放电中非平衡等离子随时间的演化过程对于设计气体开关、微电子及其它等离子体器件有着非常大的帮助。通过二维PIC-DSMC耦合算法模拟了一个大气压氮气环境下微间隙平板电极发生气体放电时电子及离子的运动演化过程,得到了气体放电过程中平板电极间电子和离子数密度分布随时间变化的趋势,讨论了阳极附近电子云的形成与演变、阴极附近存在的鞘层以及电子和离子的速度及温度分布,最后将模拟计算得到的击穿电压与帕邢曲线及相关实验结果进行了对比,为相关等离子体器件的进一步发展提供了理论基础。     

He-Ne管正柱区鞘层及电子温度的计算

本文计算小孔径He-Ne管等离子体鞘层及电子温度,并对其电势及厚度的公式进行了讨论;计算的正柱区伏-安特性与实验符合.     

Incoherent Scatter Radar Probing of the 60-100-km Atmosphere and Ionosphere

All current incoherent backscatter radars can make mesospheric or D region measurements (60-90-km altitude) under at least some conditions. This paper, which is tutorial in nature, develops the basic concepts of incoherent scatter radar measurements in the D region and the conditions under which measurements are possible are derived and shown for each radar. Conditions examined include overall system sensitivity, electron and ion spectral line widths and power distributions, and time/height averaging effects. The appropriate form of the radar equation is derived and calibration of the radar system is discussed along with the various aspects of signal processing involved. Total power only and combined total power and ion line spectral measurements are described in terms of ease of use, applicability to various radars, and parameters of aeronomic interest derivable from the measurements.