直流空心阴极放电中鞘层区电子的输运过程

采用蒙特－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，电子在鞘层区被非均匀电场加速，两次碰撞之间的步长是由电子与中性粒子的碰撞频率确定。模型中三种碰撞截面积是由实验和理论数据拟合而来。研究了电子平均能量、电子密度和电离系数在径向的分布。电子能量的空间分布结果与实验很好地符合。 关键词：     

ELECTRON DIFFUSION IN A NON-UNIFORM ELECTRIC FIELD AND A UNIFORM MAGNETIC FIELD

A Monte Carlo simulation technique has been used to model the electron transport beharlot, especially the electron diffusion motion, in the cathode fall region of a glow discharge under the influence of a non-uniform electric field and a transverse magnetic field perpen-dicular to the cathode sheath electric field. Three types of collisions (elastic, excitation and ionization) are taken into account in our model. The electron free flying time is determined by the electron-neutral atom collision frequency. We focus attention on the electron diffusion distance and velocity. The electron-neutral atom collision processes and the electron drift velocity are also studied. The results indicate that with the increase of the magnetic field the electron diffusion distance increases and the electron diffusion velocity decreases. The results Mso show that the collision processes are enhanced by the magnetic field, this is in agreement with the experimental result. However, the axial magnetic field does not affect the electron transport behavior.     

直流辉光等离子体阴极鞘层电子的输运过程

采用蒙特卡罗方法对氦直流辉光放电平板电极等离子体阴极鞘层内电子的输运过程进行了研究。利用实验数据拟合得到的电子与中性粒子的碰撞截面,计算了电子的平均能量及能量分布的空间变化,同时研究了电子的其它参数分布.     

四阳极直流辉光放电正柱区数值分析

分析了具有中间开窗电极四阳极直流辉光放电装置的氦气放电中阴极与较近阳极间放电正柱区的电子密度、电子温度和等离子体碰撞频率, 及其空间分布随放电气压变化规律。结果表明电子密度在径向上呈类似于抛物线的分布, 而碰撞频率和电子温度在整个放电管内近似均匀分布。探讨了不锈钢阳极座和矩形窗口对这些参数的影响, 为进一步进行装置仿真和实验研究提供参考。     

横向磁场对辉光等离子体阴极区电子输运过程的影响

本文动用改进的蒙特卡罗技术，研究了横向磁场对氦气直流辉光放电阴极区电子输运过程的影响。     

空心阴极类火花放电初始电离过程的PIC/MCC模拟

采用粒子模拟与蒙特卡罗相结合(PIC/MCC)的方法,应用静电模型,编写了准三维的模拟程序.该程序能够较好地描述空心阴极类火花放电初始电离过程的演化步骤.通过研究电离过程的细节,可以认为该阶段电离过程是空心阴极效应和局部强电场共同作用的结果.从起始电离到空心阴极初始阶段,局部强电场在电离过程中起到了支配作用;随后空心阴极效应占据主导地位. 关键词： 粒子模拟 蒙特卡罗 空心阴极 类火花放电     

THEORETICAL INVESTIGATION OF ELECTRON-NEUTRAL ATOM COLLISION PROCESS AND ELECTRON TRANSPORT PARAMETERS IN DC GLOW DISCHARGE OF PLASMA WITH A TRANSVERSE MAGNETIC FIELD

A Monte Carlo simulation (MCS) technique is used to simulate the cathode sheath region of a helium dc glow discharge. In such a simulation, a nonuniform electric field and a transverse uniform magnetic field are considered. When the magnetic field intensity increases from 0 to 800 G, all types of collision considered in this paper are enhanced. This result is in agreement with the experimental result. The results also show that with the increase of magnetic field intensity, the electron transport time, the electron density increase, and the electron mean energy decreases.     

Enhanced energy deposition efficiency of glow discharge electronbeams for metal surface treatment

The energy deposition efficiency and focal spot dynamics of electron beams produced by pulsed cold-cathode high-voltage glow discharges for metal surface treatment are investigated for two different cathode geometries. A concave cathode geometry in which the focusing is dominated by the convergence of the electric field lines in the cathode fall region is compared with flat cathode in which the focusing is exclusively caused by the self-generated magnetic field. Results of the treatment of AISI 4140 carbon steel samples show that the concave cathode geometry significantly increases the efficiency, reduces the threshold power necessary for melting, and is less sensitive to variations in the discharge parameters and sample position. The results of numerical modeling indicate that the observed increase in efficiency is caused by the longer persistence of the focal spot on the sample. The model can be used to predict the discharge parameters required for a desired treatment     

轰击阴极的重粒子能量分布

采用蒙特卡罗模拟对氮辉光放电等离子体中轰击极阴的重粒子（N2^ ,N^ ,Nf及N2f）能量分布随放电参数的变化规律进行了研究。结果表明：阴极臂前诸粒子的能量分布取决于粒子被加速的能量和碰撞频率,能量较低的快原子Nf的密度比高能粒子N^ 的密度最近两个量级。在活性氮粒子（N^ ,Nf）产率最高的放电条件下,适当降低放电气压,提高阴极位降和气体温度,有利于两种活性氮粒子（N^ ,Nf）达到阴极。     

Surface and bulk normal state transport properties in K(3)C(60)

The temperature dependence of the surface resistivity for a metallic K(3)C(60) ordered film in the nonsuperconducting state has been obtained by reflection electron energy loss spectroscopy. We demonstrate that the normal state electronic and transport properties of the top molecular layer of K(3)C(60) are similar to the corresponding properties measured with bulk sensitive techniques. These observations strengthen and give a general character to the experimental results obtained with surface sensitive techniques on fullerene compounds. In addition, the transport properties may deviate from the Fermi-liquid behavior above 500 K.     

Spark Discharge Action on a Cathode Surface in Air Atmosphere

New results obtained by electron microscopy investigations of cathode spot parameters are qualitatively and quantitatively analysed to the view of further understanding of the cathode processes in spark discharges.     

微空心阴极放电的Monte Carlo模拟研究

基于MATLAB与VC++混合语言，采用Monte Carlo模拟对高气压下亚毫米级微空心阴极放电（MHCD）中电子的运动过程进行了研究，计算出不同气压下的稳态时场向电子密度分布，电子能量分布以及对各种碰撞的统计等.分析表明：高气压下微空心阴极放电更能反映空心阴极效应——“来回振荡”的本质.通过模拟得到，电子在阴极间来回振荡的过程中，仍以前向散射为主.随着气压的升高，侧向散射效应逐渐体现出来. 关键词： 微空心阴极 Monte Carlo 负辉区 碰撞截面     

Study of Intense Electron Beams Produced by High-Voltage Pulsed Glow Discharges

We report the generation of high-current-density (20 A/cm2) pulsed electron beams from high-voltage (48-100 kV) glow discharges using cathodes 7.5 cm in diameter. The pulse duration was determined by the energy of the pulse generator and varied between 0.2 ?s and several microseconds, depending on the discharge current. The largest electron beam current (900 A) was obtained with an oxidized aluminum cathode in a helium-oxygen atmosphere. An oxidized magnesium cathode produced similar results, and a molybdenum cathode operated at considerably lower currents. A small-diameter (<1 mm) well-collimated beam of energetic electrons of very high current density (>1 kA/cm2) was also observed to develop in the center of the discharge. Electrostatic probe measurements show that the negative glow plasma density and the electron beam current have a similar spatial distribution. Electron temperatures of 1-1.5 eV were measured at 7 cm from the cathode. The plasma density (8.5 · 1011 cm-3 at 450 A) was found to depend linearly on the discharge current. In discharges at high currents a denser and higher temperature plasma region was observed to develop at approximately 20 cm from the cathode. We have modeled the process of electron beam generation and predicted the energy distribution of the electron beam. More than 95 percent of the electron beam energy is calculated to be within 10 percent of that corresponding to the discharge voltage.     

Droplet spot as a new object in physics of vacuum discharge

It is established experimentally that the burning of a low-current (several and tens of amperes) pulsed (microseconds) vacuum discharge is accompanied by the formation of plasma microbunches around some of the droplets leaving the cathode spot. The parameters of these bunches (electron concentration n _e～10²⁶ m^?3 and equilibrium temperature T _e～1 eV) are close to the parameters of cathode-spot plasma. The data obtained suggest that the initial temperature of droplets and the thermionic emission from them play a key role in the formation of such plasma microbunches. By analogy with the well-known cathode and anode spots in vacuum discharges, these droplet plasma formations are classified as “droplet spots.” This work reports the first results on studying the formation dynamics and the characteristics of the droplet spots. It is noted that the concept of droplet spots will require a certain refinement of the plasma formation mechanism in vacuum discharges.     

确定SF6-CO2预放电参数的激光脉冲方法

在均匀电场中,用高能激光脉冲释放初始电子以研究负电性气体的电子崩的发展,决定预放电过程的基本参数(游离系数α,吸附系数η和漂移速度v等)是一个有用的方法,本文对此方法做了详细的分析。采用这种方法对SF₆-CO₂混合气体做了研究,获得了10⁸个以上的初始电子及其分布,并给出了α/P,η/P和ν与E/P(E=电场强度,P=气体压力)的关系。本文还对所用的测量系统做了讨论,提出了改进办法。 关键词：     

一种补偿时间步长限制的粒子模拟-蒙特卡罗碰撞模型

 从碰撞次数的概率分布出发,推导出一种补偿蒙特卡罗碰撞模型,采用以正态分布计算得到的平均碰撞次数作为碰撞概率,来补偿传统方法中忽略的多次碰撞。通过模拟不同折合电场强度条件下He气放电产生电子的运动规律,验证了补偿蒙特卡罗碰撞模型的正确性。计算结果表明:补偿蒙特卡罗碰撞模型可以有效地提高计算效率,特别适用于高气压气体放电现象的粒子模拟。     

Auq+(q=47,55)离子的电子碰撞强度与速率系数

用准相对论扭曲波方法计算了Au^q+（q=47,55）离子的组态重心能级之间的电子碰撞激发强度和速率系数（简称激发参数）．着重分析了高能区光学允许跃迁的碰撞强度的行为，探讨了平面波近似的适用范围．与其他完全相对论数据比较，表明剩余的相对论效应是不大的．阐述了由约化量的5点样条值内插可得任意能量的碰撞强度和任意温度的速率系数．演示了碰撞强度随能量的变化，有效碰撞强度和速率系数随温度的变化．结果表明在类镍金两侧各延伸的4种不同荷电离子，其单电子激发参数变化小于10%，这对于使用平均原子模型     

Doppler spectroscopy of hydrogen and deuterium Balmer alpha line in an abnormal glow discharge

The results of hydrogen and deuterium Balmer alpha line shapes and line intensities study in an abnormal glow discharge are reported and analyzed. The Doppler shifts along line wings are used to determine energies of excited hydrogen and deuterium atoms. For 12 different cathodes, intensity and shape of line wings are examined and dependence upon cathode material is determined. Tentative explanation of line wings intensity dependence is related to the sputtering of cathode material and back-scattering coefficients of incident hydrogen or deuterium ions and atoms from cathode surface. The influence of the light reflected on a cathode surface to the line shape measurements along discharge axis is considered. In hydrogen, deuterium, and Ar+3%H/sub 2/ discharges, basic mechanisms of fast hydrogen generation and excitation are studied. The shape and intensities of the H/sub /spl alpha// line profiles in pure hydrogen and in argon-hydrogen mixture may be correlated with hydrogen atom-carrier gas collision excitation cross sections. In order to assess the importance of reflected fast hydrogen atoms back scattered from the cathode surface, for the Balmer line shape formation, a simulation program is used. The results are in a qualitative agreement with Balmer line shapes observations.     

Study of field-induced explosive electron emission mechanisms ofpseudospark superemission cathodes

Various mechanisms of electron emission, including the field, field-enhanced thermionic, and explosive electron emissions from pseudospark cathodes, are discussed and compared. The mechanism of the field-induced explosive electron emission due to microstructure on the cathode surface is considered to be more likely the pseudospark superemissive mechanism. A high-mean electric field up to 3-5 MV/cm on the cathode surface in the end of hollow cathode phase is enough to initiate the mechanism. The cathode spot initiation delay time (<10 ns) and explosive emission threshold current (~10⁸ A/cm² ) prior to the high current conducting phase are given by solving the initial value problem of the one-dimensional heat conduction equation, thus explaining the existing experimental data of the pseudospark cathode superemission. In the case of multigap discharge, the above mechanism occurs on nearly all cathode and interelectrode surfaces. Experimental evidence in single- and multigap pseudospark discharges supports the suggested explanation