非对称磁镜场电子回旋共振氧等离子体刻蚀化学气相沉积金刚石膜

分别应用郎缪尔双探针和离子灵敏探针对非对称磁镜场电子回旋共振氧等离子体的电子参数、空间分布和离子参数进行了测量,分析了气压对等离子体参数及空间分布的影响。利用该等离子体在优化的气压条件下对化学气相沉积金刚石膜进行了刻蚀,并研究了刻蚀机理。结果表明:电子温度为5~10 eV,离子温度为1 eV左右,而等离子体数密度在1010cm-3数量级。随气压的升高,电子和离子温度降低,而电子数密度先增大后减小。在低气压下等离子体数密度空间分布更均匀,优化的刻蚀气压为0.1 Pa。刻蚀过程中,离子的回旋运动特性得到了加强,有利于平行于金刚石膜表面的刻蚀,有效地保护了金刚石膜的晶界和缺陷。     

非对称磁镜场电子回旋共振氧等离子体刻蚀化学气相沉积金刚石膜

分别应用郎缪尔双探针和离子灵敏探针对非对称磁镜场电子回旋共振氧等离子体的电子参数、空间分布和离子参数进行了测量,分析了气压对等离子体参数及空间分布的影响。利用该等离子体在优化的气压条件下对化学气相沉积金刚石膜进行了刻蚀,并研究了刻蚀机理。结果表明：电子温度为5～10 eV,离子温度为1 eV左右,而等离子体数密度在1010 cm-3数量级。随气压的升高,电子和离子温度降低,而电子数密度先增大后减小。在低气压下等离子体数密度空间分布更均匀,优化的刻蚀气压为0.1 Pa。刻蚀过程中,离子的回旋运动特性得到了加强,有利于平行于金刚石膜表面的刻蚀,有效地保护了金刚石膜的晶界和缺陷。     

Tungsten ion source under double-pulse laser ablation system

New tungsten ion source is produced by using single and double-pulse laser ablation system. Combined collinear Nd:YAG laser beams(266+1064 nm) are optimized to focus on the sample in air. Optimization of the experimental parameters is achieved to enhance the signal-to-noise ratio of the emission spectra. The velocity distribution of the emitted plasma cloud is carefully measured. The influences of the potential difference between the bias electrodes, laser wavelength and intensity on the current signal are also studied. The results show that the increase in the tungsten ion velocity under the double-pulse lasers causes the output current signal to increase by about three folds. The electron density and temperature are calculated by using the Stark-broadened line profile of tungsten line and Boltzmann plot method of the upper energy levels, respectively. The signal intensity dependence of the tungsten ion angular distribution is also analyzed. The results indicate that the double-pulse laser ablation configuration is more potent technique for producing more metal ion source deposition, thin film formation, and activated plasma-facing component material.     

Numerical Computation of Self-sustaining Magnetically Confined Electron Clouds

In this paper the axisymmetrical self-sustaining magnetically confined electron clouds are studied by means of the numerical computational method on the basis of the fluid theory.The electron density distribution,electric potential distribution,drift angular frequency and electron temperature can be calculated with a simplified method in which the near-equilibrium state approximation is necessary.The results are,in principle,in agreement with the experiments.     

The Electron Cloud Produced by Intense Ion Beam in Penning Trap

When an ion beam pass through the Penning trap an electron cloud is produced.The distributions of the electron density,electron temperature,drift angular velocity of electrons,diffusion flow density of electrons and electric potential in the electron cloud are discussed by means of the fluid equations of the motion of electrons.     

溅射原子角分布与靶点表面形貌的关联研究

27keV的Ar⁺离子垂直轰击处于不同温度的Cd靶,用捕获膜技术和Rutherford背散射谱仪(RBS)测定溅射原子角分布,并对所有样品的靶点形貌进行扫描电子显微镜(SEM)观察。结果发现,所有的角分布都呈over-cosine形状,但是在极角为0°处实验值与cosine值的偏离△,是不同的,在靶温度为150℃时的偏离△_T小于在室温时的偏离△_R,亦即△_T<△_R,提出一个简单的模型对这种溅射角分布 关键词：     

A novel method for observation by unaided eyes of nitrogen ion tracks and angular distribution in a plasma focus device using 50 Hz–HV electrochemically-etched polycarbonate detectors

A novel ion detection method has been developed and studied in this paper for the first time to detect and observe tracks of nitrogen ions and their angular distribution by unaided eyes in the Amirkabir 4 kJ plasma focus device (PFD). The method is based on electrochemical etching (ECE) of nitrogen ion tracks in 1 mm thick large area polycarbonate (PC) detectors. The ECE method employed a specially designed and constructed large area ECE chamber by applying a 50 Hz–high voltage (HV) generator under optimized ECE conditions. The nitrogen ion tracks and angular distribution were efficiently (constructed for this study) amplified to a point observable by the unaided eyes. The beam profile and angular distribution of nitrogen ion tracks in the central axes of the beam and two- and three-dimensional iso-ion track density distributions showing micro-beam spots were determined. The distribution of ion track density along the central axes versus angular position shows double humps around a dip at the 0° angular positions. The method introduced in this paper proved to be quite efficient for ion beam profile and characteristic studies in PFDs with potential for ion detection studies and other relevant dosimetry applications.     

Ar原子序列双光双电离产生光电子角分布的理论计算

基于多组态Dirc-Fock方法和密度矩阵理论,给出了原子序列双光双电离光电子角分布的计算表达式,发展了相应的计算程序.利用该程序对Ar原子3p壳层序列双光双电离过程进行了理论研究,给出了光电离的总截面、磁截面、剩余离子取向以及光电子角分布的各向异性参数与入射光子能量的函数关系.结果显示在光电离截面的Cooper极小位置附近取向参数出现极大值,而光电子角分布的各向异性参数在该位置附近出现极小值.进一步给出了33.94和55.34 eV光子能量下序列双光双电离过程中第一步的Ar原子和第二步的Ar^+离子3p壳层光电子角分布,分析了序列双光双电离光电子角分布与单光电离光电子角分布的差异.将计算结果与文献已有的数据进行了比较,具有很好的一致性.本文的研究结果对揭示光与物质相互作用的非线性动力学机制具有重要的参考价值.     

真空电弧等离子体发射光谱诊断

真空断路器的开断容量限制其在高压大电流开断领域的应用,获取燃弧过程中的等离子体参数对于提高真空断路器的开断容量至关重要。利用发射光谱法对真空电弧内的等离子体参数进行了诊断,研究了在不同电流幅值条件下真空电弧内电子温度、电子密度、谱线强度的轴向分布规律,结合真空电弧高速图片对真空电弧内不同粒子的扩散过程与弧柱直径之间的关系进行了分析。得到的电子温度在8000～10 000 K量级,电子密度在10¹⁹～10²⁰ m⁻³量级,电子温度与电子密度从阴极向阳极逐渐下降,同时铜原子谱线强度主要集中在两极而一价铜离子谱线强度由阴极向阳极逐渐升高。铜原子谱线强度的径向分布呈现类平顶波分布、一价铜离子谱线强度的径向分布呈现类高斯分布的特点,且铜原子的谱线范围略大于弧柱直径,一价铜离子的谱线范围略小于弧柱直径,两种粒子的扩散速度存在差异。     

氩气微腔放电中特性参数的数值模拟研究

本文采用二维自洽完全流体模型,针对阳极为通孔的高气压微腔放电结构,研究了微腔放电的参数特性.数值计算得到了氩气压强为100 Torr,放电稳态时的电势分布、电子数密度分布和电子温度分布等重要参数.模拟结果表明放电区存在显著的阴极鞘层结构,电子数密度的峰值达到10²⁰ m^-3,电子温度的量级为几个eV至十几eV,该结论与实验结果相一致.数值模拟合理的解释了微腔放电的基本原理. 关键词： 微腔放电 等离子体模拟 流体模型     

The Magnetically Confined Electron Cloud Sustained by Thermionic Emission

The electron clouds in high vacuum which are confined by electromagnetic fields and sustained by thermionic emission are studied.The distributions of the electron density,the electron temperature,the drift angular velocity of electrons,the diffusion flow density of electrons and the electric potential in the electron cloud are discussed.     

Particle-in-cell/Monte Carlo simulation of radio frequencySiH4/H2 discharges

In this paper we report on a study of SiH₄/H₂ radio-frequency discharges using the particle-in-cell/Monte Carlo (PIC/MC) method. A special procedure based on the rate balance for negative ions has been developed to speed up the simulation for this kind of electronegative discharge. The electron energy distribution function and the angular and energy distribution function of ions arriving at the substrate have been studied at different discharge settings (frequency, pressure, voltage, and power). The simulations show that the electrons are heated ohmically, so the average electron energy can be increased only by increasing the voltage. A high radical density, a high and more directional ion flux, and a low average ion energy can be obtained by a combination of a high frequency and a low RF voltage. The behavior of the dissociation rate with the discharge parameters is consistent with the experimentally observed consumption of SiH₄. The simulated ion energy distribution functions are in good agreement with experimental results     

EPR and ENDOR study of an oxygen-vacancy-associated Ti center in RbTiOPO4 crystals

The dominant Ti³⁺ trapped electron center in flux-grown RbTiOPO₄ (RTP) crystals has been characterized using electron paramagnetic resonance (EPR) and electron–nuclear double resonance (ENDOR). This center is produced during an X-ray irradiation at room temperature when a Ti⁴⁺ ion traps an electron and becomes a Ti³⁺ ion, and is best studied in the 30–40 K range. The EPR spectrum contains a three-line hyperfine pattern from two nearly equivalent neighboring ³¹P nuclei, along with hyperfine lines from the ⁴⁷Ti and ⁴⁹Ti nuclei. The g matrix, determined from the angular dependence of the EPR spectrum, has principal values of 1.819, 1.889, and 1.947. Hyperfine matrices for four ³¹P nuclei are obtained from the angular dependence of the ENDOR spectrum. The proposed model for this defect is a Ti³⁺ ion adjacent to an oxygen vacancy at an OT position. Analogies are made to a similar Ti³⁺ center in KTiOPO₄ (KTP) crystals.     

圆筒电极对离子磁电加热的影响

高效的磁电加热不仅能够提高电子回旋共振(ECR)等离子体的离子温度,还能改善离子的径向和轴向分布,促进ECR等离子体在化学气相沉积金刚石膜刻蚀中的应用.将磁电加热系统中的圆环电极改进为圆筒电极,研究了圆筒电极对离子磁电加热的影响,对比了圆筒和圆环电极加热离子的区别.结果表明:在同一阳极偏压下,圆筒比圆环电极更有利于提高离子温度,圆筒电极加热时各径向位置的离子温度升高的幅度较大,其中圆筒电极内部的离子温度径向分布差异较大,而圆筒下游的离子温度径向分布比较均匀;磁电加热对离子密度的影响很小;采用圆筒电极加热时,有利于离子向轴向下游的输运,改善了离子的轴向均匀性.     

Charge Flow and Plasma Behavior in Intense Ion Beam Diodes

Intense ion beams are produced in high-power vacuum diodes of various configurations and are believed to be useful for applications in inertial confinement fusion and plasma confinement. Using magnetically insulated diodes, we investigated spatial nonuniformities of the diode plasmas, plasma expansion, ion transverse velocities in the diode gap, electron flow to the anode, and the charge distribution in the gap. Various time-dependent diagnostic techniques including recently developed spectroscopic methods have been used. We observed rapid closure of the diode gap, resulting from fast expansion of the electric field-excluding anode plasma early in the pulse. This contributes significantly to the measured ion current density enhancement. The electron cloud in the gap was seen to spread towards the anode beyond the region of the theoretical electron sheath. This is consistent with observed ion current densities being larger than the values calculated using the actual diode gap. The ion angular spread was found to increase locally due to nonuniform expansion of the cathode plasma for one class of phenomena and of the anode plasma for the other two classes. Part of these phenomena were associated with electron flow to the anode. The ion divergence angle in the gap was observed to be independent of the ion mass and to be significantly smaller than angles previously observed outside the diode.     

30cm口径离子推力器磁场设计

为了对30cm口径离子推力器的磁场设计提出合理建议,研究了四极磁场结构下,不同尺寸的磁极宽度和磁极间距对磁极表面磁场强度和放电室电子约束长度的影响,并利用Maxwell-3D磁场分析软件得到柱段和锥段永磁体分别呈30°,60°和90°夹角时的放电室磁场强度分布,根据不同磁场强度计算了电子温度、离子密度以及电离率等推力器放电参数。结果表明,当推力器放电电压为30V时,磁极长度设计为0.008m且磁极间距取为0.12m,电子约束路径大约为50m;柱段和锥段永磁体分别呈30°,60°和90°夹角时,放电室磁场等势线基本在0.002~0.005T之间;永磁体夹角为60°时磁场分布和磁空区相比30°和90°夹角更为合理,此时的电子温度约在2~6eV,等离子体密度约在4×1017~8×1017 m-3,电子碰撞频率比率约在0.2~1.8范围内。     

ICP等离子体鞘层附近区域发光光谱特性分析

为了独立控制鞘层附近区域离子密度和离子能最分布,采用光发射谱(OES)测量技术,对不同射频功率、放电气压和基底偏压下感应耦合等离子体鞘层附近区域辉光特性进行了研究.原子谱线和离子谱线特性分析表明,在鞘层附近区域感应耦合等离子体具有较高的离子密度和较低的电子温度.改变放电气压和射频功率,对得到的光谱特性分析表明,鞘层附近区域离子密度随射频功率的增大而线性增大,在低压下随气压的升高而增大.低激发电位原子谱线强度增加迅速,高激发电位原子谱线强度增加缓慢,而离子谱线强度增加很不明显.改变基底直流偏压,对得到的发射光谱强度变化分析表明,谱线强度随基底正偏压的增加而增大.随着基底负偏压的加入,谱线强度先减小而后增大;直流偏压为-30 V时,光谱强度最弱.快速离子和电子是引起Ar激发和电离过程的主要能量来源.     

30 cm口径离子推力器磁场设计

为了对30 cm口径离子推力器的磁场设计提出合理建议,研究了四极磁场结构下,不同尺寸的磁极宽度和磁极间距对磁极表面磁场强度和放电室电子约束长度的影响,并利用Maxwell-3D磁场分析软件得到柱段和锥段永磁体分别呈30,60和90夹角时的放电室磁场强度分布,根据不同磁场强度计算了电子温度、离子密度以及电离率等推力器放电参数。结果表明,当推力器放电电压为30 V时,磁极长度设计为0.008 m且磁极间距取为0.12 m,电子约束路径大约为50 m;柱段和锥段永磁体分别呈30,60和90夹角时,放电室磁场等势线基本在0.002~0.005 T之间;永磁体夹角为60时磁场分布和磁空区相比30和90夹角更为合理,此时的电子温度约在2~6 eV,等离子体密度约在41017~81017 m-3,电子碰撞频率比率约在0.2~1.8范围内。     

13.56 MHz/2 MHz柱状感性耦合等离子体参数的对比研究

通过Langmuir双探针和发射光谱诊断方法,对比研究了驱动频率为13.56 MHz和2 MHz柱状感性耦合等离子体中电子密度和电子温度的径向分布规律.结果表明:在高频和低频放电中,输入功率的增加对等离子体参数产生了不同的影响,高频放电中主要提升了电子密度,低频放电中则主要提升了电子温度.固定气压为10 Pa,分别由高频和低频驱动时,电子密度的径向分布均为"凸型".而电子温度的分布差异比较明显,高频驱动时,电子温度在腔室中心较为平坦,在边缘略有上升;低频驱动时,电子温度随径向距离的增加而逐渐下降.为了进一步分析造成这种差异的原因,在相同放电条件下采集了氩等离子体的发射光谱图,利用分支比法计算了亚稳态粒子的数密度,发现电子温度的径向分布始终与亚稳态粒子的径向分布相反.继续升高气压到100 Pa,发现不论高频还是低频放电,电子密度的径向分布均从"凸型"转变为"马鞍形",较低气压时电子密度的均匀性有了一定的提升,但低频的均匀性更好.     

Dynamics of femtosecond laser-produced plasma ions

We investigated the ion laser-produced plasma plume generated during ultrafast laser ablation of copper and silicon targets in high vacuum. The ablation plasma was induced by ≈50 fs, 800 nm Ti:Sa laser pulses irradiating the target surface at an angle of 45°. An ion probe was used to investigate the time-of-flight profiles of the emitted ions in a laser fluence range from the ablation threshold up to ≈10 J/cm². The angular distribution of the ion flux and average velocity of the produced ions were studied by moving the ion probe on a circle around the ablation spot. The angular distribution of the ion flux is well described by an adiabatic and isentropic model of expansion of a plume produced by laser ablation of solid targets. The angular distribution of the ion flux narrows as the laser pulse fluence increases. Moreover, the ion average velocity reaches values of several tens of km/s, evidencing the presence of ions with kinetic energy of several hundred eV. Finally, the ion flux energy is confined in a narrow angular region around the target normal.