低气压下占空比对细长管空心阴极辉光放电电流的影响

为了在细长管内壁获得性能良好质地均匀的膜层,本文在低气压条件下、采用细长管作真空阴极进行空心阴极辉光等离子体放电。通过研究对多种气氛(纯Ar、纯N₂、氮气氩气混合)下平均电流、电流峰值的实时测量对比了不同脉冲占空比条件下等离子体放电流,讨论和分析了多气氛下改变占空比所带来的影响。实验结果显示使用频率为40 kHz的脉冲电源,随着占空比变化,脉冲电流波形有显著变化。不同气氛波形不同,但是峰值均提高,平均电流也都上升,纯Ar气氛从20%占空比提高到70%占空比电流峰值从0.325 A上升到了0.5 A,平均电流由0.12 A上升到了0.28 A。测量管内不同位置电流的值,发现管内整体电流均匀性纯Ar和混合气氛优于纯N₂,Ar在30%~60%占空比区间内,表征均匀性的参数K30%~60%≈0.12。     

大气压氦气射频介质阻挡辉光放电的均匀性研究

为了研究大气压射频介质阻挡辉光放电的时空特性,采用一个表面覆盖有石英介质的铜电极和一个自制水电极的放电系统,在氦气中获得了大面积和较大电极间距下的辉光放电。对ICCD高速相机拍摄的径向放电图像和轴向放电图像分析揭示了射频介质阻挡辉光放电不仅具有较好的径向均匀性,而且具有很好的轴向均匀性,并不存在沿径向的发展。这是不同于中频介质阻挡辉光放电的一个显著特征。此外,注意到射频介质阻挡辉光放电在径向和轴向上的发展均与射频周期有很强的关联性。分析认为这是由于空间电荷在射频介质阻挡辉光放电的形成和发展中发挥主导作用。因此,可以认为射频介质阻挡辉光放电所具备非常好的径向和轴向均匀性,与中频介质阻挡辉光放电相比,可能会更有利于工业生产中进行均匀薄膜沉积和对薄膜表面改性处理等。     

SiH4辉光放电的质谱研究

本文报道了采用四极质谱计在制备ａＳｉ∶Ｈ薄膜的ＰＣＶＤ系统中对ＳｉＨ４射频辉光放电进行在线的质谱研究。获取了在不同电离电压下的ＳｉＨ４质谱和不同辉光放电功率下的ＳｉＨ４质谱。     

The National High Magnetic Field Laboratory: Condensed Matter Science in Continuous Magnetic Fields

The National High Magnetic Field Laboratory (NHMFL) operates three facilities in support of magnet-related research. The main facilities are located at Florida State University, Tallahassee, Florida, the ultra-low-temperature high-magnetic-field facilities are located at the University of Florida, Gainesville, Florida, and the pulsed field facilities are located at the Los Alamos National Laboratory, Los Alamos, New Mexico. These facilities support a wide variety of magnet-related research capabilities that are open to all qualified users through a peer-reviewed proposal process. This paper summarizes the research capabilities at the DC facilities at the main facility of the NHMFL and the High B/T Facility at the University of Florida. A few select scientific achievements in the high field condensed matter sciences are presented to highlight the research capabilities available to all users. The NHMFL is supported by the United States National Science Foundation and the State of Florida.     

Formation of a Thin Luminescent Layer in LiF Crystals under Glow Discharge Radiation

The formation of thin layers of luminescent defects on the faces of planar lithium fluoride crystals located in the positive column and Faraday dark space of a glow gas discharge was studied by time-resolved confocal scanning luminescent microscopy and time-correlated single photon counting. The formation of aggregated color centers in the surface layers of crystals was established using the spectral and kinetic characteristics of luminescence appearing after irradiation. The role of gas discharge electrons, ions, and photons in the defect formation mechanism was considered. The defects were shown to be formed under the influence of vacuum ultraviolet (VUV) photons. The VUV radiation intensity distribution in the discharge gap was measured by the method of thermostimulated luminescence. The main source of this radiation was the anodic and cathodic voltage drop regions in a glow discharge.     

双辉法渗金属锯条炉的温度场研究

利用格林函数，格林函数对称性和δ－函数积分性质导出温度场的分布表达式，Ｔ（ｒ）＝１／４πｋ∫ｖＧ（ｒ，ｒ′）ｆ（ｒ′）ｄＶ＋ｈ／４π∫ｓＧ（ｒ，ｒ′）Ｔ０（ｒ′）ｄＳ它表明，温度场的分布决定于炉内热源性分布和边界面温度分布，提出改善炉内温度分布所尖求取的措施，随机抽样分析结果显示，采取这些措施后温度场分布均匀性得到相当大的改善。     

Microwave Study of Surface Electrons on Helium Films in a Magnetic Field

We report preliminary results of a cyclotron resonance study of surface electrons (SE) on saturated helium films covering a PMMA substrate at T > 1 K. The real and imaginary parts of the dielectric response (k,) of the SE are measured at fixed k and in B-fields up to 10 T in a 12 GHz cavity. The cyclotron resonance of the SE is determined at different helium film thicknesses d _He and at various electron densities. At small d _He we find significant anomalies in the cyclotron resonance lineshape and position. As d _He increases the lineshape becomes progressively more symmetric and its peak moves towards the cyclotron field value expected for a free electron. To fit these data we have modified the classical Drude expression, introducing two different relaxation times for the low and high B-field regions. The phenomenological formulas fit the data quite well. A systematic theoretical analysis of these results is in progress.     

Breakdown of High-Pressure Gases in a Longitudinal Magnetic Field

High Temperature - It was discovered experimentally that a longitudinal magnetic field leads to an increase in the current density, conductivity, and partial energy input and a decrease in the...     

Search for the Stabilizing Effect of Magnetic Field on a Gas of He 2 * Excitations in Liquid Helium Phases

The absorption spectra of triplet He ₂ ^* metastable molecules in normal liquid ³ He under various pressures have been observed for the first time. Molecules are generated as a result of recombination of positive and negative ions extracted from discharge regions near sharp tips operated in field-emission/field-ionization modes. We have shown experimentally that this method allows one to create measurable concentrations of triplets without essential overheating of normal liquid in the cell. The decay of the molecules after the current through the cell is turned off have been studied in various magnetic fields up to 5.5 T. Experimental values of the mutual recombination coefficient agree with the theory of diffusion-limited recombination of excimers and show no effect of the magnetic field. The magnetic relaxation time is found to exceed 200 msec under all conditions studied.     

The Influence of a Magnetic Field on Anomalous Electron Transport in a Quasi-Two-Dimensional Electron System over Liquid Helium

No Heading The magnetoresistance _xx in a quasi-two-dimensional electron system over liquid helium has been measured for magnetic fields up to 2 T in the temperature range 0.5 – 1.7 K. It has been shown that the behavior of the value of _xx as a function of a magnetic field B in the temperature region 1.2 – 1.7 K and at temperature T < 0.9 K is different. At high temperatures the negative magnetoresistance is observed due to weak localization of carriers, at T < 0.9 K the _xx increases monotonically under increasing B. It is supposed that such a difference in the behavior of the _xx is connected with the different character of the electron scattering: elastic at high temperatures, in the region of gas scattering, and inelastic at low temperatures. The last effect gives an additional evidence either for spatial ordering of electrons or for the formation of electron polarons in quasi-two- dimensional channels.PACS numbers: 73.20.Dx; 73.90.+f     

多模式旋转磁场对电弧离子镀弧斑放电的影响分析

电弧离子镀工艺中,弧斑的放电形式、运动速率、运动方式的控制对于减少以至消除大颗粒的发射至关重要。本文采用自主研发的机械式旋转磁控弧源,围绕三种不同模式的旋转磁场下弧斑的放电行为及规律进行了研究,并从弧斑放电的物理机制出发,分析讨论了不同模式的旋转磁场对阴极斑点运动的影响机理。研究结果表明,多模式旋转磁场可以有效提高弧斑的运动速度、扩大放电面积、降低放电功率密度、减少大颗粒的发射,同时还能够大幅度提高靶材的利用率,拓展电弧离子镀的应用。     

辉光离子氮化对马氏体不锈钢性能的影响

对1Crl3马氏体不锈钢进行了辉光离子氮化处理试验,并对氮化试样的金相和硬度进行了分析测定.结果表明520℃辉光离子氮化8h,使1Crl3马氏体不锈钢的氮化层深度达到0.25mm,最高硬度达到HV732,约为基体硬度的4倍.     

The Effect of Magnetic Field on a Quantum Rod Qubit

The Hamiltonian of a quantum rod (QR) with an ellipsoidal boundary is given after a coordinate transformation, which changes the ellipsoidal boundary into a spherical one. We then study the eigenenergies and eigenfunctions of the ground and the first excited states of an electron strongly coupled to the LO-phonon in the QR under a magnetic field. The present system may be used as a two-level qubit. When the electron is in the superposition state of the ground and the first excited states, we obtained the time evolution of the electron probability density oscillating in the QR. It is found that the magnitude of the probability density is increased by the magnetic field, whereas it decreases the oscillation period of the probability density. The oscillation period is a increasing function of the ellipsoid aspect ratio, the transverse and longitudinal effective confinement lengths of the QR, but a decreasing one of the electron-phonon coupling strength and the cyclotron frequency of the magnetic field.     

The Effect of External Magnetic Field on a Vacuum Arc

The effect of an external longitudinal magnetic field on the time required for anode spot formation in a high-current (5 to 12 kA) vacuum arc is experimentally studied, and the minimal value of a magnetic field inhibiting the anode spot formation is determined. The experimental results are compared with theory. The phenomenon of break of current in a low-current (100 to 300 A) vacuum discharge upon superposition of a magnetic field with transverse component on the discharge is investigated. The probability of break of current increases with the magnetic field. The possible mechanism of break of current is discussed.     

稳恒强磁场对Al-Cu扩散偶界面中间相形成和生长的影响

研究了稳恒强磁场作用下Al-Cu扩散偶界面中间相组成和扩散行为.结果表明:强磁场作用下扩散偶中间相厚度显著增加,并且随磁场强度增大,界面中间相组成发生变化.按照抛物线规律计算了强磁场作用下扩散偶中间相的扩散系数,发现在平行和垂直于磁场的两个方向上扩散系数有显著差异,垂直于磁场方向的扩散系数比平行于磁场方向更大.强磁场促进了Al-Cu扩散偶中Al和Cu原子的扩散,加速了界面中间相的形成和生长过程.磁场作用差异导致了扩散的各向异性.利用原子扩散理论初步分析了产生上述现象的原因.     

工作参数对磁场增强高功率脉冲磁控溅射放电特性的影响

研究磁场增强高功率脉冲磁控溅射技术的放电特性在不同工作参数下的演变规律。利用数字示波器采集HiPIMS的基体离子电流用于表征其放电特性的变化。结果表明:靶放电电压不同时基体离子电流对工作气压的响应不同, 较低靶电压时基体离子电流平均值随工作气压的增加逐渐增加;而较高靶电压时基体离子电流平均值随工作气压增加迅速增加后趋于稳定。基体离子电流随基体偏压的变化表现出两个特征, 较低基体偏压时的基体离子电流在脉冲开始阶段呈现出较强的电子流波段, 而基体偏压较高时则未出现电子流。不同脉冲频率及靶电压下的基体离子电流的波形形状大致相似, 但当处于较高靶电压时存在一个明显特征, 即当脉冲结束后离子流会出现一个尖锐峰值。随脉冲宽度的增加, 基体离子电流负向电子流和正向离子流均逐渐增大。     

磁场对等规聚丙烯结晶行为的影响

随着磁场技术的发展,人们发现磁场对高分子领域所涉及的许多方面会产生影响。文中研究了等规聚丙烯在外加磁场作用下熔融再结晶的过程。研究结果表明,聚丙烯在熔融状态下易受外磁场的作用而产生诱导偶极,结晶时比未加磁场作用的分子链的构象更加有序而趋于定向结晶,熔点(Tm)升高,片晶相对于外加磁场方向择优取向并生成了明显的串晶结构。这为研究磁场对结晶高分子材料的作用机理提供了更具体的事实依据。     

The Effect of the Angular and Radial Distributions of Trajectories on the Structure of Axisymmetric Electron and Ion Beams with Compensated Charge in a Longitudinal Magnetic Field

The structure of beams with compensated charge is described using a multiflow collisionless model in which the current is split into N interacting tubes of current. The effect of the boundary angular distribution of the tubes of current, as well as of the boundary radial distribution of current, on the configuration of electron and ion beams is studied. It is demonstrated that a crisis of flow arises in the absence of an external magnetic field at a certain value of current. An external longitudinal magnetic field expands the region of noncritical flow and promotes the laminarity of flow. The boundaries of the critical mode are determined for different angular and radial distributions, and the trajectories of the tubes of current in the subcritical and supercritical regions are calculated.     

Research of the Effects of Electron Focused Electric Field upon an Enhanced Glow Discharge Plasma Ion Implantation

A new Enhanced Glow Discharge Plasma Ion Implantation methods are introduced, in which the plasma are produced by the self glow discharge excitated by high negative voltage bias. The electric field is designed to a electron focusing mode by using a small area hollow anode and a large area sample holder cathode. The pattern of equipotentials of the electric field are calculated through finite-element method. By using the special electron-focusing field, the self glow discharge are enhanced and provide denser ions to implanted into the substrate.