Interactions of the directed plasma from a cathodic arc withelectrodes and magnetic fields

Curved magnetic ducts are frequently used to remove macroscopic-sized droplets from the plasma stream of cathodic vacuum arcs. The plasma of a cathodic vacuum arc in a magnetic filter is characterized by a strongly directional ion velocity (corresponding to 20-100 eV) and magnetized electrons. In the first section of this paper the effects of these features on the I-V characteristic curves of planar probes are identified and explained using a simple model. This is then used to interpret the interaction of the plasma with the walls of a biased quarter torus duct. Two small electrodes placed on the outer and inner sections of the curved duct wall show that the I-V characteristic is determined primarily by the electron-ion current balance at the wall on the outside of the curve. The application of a bias to a planar electrode on the outer wall section was found to give the same increase in throughput as a positive bias applied to the entire duct with the advantage of a much smaller electron current being drawn by the biasing power supply. The improvement in duct throughput achievable with positive-biasing of the duct wall was found to depend on both the configuration and strength of the magnetic field in the quarter torus filter. The plasma density profile and potential were unaffected by the application of the bias     

Transport of a cathodic arc plasma in a straight, magnetized duct

Measurements are presented of the transport of a supersonic, cathodic-arc plasma through a straight, magnetized duct. These measurements are compared to previous work on curved ducts, in order to illuminate the effect of duct curvature on the transport. The axial ion flux through the straight duct decays as ions are lost to the walls. This decay is exponential, with a scale length of seven duct radii; this is two to three times longer than in most experiments on curved ducts. The scale length is independent of the magnetic field strength for fields from 5-40 mT. (For this range of magnetic fields, the electron Larmor radius varies from 0.03-0.003 duct radii; while the ion Larmor radius varies from 4-0.5 duct radii.) This differs from previous experiments with curved ducts, where the attenuation length generally increases with magnetic field. Also in contrast to experiments on curved ducts, biasing the duct wall to positive voltages similar to the ion energy produces only a slight decrease in the ion losses to the wall. The observed scale length for ion loss and its independence from the magnetic field strength are in quantitative agreement with a plasma fluid simulation. Differences in plasma transport through straight and curved ducts are discussed     

基于放射性气体源体积的虚拟源刻度技术

大气中放射性气体氙同位素的活度浓度值是判断核裂变反应的关键数据, 长期以来其准确测量一直是个难题. 针对该问题, 本文提出和定义了虚拟点源的概念, 并使用LabSOCS软件模拟了不同尺寸气体体源和不同高度点源的探测效率, 根据计算的数据建立了气体源体积和虚拟点源位置的函数关系. 理论上证实了气体源体积和虚拟点位置有良好的线性关系, 在理论上为解决虚拟源刻度技术提供了新的途径.     

大面积分散电弧等离子体的ICCD图像分析

用增强型电荷耦合检测器(ICCD)和窄带干涉滤光片相结合的方法拍摄了未饱和氩等离子体的分散电弧的非饱和图像。对不同励磁电流下电弧形态的分析比较,证实了在强电磁力的作用下弧柱趋于扩散。在电弧完全分散条件下,对ICCD拍摄非饱和图像的光强分析,表明分散电弧具有较为均匀的分布。所采集的电弧电压的脉动幅度显著降低,分散电弧稳定运行。实验中观测到了稳定的多阴极弧根和弥散阴极弧根的现象,这表明电弧已扩散。     

Study of TiN and ZrN thin films grown by cathodic arc technique

Thin films of TiN and ZrN were grown on stainless steel 316 substrate using the pulsed cathodic arc technique with different number of discharges (one to five discharges). The coatings were characterized in terms of crystalline structure, microstructure, elementary chemical composition and stoichiometric by X-ray diffraction (XRD), atomic force microscopy (AFM) and X-ray photoelectron spectroscopy for chemical analyses (XPS), respectively. The XRD results show that for TiN as for ZrN, the preferential direction occurs in the plane (2 0 0), and this result stays when increasing the number of discharges. The grain size is increased with the increase of the number of discharges for both nitrides, the roughness for the TiN film is greater than for the ZrN film; these results were determined by AFM. XPS analysis determined that there is a higher nitrogen presence in the ZrN film than in the TiN film.     

Designing of a lead ion model source for plasma separation of spent nuclear fuel

Plasma sources of model substances are required for solving problems associated with the development of a plasma separation method for spent nuclear fuel (SNF). Lead is chosen as the substance simulating the kinetics and dynamics of the heavy SNF component. We report on the results of analysis of the discharge in lead vapor with a concentration of 10¹²–10¹³ cm^–3. Ionization is produced by an electron beam (with electron energy up to 500 eV) in the centimeter gap between planar electrodes. The discharge is simulated using the hydrodynamic and one-particle approximations. The current–voltage characteristics and efficiencies of single ionization depending on the vapor concentrations and thermoelectron current are obtained. The experimentally determined ion currents on the order of 100 μA for an ionization efficiency on the order of 0.1% are in conformity with the result of simulation.     

条纹相机在真空弧离子源等离子体诊断中的应用

针对真空弧离子源,利用条纹相机将时间轴信息转换为空间轴信息的特点,结合光谱仪分光功能,建立了一套高时间分辨与光谱分辨能力的发射光谱诊断装置,其时间分辨率和光谱分辨率分别可达26 ps与0.1 nm。利用该诊断装置采集获得了单次脉冲内等离子体的时间演化特性;同时,基于局域热力学平衡等离子体的发射光谱理论,建立了一套谱线拟合的等离子体温度与密度计算模型。相比传统的Boltzmann斜率法与Stark展宽法需要寻找孤立的不受附近谱线叠加的干净线状光谱,建立的拟合光谱模型可以直接处理多条谱线因为展宽效应而叠加形成的光谱线型,计算得到等离子体中电子温度与电子密度。结果表明,在脉冲功率源的作用下,真空弧放电等离子体的电子温度与电子密度分别可达1 eV与3.51024 m-3。     

条纹相机在真空弧离子源等离子体诊断中的应用

针对真空弧离子源,利用条纹相机将时间轴信息转换为空间轴信息的特点,结合光谱仪分光功能,建立了一套高时间分辨与光谱分辨能力的发射光谱诊断装置,其时间分辨率和光谱分辨率分别可达26ps与0.1nm。利用该诊断装置采集获得了单次脉冲内等离子体的时间演化特性;同时,基于局域热力学平衡等离子体的发射光谱理论,建立了一套谱线拟合的等离子体温度与密度计算模型。相比传统的Boltzmann斜率法与Stark展宽法需要寻找孤立的不受附近谱线叠加的干净线状光谱,建立的拟合光谱模型可以直接处理多条谱线因为展宽效应而叠加形成的光谱线型,计算得到等离子体中电子温度与电子密度。结果表明,在脉冲功率源的作用下,真空弧放电等离子体的电子温度与电子密度分别可达1eV与3.5×1024 m-3。     

Bias voltage effect on the structure and property of chromium copper-diamond-like carbon multilayer films fabricated by cathodic arc plasma

Chromium copper-diamond-like carbon (Cr:Cu)-DLC films were deposited onto silicon and by cathodic arc evaporation process using chromium (Cr) and copper (Cu) target arc sources to provide Cr and Cu in the Me-DLC. Acetylene reactive gases were the carbon source and activated at 180 °C at 13 mTorr, and a substrate bias voltage was varied from −50 V to −200 V to provide the (Cr:Cu)-DLC structure. The structure, interface, and chemical bonding state of the produced film were analyzed by transmission electron microscope (TEM), IR Fourier transform (FTIR) spectra, and X-ray photoelectron spectroscopy (XPS). The results showed that the Cr-containing a-C:H/Cu coatings exhibited an amorphous layer of DLC:Cr layer and a crystalline layer of Cu multilayer structure. The profiles of sp³/sp² (XPS) ratios corresponded to the change of microhardness profile by varying the pressure of the negative DC bias voltage. These (Cr:Cu)-DLC coatings are promising materials for soft substrate protective coatings.     

Potential possibilities of a laser plasma as a negative-ion source

The potential possibilities of a plasma heated by laser radiation as a negative-ion source are analyzed theoretically. It is shown that the efficiency of negative-ion formation in a laser plasma in the heating phase reaches 10¹⁵−10¹⁶ ions/J when the parameters of the laser radiation are optimally adjusted. Zh. Tekh. Fiz. 67, 117–120 (July 1997)     

Steady-state thermonuclear plasma as a source of nuclear-physics data

Measurements of cross sections of nuclear reactions of charged particles in the kiloelectron-volt range present a difficult experimental problem because of their small size. At the same time, the need for accuracy in the determination of such cross sections continues to grow in connection with the active development of such branches of science as controlled thermonuclear fusion, astrophysics, cosmology, and nuclear physics itself. The present communication discusses the motivation for performing experiments in this energy range and the difficulties such experiments involve, and proposes a new experimental approach to measuring the cross sections of such reactions using the steady-state plasmas available in thermonuclear facilities. Zh. Tekh. Fiz. 69, 114–118 (January 1999)     

Time characteristics of an ion flux from the cathodic space of a vacuum arc

Time measurements of an ion flux from a vacuum arc are carried out with a one-channel electrostatic energy analyzer combined with a time-of-flight mass spectrometer. It is found that (i) the ion flux consists of a train of intense pulses, (ii) the charge composition of the flux varies considerably from pulse to pulse, and (iii) the most intense peak corresponds to the instant of arc quenching.     

Generation and expansion of laser-induced plasma as a spectroscopic emission source

Laser-induced plasma represents today a widespread spectroscopic emission source. It can be easily generated using compact and reliable nanosecond pulsed laser on a large variety of materials. Its application for spectrochemical analysis for example with laser-induced breakdown spectroscopy (LIBS) has become so popular that one tends to forget the complex physical and chemical processes leading to its generation and governing its evolution. The purpose of this review article is to summarize the backgrounds necessary to understand and describe the laser-induced plasma from its generation to its expansion into the ambient gas. The objective is not to go into the details of each process; there are numerous specialized papers and books for that in the literature. The goal here is to gather in a same paper the essential understanding elements needed to describe laser-induced plasma as results from a complex process. These elements can be dispersed in several related but independent fields such as laser-matter interaction, laser ablation of material, optical and thermodynamic properties of hot and ionized gas, or plasma propagation in a background gas. We believe that presenting the ensemble of understanding elements of laser-induced plasma in a comprehensive way and in limited pages of this paper will be helpful for further development and optimized use of the LIBS technique. Experimental results obtained in our laboratory are used to illustrate the studied physical processes each time such illustration becomes possible and helpful.     

A reflex electron beam discharge as a plasma source for electronbeam generation

A reflex electron beam glow discharge has been used as a plasma source for the generation of broad-area electron beams. An electron current of 120 A (12 A/cm²) was extracted from the plasma in 10 μs pulses and accelerated to energies greater than 1 keV in the gap between two grids. The scaling of the scheme for the generation of multikiloamp high-energy electron beams is discussed     

New plasma source of atomization based on a flame and electric arc and its application in atomic spectrometry

Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 50, No. 1, pp. 154–158, January, 1989.     

Small plasma focus studied as a source of hard X-ray

An experimental study on hard X-ray pulses emitted by a small plasma focus is performed, regarding its application to biological radiographs in fast dynamic situations. It is found that the radiation intensity in a single shot is high enough to obtain fine resolution radiographs in very short exposures (about 10 ns). As an example, a radiograph on a live mouse is shown. It is found that the relation between responses of different detectors, i.e., thermoluminescence dosimeters and scintillator-photomultiplier, is linear     

Demonstration of a widely tunable digital supermode distributed Bragg reflector laser as a versatile source for near-infrared spectroscopy

In this paper we report the characterization of a novel, widely tunable, diode laser source operating over the full telecom L-band (1563–1613 nm), namely the digital supermode distributed Bragg reflector (DS-DBR) laser, and its application to multi-wavelength gas sensing via absorption strategies. The spectroscopic performance of the laser has been assessed by investigating the ro-vibrational spectrum of CO₂, and wavelength modulation spectroscopy was accomplished for proof-of-principle sensitive measurements in discrete spectral regions.     

带状真空电弧磁过滤器等离子体分布特性及制备类金刚石膜研究

采用大尺寸矩形石墨靶作为真空阴极电弧源, 研制了带状真空电弧磁过滤器. 使用法拉第杯和朗缪尔探针对90 ℃弯曲磁过滤器中的带状等离子体出口所在平面的15个区域的离子能量和密度进行了测试; 用该带状真空电弧磁过滤器制备了类金刚石膜(diamond-like carbon, DLC); 对相应位置上的类金刚石膜进行了Raman分析和膜厚测量. 结果表明: 磁过滤器出口所在平面的15个划分区域中离子能量分布接近麦克斯韦分布, 离子能量分布与类金刚石膜的结构具有明显的对应特征, 离子密度分布与DLC膜膜厚分布相互之间具有相关性.