Optics of ion beams for the neutral beam injection system on HL-2A Tokamak

The ion beam optics for the neutral beam injection system on HL-2A Tokomak is studied by two- dimensional numerical simulation program firstly, where the emitting surface is taken at 100 Debye lengths from the plasma electrode. The mathematical formulation, computation techniques are described. Typical ion orbits, equipotential contours, and emittance diagram are shown. For a fixed geometry electrode, the effect of plasma density, plasma potential and plasma electron temperature on ion beam optics is examined, and the calculation reliability is confirmed by experimental results. In order to improve ion beam optics, the application of a small pre-acceleration voltage (～100 V) between the plasma electrode and the arc discharge anode is reasonable, and a lower plasma electron temperature is desired. The results allow optimization of the ion beam optics in the neutral beam injection system on HL-2A Tokomak and provide guidelines for designing future neutral beam injection system on HL-2M Tokomak.     

Simulating ion beam extraction from a single aperture triode acceleration column: a comparison of the beam transport codes IGUN and PBGUNS with test stand data

Ion beam extraction from two different ion sources with single aperture triode extraction columns was simulated with the particle beam transport codes PBGUNS and IGUN. For each ion source, the simulation results are compared to experimental data generated on well-equipped test stands. Both codes reproduced the qualitative behavior of the extracted ion beams to incremental and scaled changes to the extraction electrode geometry observed on the test stands. Numerical values of optimum beam currents and beam emittance generated by the simulations also agree well with test stand data.     

非对称双曲面线形离子阱的设计及性能研究

为提升离子阱质量分析器的分析性能,本文提出一种非对称双曲面线形离子阱结构,通过优化离子出射方向上x电极的单向拉伸距离Δr_a,引入合理的非对称射频电场,从而提高离子单向出射效率。利用SIMION和AXSIM模拟软件分析非对称双曲面线形离子阱的内部电场分布、离子运动轨迹及模拟质谱图。结果表明,在性能优化的对称双曲面线形离子阱结构的基础上,其中1个x电极单向拉伸Δr_a=0.8 mm时,通过优化AC频率和扫描速率等参数,非对称双曲面线形离子阱的离子单向出射率可达90%以上,同时m/z 609离子的质量分辨率超过5 100。经优化几何结构后的非对称双曲面线形离子阱可在保证高质量分辨率的情况下,大幅提高离子检测效率,这在小型化质谱仪的开发中具有显著的优势。     

基于微机电系统加工技术的微小型矩形离子阱的研制

矩形离子阱（RIT）不仅具有线性离子阱（LIT）捕获效率高和存储容量大等特点,还兼具圆柱形离子阱（CIT）易加工和装配的优点,具有小型化的优势。为了使RIT进一步微小型化,本研究采用微机电系统（MEMS）和激光切割技术加工微小型RIT,并通过模拟仿真分析RIT的各项参数与其内部电场成分的关系。结果表明：固定离子阱非出射方向的场半径为1.4 mm,拉伸离子出射方向的场半径为1.60 mm,在电极厚度为50 μm时,分析m/z 119离子的质量分辨率可达到452。使用MEMS工艺可制备高精度、微米级的微小型RIT。质谱分析表明,制备的微小型RIT对m/z 391的邻苯二甲酸二辛酯具有高于500的质量分辨能力,该结果验证了其结构设计的正确性以及MEMS工艺制备的可行性,为矩形离子阱的进一步微小型化奠定了良好基础。     

EIT系统复合电极结构性能分析及优化设计

本文研究了医学电阻抗成像（MEIT）系统复合电极结构对敏感场分布的影响，并提出了一个具有边界强制等势点的有限元模型，通过计算机仿真，分析了复合电极宽度对敏感场分布的影响，并对不同激励模式下敏感电极的结构尺寸进行了优化设计。     

Compact electrostatic beam optics for multi-element focused ion beams: simulation and experiments

Electrostatic beam optics for a multi-element focused ion beam (MEFIB) system comprising of a microwave multicusp plasma (ion) source is designed with the help of two widely known and commercially available beam simulation codes: AXCEL-INP and SIMION. The input parameters to the simulations are obtained from experiments carried out in the system. A single and a double Einzel lens system (ELS) with and without beam limiting apertures (S) have been investigated. For a 1 mm beam at the plasma electrode aperture, the rms emittance of the focused ion beam is found to reduce from ～0.9 mm mrad for single ELS to ～0.5 mm mrad for a double ELS, when S of 0.5 mm aperture size is employed. The emittance can be further improved to ～0.1 mm mrad by maintaining S at ground potential, leading to reduction in beam spot size (～10 μm). The double ELS design is optimized for different electrode geometrical parameters with tolerances of ±1 mm in electrode thickness, electrode aperture, inter electrode distance, and ±1° in electrode angle, providing a robust design. Experimental results obtained with the double ELS for the focused beam current and spot size, agree reasonably well with the simulations.     

Plasma characterization of dry ��-EDM

An attempt was made to characterize the dry microelectric discharge machining (??-EDM) plasma systematically by using optical emission spectroscopy. In order to characterize the plasma and its parameters such as plasma temperature, electron density, Debye length, and gamma parameter, the optical spectra were recorded for different energies and with different diameters of tool electrode. From the recorded spectra, using line pair method and modified Saha equation, plasma temperature and electron density, respectively were calculated. From these two, Debye length and plasma parameter were also calculated. These studies indicate that the plasma produced in dry ??-EDM is ideal. In addition to this, we found that the dry ??-EDM region is below the conventional EDM region in log electron density and log temperature plot. Morphological analysis was carried out on crater produced by different energies on the workpiece using a scanning electron microscope. The crater shape may dependent on the geometry of the tool tip, number of discharges, and energy of discharge.     

Improved analysis techniques for cylindrical and spherical double probes

A versatile double Langmuir probe technique has been developed by incorporating analytical fits to Laframboise's numerical results for ion current collection by biased electrodes of various sizes relative to the local electron Debye length. Application of these fits to the double probe circuit has produced a set of coupled equations that express the potential of each electrode relative to the plasma potential as well as the resulting probe current as a function of applied probe voltage. These equations can be readily solved via standard numerical techniques in order to determine electron temperature and plasma density from probe current and voltage measurements. Because this method self-consistently accounts for the effects of sheath expansion, it can be readily applied to plasmas with a wide range of densities and low ion temperature (T(i)∕T(e) ? 1) without requiring probe dimensions to be asymptotically large or small with respect to the electron Debye length. The presented approach has been successfully applied to experimental measurements obtained in the plume of a low-power Hall thruster, which produced a quasineutral, flowing xenon plasma during operation at 200 W on xenon. The measured plasma densities and electron temperatures were in the range of 1 × 10(12)-1 × 10(17) m(-3) and 0.5-5.0 eV, respectively. The estimated measurement uncertainty is +6%∕-34% in density and +∕-30% in electron temperature.     

Instrumentation News

Abstract

Two procedure files were created to automate the processing of mass spectral (MS) data files. The procedure file, RJR, was used to set up the sequence of mass spectral data files to be processed, to input the parameters for printout format, and to automatically execute the processing of the mass spectral data files. The other procedure file, RJRAQ, was used to execute the processing of mass spectral data. RJRAQ produced header information of the mass spectral data files and the integration information, generated graphic displays of the total ion chromatogram (TIC), mass spectra, and library search results, and provided hard copies of all textual reports and graphic outputs.

Several mass spectral data files, generated from the GC/MS system were used to demonstrate the automated processing of mass spectral data files.     

非对称三角形电极离子阱的单向出射性能模拟研究

三角形电极离子阱（triangular-electrode linear ion trap, TeLIT）是一种新型结构的线性离子阱,具有简单的电极结构和良好的分析性能。为进一步提高TeLIT的离子探测效率,本实验将离子出射方向的2个电极设置为不同角度,建立非对称结构的TeLIT,通过引入非对称场实现离子单向出射。通过分析电极角度差与其内部电场分布的关系,并模拟离子运动轨迹,获得离子出射情况和模拟质谱峰。理论模拟结果显示：当离子出射方向三角电极的角度差Δα=15°时,在优化的AC频率条件下,三角形电极离子阱的m/z 610离子单向出射率可达95%以上,且质量分辨率达到2647。经优化几何参数后的非对称三角形电极离子阱可在几乎不损失分辨率的情况下实现离子单向出射,大幅提高了单检测器模式下TeLIT的离子探测效率和仪器的灵敏度,使其在小型化质谱仪的开发中具有显著优势。     

Subcutoff microwave driven plasma ion sources for multielemental focused ion beam systems

A compact microwave driven plasma ion source for focused ion beam applications has been developed. Several gas species have been experimented including argon, krypton, and hydrogen. The plasma, confined by a minimum B multicusp magnetic field, has good radial and axial uniformity. The octupole multicusp configuration shows a superior performance in terms of plasma density (~1.3 x 10(11) cm(-3)) and electron temperature (7-15 eV) at a power density of 5-10 Wcm(2). Ion current densities ranging from a few hundreds to over 1000 mA/cm(2) have been obtained with different plasma electrode apertures. The ion source will be combined with electrostatic Einzel lenses and should be capable of producing multielemental focused ion beams for nanostructuring and implantations. The initial simulation results for the focused beams have been presented.     

基于DXF文件的自动编程系统研究

基于DXF文件进行数控NC代码的自动生成，并对数控代码进行传榆，实现设计与加工的一体化。这里研究了DXF文件与数控NC代码对零件信息描述的差异，给出合适的解决方法，并应用面向对象的程序设计方法进行系统的实现。系统在工程实际中得到很好的应用。     

Measurement of H- density in plasma by photodetachment

Techniques have been developed for measurement of the density of H- in a plasma by photodetachment. Photodetachment is detected by the increase in electron density with no change in positive ion density after a light pulse from a ruby laser. The authenticity of photodetachment signals can be assured by their comparison with known cross sections for photodetachment of H-. Interpretations of photodetachment data are less ambiguous than probe interpretations because photodetachment is not affected by the mass of positive ions and is not limited in usefulness by the Debye distance. Photodetachment measurements with time resolution and spatial resolution are straightforward.     

电压不稳定性对离子阱中离子运动特征的影响

在离子阱共振激发过程中,电压的微小变化可能导致离子的运动特征发生显著改变。本工作基于赝势理论,建立了电压不稳定时3D离子阱中离子运动的理论模型,并以辅助交流电压AC的毛刺和端盖电极施加的直流电压为例,揭示端盖电极上辅助交流电压AC的稳定性对离子阱性能的影响。结果表明,当辅助交流电压存在毛刺时,离子的运动速度和振幅将发生突变,扰乱离子阱内离子的冷却状态,致使部分离子在激发阶段打在阱壁上而无法被检测,从而降低了离子阱质谱仪的灵敏度。同时,该模型表明,对于处于冷却状态的离子,可以通过测量其在脉冲激励作用下的响应来测量离子运动的久期频率。若在端盖电极上施加直流电压,离子运动的平衡位置将发生明显的偏移,通过将离子检测器置于偏移的一侧,可以明显地提高离子的检测效率,从而提高离子阱质谱仪的灵敏度。     

环件冷辗扩有限元模拟中网格的自适应加密

为保证环件冷辗扩有限元模拟中网格的可靠性和计算效率,提出了一种基于单元几何特征的六面体网格自适应加密方法,实现了根据单元与模具干涉和网格畸变来自动控制网格的疏密,以获得最优化的网格和计算结果;网格剖分采用基于提取表面单元和继承层单元拓扑信息的方法,对初始网格直接进行剖分,不仅适应性广,而且有利于场变量的传递;最后通过算例验证了该自适应加密方法的有效性。     

中走丝线切割自动编程系统研究

对线切割自动编程系统进行了研究,将自动编程系统的系统构架划分为基础功能模块、DXF文件读写模块、图形绘制与编辑模块、图形文件预处理与刀具轨迹生成模块、加工仿真与代码输出模块。重点研究了系统的数据结构、DXF文件图形信息提取与处理方法、电极丝轨迹生成等关键技术,开发了基于VC＋＋的中走丝线切割自动编程系统,简化了线切割加工程序编制。     

电感耦合等离子体质谱仪中离子轨迹的计算机模拟和研究

本文使用SIMION软件,对ICPMS离子光学系统中的离子轨迹进行模拟,定性研究了Einzel透镜和Bessel箱的位置及不同离子能量对离子收集角度范围的影响;为收集光轴附近高密度粒子区中的离子,创新地引入前置极,以提高仪器的灵敏度。     

压力传感器仿真平台软件的设计

基于Visual C++和ANSYS有限元软件,开发了压力传感器仿真平台分析软件.借助Visual C++前台开发友好、方便、易用的人机交互界面,对压力传感器隔离膜片仿真分析,建立仿真平台,为压力传感器在膜片设计上提供了理论依据.根据输入参数自动生成APDL代码文本,然后在ANSYS中运行该APDL代码文本,分析结果可直接在程序中查看.     

基于VB和ANSYS的塔式起重机臂架参数化设计

用ANSYS软件提供的参数化设计语言(APDL)建立的智能分析方法,为零件参数化有限元分析提供了有力的工具.介绍了基于VB与ANSYS的参数化有限元分析方法,并以塔式起重机吊臂有限元分析为例,说明了其实现方法,根据输入参数自动生成APDL代码文本,然后在ANSYS中运行该APDL代码文本,分析结果可直接在程序中查看.     

Spatially resolved charge-state and current-density distributions at the extraction of an electron cyclotron resonance ion source

In this paper we present our measurements of charge-state and current-density distributions performed in very close vicinity (15 mm) of the extraction of our hexapole geometry electron cyclotron resonance ion source. We achieved a relatively high spatial resolution reducing the aperture of our 3D-movable extraction (puller) electrode to a diameter of only 0.5 mm. Thus, we are able to limit the source of the extracted ion beam to a very small region of the plasma electrode's hole (? = 4 mm) and therefore to a very small region of the neutral plasma sheath. The information about the charge-state distribution and the current density in the plane of the plasma electrode at each particular position is conserved in the ion beam. We determined the total current density distribution at a fixed coaxial distance of only 15 mm to the plasma electrode by remotely moving the small-aperture puller electrode which contained a dedicated Faraday cup (FC) across the aperture of the plasma electrode. In a second measurement we removed the FC and recorded m/q-spectra for the different positions using a sector magnet. From our results we can deduce that different ion charge-states can be grouped into bloated triangles of different sizes and same orientation at the extraction with the current density peaking at centre. This confirms observations from other groups based on simulations and emittance measurements. We present our measurements in detail and discuss possible systematic errors.