Scintillating screens sensitivity and resolution studies for low energy, low intensity beam diagnostics

In order to investigate the limits of scintillating screens for beam profile monitoring in the ultra-low energy, ultra-low intensity regime, CsI:Tl, YAG:Ce, and a Tb glass-based scintillating fiber optic plate (SFOP) were tested. The screens response to 200 and 50 keV proton beams with intensities ranging from a few picoampere down to the subfemtoampere region was examined. In the following paper, the sensitivity and resolution studies are presented in detail for CsI:Tl and the SFOP, the two most sensitive screens. In addition, a possible use of scintillators for ultra-low energy antiproton beam monitoring is discussed.     

An advanced molecule-surface scattering instrument for study of vibrational energy transfer in gas-solid collisions

We describe an advanced and highly sensitive instrument for quantum state-resolved molecule-surface energy transfer studies under ultrahigh vacuum (UHV) conditions. The apparatus includes a beam source chamber, two differential pumping chambers, and a UHV chamber for surface preparation, surface characterization, and molecular beam scattering. Pulsed and collimated supersonic molecular beams are generated by expanding target molecule mixtures through a home-built pulsed nozzle, and excited quantum state-selected molecules were prepared via tunable, narrow-band laser overtone pumping. Detection systems have been designed to measure specific vibrational-rotational state, time-of-flight, angular and velocity distributions of molecular beams coming to and scattered off the surface. Facilities are provided to clean and characterize the surface under UHV conditions. Initial experiments on the scattering of HCl(v = 0) from Au(111) show many advantages of this new instrument for fundamental studies of the energy transfer at the gas-surface interface.     

An electron energy loss spectrometer designed for studies of electronic energy losses and spin waves in the large momentum regime

Based on 143° electrostatic deflectors we have realized a new spectrometer for electron energy loss spectroscopy which is particularly suitable for studies on surface spin waves and other low energy electronic energy losses. Contrary to previous designs high resolution is maintained even for diffuse inelastic scattering due to a specific management of the angular aberrations in combination with an angle aperture. The performance of the instrument is demonstrated with high resolution energy loss spectra of surface spin waves on a cobalt film deposited on the Cu(100) surface.     

Production of flat top beam profiles for high energy lasers

Production of uniform (flat top) high energy laser beam profiles with relatively little beam energy loss is possible through the use of a modified kaleidoscope, multiple reflection beam scrambler.     

传递函数方法在复杂曲梁计算中的应用

曲梁在机械工程中的应用非常广泛,例如吊钩、链环等,因此对曲梁进行力学分析和变形计算是机械设计的重要内容。采用传递函数方法对复杂曲梁进行分析,根据曲梁上的载荷和曲线的形状将曲梁分成不同的单元,建立单元的分布传递函数求解模型,并在单元之间连接处作了特殊处理,通过坐标变换后再组集成梁整体平衡方程。算例表明,此方法具有很高的精确度。     

Velocities of energy and wave pulse transfer by flexural waves propagating in a beam lying on a nonlinear elastic base

Flexural oscillations of a Bernoulli-Euler beam lying on a nonlinear elastic base are considered. Equations of energy and wave pulse transfer in the system are given.     

An ultra-low energy (30-200 eV) ion-atomic beam source for ion-beam-assisted deposition in ultrahigh vacuum

The paper describes the design and construction of an ion-atomic beam source with an optimized generation of ions for ion-beam-assisted deposition under ultrahigh vacuum (UHV) conditions. The source combines an effusion cell and an electron impact ion source and produces ion beams with ultra-low energies in the range from 30 eV to 200 eV. Decreasing ion beam energy to hyperthermal values (≈10(1) eV) without loosing optimum ionization conditions has been mainly achieved by the incorporation of an ionization chamber with a grid transparent enough for electron and ion beams. In this way the energy and current density of nitrogen ion beams in the order of 10(1) eV and 10(1) nA/cm(2), respectively, have been achieved. The source is capable of growing ultrathin layers or nanostructures at ultra-low energies with a growth rate of several MLs/h. The ion-atomic beam source will be preferentially applied for the synthesis of GaN under UHV conditions.     

New technique for laboratory measurements of heat transfer coefficient

Technique and procedure for measurements of the heat transfer coefficient in experimental research of heat transfer at the liquid-solid interface are submitted. The technique enables to use the metal film applied to the surface both to heat the surface and to measure the surface temperature, thus minimizing uncontrolled heat loss and reducing the measurement uncertainty.     

Comparative studies of parameters calibration for focused ion beam deposition

This paper describes the interaction between operating parameters of target wafer surface. We use an organometallic (C) precursor gas in the focused ion beam deposition process. Under the beam intensity conditions (30kV), the influences of the on-target beam control parameters, such as dwell time, beam spacing, minimum frame time and scan type, were investigated by the deposition tests. The analysis was carried out with the variation of dimensions and shapes of the single pattern. The operating parameters considered in this research are implemented in the next double-patterning deposition. The test presented how their interaction appeared on the processing results. The analysis configured out the FIB induced deposition of single pattern with the variation of operating parameters. Additionally the result shows that the sequent beam job influenced the double-patterning deposition significantly. On-beam target conditions should be optimized for the target complicated shapes and high aspect-ratios     

A device for sublimation molecular beam deposition of erbium-doped silicon films

The device described contains a source of Er vapors in the form of a rectangular erbium strip heated to a temperature of 800–950°C by a current passing through it. The base material (Si) flow was produced by sublimation of a silicon bar cut from a single-crystal ingot. The device was used for growing epitaxial Si layers with an Er concentration of 5×10¹⁸–10²¹ cm⁻³.     

Microscopy of surfaces and applications to molecular beam epitaxy

A scanning transmission electron microscope has been specifically designed for studies of reconstructed surfaces and epitaxial growth processes. Incorporation of a molecular beam epitaxy system, Auger spectrometer and ion gun along with ultra-high vacuum make this instrument ideally suited for this type of investigation. An analysis of the reconstructed GaAs surface is also given to demonstrate the instrument capabilities.     

Developments in molecular SIMS depth profiling and 3D imaging of biological systems using polyatomic primary ions

In principle mass spectral imaging has enormous potential for discovery applications in biology. The chemical specificity of mass spectrometry combined with spatial analysis capabilities of liquid metal cluster beams and the high yields of polyatomic ion beams should present unprecedented ability to spatially locate molecular chemistry in the 100 nm range. However, although metal cluster ion beams have greatly increased yields in the m/z range up to 1000, they still have to be operated under the static limit and even in most favorable cases maximum yields for molecular species from 1 µm pixels are frequently below 20 counts. However, some very impressive molecular imaging analysis has been accomplished under these conditions. Nevertheless although molecular ions of lipids have been detected and correlation with biology is obtained, signal levels are such that lateral resolution must be sacrificed to provide a sufficient signal to image. To obtain useful spatial resolution detection below 1 µm is almost impossible. Too few ions are generated! The review shows that the application of polyatomic primary ions with their low damage cross‐sections offers hope of a new approach to molecular SIMS imaging by accessing voxels rather than pixels to thereby increase the dynamic signal range in 2D imaging and to extend the analysis to depth profiling and 3D imaging. Recent data on cells and tissue analysis suggest that there is, in consequence, the prospect that a wider chemistry might be accessible within a sub‐micron area and as a function of depth. However, these advances are compromised by the pulsed nature of current ToF‐SIMS instruments. The duty cycle is very low and results in excessive analysis times, and maximum mass resolution is incompatible with maximum spatial resolution. New instrumental directions are described that enable a dc primary beam to be used that promises to be able to take full advantage of all the capabilities of the polyatomic ion beam. Some new data are presented that suggest that the aspirations for these new instruments will be realized. However, although prospects are good, the review highlights the continuing challenges presented by the low ionization efficiency and the complications that arise from matrix effects. © 2010 Wiley Periodicals, Inc., Mass Spec Rev 30:142–174, 2011     

700t箱梁转运平台的研制与应用

阐述了700t箱梁转运平台的作用,介绍了箱梁转运平台的主要结构、工作过程和主要创新点。该转运平台是国内外首台为提高运架一体架桥机架桥效率的配套设备,2010年2月8日在广珠城际铁路线架梁施工中,成功地完成了32m箱梁转运试验,之后又进行了24m梁转运移梁,应用情况证明,转运平台各种性能完全达到了设计要求。     

Analytical studies for buckling and vibration of weld-bonded beam shells of rectangular cross-section

An approach to analytical solution is presented for vibration and buckling of thin-walled tubular beam shells typical of automotive structures, which are fabricated by joining sheet metal stampings along the two longitudinal edges with periodic spot welds, adhesive bonding, or combination of spot welds and bonding, known as weld bonding. Solutions are obtained for such beam shells of rectangular cross-section with two opposite ends simply supported. The beam shell is modeled as an assembly of the constituent walls and Levy-type formulation is used to obtain a series solution for the transverse displacement of each of the walls. The challenge of expressing the discrete point support conditions at the spot welds by a continuous function is addressed using the flexibility function approach used in literature. The flexibility function, used earlier to represent the flexibility distribution along weld-bonded edges of rectangular plates with periodic spot welds, is used here. The characteristic equations are obtained by satisfying the displacement, slope, shear, and moment equilibrium at the mating edges of the walls including the two weld-bonded edges and the compatibility conditions at the spot-weld locations. This approach to analytical solution, described here for thin-walled beam shells of rectangular cross-section, can be suitably adopted for more general cross-sections and joints along non-symmetric edges. A parametric study is undertaken to show the effect of aspect ratio of the beam shell, adhesive joint parameters, and the number of spot welds on the elastic buckling loads and the natural frequencies. Such parametric studies can be of use to designers in arriving at an optimal joint configuration of weld-bonded beam shells from buckling and vibration considerations.     

A simple method for measuring time-of-flight spectra of a gas-dynamic molecular beam

A simple and sensitive method is proposed for studying gas-dynamic seeded beams containing molecules of some salts of alkali metals and thallium with ionic bonds. This method is based on the use of dissociation of these molecules induced by collisions with xenon. A secondary electron multiplier serves as the detector of a molecular beam. The proposed method has been tested on a seeded gas-dynamic beam of CsCl molecules at a pressure of the carrier gas (hydrogen) of 1–5 atm and with energies no higher than 20 eV. This method has shown high accuracy and reproducibility of results.     

高精度动载体激光发射系统光束控制反射镜

设计了一种适于车载等运动环境下的快速控制反射镜, 用于在具有振动和冲击的工作环境下控制激光发射系统的激光光束稳定及其精确校准。根据某光学系统的性能指标要求,阐述了用于高能激光的平面反射镜的物理性能以及控制反射镜负载应有的机械特性。采用大行程的音圈电机作为控制反射镜的驱动器,并设计了精度高、抗干扰能力强的角位移测量装置作为控制反射镜的位置传感器。对所采用的4个音圈电机和4个角位移测量装置进行了合理布局,既降低了系统的转动惯量又提高了系统的可靠性和环境适应性。实验结果表明：该快速控制反射镜的定位精度优于1.4″,满足高能激光发射系统对控制反射镜的精度要求。     

Research and development of H- ion source and low energy beam transport for a kaon-neutrino factory

A baseline H(-) ion source and low energy beam transport (LEBT) system have been identified for Project X. The filament-discharge H(-) ion source has been fabricated by D-Pace, Inc. and is now in operation at LBNL. The source is capable of delivering over 10 mA of H(-) beam in cw operation with normalized 4 rms emittances less than 0.7 π mm mrad. A two-solenoid magnetic lens LEBT system has been design. The design has been validated with simulations of beam transport for 5 mA 30 keV H(-) beams using various simulation codes.     

A technique for improved focused ion beam milling of cryo-prepared life science specimens

The combination of focused ion beam and scanning electron microscopy with a cryo‐preparation/transfer system allows specimens to be milled at low temperatures. However, for biological specimens in particular, the quality of results is strongly dependent on correct preparation of the specimen surface. We demonstrate a method for deposition of a protective, planarizing surface layer onto a cryo‐sample, enabling high‐quality cross‐sectioning using the ion beam and investigation of structures at the nanoscale.     

Polycrystalline techniques for conductivity studies of organic charge transfer salts

Polycrystalline compaction conductivity measurements are extensively used to characterize newly synthesized quasi-one-dimensional organic charge transfer salts. This technique, however, can be both quantitatively and qualitatively misleading. Studies of the polycrystalline compaction and single crystal conductivities of a variety of tetracyanoquinodimethan (TCNQ) salts allow us to define the limits of reliability of the polycrystalline compaction technique, and denote its shortcomings. A new polycrystalline technique, the voltage shorted compaction (VSC), is described. The VSC has proven to be a valuable aid in characterizing the electrical properties of new materials where single crystals are difficult to produce.     

Development of dynamic response analysis algorithm for beam structures using transfer of mass coefficient

The authors developed the transfer mass coefficient method (TMCM) in order to compute effectively the dynamic response of a beam structure. In this paper, the algorithm for the dynamic response analysis of a three-dimensional beam structure is formulated. Through the computation results of numerical models, which are plane and space beam structures, obtained by the transfer mass coefficient method and the direct integration method, we verify that the transfer mass coefficient method can remarkably decrease the computation time of the direct integration method without the loss of accuracy in spite of using small computer storage. This paper was recommended for publication in revised form by Associate Editor Hong Hee Yoo Myung-Soo Choi received his B.S. and M.S. degrees from National Fisheries University of Pusan, Korea, in 1992 and 1994, respectively. He then received his Ph.D. degree from Pukyong National University in 1999. Dr. Choi is currently an Assistant Professor at the Department of Maritime Police Science at Chonnam National University in Yeosu, Korea. His research interests include mechanical vibration, structural dynamics, and optimum design. Jung-Joo Suh received his B.S., M.S. and Ph.D. degrees from National Fisheries Uni-versity of Pusan, Korea, in 1972, 1985 and 1995, respec-tively. Dr. Suh is currently a Professor at the Faculty of Marine Technology at Chonnam National University in Yeosu, Korea. His research interests include internal combustion engines and numerical analysis. Dong-Jun Yeo received his B.S., M.S. and Ph.D. degrees from National Fisheries University of Pusan, Korea, in 1981, 1985 and 1996, respectively. Dr. Yeo is currently a Professor at the Faculty of Marine Technology at Chonnam National University in Yeosu, Korea. He serves as an Academic Director of the Korean Society for Power System Engineering. His research interests include structural dynamics, vibration, and analytic techniques. Jung-Kyu Yang received his B.S. degree from Pusan Fisherise College, Korea, in 1973. He then received his M.S. and Ph.D. degrees from Chungnam National University in 1985 and 1996, respectively. Dr. Yang is currently a Professor at the Faculty of Marine Technology at Chonnam University in Yeosu, Korea. His research interests include combustion engineering, air flow characteristics, and numerical analysis. Jung-Hwan Byun received his B.S. and M.S. degrees from National Fisheries University of Pusan, Korea, in 1992 and 1995, respectively. He then received his Ph.D. degree from Pukyong National University in 1997. Dr. Byun is currently an Associate Professor at the Faculty of Marine Technology at Chonnam National University in Yeosu, Korea. His research interests include numerical analysis and synchronous control.