A beam theory for thin-walled composite beams

A beam theory is presented that is formulated in terms of the in-plane elastic properties of the panels of the cross-section of a thin-walled composite beam. Shear deformation is accounted for by using a suitable form of the Timoshenko beam theory together with a modified form of the shear coefficient. The theory gives both the bending deflection and the shear deflection of a beam loaded by an applied transverse load. Numerical and graphical results obtained from a computer code show the effects of using different composite material systems and lay-ups in the panels of typical beams.     

Metal cluster complex primary ion beam source for secondary ion mass spectrometry (SIMS)

To develop a solution-type ion beam source utilizing a wide variety of metal cluster complexes that are stable only in organic solvents, we have investigated an electrospray method for transferring ions from solutions to gas phase. As initial experiments, we have studied electrospray characteristics of ethanol solutions containing a room-temperature molten salt (i.e., an ionic liquid) and acetic acid as alternatives to solutions of metal cluster complexes. In electrospray experiments, we used a stainless-steel capillary with an inner diameter of 30 μm. Experimental results showed that electrosprayed currents increased with applied voltage in both positive-ion and negative-ion modes. In addition to positive currents, stable negative currents were also confirmed to be produced. Current exceeding 250 nA was produced at 2 kV with a flow rate of 2 μL/min at a concentration of 1 × 10⁻³ mol/L. It was confirmed that several nA out of electrosprayed currents were delivered through an orifice (120 μm internal diameter) into a vacuum chamber. Experimental results indicate that the electrospray method seems to be applicable to an ion beam source for utilizing massive metal cluster complexes in solutions.     

A simple efficient SIMS apparatus for use on accelerator beam lines

A simple SIMS system is described which can be used on an isotope separator beam line to provide immediate analysis of an implanted sample without breaking vacuum. A further feature of the device is a retarding grid which will allow elimination of low energy components in the secondary ion spectra and can also be used to determine the energy distribution of the secondary species. Preliminary results for aluminium samples are given.     

Rotating target for high power neutral beams

For the development of 160 keV neutral deuterium beams, needed for the plasma heating in JET, a test bed was constructed in our laboratory at FAR. An important element of the test bed is a rotating target which can handle high power beams (∼ 5 MW) with power densities up to 20 kW/cm² for long pulse operation (∼ 10 s). Here we describe the rotating target and its long term operation.     

HL-2A中性束注入器送气实验

为满足HL-2A中性束加热的需求,我们为HL-2A的NBI注入器研制了脉冲送气回路及其控制系统,系统的核心流量控制部件为PEV-1压电晶体阀,主要是根据气压测量结果调整压电阀电源输出脉冲电压波形来控制压电阀的流导.为克服了压电阀性能参数离散,对不同离子源的送气回路进行了单独标定.送气实验结果表明,离子源放电室气压控制精度达到了0.05Pa,通过调整不同压电阀电源输出波形,减小了束线4个离子源送气回路之间相互影响,得到了平稳的离子源工作气压.     

A microprocessor controlled on-line beam profile scanner for polarized beams

A beam profile scanner system for measuring the distribution of polarization and intensity is described. The thickness of a special scatterer can be adjusted easily, so that it does not disturb the actual measurement. The scatterer is moved through through the beam at a given speed. Whenever a scattered event of interest occurs, the system records its location. In this way the intensity and polarization distribution spectra are obtained. The deceleration and acceleration at the turning points of the motion are carefully programmed so as to minimize wear of the mechanical components.     

A closed form solution for the static analysis of continuous skew-curved beams

Summary Based on the principle of superposition, the closed form solution for the static analysis of a continuous skew-curved beam in the most general case of response and loading is presented. Each differential element of the centroidal axis of the beam is given six degrees of freedom: three translations and three rotations. Three internal forces and three internal moments are assumed to act at each point of the centroidal axis of the beam. Finally, the correctness of the method is shown through an application to a special case of a continuous skew-curved beam.

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Eine geschlossene statische Lösung für den räumlich gekrümmten Durchlaufträger

Zusammenfassung Mit Hilfe des Superpositionsprinzipes wird der allgemeinste Fall von Verformung und Belastung untersucht. Jedes Differentialelement der Schwerachse des Tragbalkens hat sechs Freiheitsgrade, drei Translationen und drei Rotationen. Es wird angenommen, daß drei innere Kräfte und drei innere Momente in jedem Punkt der Schwerachse des Balkens wirken. Die Richtigkeit dieser Methode wird durch Anwendung auf einen Sonderfall gezeigt.

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With 3 Figures     

A beam profile monitor for heavy ion beams at high impact energies

A beam profile monitor for heavy ion beams has been developed for the use in experiments at the Heavy Ion Synchrotron SIS at Gesellschaft für Schwerionenforschung Darmstadt (GSI). Four thin scintillation fibres are mounted on one wheel and scan the ion beam sequentially in two linearly independent directions. They are read out via one single photomultiplier common to all four fibres into one time spectrum, which provides all information about beam position, beam extension, time structure and lateral homogeneity of the beam. The system operates in a wide dynamic range of beam intensities.     

Effective beam parameters and the turbulent beam waist for convergent Gaussian beams

Expressions are developed for the location and the size of the beam waist for a convergent Gaussian beam in statistically homogeneous and isotropic atmospheric turbulence. Subsidiary expressions are presented that lead to the maximum distance from the transmitter at which the beam waist can be located under given optical turbulence conditions and the optimal initial radius of curvature required for placing the beam waist at a desired location. The free-space beam radius W of a Gaussian beam satisfies the relationship ?W/?z = - W/R, where z represents the path length and R is the phase-front radius of curvature at z. By enforcing this relation on the effective beam spot size in turbulence W(e), we can define an effective radius of curvature R(e). In addition to specifying the beam waist, R(e) leads to a pair of effective beam parameters θ(e) and Λ(e) that provide a natural extension to the complex amplitude plane. Within this context, general propagation characteristics may be described, including the coherence properties of a Gaussian beam in both weak and strong optical turbulence.     

中性束注入器真空系统设计

中性束注入器（NBI）真空系统的性能对束传输效率以及整个束线内相关部件的使用寿命与使用安全影响极大。本文结合中性束注入器对真空系统的要求，对真空室的结构选择及气源分布进行了分析并对各气源的气量大小进行了计算。为NBI设计了一套以4．2K液氦低温冷凝泵为真空主抽泵并配以涡轮分子泵机组的抽气系统，采用此真空系统的NBI系统具有良好的真空性能。     

A new cavity configuration for cesium beam primary frequencystandards

In the design of cesium beam frequency standards, the presence of distributed cavity phase shifts (associated with residual running waves) in the microwave cavity, due to the small losses in the cavity walls, can become a significant source of error. To minimize such errors in future standards, it has been proposed that the long Ramsey excitation structure be terminated with ring-shaped cavities in place of the conventional shorted waveguide. The ring cavity will minimize distributed cavity phase variations at the position of the atomic beam, provides only that the two sides of the ring and the T-junction feeding the ring are symmetric. A model is developed to investigate the validity of this concept in the presence of the small asymmetries that inevitably accompany the fabrication of such a cavity. The model, partially verified by laboratory tests, predicts that normal tolerances will allow the frequency shifts due to distributed cavity phase variations to be held at the 10^-15 level for a beam tube with a Q of 10⁸     

The properties of low energy neutral particles in a neutral beam source: A molecular dynamics study

Application of a hyperthermal neutral beam source is one of the candidate methods of reducing plasma induced damage problems. The neutral beam is generated by vertical collisions between energetic ions and a reflector composed of metal. However, it is difficult to measure the neutral angle and energy distribution experimentally. We simulate the hyperthermal neutral beam (HNB) generation using a molecular dynamics algorithm. In order to obtain a low energy neutral beam, ions with various energies are vertically projected onto the reflector surface. A rough surface structure that has been experimentally measured is used for a realistic simulation. The energy distributions are obtained and the ratio of energy of reflected neutral particles agrees with experimental data.     

中性束注入系统热测靶设计

介绍了中性束注入系统热测靶的测量原理,提出了热测靶的设计方案,并对测量误差进行了分析,介绍了中性束注入系统束线上束流功率和功率密度分布的测量方法,对中性束注入系统也作了简单介绍.     

A simple element for static and dynamic response of beams with material and geometric nonlinearities

A unified simple 6 degrees-of-freedom beam finite element and the associated computational procedures have been developed for the fast and efficient solution of a wide class of static and dynamic response problems of the beam type with material and/or geometrical nonlinearities. The material nonlinearity is treated by including its effect in the governing equations by forming the stiffness matrix of each element using a two-dimensional grid of Gauss points and using the material properties at each point corresponding to the uniaxial strain at that point. Examples are provided for metal and reinforced concrete beams. A powerful yet straightforward method for the solution of elastica problems of beams and frames, using the beam element developed by the senior author, has been extended for determining the dynamic response of beams undergoing large displacements, including large rotations. The solution procedure involves piecewise linearization of response equations and iterations at each incremental step to achieve equilibrium. The solution procedure is simple and easy to apply. A variety of problems is solved to determine the applicability of the proposed simple formulations. Excellent agreement with existing analytical solutions which employ higher order elements demonstrates the efficiency and versatility of the present simple beam element in nonlinear analysis.     

A general finite element for beams or beam-columns with or without an elastic foundation

A general finite element is derived for beams or beam-columns with or without a continuous Winkler type elastic foundation. The need to discretize members into shorter elements for convergence towards an ‘exact’ solution is eliminated by employing in the derivation of the element exact shape functions obtained from the equation of the elastic line. Inter-nodal values of deflections, bending moments and shear forces are obtained using the exact shape functions and trigonometric series. The effect of heavy compressive or tensile axial forces on bending stiffness is treated as a linear problem by considering the axial force as a constant parameter affecting the stiffness. FORTRAN subroutines to compute the stiffness matrix, equivalent nodal forces, deflected shape, bending moments and shear forces are provided and verified by an example.     

A unified approach for the static and dynamic analyses of intermediate debonding in FRP-strengthened reinforced concrete beams

A spectral method is proposed for solving static and dynamic problems in FRP-strengthened reinforced concrete beams in a unified way. In order to appropriately simulate the debonding failure a mechanical model considering nonlinear stress–strain relationships for concrete and steel is used. The FRP-to-concrete interface is modelled using a realistic bilinear local bond-slip law. Numerical results with the proposed model for the interfacial shear stress distribution and the load–displacement response are derived for beams statically tested. Using the same spectral model the influence of interfacial delaminations on the dynamic characteristics of the structures is studied. The feasibility of the proposed method for performing dynamic analyses for high frequency excitations in a very simple and non-expensive way makes this study very useful in non-destructive testing analyses as a tool for diagnoses and detection of debonding in its initial stage by monitoring the change in dynamic characteristics.     

A GLOBAL/LOCAL approach to lengthwise cracked beams: static analysis

A simple model is developed for the calculation of stress intensity factors for a lengthwise cracked beam subjected to transverse loading. The simple model is based on a GLOBAL/LOCAL approach that separates the GLOBAL structural behavior from the LOCAL crack tip zone dominated by singular stresses. The GLOBAL model is that of a frame while the LOCAL model is based on a novel application of the J integral. The accuracy of this approach is assessed by comparing it to a fully two dimensional analysis of an elastic layer containing a lengthwise crack.     

A dual beam study with isotopic X- and gamma-rays for in vivo lymph pool assay

Dual beam absorptiometry utilizes differential absorption of X- and gamma rays of differing energy to determine an absorber's component ratio. This principle has been applied to diverse physical and biological problems. Our method, using the 22 and 88 keV emissions from ¹⁰⁹Cd, resolves the lean and non-lean mammalian tissue fractions. Accuracy of 1%, and reproducibility of 1–2% is attainable in in vitro measurements. Techniques have been developed to apply this system to the more complicated applications involved in human studies. A scanning device capable of measuring limbs has been developed. Mathematical treatment provides an integrated value of lean fraction over the scanned area. Lymphedema is a painful malady in which blockage of lymph flow causes swelling and distension of the extremities. Compressive therapy is the preferred medical treatment. There has been no accurate quantitative index of the efficacy of this therapy. Our research program uses dual beam analysis as a unique quantitative measure of the lymph transport. Lymph pool change is equated to change in the lean. Five measurements are made on subjects undergoing a two week regimen of compressive therapy. These absorptiometric results are analyzed for correlation to other indices of treatment effect. Data shows a progressive decrease in the lean tissue component over the treatment period. Changes seen vary with the individual and the severity of involvement. This study showed that the largest transport rate occurs in the first treatment days. Absorptiometry accurately monitors total adipose mass, total non-adipose mass, extremely cross section, and change in lymph pooling.     

A co-rotational weak-form quadrature planar beam element for geometric nonlinear static and dynamic analysis

The co-rotational formulation of quadrature planar beam element undergoing large displacement and large rotation is presented. A local frame co-rotates with the differential element and decomposes the motion into a rigid body movement and a strain-producing deformation. General explicit formulations of elemental vectors and matrices, including internal force vector, external force vector, tangent stiffness matrix, and mass matrix, are derived via the numerical integration together with the differential quadrature law. Thus, the element nodes and numerical integration method can be chosen arbitrarily based on the accuracy requirement and problem type. A number of case studies on the static, postbuckling, and dynamic response of beams and frame structures are conducted. The convergence study shows that the co-rotational quadrature element has an exponential rate of convergence and the reduced Gauss integration yield the highest accuracy. It is seen that the proposed co-rotational quadrature beam element is simple in formulations, computationally efficient, and capable of capturing the complex nonlinear behavior of beam and frame structures with high precision.     

Radial current in tokamak during neutral beam injection

Generation of radial current I _r during the ionization of fast deuterons in their neutral beam injected into a tokamak is considered. The current I _r and force F determined by the [I _r × B] product vary in a complicated manner along the tokamak radius. For this reason, the torque that arises together with force F also nonuniformly varies along the radius, which can lead to a shear in the rotation velocity. A sufficiently large magnitude of this shear can result in reduction of both micro- and macroinstabilities in tokamak plasma [1, 2]. The influence of injected beam characteristics and other experimental parameters on the spatial distribution of I _r in the TUMAN-3M tokamak is considered.