强流质子直线加速器中束晕现象研究

从束流包络方程与单粒子运动方程联立模型出发，考虑了纵向能量方程的耦合，研究了强流质子直线加速器中的束晕现象。采用相交间的Ｐｏｉｎｃａｒｅ截面方法和实空间Ｐｏｉｎｃａｒｅ截面方法，研究了周期聚焦系统失配的情况下束晕的形成以及加速对束晕形成的影响。     

100 MeV回旋加速器束流加速轨道的COMA模拟跟踪

利用多粒子跟踪程序COMA来模拟CYCIAE-100的加速过程。在束流强度和初始发射度固定的情况下，分析研究加速过程中束团的能散、滑相、相图的变化，发射度的变化，以及束流包络的变化情况。     

电子直线加速器注入器中束流横向发散度的计算

在联立电子直线加速器中粒子运动方程的基础上,建立了一种计算束流横向发散度的方法,将束流划分为若干个等电荷的同心环,追踪它们的代表粒子在注入器中的运动,依照所有粒子的γ、P_r和方位角θ值,计算出束流的均方根发散度。在实例计算中给出了粒子的运动轨迹和相位会聚图象以及注入器出口处粒子的相图,计算了束流的均方根发散度,并对阴极磁场和轴向聚焦磁场对横向发散度的影响作了讨论。     

回旋加速器静电引出通道的计算

本文介绍三叶扇形可变能量等时性回旋加速器的束流静电引出通道的设计方法和特点,讨论了静电引出通道设计的基本粒子动力学要求,并根据静电通道的几何参数,对静电引出通道的单粒子运动方程作数值积分,从而确定了通道入口相对扇形磁场的合理方位角、通道分段的跨度及通道经向张口的程度,推导了单粒子运动方程等效的线性化简谐振荡方程。由束流光学的σ矩阵变换方法计算了通道入口的经向接受度及引出束包络,给出了引出束穿越边缘磁场的图象,证明在第一段静电通道内,引出束几乎正交地穿透等高斯线     

束流输运网络中的束晕-混沌控制

强流下束流输运网络中会产生束晕-混沌现象,给加速器装置带来损害。因此,希望通过数值模拟和理论分析找到一种更加有效的控制束晕-混沌现象的方法。首先,利用控制方法实现粒子包络轨道同步。把周期电磁聚焦元件都看成1个网络的节点,每个节点中粒子束流包络运动满足以下方程式:d1d2xxt=(1)ddx t2=?(a b cos x3)2x1 xK1 x113(2)d3dxt=ω(3)其中,a=1.65,b=1.25,ω=2π。束晕混沌系统粒子轨迹受各种力的作用而产生杂乱无章的轨迹。在x2方向上设计了控制器G(i)=m(x(i,2)-n)2控制粒子运动包络,这样式(2)就是受控方程:ddx t2=?(a b cos x3)2x1 xK…     

强迫力对非线性传输的影响

从具有强迫项的6维非线性粒子运动方程组出发,导出了具有强迫力时的6维非线性轨迹传输方程和包络传输方程。     

CYCIAE-100中心平面的Br对束流发射度的影响计算

在回旋加速器中，如果磁极的镜像对称被破坏，将在加速器的中心平面上产生一水平分量的场Br，在粒子相应轴向共振的作用下，这样的场将使中心粒子的运动偏离中心平面，进而使束流发射度发生变化。在回旋加速器中粒子由于径向磁场作用偏离中心平面运动的方程可表示为：     

强流AVF型回旋加速器中的空间电荷效应和束晕

首先,详细推导了AVF型回旋加速器中束团粒子在曲线坐标系中的动力学方程(考虑和不考虑空间电荷相互作用力两种情况)。然后,在假定动力学方程中各参数值的前提条件下,用Lunge-Kutta方法对考虑空间电荷时的动力学方程进行了数值计算。结果表明,束晕的形成和发展同样也是强流回旋加速器中束流损失的一个主要原因。但束晕形成的机制不同于直线加速器的情况,它不是由共振和混沌引起,而是由于粒子的排斥运动和束团内粒子的涡流运动引起的。     

非线性相移因子与渡越能量附近粒子的动力学行为

束流穿越渡越能量后动量分散增加,束流品质退化。在经典力学框架内和小振幅近似下,考虑到相移因子的二阶非线性、射频噪声和辐射衰减的影响,把同步加速器的粒子同步运动方程化为具有阻尼项、受迫项的二阶非线性微分方程。对系统的相平面特征和振幅响应进行了数值分析;用摄动法讨论了系统的稳定性及1/3共振线附近粒子的运动行为:分析了系统的跳跃现象和系统的临界条件。结果表明,零次相移因子越大和三阶非线性越小系统越稳定。     

电子直线加速器低能区粒子三维运动的计算

采用变半径盘电荷模型和环状束流模型对电子直线加速器低能区作粒子三维运动的计算,给出了粒子在各向的位移及其变化速率,以及束流轨迹和在各相平面的均方根发射度的大小与束流发射度图象。     

环形电子束在周期永磁场中传输的理论研究

通过对环形电子束中电子的受力分析，得出了在周期永磁场(PPM)中电子束传输的条件和电子束的形状。研究认为可以使用PPM对环形电子束进行传输。     

Design study of a multibeam type IH-RFQ linac to accelerate high intensity and low energy heavy ion beams

A multibeam Radio Frequency Quadrupole (RFQ) linac with an Interdigital H-mode (IH) structure has been developed for high intensity heavy-ion beam acceleration. The defocusing force of space charge effect is proportional to the beam current and to the inverse square of the beam velocity. Therefore, multibeam acceleration is an attractive scheme to suppress this in the low energy region. The electromagnetic field distribution and the beam dynamics were studied for a prototype. We discuss the configuration of the multibeam IH-RFQ linac and the results of these simulations.     

PWR堆芯燃料组件非线性梁模型研究

In order to describe the nonlinear characteristics of the fuel assembly, a lateral beam model of assembly is built by the finite element method. The beam model is embedded with the hysteretic model to simulate the nonlinear effect occurred at lateral deformation. The calculation shows that the bending deformation and force can be derived from the nonlinear beam model, which is beneficial for the analysis of fuel assembly accidents.     

MEVVA离子源凸形引出电极的研制

介绍了金属蒸气真空弧(Metal vaporvacuumarc,MEVVA)离子源的凸形引出电极的研制.研究表明,凸形引出电极可以完成离子束的强制发散功能,从而在较短的引出距离和较小的引出电极面积的条件下得到大的束斑和均匀可应用的束流分布.通过对几种不同的电极结构的比较研究,得到了满足应用要求的凸形引出电极.     

Self-focusing of Gaussian Laser Beam Through Collisionless Plasmas and Its Effect on Second Harmonic Generation

This paper presents an investigation of self-focusing of gaussian laser beam in a collisionless plasma and its effect on second harmonic generation. In the presence of gaussian beam, the carriers get redistributed from the high field region to low field region by ponderomotive force and transverse density gradient is established in plasma which in turn generates the plasma wave at pump frequency. This plasma wave interacts with incident laser beam and a second harmonic is generated. Furthermore, if the initial power of input beam is more than the critical power for self-focusing, the beam gets self-focused and hence the generated plasma wave and second harmonic which depend upon the background electron concentration and power of the main beam also get modified accordingly.     

Enhanced Raman Scattering of Elliptical Laser Beam in a Collisionless Plasma

This paper presents the Enhanced Raman scattering of a elliptical laser beam in a collisionless plasma. The transverse intensity gradient of a pump beam generates a Ponderomotive force, which modifies the background plasma density profile in a direction transverse to pump beam axis. This modification in density effects the incident laser beam, plasma wave and back-scattered beam. Non-linear differential equations for the beam width parameters of pump laser beam, plasma wave and back-scattered beam are set up and solved numerically. The interplay between the self-focusing of the main beam and SRS has been studied in detail. The analysis clearly shows a coupling between the main beam and the plasma wave, therefore an increase in the self-focusing of the pump beam at lower intensities increases the self-focusing of the plasma wave which inturn leads to an increase in the back-reflectivity of the scattered wave. Further, it is also predicted that strong self-focusing of the pump beam at higher plasma density leads to strong self-focusing of the plasma wave and results in an increase in SRS reflectivity.     

Dynamic response of a multi-span beam to transverse impact

The general case of impact between a continuous beam on many supports and a moving mass striking the beam transversely at any point has been analysed. Expressions for the deflection of the beam at any point along the beam, the impact force and the duration of impact have been theoretically derived employing the operational method developed by Heaviside. The results are presented in convenient, easily computable form and are applicable for a beam of any number of spans, struck at any point. Experiments have been performed on a three-span beam using a photographic method of measurement. The agreement between the theoretical and experimental results is excellent. The formulations presented are expected to provide the basis for the development of a rapid and reliable method for designing multi-span beams to withstand impact loading.     

PWR堆芯燃料组件非线性梁模型研究

为描述燃料组件的非线性特性，采用有限元方法建立燃料组件横向梁模型，并引入迟滞模型，用于模拟燃料组件横向变形时的非线性效应。计算结果表明:该非线性梁模型能够更准确地获得组件的弯曲变形和受力，有助于开展燃料组件事故分析。      

Effect of axial restraint on mechanical behavior and average crack spacing of reinforced concrete flexural members

This study was performed to verify the effect of axial restraint on the mechanical behavior and average crack spacing of reinforced concrete (RC) flexural members. Experiments for mechanical behavior have been performed on axially restrained and unrestrained RC beams. And, the average crack spacing has also been investigated in other RC beam tests under the axially restrained condition.The test results show that the capacity of the axially restrained beam was higher than that of the unrestrained beam. For restrained flexural members, axial deformation was restrained, deformation capacity was decreased, plastic behavior was delayed, and possibility of compressive failure was increased due to the axial restraint force.The major variables affecting the average crack spacing were steel stress, axial force, circumference of reinforcing bar, and effective tension area of concrete. However, the effect of concrete compressive strength was minimal. A prediction equation utilizing the identified variables was proposed for determining the average crack spacing of the axially restrained RC flexural members.     

Creation mechanism of pores by ion beam modification of fluoropolymer film membranes

Producing structures in membranes at the nanometer scale can serve several applications such as to localize molecular electrical junctions and switches, and to function as masks. In previous work we demonstrated the fabrication of porous membranes in masked fluoropolymer films using scanned ion beam bombardment. The process dispenses the use of time consuming chemical and etching processes. Here we report on the creation mechanism of pores using ion bombardment. Aspects of the ion beam interaction with matter are explained as well as an analysis of the shape of the fabricated structures. The pores were produced using our feedback controlled ion beam apparatus and were analyzed using optical and atomic force microscopic (AFM) analyses.