Transaxial mirror with combined static electric and magnetic fields

Combined transaxial mirrors are studied. In the areas of motion of charged particles, the fields of these mirrors are symmetric relative to the axis and mid-plane representing the plane of symmetry for the electric field and the plane of asymmetry for the magnetic one. An image equation is inferred and simple relationships between the linear and angular dispersions with respect to mass and energy are obtained. Aberration properties of the mirrors in the directions parallel to the mid-plane are considered. Expressions for the coefficients of the third-order geometric aberration corresponding to the beam divergence angle in the mid-plane are obtained. These expressions are especially simple when both object and image are located in the principal planes of the mirror. The aforementioned coefficients are expressed via parameters characterizing the mirror under the first-order approximation.     

磁约束等离子体推进器磁体系统的电磁力和机械应力分析

根据磁约束等离子体推进器磁体系统的设计参数,通过ANSYS有限元分析软件在电磁-结构耦合场方面的计算,得到磁体系统的轴向电磁力和机械应力的分布。计算超导磁体在通电情况下,磁体中平面上所有节点所受的轴向电磁压缩力以及磁体间的相互作用力;计算出磁体外层用不锈钢钢丝加固前后机械应力分布情况的变化。     

Influence of radial magnetic field on emittance in the median plane at CYCIAE-100

A 75—100 MeV H- compact cyclotron CYCIAE-100 is being constructed at China Institute of Atomic Energy (CIAE). About 200 μA proton beam will be provided by CYCIAE-100. The imperfection of magnetic fields will remarkably affect the acceleration orbit and beam envelope in CYCIAE-100. The effects to the accelerating beam by the imperfection fields, especially the field components Br on the mid-plane will be analyzed in detail with tracking code COMA. Poles misalignment that causes magnetic imperfection will be described in the paper. According to the simulation results, the tolerance of the poles machining and assembly will be illustrated in this paper.     

Nb3Sn超导电磁铁

本文报导了关于筒形Nb₃Sn磁体的研究结果。观察到磁通跳跃现象。“冻结”场的分布和历史及激发场的分布紧密相关。“冻结”场可以不是中心对称的,这进一步证明了烧结的Nb₃Sn材料是非均匀介质。我们描述了新的磁体结构,避免了磁通跳跃。除利用铁心来捕获磁通外,在激发和测量磁场的方法上均具有一定的特点。利用圆筒状Nb₃Sn作为压挤磁通的活塞,在1.5°K时,曾获得的最高场强是28.5KG。     

Closed-form solution of mid-potential between two parallel charged plates with more extensive application

Efficient calculation of the electrostatic interactions including repulsive force between charged molecules in a biomolecule system or charged particles in a colloidal system is necessary for the molecular scale or particle scale mechanical analyses of these systems. The electrostatic repulsive force depends on the mid-plane potential between two charged particles. Previous analytical solutions of the mid-plane potential, including those based on simplified assumptions and modern mathematic methods, are reviewed. It is shown that none of these solutions applies to wide ranges of interparticle distance from 0 to 10 and surface potential from 1 to 10. Three previous analytical solutions are chosen to develop a semi-analytical solution which is proven to have more extensive applications. Furthermore, an empirical closed-form expression of mid-plane potential is proposed based on plenty of numerical solutions. This empirical solution has extensive applications, as well as high computational efficiency.     

托卡马克等离子体不同平衡位形下的电子回旋波电流驱动

在给定的等离子体总电流和中心电流密度条件下,数值求解平衡方程,求出不同拉长比和三角形变因子的托卡马克等离子体温度、密度、磁场分布,然后通过求解波迹方程和Fokker-Planck方程,分别计算这些位形下的电子回旋波波迹和电流驱动.结果表明：电子回旋波X模从顶部发射时,随着拉长比的增大,波迹会向弱场侧偏移.电子回旋波X模从弱场侧发射时,电子回旋波在等离子体中传播沉积的功率份额随着拉长比的增大而增加,驱动电流位置随着三角形变因子的增大向等离子体中心移动.驱动电流位置随环向和极向发射角的减小向中心移动,对应的电流密度峰值也变大.     

Hot Ion Plasma Heating Experiments in SUMMA

Initial empirical results are presented for the hot-ion plasma heating experiments conducted in the new SUMMA (Superconducting Magnetic Mirror Apparatus) at NASA Lewis Research Center. A discharge was formed by applying a radially inward DC electric field near the mirror throats. Data were obtained at midplane magnetic flux densities from 1.0 to 3.5 tesla. Charge-exchange neutral particle energy analyzer data were reduced to ion temperatures using a plasma model that included a Maxwellian energy distribution super-imposed on an azimuthal drift, finite ion orbits, and radial variations in density and electric field. Using this plasma model, the highest ion temperatures computed were 5 keV, 1.2 keV, and 1 keV for He+, H2+, and H+, respectively. These were obtained at a mid-plane magnetic flux density of 1.6 T. Ion temperature was found to scale roughly as (P/B)n, where P/B is the ratio of power input to magnetic flux density and n is about 1 for hydrogen and 2 for helium. Optical spectroscopy line-broadening measurements yielded ion temperatures about 15 percent higher than the charge-exchange neutral particle analyzer results for hydrogen and about 50 percent higher for helium. Spectroscopically obtained electron temperatures ranged from 3 to 30 eV.     

Effect of gap flow on the shallow wake of a sharp-edged bluff body – turbulence parameters

This experimental study was carried out to investigate the turbulent wake generated by a vertical sharp-edged flat plate suspended in a shallow channel flow with a gap near the bed. The objective of this study is to understand the effect of the gap flow on the turbulent wake by studying two different gap heights between the channel bed and the bottom edge of the bluff body. These two cases were compared to the no-gap case which is considered as a reference case. The maximum flow velocity was 0.45 m/s and the Reynolds number based on the water depth was 45,000. Extensive measurements of the flow field in the vertical mid-plane and in the horizontal near-bed, mid-depth, and near-surface planes were made using particle-image velocimetry (PIV). This paper is the second part of an extensive study to characterise the gap-flow effects and is primarily focused on the mean and instantaneous turbulence quantities as well as coherent structures.

The results revealed that the gap flow increased the transfer of the turbulent kinetic energy (TKE) from the streamwise to the vertical component along the vertical mid-plane. In addition, there is a corresponding increase and spread of the transverse component in the transverse direction as the flow evolves in the downstream direction. The momentum exchange by the Reynolds stress is significantly weak in the vertical mid-plane particularly in the lower half of the water depth, but the gap flow enhanced the momentum exchange in the upper half of the water depth by up to 1% of the freestream velocity squared. Furthermore, the intensity and bursting direction of the turbulence fluctuations in the far field are also affected by the gap flow when it is large. Furthermore, the proper orthogonal decomposition results revealed that the flow contains a large number of structures, and their interactions are responsible for deforming and/or tearing apart the structures, and transferring fluid throughout the velocity field.     

Effect of gap flow on the shallow wake of a sharp-edged bluff body – mean velocity fields

This experimental study was carried out to investigate the turbulent shallow wake generated by a vertical sharp-edged flat plate suspended in a shallow channel flow with a gap near the bed. The objective of this study is to understand the effect of the gap flow on the wake by studying two different gap heights between the channel bed and the bottom edge of the bluff body. These two cases will be compared to the no-gap case which is considered as a reference case. The maximum flow velocity was 0.45 m/s and the Reynolds number based on the water depth was 45,000. Extensive measurements of the flow field in the vertical mid-plane and in the horizontal near-bed, mid-depth, and near-surface planes were made using particle image velocimetry. This paper is part of an extensive study to characterise the gap-flow effects and is primarily concerned with the mean velocity fields, while a companion paper discusses the turbulence characteristics. The size of the wake identified in the horizontal planes is found to vary in the three planes, where the gap flow enhances the entrainment in the near-wake region in the near-bed velocity field. The results also revealed that, if the gap flow is weak, it is engulfed by the recirculation zone formed just behind the bluff body whose axis is perpendicular to the vertical mid-plane. On the other hand, if the gap flow is relatively strong, it penetrates in the downstream direction and only a portion of it is diverted upward to feed the recirculation zone.     

改善ITER 弹丸注入芯部加料的研究

研究了五种不同组合的固态氢同位素靶丸H₂、HD、D₂、DT 和T₂ 在聚变等离子体中的消融率。结果表明, 燃料靶丸的同位素效应, 可导致更深的靶丸消融物质沉积。在同样的本底等离子体条件和弹丸初始参数下, 注入氚丸比氢丸的穿透深度增加约40%。适度减轻一些ITER 的加料困难。进一步的研究表明从中平面高场侧注入靶丸对芯部加料有显著改善。考虑托卡马克非均匀磁场的影响, 被电离的消融云内的垂直漂移电流产生极化, 引起带电消融物沿大半径方向朝外漂移。数值模拟计算表明, 只要用初始速度为每秒几百米的低速弹丸, 便能使靶丸的消融物质沉积到ITER 等离子体中心。     

Aspect ratio effects on natural convection in a water-saturated porous cavity near its density maximum

In this study, two-dimensional steady-state solutions of buoyancy-driven convection in a water-saturated porous cavity is conducted numerically for a range of different aspect ratios. The left vertical wall is considered into a partially heating location. The Brinkman–Forchheimer extended Darcy model is used to investigate the average heat transfer rate. The governing equations are solved using a finite volume method. The results obtained for various values of parameters are presented graphically in the form of streamlines, isotherms and velocity at mid-plane of the cavity. In addition, numerical results for the average Nusselt number are presented for various parametric conditions.     

HL-2A等离子体边缘的快速单探针测量

介绍了对HL-2A装置中平面边缘等离子体的单探针测量。单探针是安装在可径向移动、并可绕轴旋 转360o的传动杆上的。在1MHz的快速采样频率下,测量了主等离子体边缘的温度、密度、悬浮电位、空间电位、极 向等离子体流速的径向分布。测量的结果表明,利用单探针测量的主等离子体边缘参数与朗缪尔四探针测量结果 基本一致。     

冷冻靶制备中辅助加热的理论和数值分析

 为了补偿惯性约束聚变（ICF）冷冻靶冷却过程中非球对称腔体的热流分布,通常在冷却的同时在腔外壁上施加辅助加热。在间接驱动靶中建立了1维热传导理论模型,分析所需辅助热流密度,同时在2维轴对称模型下,利用计算流体力学的FLUENT程序,对辅助加热机制进行了热力学模拟。当把辅助加热设在腔外壁的中平面上下各1.3 mm的范围时,得到了最佳辅助热流密度为635 W/m²,与理论结果基本一致。     

Visualizations of the transitional flow patterns at the mid-span between shrouded co-rotating disks

Transitional air flow patterns at the mid-plane of gap between co-rotating disks in a stationary cylindrical enclosure are visualized under the acceleration condition of disks. The flow visualization is performed using olive oil particles with a laser sheet and CCD camera. On disk spinning-up, the transition flow patterns are clearly observed. The affect of magnitude of acceleration on the onset of transition and the relations of the number of vortex cells in fully turbulent regime of the flow in an outer region of the flow field to the rotating speed are also investigated. The centrifugal effect of particle is evaluated from the comparison with visualization results using hollow glass spheres.     

HL-2M 装置极向场线圈的结构设计与制造

介绍了 HL-2M 装置极向场(PF)线圈的结构设计和制造。16 饼 PF 线圈布置在环向场(TF)线圈空腔之 内、真空室外,沿中平面对称分布。PF 线圈采用中空矩形铜导体绕制,其中 PF1~PF4 线圈为双层螺旋绕制结构, 最大运行电流 14.5kA;PF5~PF8 线圈为多层盘式绕制结构,最大运行电流 38~42kA。      

中国超导聚变工程实验堆氦冷固态包层中子学设计分析

根据中国聚变工程实验堆(CFETR)设计要求,参考氦冷固态包层实验包层模块(HCCB TBM)的设计经验,完成了CFETR固态包层的中子学设计分析,并评估了中平面位置可开窗口的最大面积。设计分析结果表明,基于增殖单元的固态包层中子学设计方案的氚增殖比(TBR)达到了1.243,满足CFTER氚自持设计要求;中平面可以开出的辅助窗口的最大面积为11.43m²。     

Non-linear flexural waves in thin layers

Non-linear flexural waves in thin plates or layers have been analyzed in this paper. The equation of motion of the plate is derived assuming that the motion is antisymmetric about the mid-plane of the plate and that the plate is thin. The plate is considered to be elastic. The Von Karman non-linear strains and Landau elastic constants have been used to model geometric and material non-linearities, respectively. An asymptotic analysis of wave motion is presented using the method of multiple scales. Evolution equations are derived for small amplitude traveling flexural elastic waves. Numerical results show waveform distortion, amplitude amplification, and harmonic generation.     

Effects of processing parameters on fatigue properties of LY2 Al alloy subjected to laser shock processing

We address the effects of processing parameters on residual stresses and fatigue properties of LY2 Al alloy by laser shock processing (LSP). Results show that compressive residual stresses are generated near the surface of samples due to LSP. The maximum compressive residual stress at the surface by two LSP impacts on one side is higher than that by one LSP impact. The maximum value of tensile residual stress is found at the mid-plane of samples subjected to two-sided LSP. Compared with fatigue lives of samples treated by single-sided LSP, lives of those treated by two-sided LSP are lower. However, these are higher than untreated ones.     

复杂型腔充模中纤维取向的动态模拟

基于描述短纤维增强复合材料充模过程的气-固-液三相模型及同位网格有限体积法, 实现了纤维增强复合材料沿复杂型腔水平中面充模过程的动态模拟. 不仅得到了界面位置、各物理量的信息, 而且得到了纤维在型腔中的运动情况(包括纤维的平动和取向). 结果表明, 与沿型腔厚度方向纤维取向的表层-芯层结构不同, 纤维沿型腔水平中面的取向与型腔结构有关, 入口处纤维取向环绕型腔入口, 沿水平或竖直方向纤维取向与来流方向垂直, 型腔拐角处纤维取向指向拐点.     

HL-2A等离子体边缘极向剩余胁强的研究

首次报导了托卡马克等离子体边缘与湍流相关的极向剩余胁强剖面的测量结果。采用外中平面往复式静电探针阵列对HL-2A托卡马克边缘的极向湍流动量输运进行研究。在没有外部动量注入的欧姆放电下,剩余胁强为有限值、且其空间剖面在等离子体边缘具有明显的径向梯度,表明托卡马克等离子体边缘存在极向动量源。由动量源产生的动量主要以扩散形式向与剩余胁强相反的方向传播,最终的结果是等离子体边缘存在有限的雷诺胁强。在最后闭合磁面以内0.5~2cm区域,剩余胁强的梯度提供自发旋转的力矩,由该力矩引起的动量产生与由速度梯度引起的动量扩散共同导致了雷诺胁强出现负梯度,造成动量沉积,从而驱动极向平衡流。