弯曲光纤布拉格光栅靶式流量传感器的研究

设计了一种基于光纤布拉格光栅(FBG)的弯曲靶式流量传感器,采用COMSOL软件仿真了弯曲靶臂受力时的应变分布规律,并将两支FBGs分别粘贴于靶臂的外侧和内侧进行应力测试,仿真与实验结果表明在外力作用下靶臂外侧和内侧分别产生拉应变和压应变,FBGs反射中心波长产生红移和蓝移。同时,测试了该结构的温度特性,在20 ℃~40 ℃两支FBGs反射中心波长均与温度呈线性关系,从而可消除温度对测量结果的影响。随后搭建了弯曲靶式FBG流量传感器测量装置,在0~800 L/H范围内的测量结果表明,两支FBGs反射中心波长与水流量呈较好的线性关系,其流量灵敏度为48 L/H。     

ITER偏滤器朗缪尔探针的设计与研制进展

对ITER 偏滤器朗缪尔探针进行了物理需求分析和结构设计,确定了探针离偏滤器靶板瓦表面的高度范围。通过结构设计和模拟仿真,得到了探针在稳态热负载条件下的温度场分布和应力状况,探针的最高温度低于相应的偏滤器靶板瓦最高温度,探针各个部件的应力低于材料的屈服强度。同时对探针进行了加工工艺和连接工艺的探索研发,初步确定探针体和钨屏蔽结构选用锻造钨材料,而且使用锻造钨试制了探针体和钨屏蔽结构。探针体与钨屏蔽结构之间使用氧化铝陶瓷绝缘,并使用特殊的工艺连接探针体、陶瓷和钨屏蔽结构。     

激光脉冲波形对烧蚀Si靶表面温度的影响

利用双温方程对激光烧蚀Si靶的过程进行了数值模拟,并结合合适的初始条件和边界条件,研究了在飞秒、皮秒激光作用下,脉冲波形(矩形、梯形、三角形和高斯形)对Si靶表面载流子和晶格温度分布的影响。结果表明:激光功率密度是影响载流子温升的主要因素,矩形脉冲激光烧蚀Si靶表面载流子的峰值温度最高,而高斯分布的脉冲引起靶面载流子峰值温度最低。可见,激光脉冲波形对Si靶表面载流子的温度分布具有重要影响。所得结果可为制备高质量的薄膜提供理论依据。     

辉光放电等离子体源离子注入的蒙特卡罗模拟

用蒙特卡罗方法，模拟计算了辉光放电等离子体源离子注入平面靶表面的能量分布和入射角分布。研究了靶室不同气压和不同温度下能量分布和入射角分布的变化。     

基于靶面温度测量的激光强度时空分布重构方法

基于靶面温度分布测量反演激光强度时空分布的重构表达式中,被积函数包含的奇异阿贝尔核函数导致了求解积分表达式的病态和解的不稳定。为了解决这一积分求解问题,基于广义函数理论和正则变换方法,对积分函数进行了重新构造,获得了基于靶面温度时空分布测量反演入射激光强度分布的重构算法,并分析了重构结果对温度测量误差的敏感性。借助数值模拟方法对重构算法进行了验证,数值计算给出了重构强度误差与靶板厚度和辐照时间的关系。验证结果表明,两种背光面边界条件下反演获得的激光束时空分布,不仅与原始模型激光束达到了较好的一致,而且不受薄板条件的限制。算法对强激光辐照效应的靶面激光参量监测有实用性。     

强脉冲离子束辐照金属材料表面热力学效应计算

 简要讨论了强脉冲离子束与金属靶材料相互作用的理论模型,以此为基础应用数值计算的方法模拟计算了离子能量为1.0 MeV和300 keV,束流密度分别为10 A/cm²、50 A/cm²、100 A/cm²的质子束与金属铝靶材料相互作用时的热力学效应,给出了铝在辐照后内部的温度分布、温度梯度分布,以及温度变化速率（加热速率与冷却速率）、热激波的产生与传播过程及与应力等模拟计算结果。     

激光时空分布对钢靶温度场及热软化的影响

 用有限元模型数值模拟了能量和作用时间相同而时空分布不同的连续波激光辐照下，带涂层钢靶的温度场和热软化分布。结果表明，光强空间分布不同时，靶后表面温度分布虽有不同程度的差别，但材料中部的热软化差别很小，仅热软化的范围略有改变；光强时间分布不同时，靶面温升的历史不同，但最终温度和温度分布都趋于一致。模拟分析结果与实验结果一致。     

飞秒激光-固体靶相互作用中γ射线发射研究

采用137Cs-γ标准源对LiF热释光探测器进行了标定，将其用于测量激光-固体靶相互作用产生的γ射线的空间分布和能量分布。结果显示：γ射线主要在激光反射方向和靶法线方向附近区域发射；γ射线能量分布为类麦克斯韦分布，拟合的温度约为12.52 keV 。     

利用轫致辐射谱回推超热电子温度

超短超强激光打靶产生的超热电子与固体靶相互作用时会产生轫致辐射X射线。利用蒙特卡罗方法,对电子在固体靶中传输产生的轫致辐射X射线进行了模拟。1 MeV电子束与固体靶作用产生的轫致辐射谱模拟结果表明,轫致辐射谱高能段斜率受靶厚度及靶材料的影响不明显。麦克斯韦分布的电子束及单能电子束与30 m铜靶作用的模拟结果显示,两种电子源产生的轫致辐射谱在电子束能量或温度较高时基本一致。给出了一种利用轫致辐射谱斜率反推超热电子温度的定标方法。模拟了不同温度下超热电子产生的轫致辐射光子的能量角分布及光子数角分布,结果显示辐射光子能量通量和光子数随着电子温度的提高越来越向前倾,并给出了另外一种由轫致辐射能量角分布反推超热电子温度的定标关系。     

飞秒激光-固体靶相互作用中γ射线发射研究

采用137Cs-γ标准源对LiF热释光探测器进行了标定,将其用于测量激光-固体靶相互作用产生的γ射线的空间分布和能量分布。结果显示：γ射线主要在激光反射方向和靶法线方向附近区域发射;γ射线能量分布为类麦克斯韦分布,拟合的温度约为12.52 keV 。     

Determination of stress-induced intrinsic birefringence in a single-mode fiber by measurement of the two-dimensional stress profile

The two-dimensional (2-D) axial stress profile of a single-mode fiber is obtained with an optical tomographic measurement technique. All stress components of the fiber are calculated from a measured axial stress profile. We demonstrate that the differential group delay induced by intrinsic nonsymmetric stress as well as the induced linear birefringence between two orthogonal polarization modes can be determined with an analytic technique based on a vector perturbation method from a measured asymmetric 2-D stress distribution.     

Measurement and Analysis of Spall Characteristics of High-Pure Aluminium at One-Dimensional Strain Loading

With an impact velocity varying from 196.9m/s to 317.9m/s and ratios of flyer/sample thickness of 2：4 and 3：6, the free-surface velocity profiles of the shock compressed high purity aluminium （HPA 99.999%） samples are measured with a velocity interferometer system for any reflector. Based on the vibrating features of the velocity profiles, the damage behaviour of HPA is analysed. The results indicate that the vibrating amplitude increases with increasing shock stress, and the subsequent reverberations describing the spall become more obvious. When the shock stress in the material is below a critical or smaller than the threshold level, the free-surface velocity profile replicates virtually the form of the compression pulse inside the sample. When the impact stress exceeds a critical value （1.4 GPa）, the micro damage would appear, and the free-surface velocity profile changes significantly, showing a series of short-duration reverberations in the profile. When the impact stress exceeds the threshold of damage, a compressive disturbance called the ＂spall pulse＂ appears in the free-surface velocity profile, and the subsequent reverberation becomes regular again. The measured spall strength of HPA is much higher than those of commercially pure aluminium reported in many references. In addition, the strength of HPA is similar to that of single-crystal aluminium.     

Surface and subsurface stress evaluation in case-carburised steel using high and low frequency magnetic barkhausen emission measurements

The effect of near-surface and subsurface stresses on the magnetic Barkhausen emission (MBE) profile has been studied in case-carburised and tempered En36 steel. The high- and low-frequency MBE measurements were made, on both tensile and compressive sides of the rectangular bar specimens with case-depth of 0.95 mm loaded in cantilever beam, under different stress levels as well as after unloading from different higher stress levels. The high-frequency MBE profile showed a single peak while the low-frequency MBE profile showed two peaks. Under applied elastic stresses, both types of measurement showed increase in MBE under tension and decrease in MBE under compression. But, the MBE profiles measured after unloading from higher stresses showed different behaviour. On the tensile side, the high-frequency MBE profile did not change significantly due to pre-stress. But, in the low-frequency MBE profile, the first peak increases and the second peak decreases with increase in pre-stress. On the compressive side, the peak height of high-frequency MBE profile decreased gradually with increase in pre-stress. The first peak of the low-frequency MBE profile also decreased gradually with increase in pres-stress level. But, the second peak of the low-frequency MBE profile decreased by about 10% at a pre-stress level of −1094 MPa and remained more or less the same even after unloading from −1783 MPa. The MBE behaviour has been correlated to the residual stress (RS)-depth profile measured using X-ray diffraction method. This correlation clearly indicates that the high-frequency MBE reflects only the changes in surface RS level. It does not indicate RS changes occurring at depths >20 μm below the surface. The low-frequency MBE profile reflects the changes in the RS distribution occurring in the near-surface as well as deeper subsurface layers.     

550-W diode-pumped Nd:YAG disk laser

When a thin laser crystal disk is used with a nearly flat-top pump profile, the heat flux can be considered to be one-dimensional. This results in a homogeneous temperature and stress profile within the laser medium leading to reduction of thermal effects. A nearly flat-top pump profile is achieved with a two-pass cylindrical-lens coupling system. An average output power of 550 W is obtained by an average pumping     

延性材料动态拉伸断裂早期连通过程的逾渗描述

 借鉴逾渗理论,提出了新的应力松弛函数,简称PR函数（Percolation-Release Function）,用以描述断裂发生前由于微孔洞连通而引起的快速应力松弛过程,具有较为明确的物理意义。通过其与损伤度函数模型进行耦合,对无氧铜和45钢平板撞击层裂进行了数值模拟。结果表明：数值计算不仅有效地再现了界面的应力历史和自由面速度历史,而且再现了靶中的损伤分布;新的逾渗松弛函数具有较好的适用性。     

Experimental study of vertical stress profiles of a confined granular bed under static and dynamic conditions

In a wet agglomeration process inside a low shear mixer, the blade function is to induce i) homogenization of the liquid sprayed on the powder surface and ii) a stress field able to transfer the mechanical energy at the particle scale. In this work we study the mechanical state of a confined powder bed through the analysis of stress distributions (by force measurements) in a rectangular cell in two cases: for a classical model powder (i.e. glass beads) and a complex powder (i.e. wheat semolina). Two types of vertical stress profiles are obtained according to the type of measurements carried out in the powder bed, either locally (at different positions in the cell) or globally (at the entire base). The global vertical stress profile follows Janssen's model and the local vertical stress profile highlights a critical length, identified as the percolation threshold of the force network, and a shielding length near the bottom, which is similar to an influence length of the side walls. In the context of wet agglomeration, the results allow to consider the role of the characteristic lengths in the mixing bowl under vertical mechanical solicitation.     

Optical Measurement Techniques for Optical Fiber and Waveguide Devices

We describe three major optical characterization methods for fiber and fiber devices. A simple servo controlled scanning fiber-optic confocal microscope is proposed for determining the refractive index profile of an optical fiber. To measure the chromatic dispersion of a short length fiber a Mach-Zehnder fiber interferometer with a novel interferometric distance meter is introduced. At the end, a tomographic method is demonstrated for determining the 2-D stress profile of a fiber.     

二极管泵浦Nd:YAG薄片激光器技术研究

固体激光器向高平均功率发展的最大障碍是激光介质的热效应.采用薄片激光介质可以实现热流近一维分布,因而是解决固体激光器热效应的有效手段之一,但许多因素都会影响薄片的一维热分布.对薄片热分布的主要影响因素进行的计算分析表明,在均匀泵浦条件下,泵浦区径向温度的均匀性不仅和泵浦区面积与薄片厚度之比有关,而且和冷却区与泵浦区的相关尺寸有关.采用均匀耦合技术并合理设计薄片的散热冷却结构以实现热流近一维分布,用平均功率336 W的激光二极管阵列泵浦一块NdYAG薄片,获得了平均功率超过120 W的准连续激光输出.     

Stress distributions in diblock copolymers

We demonstrate how a generalized self-consistent field theory for polymer melts that includes elastic stress and strain fields can be applied to the study of AB diblock copolymers melts. By obtaining the stress distributions for volume conserving strain loadings where lamellar and hexagonal morphologies are stable, we show that the local stress is reduced at the domain interface but slightly enhanced in the immediate vicinity of the interface. The overall stress profile is the result of the combined effects of chain connectivity across the interface, which yields a positive contribution, and the immiscible nature of the monomers, which leads to a stress reduction because of interfacial tension.     

The analytical investigation of the super-Gaussian pump source on the thermal, stress and thermo-optics properties of double-clad Yb:glass fiber lasers

Fiber lasers have attracted considerable attention when their power can realistically be scaled to kilowatt level and beyond. In this paper, we assumed that the fiber core and first clad are exposed to a pump source with a super-Gaussian profile of order four. The effects of this non-uniform heat deposition on thermal, stress and thermooptics properties such as temperature-dependent change of refractive index and thermally induced stress have been comprehensively studied and their equations analytically derived.