复杂通道内激光传输的气体热效应

 借助现有的流体力学分析软件,运用用户自定义函数的方式,建立了一套完整的光场流场耦合相互作用仿真模型。针对一种特殊的激光内传输通道,对光场流场耦合相互作用的气体热效应问题进行了仿真计算。仿真结果表明:通道内气体速度分布是非常不均匀的,但在无激光加热时,气体密度基本保持均匀分布;将激光加热效应引入到流场以后,气体密度分布会发生明显变化;激光加热引起的气体非均匀密度分布使得激光通过传输通道后,产生双鱼眼型结构的光场相位分布。     

微型法拉第筒阵列束流均匀性测量

研制了一种用于测量强流脉冲电子束束流均匀性的微型法拉第筒阵列,其直径为22mm,由5个微型法拉第筒组成,最大可测束流密度为38A/mm2。利用该系统测量了二极管阳极靶面的束流密度,得到了阳极靶面束流均匀性的分布情况。结果显示,阳极靶面中心处束流密度高于靶面其他位置,靶面束流存在弱箍缩,束流局部均匀,大面积不均匀,束流密度呈径向分布。该结果与理论预期和仿真计算符合较好。     

谐振子势与高斯势的联合势阱中两分量旋转玻色爱因斯坦凝聚体的基态特性和自旋纹理

研究了两分量旋转玻色爱因斯坦凝聚体在谐振子势与高斯势的联合势阱中的基态特性和自旋纹理。通过托马斯-费米近似得到每组分凝聚体在相混合态时密度分布首次形成中心洞的临界旋转角频率,并根据旋转角频率与临界旋转角频率的关系,给出了两分量凝聚体的三种不同的基态密度分布:两个都是盘、一个是盘和另一个是环、两个都是环。对于相分离的情况,针对两分量粒子数严重不平衡的凝聚体分别作托马斯费米近似,解析地给出了两分量凝聚体的两种对称基态密度分布。同时研究了凝聚体在两分量的界面处形成的两种赝自旋纹理,它们分别是巨斯格明子和同轴双环斯格明子。     

晶种分布对氧化锌纳米棒生长的影响

采用水热法在氧化锌晶种修饰的衬底上生长氧化锌纳米棒,利用扫描电子显微镜(SEM)和X射线衍射仪(XRD)系统地分析了晶种分布状态对氧化锌纳米棒排列的影响.SEM结果表明随着晶种密度的增大,氧化锌纳米棒从排列无序向具有高度取向的紧密有序纳米棒阵列转变,反映纳米棒端面垂直生长优化;XRD表征显示,随着晶种密度的增大,(002)峰增强,(110)峰减弱,即端面衍射增强,侧面衍射减弱,与SEM结果相对应.同时在生长的氧化锌纳米棒中存在链状和花状的簇结构,分析表明这些簇结构与晶种在衬底上的特殊分布状态有关.     

气体靶密度的数值计算与实验研究

 采用了1维简单模型来模拟气体靶的空间密度分布情况，并且该计算值得到了实验的验证。使用M-Z干涉仪诊断锥型喷嘴喷射的气体靶密度分布，得到了不同压力和不同延时下的干涉图样。自行编写了实验数据处理程序，得到了不同情况下气体密度的空间分布。在相互作用实验中，由气体分子密度随压力的变化，可以确定合适的压力，以获得预期的气体靶密度；由气体分子密度随时间的变化，可以确定激光与气体的作用时刻。     

超短超强激光导引及对电子加速的影响

使用粒子模拟程序对30 fs超短超强激光在均匀与抛物型两种密度分布等离子体中的传输, 以及在稳定传输状态下尾场的电子注入与加速形成的电子能谱进行了模拟与分析. 固定入射激光束斑尺寸, 在(0.4-2)×10¹⁹/cm³等离子体密度范围, 对比分析了归一化峰值强度从1-6范围的激光脉冲在上述两种密度分布等离子 体中传输时激光束斑尺寸的演化, 结果表明抛物型分布的等离子体密度通道能够对超短超强脉冲实现良好的导引, 有利于高能电子加速. 对于较高密度情况,即使在均匀等离子体中依靠相对论自聚 焦等机制也可以实现良好的自导引传输,有利于实验简化以及产生更大电量的加速电子.     

磁化等离子体的鞘层结构

采用流体方法数值研究了斜磁场作用下的等离子体鞘层结构.模拟结果显示磁场对鞘层结构有显著的影响,特别是在磁鞘边界附近离子的密度分布产生了明显的变化.分别讨论了离子垂直入射和斜入射两种情况,当离子斜入射进鞘层时,其运动情况要相对复杂一些.在适当的条件下,洛伦兹力的作用使离子在某些区域产生相对聚集,离子密度分布产生波动. 关键词： 鞘层 等离子体 磁场     

势场中粒子行为的量子计算与模拟

从量子力学的基本原理出发,采用指数差分方法,利用Matlab,模拟了入射不同势场后的粒子密度分布情况.结果表明,改变势场分布及粒子入射方式,粒子密度分布会产生显著变化.该模拟适用面广,可应用于不同的物理问题.     

SiC/C界面辐照性能的分子动力学研究

本文通过分子动力学模拟的方法,研究了5种含不同空间结构的SiC/C界面的材料受辐照后的缺陷分布随时间以及PKA位置的变化关系,并与单质SiC中缺陷分布情况进行对比.利用径向分布函数分析了辐照对界面原子排列情况的影响.研究结果表明,SiC/C界面的抗辐照能力明显低于SiC内部,不同的空间结构对界面缺陷数量存在一定影响.由径向分布函数推得界面区域石墨原子密度高则界面原子排列情况受辐照影响越大.     

锗R8相结构的压力效应及电子性质

 使用第一性原理方法研究了锗R8相在压力下的电子结构。计算基于平面波基组,使用模守恒赝势和局域密度近似。对锗R8相结构参数的压力依赖性也进行了研究,包括晶格常数、伞状角、原子位置参数随压力的变化情况。计算得到的R8相的能带结构表明,锗R8相属于半金属相。对总的态密度和分波态密度进行了分析,并考虑了轨道分布情况,态密度呈现出带边的锐化。同时得到锗R8相的两种不同键的键长随压力的变化情况,并分析了这种变化的起因。     

Determination of Plasma Density Profile and Other Parameters of Cylindrical Plasma Columns with an Electroacoustic Probe

A new diagnostic method based on the excitation of thermal resonances using an electroacoustic probe has been developed to determine the electron density profile and other plasma parameters of a cylindrical warm-plasma column. A coaxial electroacoustic probe is used to excite and detect the dipole and thermal resonances as the plasma density is varied. The electron density profile is expressed functionally in terms of unknown profile parameters. The profile and other parameters of the plasma column are then determined numerically based on some theoretical formulas and experimental results.     

Impact of bias current distribution on the noise figure and power saturation of a multicontact semiconductor optical amplifier

We present an experimental investigation of a multicontact semiconductor optical amplifier. This first-generation device allows for direct control of the carrier density profile along the length of the waveguide. This is used to control the device noise figure, with a minimum value of 5 dB observed at a gain of 15 dB for an optimum carrier density profile. The opposite carrier density profile results in an increase of the power saturation by 3 dB.     

The Study of Fueling Method and Particle Confinement Improvement

Several high performance tokamak operation regimes have been achieved experimentally in the experiments with the peaked density profiles. The regimes include the improved Ohmic confinement in ASDEX, the pellet enhanced performance mode in Alcator-C, and the super-shot mode in TFTR. In these regimes, peaked core density profiles are always existent, and almost always go with the internal transport barriers, these barriers generally produced by sheared radial electric field. In addition to enhance confinement, the peaked density profile is also needed for the optimized fusion reaction rate and alpha heating power in tokamak plasma, and combined peaked density profile and peaked temperature profile, would make the ignition condition easy obtained. It is desirable to seek and analyze the density profile control schemes that effectively lead to density profile peaking in particle transports experimental investigation.     

Particle confinement and density profile behaviour on HL-1M

In this paper the density profile behaviour and the particle confinement operation regime on HL-1M have been studied under the pellet injection (PI), supersonic molecular beam injection (SMBI), gas puffing (GP) and lower hybrid current drive experimental situations. The relationships between density profile, particle confinement time and edge safe factor have been explored. The density profile, which is measured by six-channel far-infrared ray laser interferometer has been analysed by using the peaking coefficient calculation code. Changes of the outward and inward diffusion velocities before and after the peaking of the central density profile have been calculated using the global particle balance equations. The particle confinement operation regimes have been discussed. The peaking density profile can be easily obtained under the condition of efficient fuelling. In ohmic discharges, confinement time increases as the peaking density profile factor rises, and is saturated at a critical value related to the fuelling efficiency. The particle confinement time of SMBI lies between the values of GP and PI, and its value is about 3-5 times of the energy confinement time.     

强激光辐照非均匀等离子体引起临界点密度变陡

本文在临界密度区域内激光场趋于零的假设下,系统地研究了由强激光辐照非均匀等离子体引起临界密度变陡的现象,给出了较为精确、完备的描述等离子体密度结构的各种参数和等离子体密度的坪台结构。     

共振吸收的自洽场结构和密度轮廓分布

 用二维多时标全电磁相对论粒子模拟程序，对斜入射P极化强激光与具有线性密度分布的非均匀等离子体平板相互作用中的共振吸收进行了模拟计算，给出了冕区自洽场的结构和等离子体密度轮廓分布，粒子模拟结果观察到了临界面附近等离子体波的激发、等离子体密度轮廓的变陡和空穴的产生。     

Magnetic field generation via linear conversion of laser radiation into leaking surface waves in laser produced plasmas

The generation of large amplitude (MG) quasi-stationary magnetic fields in a laser produced plasma with density profile steepening in the domain of the critical point is considered. The spatial structure of the generated magnetic fields in this domain is obtained. It is shown that the density profile steepening causes a significant enhancement of the generated magnetic fields with respect to a linear profile. The saturation level of the generated magnetic fields is evaluated.     

Determination of nonneutral plasma microstate from synchrotron radiation measurements

The spectrum of the synchrotron radiation emitted from the University of Maryland mirror confined nonneutral plasma is measured during the decay of the pulsed magnetic field and used to obtain the energy distribution ?(γ) and electron density profile n_e⁰(r). One result is that the electron density profile evolves from a relatively thin E-layer to a broad profile with density build-up on axis.     

On the summation of the virial expansion for the local density of a gas in contact with a solid

We investigate the density profile of a fluid in contact with a wall. Our analysis is based on the summation of the virial expansion for the local density and the resulting integral equation for the density profile involves the two particle direct correlation function of a non-uniform fluid.     

Scattering length density profile of Ni film under controlled corrosion: A study in neutron reflectometry

We report the density depth profile of an as-deposited Ni film and density profile for the same film after controlled electrochemical corrosion by chloride ions, measured by unpolarized neutron reflectometry. The neutron reflectometry measurement of the film after corrosion shows density degradation along the thickness of the film. The density profile as a function of depth, maps the growth of pitting and void networks due to corrosion. The profile after corrosion shows an interesting peaking nature.