Parameter study for enhanced high gain harmonic generation scheme

An easy-to-implement scheme called Enhanced High Gain Harmonic Generation is expected to be able to significantly enhance the performance of HG-FEL. In this paper we investigate the effects of the system parameters in the new scheme, including the electron energy detuning, initial electron-beam energy spread, seeding laser power, dispersive field strength and amount of the phase shift, etc. The numerical results from GENESIS (3D-code) are presented and show that the new scheme has acceptable parameters tolerance requirements and is no more or even less sensitive to the system parameters than that of the existing scheme; With the electron energy above the resonance, the efficiency is enhanced for both the new scheme and the existing scheme compared with the resonant energy case.     

Application of electric field ionization method to detect the high-lying Rydberg states of Eu I

The 4f~76s(~9S)np 8 P J (J = 5/2, 7/2, 9/2) Rydberg series converging to the first ionization limit 4f 7 6s 9 S 4 of the Eu atom using the three-step laser excitation and electric-field-ionization (EFI) method are studied. First, the Eu atom is excited from the 4f 7 6s 2 8 S o 7/2 ground state to the 4f 7 6s7s 8 S o 7/2 state through the 4f 7 6s6p 10 P 9/2 state by the first two dye lasers. Next, it is populated to many higher-n members of the 4f 7 6s( 9 S)np 8 P J Rydberg series by the third dye laser whose wavelength is scanned within a certain range. Finally, the atom in these higher-n states is ionized by the external pulsed electric field. With the field strength up to 2 kV/cm, we can detect the atom in 4f 7 6s(9 S)np 8 P J states with n 40. With the given laser line width, the level energies of Rydberg states with n as high as 72 can be determined. We not only confirm the previous data on the 4f 7 6s(9 S) np 8 P J Rydberg series, but also extend the n-value assignment significantly by detecting more states.     

均匀磁场中的磁介质之磁化电流确定及场强分析

本文对磁介质磁化特性进行了分析,解释了磁化电流的形成,进一步推导验证了磁化电流与磁化强度、磁感应强度以及磁场强度之间的关系。这是在电磁场理论课程教学实践中总结出的从不同角度解释和分析磁化电流的方法。     

地质力学磁力模型试验磁场梯度研究

地质力学磁力模型试验与离心机模型试验的核心思想类似,都是通过施加外加力场来达到增加试验材料应力水平的目的.本文根据磁性颗粒的磁场力公式,指出磁场梯度为恒定值是磁性材料受力均匀的必要条件之一.根据磁滞回试验测得的磁性材料的磁化强度,推导获得了均匀力场的磁场梯度下限值.采用数值模拟方法,计算了单圆台线圈、两同向电流对接线圈、两反向电流对接线圈这3种磁场生成方案的磁场梯度,比较分析该3种磁场梯度的均匀性,研究表明单线圈磁场生成方案所产生的磁场梯度较均匀且磁场空间较大,因此选择单线圈为磁力模型试验的磁场生成方案.     

基于Comsol Multiphysics的新型高压直流继电器电弧仿真分析

传统直流电磁继电器采用电磁驱动方式，分断间距为2~3 mm，在工作负载增大时需增加线圈匝数，导致继电器质量增加、灭弧难度增大。为解决上述问题，采用微电机蜗轮蜗杆作为驱动机构、分断间距相比传统电磁继电器大数倍的新型高压直流继电器设计方案，并利用多物理场耦合软件Comsol Multiphysics，基于磁流体动力学（MHD）理论建立了直流继电器的二维电弧仿真模型。考虑到分断间距、电流、磁场强度以及分断速度等条件对电弧的影响，分析了不同上述条件下电弧的运动特性，得到了适定参数下较为合理的间距、工作电流、磁场强度和分断速度，为新型高压直流继电器灭弧系统的结构设计提供参考。     

利用亥姆霍兹线圈测量真空磁导率

采用FD-HM-Ⅰ型亥姆霍兹线圈,利用高灵敏度毫特斯拉计,探测亥姆霍兹线圈公共轴线中点的磁感应强度.通过改变亥姆霍兹线圈中电流的正、反方向,消除了地磁场影响,从而精确测定了真空磁导率.     

声子色散和磁场对极化子基态的影响

采用线性组合算符和幺正变换的方法,得出极化子基态能量与色散系数、耦合强度以及磁场强度之间的关系.数值计算表明：对弱耦合极化子,振动频率λ随磁场强度的增大而单调增大;基态能量E0随磁场强度增大而增大、随耦合系数α增大而单调下降、随色散系数γ增大而减小.对强耦合极化子,基态能量E0随磁场强度增大而增大、随耦合系数α增大而单调下降、与声子色散无关.     

爬壁机器人履带吸盘的多体渐变磁化系统设计

介绍了基于多体渐变磁化系统理论研究设计的有别于传统普通吸盘结构的爬壁机器人履带吸盘结构。根据稀土永磁履带吸盘结构和性能特点， 建立了履带吸盘的简化模型和吸盘与金属壁面间隙工作空间的镜像模型。基于以上模型和稀土永磁体内部磁化强度与均匀分布的特性，推导出间隙工作空间在y方向的磁场强度的多次谐波方程表达式，证明该结构的吸盘比传统普通吸盘有更良好的磁场性能。通过对比实验验证，该履带吸盘的吸力比普通吸盘大得多，完全能满足爬壁机器人爬行性能的要求。     

磁场对水扩散系数影响的分子动力学模拟研究

将水系统视为正则系综，采用分子动力学模拟（Molecular dynamics simulation简称MD）方法对磁场条件下水的扩散系数进行了计算。结果表明水的扩散系数与外加磁场强度的关系是多极值关系，且在B＝0.25T以及常温下磁化效果最为明显；通过对径向分布函数的计算发现：磁处理对水理化性质的影响，主要是由于磁场改变了水的径向分布函数，使水的结构发生变化，从而影响了水的扩散系数，增大了水分子的活性和渗透性。