Effects of q-profiles of a weak magnetic shear on energetic ion excited q=1 mode in tokamak plasmas

In this paper, we study the effect of safety factor profiles, particularly with a very weak magnetic shear, on the m/n = 1mode excited by energetic ions in tokamak plasmas. It is found that the profile plays a significant role in the onset of the mode, and the thresholds for the instability are also derived. The numerical results for configurations with conventional or reversed non monotonic magnetic shears are discussed. The effects of radial location of rational surfaces, edge q value, and flatness of q-profile on the energetic ion excited mode are further analyzed in detail.     

离子对电磁波传播特性的影响

对等离子体中电磁波传播的平板几何模型进行了修正, 讨论了离子对电磁波在大气压均匀非磁化弱电离等离子体中的反射、吸收和透射等传播特性的影响。数值分析的结果表明: 大气条件下, 离子对电磁波在均匀非磁化弱电离等离子体中传播特性的影响是显著的, 同时给出等离子体对电磁波的最大吸收值和吸收宽带。     

静电近似下抛物形电导率模型电弧的螺旋不稳定性

在静电近似下,给出了圆柱等离子体中电弧放电螺旋不稳定性的一个简化线性分析,得到了显式解析解,由这个解能给出稳定性判据及不稳定性增长率等定量结果,在外加均匀磁场情况下,理论结果与实验观测结果符合得很好。     

面向磁约束聚变实验的先进中子发射谱仪诊断的研究

本文评述了EAST和HL－2A托卡马克装置上开展的聚变发射中子谱仪研究的进展．面向等离子体物理研究和ITER装置中子诊断技术发展的最新需求,针对EAST和HL-2A托卡马克装置的低中子产额（10^9-10^11s^-1）场,设计和发展了全数字化的液体闪烁谱仪和芪晶体中子谱仪．进行了EAST和HL-2A放电实验聚变中子产额随时间演化规律的研究,开展了HL-2A装置上NBI辅助加热效果的评估和EAST聚变等离子体锯齿震荡的中子通量诊断．使用液体闪烁谱仪和芪晶体中子谱仪测量实现了EAST放电的芯部聚变离子温度诊断,首次将托卡马克装置实验中子能谱直接诊断离子温度的下限推到1keV以下．在EAST装置上建设的双环式球形阵列中子飞行时间谱仪将为托卡马克装置辅助加热和快离子物理研究打下坚实的基础．     

Optimizing bowtie structure parameters for specific incident light

We investigate optical properties of a bowtie-shaped aperture using the finite difference time domain method to optimize its geometric parameters for specific incident lights.The influence of the parameters on local field enhancement and resonant wavelength in the visible frequency range is numerically analysed.It is found that the major resonance of the spectrum is exponentially depended on the bowtie angle but independent of the whole aperture size.The simulation also demonstrates that increasing the aperture size raises the local field intensity on the exit plane due to an enlarged interaction area between the light and the metal medium.And the near-field spot size is closely related to the gap.Based on these results,the design rules of the bowtie structure can be optimized for specific wavelengths excited.     

Excitation of chorus-like waves by temperature anisotropy in dipole research experiment (DREX): A numerical study

Due to their significant roles in the radiation belts dynamics, chorus waves are widely investigated in observations,experiments, and simulations. In this paper, numerical studies for the generation of chorus-like waves in a launching device,dipole research experiment(DREX), are carried out by a hybrid code. The DREX plasma is generated by electron cyclotron resonance(ECR), which leads to an intrinsic temperature anisotropy of energetic electrons. Thus the whistler instability can be excited in the device. We then investigate the effects of three parameters, i.e., the cold plasma density nc, the hot plasma density nh, and the parallel thermal velocity of energetic electrons, on the generation of chorus-like waves under the DREX design parameters. It is obtained that a larger temperature anisotropy is needed to excite chorus-like waves with a high nc with other parameters fixed. Then we fix the plasma density and parallel thermal velocity, while varying the hot plasma density. It is found that with the increase of nh, the spectrum of the generated waves changes from no chorus elements, to that with several chorus elements, and then further to broad-band hiss-like waves. Besides, different structures of choruslike waves, such as rising-tone and/or falling-tone structures, can be generated at different parallel thermal velocities in the DREX parameter range.     

Numerical Simulation on Expansion Process of Ablation Plasma Induced by Intense Pulsed Ion Beam

We present a one-dimensional time-dependent numerical model for the expansion process of ablation plasma induced by intense pulsed ion beam （IPIB）. The evolutions of density, velocity, temperature, and pressure of the ablation plasma of the aluminium target are obtained. The numerical results are well in agreement with the relative experimental data. It is shown that the expansion process of ablation plasma induced by IPIB includes strongly nonlinear effects and that shock waves appear during the propagation of the ablation plasma.     

全场热源分析方法及其在实验固体力学研究中的应用

金属材料在塑性变形及疲劳过程中均伴随着能量的耗散,耗散能的大小与分布可充分反映材料内部的应力应变状态与损伤程度。全场热源分析方法借助于红外热成像技术,通过建立合适的热传导模型将由实验获取的温度场转化为热源信息,进而实现对耗散能的估值。本文介绍了基于实验力学的全场热源分析方法,建立从二维到"零维"的热传导模型,解决由温度场到热源的计算反求问题;然后利用该方法针对三种典型的固体力学问题展开研究,包括应力集中效应、塑性失稳现象以及疲劳问题。研究结果表明,全场热源分析方法可有效表征非均匀变形过程及疲劳损伤。     

磁场中等离子体鞘层的结构

采用流体力学理论，研究了斜磁场作用下的等离子体鞘层结构.在不同大小及方向的磁场作用下，对鞘层的离子，电子密度分布，离子流速度分布，电势分布和Bohm判据进行了讨 论.结果显示磁场对鞘层的结构有明显的影响.在静电力和洛仑兹力的作用下，离子流作螺旋进动，离子密度分布产生振荡. 关键词： 磁鞘 等离子体 磁场