初级试验平台磁绝缘传输线的电路模拟

 初级试验平台磁绝缘传输线的电路模拟描述了电压脉冲从水传输线、绝缘堆、内外磁绝缘传输线到丝阵负载的传播及作用过程。在模拟中将脉冲传输经过的所有电路结构,等效成具有不同电长度及阻抗的273个传输线单元,其中包括195个磁绝缘传输线单元;通过计算得到了各个传输线单元的传导电流、界面电压,磁绝缘传输线单元的损失电流、流动阻抗、接地电阻,以及丝阵负载内爆过程中的半径变化、电流及电压等,并对主要计算结果进行了分析比较。模拟结果的可靠性及精度有待于相关实验结果的检验。     

EAST离子回旋加热天线传输线结构设计

阐述了EAST离子回旋加热天线传输线的结构设计。用有限元的方法对EAST离子回旋加热天线传输线内导体结构进行了分析,获得了内导体的受力情况。根据内导体的受力情况适当加大波纹管厚度和设计内导体支撑,通过ANSYS分析优化确定了波纹管的厚度和内导体布置的位置。此外,还计算了传输线的热损耗、热变形、电压驻波系数和最大功率容量,计算结果进一步验证了传输线结构的可行性。     

Design parameters of stainless steel plates for maximizing high frequency ultrasound wave transmission

This work validated, in a higher frequency range, the theoretical predictions made by Boyle around 1930, which state that the optimal transmission of sound pressure through a metal plate occurs when the plate thickness equals a multiple of half the wavelength of the sound wave. Several reactor design parameters influencing the transmission of high frequency ultrasonic waves through a stainless steel plate were examined. The transmission properties of steel plates of various thicknesses (1–7 mm) were studied for frequencies ranging from 400 kHz to 2 MHz and at different distances between plates and transducers. It was shown that transmission of sound pressure through a steel plate showed high dependence of the thickness of the plate to the frequency of the sound wave (thickness ratio). Maximum sound pressure transmission of ∼60% of the incident pressure was observed when the ratio of the plate thickness to the applied frequency was a multiple of a half wavelength (2 MHz, 6 mm stainless steel plate). In contrast, minimal sound pressure transmission (∼10–20%) was measured for thickness ratios that were not a multiple of a half wavelength. Furthermore, the attenuation of the sound pressure in the transmission region was also investigated. As expected, it was confirmed that higher frequencies have more pronounced sound pressure attenuation than lower frequencies. The spatial distribution of the sound pressure transmitted through the plate characterized by sonochemiluminescence measurements using luminol emission, supports the validity of the pressure measurements in this study.     

Enclosed laser ablation of 20 nm aluminium films using a continuous wave diode laser: II—Theoretical heating considerations and proposed mechanisms

Laser ablation using a 120 W continuous wave diode laser was carried out upon a thin aluminium layer which had been hermetically sealed between two layers of polymer. The results (presented in Part I) have shown that the film could be partially transparentised but with an efficiency which was far less than that seen for a Q-switched laser. In this paper, the thermal effects within the films are analysed and a mechanism by which enclosed surface laser ablation occurs is proposed.     

Generation of short electrical pulses and millimeter wave oscillations on a resonant tunnel diode nonlinear transmission line

Nonlinear wave propagation effects on a resonant tunnel diode nonlinear transmission line are considered. It is shown by computer experiments that this line can be used for short electrical pulses generation as pairs kink–antikink structures, as well as millimeter wave oscillator.     

磁绝缘传输线实验用电阻分压器型大功率负载设计

研制了一种用于磁绝缘传输线（MITL）实验的分压器型大功率水电阻负载,其阻值可在2.0~14.0 变化。利用MATLAB系统辨识工具箱和ANSYS电磁分析模块,分别获取了分压器的系统传递函数和沿面电场分布,给出了其幅频响应特性和沿面闪络可靠性分析,负载设计充分考虑了集肤效应和温升的影响。该负载已用于强光一号1.0 m长MITL特性研究实验,并获得了较好的测量波形,在负载阻值2.1 条件下,负载峰值电压为1.2 MV,峰值电流为494.4 kA,峰值时间约125 ns。将实验测量结果同TLCODE计算结果进行了对比,获得了较为一致的对比结果。     

磁绝缘传输线实验用电阻分压器型大功率负载设计

研制了一种用于磁绝缘传输线（MITL）实验的分压器型大功率水电阻负载,其阻值可在2.0~14.0 变化。利用MATLAB系统辨识工具箱和ANSYS电磁分析模块,分别获取了分压器的系统传递函数和沿面电场分布,给出了其幅频响应特性和沿面闪络可靠性分析,负载设计充分考虑了集肤效应和温升的影响。该负载已用于强光一号1.0 m长MITL特性研究实验,并获得了较好的测量波形,在负载阻值2.1 条件下,负载峰值电压为1.2 MV,峰值电流为494.4 kA,峰值时间约125 ns。将实验测量结果同TLCODE计算结果进行了对比,获得了较为一致的对比结果。     

基于人工传输线的小型微带Wilkinson功分器

提出了一种基于人工传输线的小型微带Wilkinson功分器,该器件使用由LC元件构成的人工传输线取代传统传输线,并使用交指电容和贴片电阻进行端口隔离。设计制作的Wilkinson功分器中心频率为915MHz的微带3dB功分器,等幅同相地将输入功率分配到2个输出端口,尺寸仅有传统Wilkinson功分器的25%,端口幅度平衡度±0.2dB,相位平衡度±1°。实验结果表明:功分器带宽为0.49～1.20GHz,插入损耗小于3.2dB,回波损耗大于10dB,仿真结果和测量结果吻合较好。     

Design considerations for a fibre-optic based polarimeter

A polarization modulation technique is presented which utilizes the manipulation of a wide band, incoherent source. An application to the measurement of sugar concentration is described. A conceptual fibre-optic sensor, based on the technique, is discussed. Particular attention is given to the design of a dielectric multilayer filter which will provide the means of dividing the spectrum into polarized and unpolarized components with the latter being used to calibrate the former.     

Transition edge sensor system for material analysis using transmission electron microscope

We have developed a Transition Edge Sensor (TES) – Energy Dispersive Spectroscopy (EDS) for Transmission Electron Microscope (TEM) based on a dilution refrigerator. The dilution refrigerator was cooled by liquid helium (L-He), which was supplied from an L-He container separated from the dilution refrigerator. We adopted the hybrid magnetic shields combining a permalloy shield and a NbTi/Nb/Cu superconducting shield to operate the TEM–TES system under a magnetic field of 200 mT. The permalloy shield was used to prevent the ambient magnetic field until the NbTi superconducting shield cooled from room temperature (RT) to 2 K. The critical magnetic field was 220 mT for the TES change from a superconducting state to a normal state. The SQUID – current vs. bias current curve, under the condition that the snout was inserted in the TEM, was equal to the curve of the snout that was out of the TEM. The C (0 0 2) planes could be observed at 120 kV under the condition the snout was inserted in the TEM.     

激光二极管高效铜微通道冷却器设计

通过对铜微通道冷却器的散热分析,设计出５层结构的模块式铜微通道冷却器。采用常规的线切割工艺加工,散热通道宽大约200μm,深300μm,各层间用真空钎焊的方法组装。该冷却器对于腔长06mm、宽10mm的线阵激光二极管芯片热阻为0.58℃/W。通过面阵激光二极管封装实验证明,该冷却器可用于10％占空比工作的面阵激光二极管封装。     

磁绝缘传输线电压测量用自积分式电容分压器研制

研制了一种用于磁绝缘传输线（MITL）电压测量的自积分式电容分压器;利用PSpice软件和标定实验数据,建立了该分压器等效电路模型,给出了分压器系统传递函数,并分析了分压器频率响应特性。计算结果表明:该分压器对于被测信号大于5 MHz频率分量部分的相频和幅频响应无明显畸变。基于强光一号长1.0 m、阴阳极间隙2 cm的同轴型MITL实验平台对该分压器实际工作性能进行了考核。实验结果表明,在相对少量场致发射电子抵达阳极表面的条件下,该分压器能够有效测量MITL沿线电压波形（2.07 负载条件下,电压峰值约600 kV、峰值时间约80 ns）。     

分析端接频变负载的多导体传输线FDTD新方法

提出了一种新的有效求解端接频变负载的时域有限差分法（FDTD）.该方法将频域导纳经矢量匹配后以有理式表示,通过逆傅里叶变换将其转换到时域,基于分段线性递归卷积法,推导出该导纳两端的电压和电流关系,将其代入到传输线FDTD模型中,得到了求解端接频变负载多导体（MTL）传输线FDTD的一般公式.对一典型电路进行了仿真,和以状态变量法求解任意负载的结果进行了对比,两者基本重合,说明该方法用来求解频变负载是有效的. 关键词： 多导体传输线 分段线性递归卷积 时域有限差分法 任意负载     

共顶点同轴圆锥形及圆盘形传输线的电参数计算公式

 用安培环路定理、高斯定理推导了共顶点同轴圆锥形及圆盘形两种重要的理想传输线电参数的计算公式，给出了电场、电感、电容及阻抗的解析表达式或数值求解方法；用实例验证了推导的公式和介绍的方法；应用验证后的公式或方法对一个设计进行了估算，得到了合理的结果。     

一种陶瓷径向绝缘强流二极管耐压结构设计

 对外径230 mm的陶瓷绝缘板,依据强流真空二极管径向绝缘的设计思想,设计加工了“锥-柱”型阳极外壳,并在传输线内筒和阴极杆末端位置增加了均压罩和屏蔽环结构。利用静电场有限元程序计算了陶瓷-真空界面电场分布,通过对外壳细节结构以及均压罩、屏蔽环形状和位置的调整,使得真空界面上沿面场强和三结合点处场强均得到了有效控制。在单线长脉冲加速器上进行了实验研究,结果显示,二极管能够耐受400 kV、脉宽大于200 ns的脉冲电压,运行稳定,达到了理论设计要求。     

一种陶瓷径向绝缘强流二极管耐压结构设计

对外径230 mm的陶瓷绝缘板,依据强流真空二极管径向绝缘的设计思想,设计加工了“锥-柱”型阳极外壳,并在传输线内筒和阴极杆末端位置增加了均压罩和屏蔽环结构。利用静电场有限元程序计算了陶瓷-真空界面电场分布,通过对外壳细节结构以及均压罩、屏蔽环形状和位置的调整,使得真空界面上沿面场强和三结合点处场强均得到了有效控制。在单线长脉冲加速器上进行了实验研究,结果显示,二极管能够耐受400 kV、脉宽大于200 ns的脉冲电压,运行稳定,达到了理论设计要求。     

Moiré fringes as two-dimensional autocorrelation of transmission function of linear gratings and its application for modulation transfer function measurement

In this work, we show that the transmission moiré pattern is two-dimensional autocorrelation of transmission function (2D-ACTF) of two superimposed linear gratings that make a small angle with each other. In this approach, the properties of moiré fringes vs. the relative displacement of the gratings are formulated. By measuring 2D-ACTF of two similar gratings, we evaluate the modulation transfer function (MTF) of the gratings’ generating system. This work is the generalized form of our previous works. The implied MTF measurement method is easier and faster than our previous methods.     

Design considerations for SERS detection in colloidal solution: reduce spectral intensity fluctuation

The intensity fluctuation of surface‐enhanced Raman scattering (SERS) has seriously hampered its practical applications. The previous studies that involved SERS intensity fluctuation mostly focus on the assembled substrates or single molecule and single nanoparticle but have few attention on colloidal solutions containing numerous molecules and/or nanoparticles. Here, we studied the time‐elapsed SERS spectra of three different analytes in colloidal solution. Their peak intensities fluctuated simultaneously and uniformly throughout the acquisition process and had no correlation with their wavenumber wandering. Gravity‐induced inhomogeneous distributions of Ag nanocubes in solution led to the spatial and temporal variations of peak intensities, which could be reduced by altering the integration time, particle concentration, and solvent viscosity and density. Furthermore, the dissimilar interactions between analytes and Ag nanocubes showed non‐detectable influence over their intensity fluctuations. This investigation gives out the significant guidance for SERS detection in colloidal solution. Copyright © 2015 John Wiley & Sons, Ltd.     

冷却塔风机传动轴断裂监控系统设计

为解决冷却塔风机传动轴运行过程中断裂甩出的问题,在分析传动轴断裂现象及原因的前提下,提出了在联轴器上安装扇形片,以槽型光电开关为信号采集元件,以可编程控制器为信号处理元件的传动轴断裂监控新方法。利用槽式光电开关反应速度快,不受环境光影响的特点,提高监测的精准性;利用交错的扇形片相互旋转时夹角缝隙对旋转角度的放大作用,将联轴器细微错位放大,提高系统监控的灵敏性。监测系统实现了对传动轴断裂的预先判断,程序控制风机停机报警,保护传动轴及相关设施。     

共顶点同轴圆锥形及圆盘形传输线的电参数计算公式

用安培环路定理、高斯定理推导了共顶点同轴圆锥形及圆盘形两种重要的理想传输线电参数的计算公式,给出了电场、电感、电容及阻抗的解析表达式或数值求解方法;用实例验证了推导的公式和介绍的方法;应用验证后的公式或方法对一个设计进行了估算,得到了合理的结果。