一种基于电流频率变换法的微弱电离电流测量电路

<正>一般将nA量级及以下的电流信号称为微弱电流信号,电离辐射探测中常需开展微弱电离电流测量。微弱电离电流的测量因待测信号极其微弱需克服各类干扰源的影响,同时需达到较宽的测量范围,故具有较大挑战。为完成辐射防护用电离室输出微弱电流信号的测量,设计了一款基于电流频率变换法的宽量程微弱电离电流测量电     

宽量程fA级电离室电流测量

针对辐射探测中电流电离室输出电流十分微弱,且电流范围较宽,模拟电路处理困难,难以达到精确测量等问题,设计了可检测nA级到fA级的宽量程电流电离室微弱电流计.提出了以高精度前置放大电路、高分辨率模数转换为基础,从电气隔离、恒温控制、电磁屏蔽等方面,解决模拟处理电路微弱信号易受温度漂移、湿度、电磁干扰影响等问题的方法,从而...     

长时间电流积分数字仪的设计

本文介绍的长时间电流积分数字仪,是用电流-频率(I-F)转换电路将微弱电流转换成脉冲信号,结合后级脉冲计数器及处理控制电路,实现对10pA-10μA量级输入电流的长时间测量。该仪器可用于电离室、法拉第筒等输出电流或电荷的测量,测量时间范围1s-192h。该电路的设计实现,为长时间测量电流或电荷,并进行束流监测提供了一种可行、通用、高性价比的好方法。     

微型反应堆宽量程电流数据采集系统

设计了1套用于微型中子源反应堆(简称微堆)中子信号的宽量程微电流数据采集系统,用于微堆物理实验的监测。系统中使用具有极低偏置电流的斩波稳零运算放大器作为主放大器、数据选择器作为增益切换的主要器件、C8051FXXX系列片上系统(SoC)中的020作为ADC和控制芯片。其电流检测范围为10-11～10-6 A,分为6个量程,各量程间自动切换,能通过串口与PC通讯。在原型微堆上验证了设计的正确性。     

高性能微电流集成放大器的设计

介绍了用ICL7650运算放大器设计高性能微电流集成放大器的方法,阐述了电路的工作原理和提高放大器性能的措施,给出了实际应用的实验结果。该放大器测量范围10^-9～10^-12A,自换量程,自动校零,测量准确,工作稳定。     

新型微弱电流检测前置放大电路设计

针对常规微弱电流测量电路输入信号范围窄和微弱电流信号容易淹没在背景噪声、元器件固有噪声、电源噪声等干扰中而影响测量结果正确性问题,设计了一种新型微弱电流检测前置放大电路。该设计在分析常规跨阻抗法、对数压缩法前置放大器优缺点的基础上,通过改进设计电路和增加开关消噪电路,加宽了输入电流的测量范围、降低了检测系统的噪声影响、提高了检测速度。实验表明该电路具有较强的噪声抑制能力和较高的检测精度,有一定的实用价值。     

n-γ电离室输出电流测量中I-F变换器的设计

介绍了一种用在辐射剂量仪中，对极微弱的电流信号进行放大测量的电路，并对其实现方案及各部分的特殊要求进行了详细的讨论。     

束流均匀性测量前端读出电子学电路的设计

针对重离子治癌中的束流监测需要,用T型反馈电阻网络组成的电流-电压转换(IVC)电路将大面积二维位置灵敏平行板雪崩探测器( PPAC)输出的多路10pA～100 nA的微弱电流转换成-2V～-20 mV的电压信号,配合数据获取处理系统实现了近代物理研究所重离子治癌中的束流均匀性测量.实验表明该电路具有速度快、精度高等优...     

数字化PWM技术在电流传感器中的运用

提出了利用DSP实现PID控制,结合DSP芯片内部定时器模块产生PWM信号,最后由该信号通过反馈电路产生相应的补偿电流,根据被测电流与补偿电流的安匝比关系即可得到待测电流值。经过实验测试,该设计可用于交直流信号测量。研究证明,该技术使新型电流传感器具有高稳定性。     

双脉冲法精确测量PMT脉冲线性电流的实验设计

PMT脉冲线性电流是PMT在脉冲工作方式下的重要参数,它直接关系到实验结果的可靠性。本文对比各种测量PMT脉冲线性电流方法的优缺点,从提高测量精度方面考虑,设计了基于双脉冲法的测量PMT脉冲线性电流的实验,通过挑选稳定性高的LED作为光源,利用DG2020信号发生器给LED灯供电,采用通道循环功能加长信号时间间隔,使用分路输出到两台示波器接收信号,应用示波器多次采集自动取平均的功能等方法在实验细节上进行设计,提高测量精度。通过实验测到了PMT脉冲输出电流偏离线性直线1%处的电流,并获得了PMT脉冲输出的mA级至A级电流全曲线。     

弱电流测试仪的研制

介绍了最近研制的弱电流测试仪，它的原理和设计要点。该仪器是一 便携式弱电流测试仪，可以测量10^-10-10^-4A范围的弱小电流。该仪器具有测量精度高、工作稳定、结构简单、便携等优点。     

穆斯堡尔谱学现状

穆斯堡尔谱学已成为了解原子核与其周围环境间超精细相互作用的重要方法。本文介绍了穆斯堡尔谱学方法的特点及近年来在方法学和应用方面的进展。最后展望了穆斯堡尔谱学的将来。     

A novel fault current limiter topology design based on liquid metal current limiter

The liquid metal current limiter (LMCL) is regarded as a viable solution for reducing the fault current in a power grid. But demonstrating the liquid metal arc plasma self-pinching process of the resistive wall, and reducing the erosion of the LMCL are challenging, not only theoretically, but also practically. In this work, a novel LMCL is designed with a resistive wall that can be connected to the current-limiting circuit inside the cavity. Specifically, a novel fault current limiter (FCL) topology is put forward where the novel LMCL is combined with a fast switch and current-limiting reactor. Further, the liquid metal self-pinch effect is modeled mathematically in three dimensions, and the gas-liquid two-phase dynamic diagrams under different short-circuit currents are obtained by simulation. The simulation results indicate that with the increase of current, the time for the liquid metal-free surface to begin depressing is reduced, and the position of the depression also changes. Different kinds of bubbles formed by the depressions gradually extend, squeeze, and break. With the increase of current, the liquid metal takes less time to break, but breaks still occur at the edge of the channel, forming arc plasma. Finally, relevant experiments are conducted for the novel FCL topology. The arcing process and current transfer process are analyzed in particular. Comparisons of the peak arc voltage, arcing time, current limiting efficiency, and electrode erosion are presented. The results demonstrate that the arc voltage of the novel FCL topology is reduced by more than 4.5 times and the arcing time is reduced by more than 12%. The erosions of the liquid metal and electrodes are reduced. Moreover, the current limiting efficiency of the novel FCL topology is improved by 1%‒5%. This work lays a foundation for the topology and optimal design of the LMCL.     

微秒脉冲电流的测量

简要介绍Ｒｏｇｏｗｓｉｋ线圈的测量原理,给出了测量系统的构成和测量结果,测量结果表明,采用谐振逆变电源作充电器和采用流管作放电回路主开关,使得脉冲发生器具有脉冲放电幅度晃动小等优点。     

High current superconductors for DEMO

In the assumption that DEMO will be an inductively driven tokamak, the number of load cycles will be in the range of several hundred thousands. The requirements for a new generation of Nb₃Sn based high current conductors for DEMO are drafted starting from the output of system code PROCESS. The key objectives include the stability of the DC performance over the lifetime of the machine and the effective use of the Nb₃Sn strand properties, for cost and reliability reasons. A preliminary layout of the winding pack and conductors for the toroidal field magnets is presented. To suppress the mechanism of reversible and irreversible degradation, i.e. to preserve in the cabled conductor the high critical current density of the strand, the thermal strain must be insignificant and no space for micro-bending under transverse load must be left in the strand bundle. The “react-and-wind” method is preferred here, with a graded, layer wound magnet, containing both Nb₃Sn and NbTi layers. The implications of the conductor choice on the coil design and technology are highlighted. A roadmap is sketched for the development of a full size prototype conductor sample and demonstration of the key technologies.     

An active-passive beam current transformer

In this article, a new type current transformer was developed using an active-passive circuit to improve low frequency response of the system without impairing high frequency response. The active-passive current transformer with In-flange was fabricated. Theoretical analysis, numerical simulations and experimental results are given.     

Some current problems in beam-foil spectroscopy

The use of tilted foils to produce alignment and orientation excitation asymmetries in fast ion beams is reviewed. These asymmetries, their observed dependence on various experimental parameters (ion energy, foil tilt angle, observation geometry, etc.) and their utilisation for the study of atomic and nuclear structure properties are discussed. In addition, measurements are described that utilise differential decay curve measurements to suppress cascade effects and to determine decay rates into forbidden or inhibited radiative and autoionising intercombination channels.