超导体的交流磁化率测量

本文探讨利用交流磁化率研究超导电性.测量了MgB2样品的若干超导电参量,包括临界温度Tc,上临界磁场Hc2,临界电流密度Jc,不可逆场Hirr等与温度的关系,交流损耗与频率和温度的关系等.此外还简要介绍了交流磁化率在磁通动力学和非线性性质方面的研究方法.     

超导体电输运及交流磁化率双模式测量系统研制

介绍了一种基于小型制冷机的超导转变温度电输运和交流磁化率双模式单腔测量装置。该装置包括电输运法测量和交流磁化率法测量两部分,分别实现对高温超导薄膜样品的超导转变温度的测量。电输运法测量部分利用四点法测量原理对超导薄膜的电阻进行测量,获取电阻随温度变化的曲线;同时利用电流换向法消除热电势带来的测量误差,以进一步提高测量的精度。交流磁化率法测量部分利用的是电磁感应原理和超导磁效应。该部分包含有初级线圈和次级线圈,超导样品放置于两线圈之间。初级线圈用于产生交变激励磁场,次级线圈的输出信号反应了超导样品磁化率的变化,其输出信号由锁相放大器获取。测量过程中使用计算机自动记录测量数据。     

高温超导球的交流磁化率

本按电动力学方法计算了滋事态超导球的交流磁化率，指出交流磁化率在线性响应的热助磁通流情况下的解，其虚部的峰值位置与测量频率的关系Ｔｐ（ｗｐ）可用来确定磁 通     

超导电性的交流磁化率研究

本文综述了交流磁化率在超导电性物理研究方面的进展.主要包括如何用交流磁化率确认超导电性,测定各种超导电参量(临界温度,临界磁场等),研究涡旋物质的强度(临界电流密度,不可逆场等),涡旋动力学(磁弛豫,钉扎能等).     

超导混合态椭球的交流磁化率

本文研究了处于混合态非均匀磁化的高温超导椭球在线性响应区的交流磁化率，给出了不同离心率的非均匀磁化椭球在直流磁场和小交流磁场中的交流磁化率的解析解析阐明了样品几何形状（退磁因子）对交流磁化率的影响文中研究了处于超地椭球的交流磁化率。     

在小型制冷机中测量薄片交流磁化率以决定超导转变温度的装置

本文介绍了一种利用电磁感应原理和超导磁效应,在小型制冷机中测量超导体转变温度的装置.本装置包括密闭的真空室、压缩制冷机、真空泵、真空计、锁相放大器、温控仪、计算机、线圈绕组.其中,线圈绕组置于真空室内,由初级线圈和次级线圈组成,初级线圈和次级线圈分别绕制在两个线圈骨架上;被测超导薄片材料放置于初级线圈和次级线圈之间;压缩制冷机用来为超导材料制冷;真空泵用来对真空室抽真空;温控仪用来测量和控制真空室内的温度;锁相放大器为初级线圈提供交流电压信号,并测量次级线圈的电信号以得到交流磁化率值;计算机记录温控仪测得的温度数据和锁相放大器测得的次级线圈的电压信号,并显示锁相放大器测得的次级线圈的电压信号随温度变化的曲线.实验证明该装置可以通过测量超导体交流磁化率的变化测得超导转变温度,具有自动化测量及测试成本低等特点.     

交流磁化率方法研究磁通钉扎能与电流关系

本介绍如何利用交流磁化率测量高温超导体与电流密度Ｊ，直流场Ｈｄ和温度Ｔ有关的磙通钉能Ｕ。根据磁通扩散理论和随外场变化的交流磁化率虚部ｘ峰温的系统实验研究，就可以得到上述能量函数，对掺Ｐｂ和Ｂａ的ＴｌＳｒ２Ｃａ２Ｃｕ３Ｏｙ超导体的系统交流磁化率的测量和分析得到的结果Ｕ。     

熔融织构的YBCO超导体的交流磁化率频率响应

在涡漩玻璃理论的基础上，我们推导出了交流磁化率的虚部峰值温度和频率的标度方程，可表示为Tp=Cf^1/（v（z-1））．实验结果表明我们的标度方程和实验符合得很好．利用标度方程可以确定样品在磁场下的涡漩玻璃转变温度Tg和指数v（z-1）的数值．     

锁相放大器的新进展

主要介绍了模拟锁相放大器和数字锁相放大器原理、特点、过渡和发展过程.通过数字锁相放大器的硬件的模块化结构、灵活的算法设计、软件的升级能力、应用的范围和特点以及性价比等,说明锁相放大器发展的前景和动力.     

Multiple self-mixing interferometry based on lock-in amplifier analysis for vibration measurement

Optical Review - In this paper, a novel phase demodulation method for multiple self-mixing interferometry (MSMI) is proposed, which can improve the resolution and accuracy of vibration measurement...     

Diode-laser derivative spectroscopy without lock-in amplifier

A derivative spectroscopy allowing the spectrum to be observed in real time at the analogue oscilloscope is developed. A differentiating amplifier is used instead of a lock-in amplifier to obtain the signal proportional to the derivative of the absorption line profile. This approach allows a region of the spectrum to be rapidly identified and the diode-laser spectrometer to be tuned to the strongest absorption line.     

基于锁定放大器的声速测量法

介绍一种用锁定放大器替代示波器确定声波相位,进行声速测量的方法.利用锁定放大器的高灵敏度、高信噪比的特点,能有效地提高实验装置的抗干扰性和测量准确度,被测量对象也可由原单一频率的超声波改变为任意频率的声波.本实验不确定度<5%,若采用更精密的仪器,实验不确定度很容易达到0 5%.     

锁定放大器原理及应用实验的教学探讨

提出了锁定放大器原理实验应以掌握相关检测原理为重点，以观察、分析相敏检波器的相位特性为主要内容的建议，阐述了应用实验内容的选取原则，并设计了两个应用实验方案。     

Nonlinear absorption microspectroscopy of single perylene nanocrystals with a multichannel double lock-in amplifier

Nonlinear confocal absorption microspectroscopy of single nanocrystals at low temperatures was introduced in the study of perylene nanocrystals. By the stationary pump-probe method, single nanocrystals were photoexcited into metastable excited states, and difference absorption spectra due to excited-state absorption and ground-state depletion were simultaneously recorded using a multichannel lock-in amplifier. It was revealed that the free Frenkel exciton band for single perylene nanocrystals is broader in width than that for the bulk crystal at low temperatures, suggesting that the exciton band is inhomogeneously broadened even for single perylene nanocrystals.     

Space-domain lock-in amplifier based on a liquid-crystal spatial light modulator

We present a two-dimensional (2D) spatial lock-in amplifier that provides a contrast ratio of more than 10,000:1 for transmitted and blocked intensity patterns using a conventional liquid-crystal spatial light modulator. The device is based on spatial-domain modulation-demodulation of intensity patterns under coherent imaging conditions. The operation of the 2D lock-in amplifier is illustrated by implementing Young's double-slit arrangement for measurements of the mutual coherence between individual emitters of a 2D phase-coupled array of vertical cavity surface emitting lasers.     

A photoacoustic signal detection technique by using gated vector lock-in amplifier

An electronic gating technique is introduced in photoacoustic signal detection. It eliminates the classical effects of vibrational noise associated with mechanical scanners.

The new system samples the photoacoustic signal only during the time when the mechanical scanner is stationary. The signal is fed into the lock-in amplifier together with the reference signal. The amplifier output corresponding, to the sample characteristics is recorded by the computer during the above interval.

The new technique detects the subsurface features in metals similar to the conventional beam scanning techniques. Comparisons between the two shows that the photoacoustic signal amplitudes were identical for the same sample characteristics.

One outstanding advantage is its low cost relative to the cost of the beam scanners currently available on the market.     

A new measurement method of coatings thickness based on lock-in thermography

Coatings have been widely used in modern industry and it plays an important role. Coatings thickness is directly related to the performance of the functional coatings, therefore, rapid and accurate coatings thickness inspection has great significance. Existing coatings thickness measurement method is difficult to achieve fast and accurate on-site non-destructive coatings inspection due to cost, accuracy, destruction during inspection and other reasons. This paper starts from the introduction of the principle of lock-in thermography, and then performs an in-depth study on the application of lock-in thermography in coatings inspection through numerical modeling and analysis. The numerical analysis helps explore the relationship between coatings thickness and phase, and the relationship lays the foundation for accurate calculation of coatings thickness. The author sets up a lock-in thermography inspection system and uses thermal barrier coatings specimens to conduct an experiment. The specimen coatings thickness is measured and calibrated to verify the quantitative inspection. Experiment results show that the lock-in thermography method can perform fast coatings inspection and the inspection accuracy is about 95%. Therefore, the method can meet the field testing requirements for engineering projects.     

PE-7265型锁相放大器在旁侧光谱实验中的应用

针对He-Ne激光器旁侧光谱实验，开发了PE-7265锁相放大器的RS232，ADC1，ADC2，ADC3及CH1等接口，并将这些接口应用于该实验，得到了较好的实验结果。