一种高温超导薄膜临界电流密度感应法无损测量装置

A nondestructive inductive measuring device for critical current density determination in high temperature superconducting film

临界电流密度(Jc)是超导薄膜、块材、带材等材料的基本性能参数,决定了超导器件及设备的性能和稳定性,简易、准确的无损Jc测量方法对超导材料特性研究及超导器件的性能保障具有重要意义。本文介绍一种基于三次谐波测量的高温超导薄膜局部临界电流密度测量方法和测量装置。研究显示,在一定幅值的初级线圈交流磁场激励下,Ⅱ型超导体会产生非线性响应,通过分析次级线圈中三次谐波分量的幅值变化,可以推算超导体的局部临界电流密度。我们搭建了一套基于此原理、适用于液氮条件的测量装置。通过对比实验,对测量的准确性进行了验证,尤其针对微弱的微纳伏量级被测信号,采取了必要的噪声抑制措施,并通过对测量数据的校正,提高了测量的准确度。实验研究显示,基于三次谐波测量的方法对于超导薄膜的临界电流密度的测量准确度较高,进行误差修正后,测量装置的误差小于10%。超导薄膜感应法测量装置的搭建十分方便,而且应用灵活,对于大面积超导薄膜的临界电流密度分布测量具有十分显著的优势。

The critical current density （Jc） is one of the most important parameters of the high temperature superconducting films, bulks and tapes, determining the superconducting performance and stability of relevant devices and systems. Simple and accurate measurements of Jc are very important for material research and quality assurance of superconducting devices. In this paper, a nondestructive inductive measuring device based on third harmonic voltage measurements for Jc determination in high temperature superconducting films was introduced. Nonlinear response of the type - Ⅱ superconducting films could be observed when an AC magnetic field was applied to excite it. Then the Jc could be calculated by analyzing the third harmonic voltage of the response signal. A system based on this method was built and tested. The results were compared with traditional measurement method. Noise suppression and data correction were taken for accurate measurements of the weak output signal as well. The measurement demonstrates that there is a high accuracy for Jc measurements using our device, a measuring error smaller than 10% can be obtained. This inductive measuring device is easy to build and very convenient for laboratoryresearch use, offering a useful way for Jc distribution measurements of high temperature superconductorlarge - area films.