高温超导量子干涉器磁测量中的电磁反演

基于Biot-Savart定律和空间滤波技术,采用二维傅里叶变换,研究磁场到电流的反演. 对高温超导量子干涉器(SQUID)测得的载流导线周围的磁场分布以及圆孔缺陷周围的涡流场激发的磁信号进行反演处理,并对所得的结果,特别是在傅里叶空间对截止频率的选择进行了初步探讨. 结果表明,较高的截止频率值能有效提高反演结果的空间分辨率,但增加了噪声信号对反演结果的影响;相对较低的截止频率值能更明显地去除噪声信号,同时导致反演结果的失真,降低了反演结果的空间分辨率. 利用缺陷周围的磁场数据反演出的电流分布,能够准确反映出被测样品中缺陷的位置、形状等基本情况.

Magnetism-current inverse in high-temperature superconducting quantum interference device magnetic field measurement

Based on the Biot-Savart law,spatial filtering technology and two-dimensional Fourier transform,the inverse problem of magnetic field to current distribution was researched.The inverse method was applied to the real magnetic field data measured by a high-temperature superconducting quantum interference device(SQUID),and the magnetic field was produced by a lead with current and vortex around a columniform crack.The inverse results,especially how to select the filtering frequency in a Fourier space,were discussed.The results show that a larger cutoff frequency can improve the spatial resolution of the current image,but increase the noise signal.If a smaller cutoff frequency is selected,much of the noise can be eliminated,but the resulted inverse signal will be anamorphic,and the spatial resolution is decreased.Using the magnetic field data excited by vortex around a column form defect,the inversed current result can give the information about the location and the form of the defect exactly.