Performance of high-TC SQUID magnetometers for application in biomagnetism

Single layer direct-coupled YBCO SQUID magnetometers have been fabricated and characterized for the purpose of MCG measurements in magnetically disturbed environment. Two types of magnetometers have been designed and fabricated using 10 mm×10 mm substrates. We could operate the conventional 3-mm-wide solid pickup loop magnetometers more stably than the 12-parallel-line pickup loop magnetometers in laboratory environment. We developed a first-order electronic gradiometer system with the SQUID magnetometers with axial displacement of 80 mm without any mechanical alignment of magnetometers. The system with a software filter using calculation of discrete Fourier transform could record clear magnetocardiogram in a weak magnetic-shield-room.