Integrated Directly Coupled High-Tc dc Superconducting Quantum Interference Device Magnetometers

• Main Authors: Chen, Jau-Han, 陳昭翰
• Other Authors: Yang, Hong-Chang
• Language: en_US
• Published: 2002
• Online Access: http://ndltd.ncl.edu.tw/handle/48874790620497870493

博士 === 國立臺灣大學 === 物理學研究所 === 90 === The main work of my dissertation is to develop high-Tc dc SQUID magnetometers for biomagnetic applications, especially for magnetocardiography (MCG). The integrated directly coupled dc SQUID magnetometers are developed toward this purpose, because the practical MCG system needs multichannel SQUIDs to perform real time measurement for large area magnetic field mapping. Two and four channel identical directly coupled dc SQUID magnetometers were fabricated on a 10 mm ´ 10 mm SrTiO3 bicrystal with an in-plane misorientation angle of 24º. The best device is one of the dual-channel SQUID magnetometers that the flux noise is about 20 mFo/Hz1/2 at above 20 Hz under magnetic shielding environment. The corresponding magnetic field resolution is around 250 fT/Hz1/2. The magnetic field intensity of heart is about several tens pT. Therefore, the devices should be suitable to construct a multichannel MCG system. The outputs of the four-channel magnetometers can be added and subtracted by homemade analog electronic circuits to form two electronic planar first-order gradiometer and an electronic planar second-order gradiometer. Hence, by using such four-channel magnetometers single chip, the magnetic field, the first-order spatial derivative of magnetic field, Bz/x and Bz/y, and the second-order spatial derivative of magnetic field, 2Bz/xy, can be measured at the same time.