High resolution SQUID imaging of current and magnetization distributions

Interpretation of high-resolution SQUID (superconducting quantum interference device) magnetometer data is facilitated by inverting them into current or magnetization images. Different deconvolution algorithms utilizing the finite element method (FEM), spatial filtering (SF) and lead field analysis (LFA) are compared. The authors applied an appropriate algorithm to magnetic field data produced by current distributions in high-T/sub c/ superconducting thin films (TlBaCaCuO), by the diamagnetic magnetization of plexiglass and by planar and cylindrical current-carrying conductors with flaws. They demonstrate and compare the performances of the algorithms and conclude that, with all of the approaches, the deconvolved images are easier to interpret than the original field maps. The FEM and SF can both solve for discontinuous sources. The FEM allows the solution to be constrained with boundary conditions but it is much slower than SF, which cannot constrain the solution. LFA is numerically simple for complex geometries but it is slow and cannot deal with discontinuous sources.<>