SPATIAL RESOLUTION AND SENSITIVITY OF MAGNETIC SUSCEPTIBILITY IMAGING

A scanning susceptometer may be used to image the two-dimensional distribution of magnetic susceptibility in thin samples. We present high resolution magnetic field data recorded above complex shapes of plexiglass, scanned in a uniform applied field. Deconvolution of these data yielded magnetization distributions that were accurate images of the samples. We found that the susceptibility of plexiglass is -9.0 x 10(-6) (SI) and demonstrated that our system is sensitive to susceptibility contrasts as small as 5 x 10(-7) (SI), with a spatial resolution better than 1 mm. This performance is limited by the strength of the applied field, by the size and distance from the sample of the sensing coils and by SQUID noise. We estimate that we could increase spatial resolution by a factor of two, and sensitivity to susceptibility contrast by at least one order of magnitude by using an imaging susceptometer whose SQUIDs are integrally mounted within a superconducting magnet.