HTS SQUID microscope head with permalloy flux guide

In order to improve the spatial resolution of an HTS SQUID microscope, permalloy rods with sharpened tip angles of 50(degree) to 170(degree) were placed in front of a SQUID as magnetic flux guides. A current carrying meander line on a printed circuit board with lines and spaces of two widths, 0.3 mm and 0.5 mm, was used as a magnetic field source. The magnetic field distribution was better resolved with the smaller tip angle. Also, a rod with a smaller tip diameter of curvature of 30 (mu)m could resolve the magnetic field distribution better than one with a 100 (mu)m diameter. It was further found that using a magnetic shield around the magnetic flux guide to suppress the inefficient magnetic field allowed the magnetic field image to be better resolved. The limits of the systemʹs spatial resolution were examined with a 100 (mu)m wide meander line. Magnetized laser-printed characters of font size from 2 points to 5 points were also imaged. It was found that this method has a higher magnetic sensitivity and spatial resolution than a large SQUID system, and allows the position and distance from the sample to be adjusted.