A large-scale low-temperature scanning Hall probe microscope was developed for imaging the entire magnetic field in close proximity to magnetic and superconducting samples at 4.2 to 300K. The microscope combined a large scanned area and fine spatial and magnetic field resolution. The instrument was designed as an insert of standard He flowing cryostats. The Hall sensor scanned an area up to 7 x 25mm2 over the whole temperature interval with a spatial resolution better than 5µm. The presented system was used for the study of ex situ prepared MgB2 filament. It was shown that external magnetic field induced local super-currents into the MgB2; from which the critical current could be estimated. This reflected the microstructure and spatial homogeneity of the superconductor.

Large-Scale High-Resolution Scanning Hall Probe Microscope used for MgB2 Filament Characterization. V.Cambel, J.Fedor, D.Gregusová, P.Kovác, I.Husek: Superconductor Science and Technology, 2005, 18, 417-21