Squid-based magnetic microscope

Two types of scanning magnetic microscopes (MM) are known nowadays: force magnetic microscopes (FMM) and non-force MM (NFMM) ones. The second type of MM can be used to measure a distribution of the vertical component of magnetic fields over surfaces, including cases such as in a cavity of solid test objects (TO) and inside a liquid TO, without external forces or magnetic influences on the TO. A NFMM with a SQUID detector (SQUID-MM) has the highest magnetic sensitivity among all types of MM. Because of these SQUID-MM features, it is suitable for use in developments of smart materials. For example, it may be used for: counter-terrorism investigations by surveying and decoding of the slight slots left after deletion of the magnetic records on a computer disc by traditional magnetic "scrubber" procedures; surveying and decoding of minute magnetic indications left after a mechanical scrubber procedure of mechanically stamped records of serial numbers on cars and other objects; surveying and measuring magnetic properties of small magnetic particles of the object under investigation for identification of the object; high-sensitivity reading of magnetic records on perspective superconducting carriers. The design of our three-channel SQUID-MM is described in this article. Magnetic 3D scan-pictures of several TO's are presented also for demonstration.