A scanning SQUID microscope for samples at room temperature

We report on the development of a scanning SQUID microscope for measurement s of samples at room temperature. A thin film niobium DC-SQUID is used with conventional read-out electronics. It is placed above the thin bottom wind ow of a fiberglass cryostat, allowing us to realize a distance of about 75 mu m between SQUID and sample. The evaporation rate for the liquid helium w as about 0.3 l/h, Because the effective SQUID area can easily be brought be low 10 mu m(2), the obtainable spatial resolution of such a scanning SQUID microscope is limited mainly by the distance between SQUID and sample. The sample is moved under the cryostat with a computer controlled XY-stage. Pro visions are made for quick sample changes which are important for the pract ical application of such a device.