A scanning superconducting quantum interference device microscope for room temperature samples

We have constructed a scanning low-Tc superconducting quantum interference device(SQUID) microscope,in which the SQUID is mounted on the lower end of a copper rod and cooled to liquid helium temperature,There is a 65um thick sapphire window under the SQUID.The sample at room temperature underneath the window can be scanned to produce magnetic images.The microscope has a spatial resolution of 100-150um and a magnetic filed sensitivity of 3-60pT/Hz in a magnetically unshielded environment.We have used this scanning SQUID microscope to mesasure various room temperature samples.