LTS SQUID microscope with micron spatial resolution

We describe a multichannel LTS SQUID microscope with micron spatial resolution. The system achieves micron resolution by the use of small (14 μm) detection coils and narrow gap between the coils and the object(s) being scanned. Samples are mounted inside an exchange-gas can at the lower end of a cryogenic probe. This houses all of the cryogenic portions of the microscope and is filled with helium exchange gas. A 5 mm×5 mm scanning stage is used to scan the sample, which is at cryogenic temperatures. Stepping motors on the scanning stage allow step sizes as small as 0.16 μm. The SQUIDs are mounted on a cantilever structure with nine separate detection coils on the end of the structure. Flux noise of the SQUIDs is better than 5 μΦ_o/√Hz. Sensitivity is better than 100 pT/√Hz with a bandwidth of dc-10 kHz. Open architecture software provides control of all critical system components, along with data acquisition and analysis. We have demonstrated spatial resolutions better than 2 μm. We discuss the impact of the external field coils for susceptibility measurements.