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 /spl mu/m) 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/spl times/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 /spl mu/m. 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 /spl mu//spl Phi//sub o///spl radic/Hz. Sensitivity is better than 100 pT//spl radic/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 /spl mu/m. We discuss the impact of the external field coils for susceptibility measurements.