HIGH-TRANSITION TEMPERATURE SUPERCONDUCTING QUANTUM INTERFERENCE DEVICE MICROSCOPE

A microscope has been constructed in which a high-transition temperatu re dc superconducting quantum interference device (SQUID) in vacuum is brought to within 140 mu m of samples at room temperature and pressur e. The SQUID is mounted on the upper end of a sapphire rod, cooled to liquid nitrogen temperature, below a 75-mu m thick sapphire window. Sa mples can either be placed directly on the window or scanned over the SQUID to produce magnetic images. A square-washer SQUID with inner and outer dimensions of 30 and 50 mu m can resolve 130 mu m magnetic feat ures. The instrument is intended primarily for biological applications . (C) 1996 American Institute of Physics.