Multi channel high-T/sub c/ scanning SQUID microscope

We have constructed and tested a multichannel scanning SQUID microscope. An array of up to 8 high-T/sub c/ YBCO SQUIDs are mounted on a single chip at the end of a 77 K cold finger. Each SQUID loop measures 30 /spl mu/m by 60 /spl mu/m, and the SQUID's are spaced by about 200 /spl mu/m. The normal to the surface of the chip (and the SQUID loop) is aligned parallel to the main scanning direction. A vacuum space and a thin (<25 /spl mu/m) sapphire window separate the SQUID chip from the sample, which is in air at room-temperature. The microscope has been tested by imaging defects in wires and short circuits in computer chips. We discuss the advantages of the multichannel system over the single channel system, as well as some of the obstacles encountered.