35 /spl planck/ two-stage SQUID system for gravity wave detection

We have designed, built and tested a two-stage SQUID measuring system which is primarily intended for use in a 50 mK omnidirectional gravity wave detection system. We fabricated three Nb-Al/AlO/sub x/-Nb trilayer SQUIDs on a single chip: there is one sensor SQUID and two readout SQUIDs which amplify the output of the sensor SQUID. At a temperature of 90 mK, we measured an intrinsic energy sensitivity of the sensor SQUID of /spl epsi//sub v/=S/sub /spl Phi///(2L)=35/spl planck/ at 1 kHz, of which 24/spl planck/ is white noise and 11/spl planck/ is 1/f noise.