Performance of a Flux Locked Series SQUID Array

The operation of a SQUID array with 100 dc SQUIDs has been demonstrated using a single flux-locked loop. The SQUID array had a maximum dynamic range of ±1.3 X 108/ √Hz in the low frequency region, a high slewing rate over a wide frequency range, and an extrinsic white noise energy sensitivity of 6 X 10 -31J/ Hz. These data were obtained with a very simple feedback circuit made from three inexpensive operational amplifiers that operated in the dc-feedback mode. The feedback loop did not have any impedance matching circuit between the SQUID array and the room temperature electronics. Our results show that a SQUID array can have a significant impact on those applications that demand good noise performance and a very high dynamic range. © 1993 IEEE. All rights reserved.