Practical DC SQUIDs with extremely low 1/f noise

A large number of highly robust and reliable thin film DC SQUIDs have been designed and fabricated which have excellent low frequency noise properties. Measurements performed on isolated devices have yielded a limit on the low frequency (1/f) flux noise component which is at least a factor of 60 below the average value reported for devices of this kind. The corresponding energy factor in the white noise region is 770 h at 0.1 Hz. The input coil inductance is 0.7 μH and the coupling efficiency α = 0.9. The substantial reduction of the low frequency noise in these SQUIDs demonstrates that improvements in the performance of these devices in the white noise region can be obtained without sacrificing the low frequency resolution.