Reliable low noise DC-SQUID

A novel type of multiloop DC SQUID (superconducting quantum interference device) has been fabricated. The device is made of six different layers deposited on a 2-in silicon wafer; the layers are patterned by means of optical lithography. Every chip is a square 6.35 mm on a side and contains two SQUIDs and their input coils; the typical coil inductance is about 1 ?H. The junctions are 2 ?m 2 planar windows on SiO made of Nb-NbO x-PbAuIn with a current density of 500 A/cm 2 and V m ≈ 20 mV. The device was ...