DC SQUID preamplifier for DC-SQUID magnetometer

A DC SQUID (superconducting quantum interference device) magnetometer with DC SQUID preamplifier has been designed and experimentally tested. The total magnetometer noise was reduced to the intrinsic noise level of the input DC SQUID, and magnetometer cryogenic containment was minimized by using the DC SQUID preamplifier. Two identical thin-film DC SQUIDs with 15- mu m/sup 2/-area resistively shunted Nb-AlO/sub x/-Nb junctions were utilized. The resulting magnetometer had a coupled energy sensitivity equivalent to 3*10/sup -31/ J/Hz in the range from 1 Hz to 30 kHz and about 100-dB dynamic range.<
>