Superconducting magnetometers

Under the proper circumstances a current carrying superconductor can generate voltage. This voltage is produced by supercurrent oscillations at frequency ω = 2e/ħV — a phenomena similar to the Josephson effect in superconducting tunnel junctions. Various structures have been fabricated in which this quantum relation dominates the electrical behavior. These thin film structures have been developed into reliable sensor elements which have been incorporated into various electronic instruments — particularly magnetometers. These instruments include a differential magnetometer with a one second response time and sensitivity greater than 10-10 gauss and a digital magnetometer counting in increments of 1/4h/2 e at a rate up to 104 per second. The fundamental principles of these instruments will be discussed as well as their present operational limitations