Potential use of high Tc SQUIDS for airborne electromagnetics

Abstract

High Tc SQUIDs are magnetic-field sensors which operate at liquid nitrogen temperatures and presently have noise performance operating in the earth's magnetic field of 200 fTHz?1/2 at 1 kHz. Recent results indicate that operation of SQUIDs in transient electromagnetics (TEM) can offer alternatives to the commonly used induction coils providing a broad frequency response, compact physical dimensions and the potential to measure the B field directly, compared with dB/dt of induction coils. This paper describes the potential of High Tc SQUIDs for airborne geophysical applications and the advantages they may have over other commonly used magnetic-field detectors. Studies have been undertaken to understand SQUID behaviour in ambient magnetic fields such as the earth's magnetic field, and design requirements that would be necessary to move towards systems suitable for field trials are described.