Abstract
I report on the research and development of a data acquisition system, based on a time domain electromagnetic (TDEM) method using a highly sensitive high-temperature superconductor (HTS) SQUID vector magnetometer operating at 77 K, which is suitable for mineral exploration by the Metal Mining Agency of Japan (MMAJ). The MMAJ has achieved stable long-term operation of all three channels during field trials. The SQUID system meets high requirements for slew rate (7.3 mT/s), dynamic range (100 dB) and bandwidth (DC∼100 kHz). It offers deeper penetration of depth than the induction coil system because it is capable of recording the step response that decreases with time slower than the impulse response of the induction coil system. The MMAJ's SQUID system will perform gradient observations that can provide much better resolution of deeper conductive targets than conventional EM field component observations. We have obtained good reproducibility of SQUID data and good correlation between the output signals of the reference induction coils and the derivatives of the SQUID signals in TDEM field trials.
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