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IEICE TRANSACTIONS on Electronics

Development of TDEM Data Acquisition System Based on High Tc SQUIDs for Mineral Exploration

Hajime OTA, Tatsuoki NAGAISHI, Eiichi ARAI

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Summary :

The Time Domain Electromagnetic Method (TDEM) survey is one of the several geophysical exploration methods. In the conventional TDEM survey, an induction coil is used as the magnetometer. However, the measurement depth is limited to about 500 m. Using high Tc SQUIDs, there are expectations of large bandwidth and high sensitivity for the TDEM. We developed the high Tc SQUID TDEM system. We have reduced the system noise by developing a 20 mm20 mm step-edge type direct coupled SQUID and a low noise direct readout flux locked loop (FLL) circuit. We have also improved the slew rate, optimizing the parameter of the FLL circuit. Consequently, the system noise of less than 0.2 pT/Hz1/2 at 1 kHz was achieved in the earth's magnetic field. The slew rate was 7.3 mT/sec. We conducted field trials and confirmed that the TDEM using high Tc SQUIDs obtains information of deeper region with high precision compared with the TDEM using induction coils.

Publication
IEICE TRANSACTIONS on Electronics Vol.E88-C No.2 pp.192-197
Publication Date
2005/02/01
Publicized
Online ISSN
DOI
10.1093/ietele/e88-c.2.192
Type of Manuscript
Special Section PAPER (Special Section on Superconducting Electronic Devices and Their Applications)
Category
SQUIDs

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