Development of HTS-SQUID magnetometer system with high slew rate for exploration of mineral resources

• Published in: Superconductor science & technology Vol. 26; no. 11; pp. 115003 - 7
• Main Authors: Hato, T, Tsukamoto, A, Adachi, S, Oshikubo, Y, Watanabe, H, Ishikawa, H, Sugisaki, M, Arai, E, Tanabe, K
• Format: Journal Article
• Language: English
• Published: Bristol IOP Publishing 01.11.2013; Institute of Physics
• Subjects: Battery; Cables; Condensed matter: electronic structure, electrical, magnetic, and optical properties; Cross-disciplinary physics: materials science; rheology; Cuprates superconductors (high tc and insulating parent compounds); Dewars; Dynamical systems; Dynamics; Exact sciences and technology; Glasses (including metallic glasses); Magnetic fields; Materials science; Physics; Receivers; Slew rate; Specific materials; Superconductivity; Superconductors; Barium Copper Samarium Oxides Mixed; Interference; Glass; Magnetic field effects; Signal-to-noise ratio; Nitrogen; Cantilever beam; Transients; Multilayers; Transmission electron microscopy; Battery; High-Tc superconductors; White noise; Step edge junction
• ISSN: 0953-2048; 1361-6668
• DOI: 10.1088/0953-2048/26/11/115003

For the transient electromagnetic (TEM) method using a high-temperature superconducting interference device (HTS-SQUID), we have developed a magnetometer system with a wide dynamic range, a high slew rate, and superior transportability. To achieve high tolerance to a higher excitation magnetic field, we utilized a SQUID magnetometer containing ramp-edge junctions with La0.1Er0.95Ba1.95Cu3Oy and SmBa2Cu3Oy electrode layers, which was fabricated by using an HTS multi-layer fabrication technique. To operate the magnetometer stably in a rapidly changing magnetic field, we chose the proper materials for the RF shield of liquid nitrogen (LN2) glass Dewar and cables. The white noise level and the slew rate of the system were measured to be 30 fT Hz−1 2 and 10.5 mT s−1, respectively. The resultant signal-to-noise ratio was higher than that of the previous system and improved the exploration depth, which was successfully demonstrated in field tests. The weight of the Dewar, which retains the LN2 for 17 h, is 2.5 kg. The total weight of our system including the LN2 Dewar, a probe with a flux-locked loop (FLL) circuit, a battery, a receiver, and a 30 m-long cable between the FLL and the receiver is as low as 25.6 kg.