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Open AccessArticle

Development of a Rigid One-Meter-Side and Cooled Coil Sensor at 77 K for Magnetic Resonance Sounding to Detect Subsurface Water Sources

by Jun Lin 1,2, Guanfeng Du 1,2, Jian Zhang 1,2, Xiaofeng Yi 1,2, Chuandong Jiang 1,2,* and Tingting Lin 1,2,*
College of Instrumentation and Electrical Engineering, Jilin University, Changchun 130061, China
Key Laboratory of Geophysics Exploration Equipment, Ministry of Education of China, Changchun 130061, China
Authors to whom correspondence should be addressed.
Academic Editors: Ashutosh Tiwari and Bharati Tudu
Sensors 2017, 17(6), 1362;
Received: 22 April 2017 / Revised: 4 June 2017 / Accepted: 6 June 2017 / Published: 12 June 2017
(This article belongs to the Special Issue Magnetic Sensors and Their Applications)
Magnetic resonance sounding (MRS) using the Earth’s magnetic field is a noninvasive and on-site geophysical technique providing quantitative characteristics of aquifers in the subsurface. When the MRS technology is applied in a mine or tunnel for advance detecting the source of water that may cause disastrous accident, spatial constraints limit the size of coil sensor and thus lower the detection capability. In this paper, a coil sensor for detecting the weak MRS signal is designed and the signal to noise (SNR) for the coil sensor is analyzed and optimized. The coil sensor has a rigid structure and square size of 1 m for deploying in a narrow underground space and is cooled at a low temperature of 77 K for improving the SNR. A theoretical calculation and an experimental test in an electromagnetically shielded room (EMSR) show that the optimal design of coil sensor consists of an 80-turn coil and a low-current-noise preamplifier AD745. It has a field sensitivity of 0.17 fT / Hz in the EMSR at 77 K, which is superior to the low temperature Superconducting Quantum Interference Device (LT SQUID) that is the latest application in MRS and the cooled coil with a diameter of 9 cm when detecting the laboratory NMR signal in kHz range. In the field experiment above the Taipingchi Reservoir near Changchun in China, the cooled coil sensor (CCS) developed in this paper has successfully obtained a valid weak MRS signal in high noise environment. The field results showed that the quality of measured MRS signal at 77 K is significantly superior to that at 298 K and the SNR is improved up to three times. This property of CCS makes the MRS instrument more convenient and reliable in a constricted space underground engineering environment (e.g., a mine or a tunnel). View Full-Text
Keywords: coil sensor; magnetic resonance sounding; 77 K; SNR coil sensor; magnetic resonance sounding; 77 K; SNR
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Lin, J.; Du, G.; Zhang, J.; Yi, X.; Jiang, C.; Lin, T. Development of a Rigid One-Meter-Side and Cooled Coil Sensor at 77 K for Magnetic Resonance Sounding to Detect Subsurface Water Sources. Sensors 2017, 17, 1362.

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