Array high-sensitivity room temperature coil system for SNMR detection in shallow depth

摘要

The noninvasive method of surface nuclear magnetic resonance (SNMR) is a geophysical technique that is directly sensitive to hydrogen protons, besides it can exploit the NMR phenomenon for a quantitative determination of the subsurface groundwater distribution. Traditionally, SNMR utilizes large surface coils for both transmitting excitation pulses and recording the groundwater response. While, in recent research, a low Tc-SQUIDs is taken as a new sensor to replace the large receiving coil (Rx), which performing the best sensitivity for the shallow depth. Nevertheless, SQUID is with the problems of flux trapping and operational difficulties. In this paper, we introduce a room temperature coil system. A Cu coil with diameter of 1 m and a low noise preamplifier was systematically investigated and reached a sensitivity of 0.2fT/Hz~(1/2). Four preamplifiers are chosen for optimizing the pickup coils. The resolution studies for the array coil systems were performed, and the optimum distance between the adjacent pickup coils to achieve a better experimental results especially for the shallow depth. Our study enable the further use of the room temperature coil for SNMR shallow depth detections.