Research and Realization of Short Dead-Time Surface Nuclear Magnetic Resonance for Groundwater Exploration

Surface nuclear magnetic resonance is a geophysical method designed for direct groundwater exploration, but its applications for conducting research on contamination analysis in the vadose zone are limited due to instrumental dead time. To address this challenge, we have modeled and simulated the phenomenon and impact of the transmitter loop discharge, relay oscillation, and delay of the amplifier caused by the instrumental dead time. Next, we propose and develop a Q-toggle dead-time shortening circuit for suppressing oscillation and improving signal quality. Laboratory and field tests demonstrate that this circuit is sensitive to low-amplitude and fast-decay signals and can successively increase the detection resolution of the instrument receiver. Finally, the inversion results confirm that this improvement can be used to accurately characterize the water content in the vadose area.