First evidence of detecting surface nuclear magnetic resonance signals using a compact B‐field sensor

Abstract

The noninvasive detection and characterization of subsurface aquifer structures demands geophysical techniques. Surface nuclear magnetic resonance (SNMR) is the only technique that is directly sensitive to hydrogen protons and, therefore, allows for unambiguous detection of subsurface water. Traditionally, SNMR utilizes large surface coils for both transmitting excitation pulses and recording the groundwater response. Recorded data are thus a voltage induced by the time derivative of the secondary magnetic field. For the first time, we demonstrate that the secondary magnetic field in a SNMR experiment can be directly detected using a superconducting quantum interference device magnetometer. Conducting measurements at a test site in Germany, we demonstrate not only the ability to detect SNMR signals on the order of femtoTesla but also we are able to satisfy the observed data by inverse modeling. This is expected to open up completely new applications for this exciting technology.

First evidence of T2* in SNMR measurements with SQUID sensors

“…We propose the direct measurement of the SNMR relaxation through the use of SQUID sensors acting as point receivers. We show how the measurement of the SNMR signal using a tri-axial B-field sensor allows for the recovery of complementary information of the relaxation, and demonstrate the first evidence of the measurement of using a SQUID sensor in the Schillerslage test site, near Hannover Germany (Davis et al, 2014;Dlugosch et al, 2010).…”

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

“…The green curves in Figure 2 show that when a 160-turn coil and AD745 are connected and when an 80-turn coil and OP27 are connected, the coil sensor has the lowest value of field sensitivity $B$. The minimal detectable magnetic field values are 0.59 $\mathrm{fT}/\sqrt{\mathrm{Hz}}$ and 0.63 $\mathrm{fT}/\sqrt{\mathrm{Hz}}$, respectively, and both are superior to the field sensitivity of 1.5 $\mathrm{fT}/\sqrt{\mathrm{Hz}}$ for the SQUID that firstly detect the MRS signal in the field measurement [27] and 2 $\mathrm{fT}/\sqrt{\mathrm{Hz}}$ for a cooled coil with a diameter of 9 cm that used in laboratory for receiving the signal in kHz range [17]. …”

Exploring on the Sensitivity Changes of the LC Resonance Magnetic Sensors Affected by Superposed Ringing Signals

“…The field resolutions of liquid-nitrogen-cooled (high- T c) SQUIDs and liquid-helium-cooled (low- T c) SQUIDs reach 30~50 fT/√Hz and 1 fT/√Hz respectively [ 6 , 7 , 8 , 9 ]. Recently, low- T c SQUIDs have also been used for SNMR detection [ 10 ]. Although SQUIDs yield the best field sensitivity, they are not commonly applied because of their susceptibility to flux trapping, their need for cooling to liquid He temperatures, and the operation difficulty.…”