Numerical simulation and analyze of magnetic resonance sounding with adiabatic pulse for groundwater exploration

Abstract

Magnetic resonance sounding (MRS) technology used to detect groundwater directly and quantificationally, which owns the advantages of rich information and low cost. In these years, it has shown significant potential applications in hydrological detections. Considering the traditional measurements with the geomagnetic field, the nano-valt MRS signals are easy to suppress to environmental noise. As one of the MRS signal enhancement methods, the adiabatic pulse was quite popular recently. It is transmitted with variable frequency and amplitude pulse satisfying the adiabatic condition, which can enhance the signal amplitude and signal-to-noise ratio several times. However, there are only a few reports about this method, especially its geophysical modeling. Thus, we introduce the calculating progress of transverse magnetization and kernel function for this method. By employing the interpolation, the computation cost of forward modeling is obviously reduced. Moreover, several different settings of adiabatic transmitting factors are also proceeded to obtain certain results. In conclusion, a pulse moment with 80 ms transmitting duration and 30 quality factor produces a maximum signal amplitude that is enhanced 16.56 times for deep areas. The research in this paper could provide powerful support for MRS method used in noisy environments.