Hiller Thomas, Costabel Stephan, Dlugosch Raphael, Splith Tobias, Müller-Petke Mike
Federal Institute for Geosciences and Natural Resources, Wilhelmstr. 25-30, Berlin, 13595, Germany.
Leibniz Institute for Applied Geophysics, Stilleweg 2, Hannover, 30655, Germany.
Magn Reson Lett. 2023 Apr 11;3(2):140-149. doi: 10.1016/j.mrl.2023.03.008. eCollection 2023 May.
A recent study demonstrated that in small-scale prepolarized surface nuclear magnetic resonance (SNMR-PP) measurements with a footprint of a few square meters, customized PP switch-off ramps can serve as an efficient excitation mechanism, eliminating the requirement for a conventional oscillating excitation pulse. This approach enables the detection of short relaxation signals from the unsaturated soil zone and can, therefore, be used to directly provide soil moisture and pore geometry information. Because ultimately such small-scale SNMR-PP setups are intended for a mobile application, it is necessary to develop strategies that allow for speedy measurement progress and do not require noise cancellation protocols based on reference stations. Hence, we developed a new concentric figure-of-eight (cFOE) loop layout that combines the direction independence of a circular loop with the intrinsic noise cancellation properties of a classical FOE-loop. This approach significantly decreases the measurement time because suitable signal-to-noise ratios are reached much faster compared to a classical circular loop and will bring us one step further toward fast and non-invasive soil moisture mapping applications.
最近的一项研究表明，在占地面积为几平方米的小规模预极化表面核磁共振（SNMR-PP）测量中，定制的PP关断斜坡可作为一种有效的激发机制，消除了对传统振荡激发脉冲的需求。这种方法能够检测来自不饱和土壤区域的短弛豫信号，因此可用于直接提供土壤湿度和孔隙几何信息。由于最终此类小规模SNMR-PP装置旨在用于移动应用，因此有必要制定能够实现快速测量进程且不需要基于参考站的噪声消除协议的策略。因此，我们开发了一种新的同心8字形（cFOE）线圈布局，它将圆形线圈的方向独立性与经典FOE线圈的固有噪声消除特性相结合。与经典圆形线圈相比，这种方法能显著缩短测量时间，因为能更快达到合适的信噪比，这将使我们在快速、非侵入式土壤湿度测绘应用方面又迈进了一步。
