Novel circuit arrangement for transmit and receive signals paired with secondary resonator for ultra-low field NMR spectroscopy

One of the major challenges in low-field NMR is the inherently low signal-to-noise ratio (SNR). At low magnetic fields, ambient noise and electromagnetic interference can hamper the detection of the weak NMR signal, making it unsuitable for many MR applications. In this study, we explore the use of a high-quality resonator for both transmitting and receiving the NMR signal at ultralow magnetic field strengths. The resonator is composed of two inductors: a low-quality inductor which house the NMR sample in series with a high-quality inductor wrapped around a ferrite core, to boost the overall inductance and Q of the coil. Although the setup may appear relatively straightforward, selecting the appropriate inductor core and winding material proved to be critical. Here we present circuit simulations, along with experimental data acquired using samples containing hyperpolarized 1H and 129Xe spins to demonstrate its enhanced performance compared to traditional NMR resonator geometries.