A Superconducting Quantum Interference Device Measurement System for Ultra Low-Field Nuclear Magnetic Resonance

Proton Relaxometry of Tree Leaves at Hypogeomagnetic Fields

“…The atomic-magnetometry detection modality has been instrumental in the subfield of zero-to-ultralowfield (ZULF) NMR [24,25,26], where ULF is commonly used in literature to refer to fields below the geomagnetic (Earth) field of tens of microtesla, such that magnetic shielding or active field cancellation is required. Due to varying definitions of ULF by different authors, some absolute [27] and others referenced to the spin system under study-e.g., J-coupling between spins dominates Zeeman interactions with the external field [28]-we choose instead to use the unambiguous term "hypogeomagnetic" in this publication.…”

“…The atomic-magnetometry detection modality has been instrumental in the subfield of zero-to-ultralow-field (ZULF) NMR [24, 25, 26], where ULF is commonly used in literature to refer to fields below the geomagnetic (Earth) field of tens of microtesla, such that magnetic shielding or active field cancellation is required. Due to varying definitions of ULF by different authors, some absolute [27] and others referenced to the spin system under study—e.g., J -coupling between spins dominates Zeeman interactions with the external field [28]—we choose instead to use the unambiguous term “hypogeomagnetic” in this publication. The hypogeomagnetic regime has already been used for direct detection of biomagnetic fields produced by plant electrical activity, including action potentials and wounding potentials [29, 30, 31]; however, according to our understanding, NMR signals originating from plants have not yet been explored in this regime.…”

“…In addition to the fundamental question of how proton relaxation properties behave at hypogeomagnetic fields, the regime is interesting from a practical NMR standpoint, due to the low cost, portability, and low energy consumption of experimental components. Although NMR detection using superconducting-quantum-interference-device (SQUID) magnetometers [27, 32] offers comparable sensitivity to atomic magnetometers at hypogeomagnetic fields (as well as a larger frequency bandwidth), the need for bulky cryogenic cooling limits the applicability of SQUID-based devices. The smaller footprint of atomic magnetometers also allows placement of multiple sensors around a sample, rather than in a single detection plane.…”

Proton relaxometry of tree leaves at hypogeomagnetic fields

“…The atomic-magnetometry detection modality has been instrumental in the subfield of zero-toultralow-field (ZULF) NMR (Blanchard et al, 2021;Tayler et al, 2017;Put et al, 2021;Tayler et al, 2018;Bodenstedt et al, 2021), where ULF is commonly used in literature to refer to fields below the geomagnetic (Earth) field of tens of microtesla, such that magnetic shielding or active field cancellation is required. Due to varying definitions of ULF by different authors, some absolute (Hartwig et al, 2013) and others referenced to the spin system under study-e.g., J-coupling between spins dominates Zeeman interactions with the external field (Blanchard and Budker, 2016)we choose instead to use the unambiguous term "hypogeomagnetic" in this publication. The hypogeomagnetic regime has already been used for direct detection of biomagnetic fields produced by plant electrical activity, including action potentials and wounding potentials (Trontelj et al, 1994;Jazbinsek et al, 2000;Fabricant et al, 2021); however, according to our understanding, NMR signals originating from plants have not yet been explored in this regime.…”

“…In addition to the fundamental question of how proton relaxation properties behave at hypogeomagnetic fields, the regime is interesting from a practical NMR standpoint, due to the low cost, portability, and low energy consumption of experimental components. Although NMR detection using superconductingquantum-interference-device (SQUID) magnetometers (Hartwig et al, 2013;Espy et al, 2013) offers comparable sensitivity to atomic magnetometers at hypogeomagnetic fields (as well as a larger frequency bandwidth), the need for bulky cryogenic cooling limits the applicability of SQUID-based devices. The smaller footprint of atomic magnetometers also allows placement of multiple sensors around a sample, rather than in a single detection plane.…”