Compact magnetic field cycling system with the range from nT to 9.4 T exemplified with 13C relaxation dispersion and SABRE-SHEATH hyperpolarization

Abstract: We present a compact magnetic field cycling system for high-resolution NMR spectrometers. The system enables the transfer of the sample from B0 field of 9.4 T to about nT and all fields in between within 1 second. Utilizing a flexible gear rod made the shuttling system more compact, reducing the height to about the height required for filling liquid helium - hence, it can be installed in average-size NMR laboratories (the height of NMR with MFC is only 3.32 m). The system utility is exemplified by measuring T1 relaxation dispersion of the most common liquid state hyperpolarization tracer - [1-13C]pyruvate - and magnetic field dependences of signal amplification by reversible exchange enabling alignment transfer to heteronuclei (SABRE-SHEATH) hyperpolarization of [15N]pyridine. Using the system, we uncovered the exact relaxation of the pyruvate for a common preclinical dDNP sample composition and gave quantitative estimates for the retained polarization after sample transfer. We modified the observation protocol of SABRE-SHEATH polarization, which, with the high reproducibility of the MFC, provided us with a method to measure the chemical exchange rates of hyperpolarized compounds.