Precision magnetometry at cryogenic temperatures with gaseous ³He NMR probes.

This article focuses on the development and characterization of compact gaseous helium-3 (^3He) Nuclear Magnetic Resonance (NMR) probes for precision magnetometry of magnetic fields above 0.1 Tesla across a wide temperature range from ambient down to 4 K. The probes utilize sealed high-pressure ^3He gas samples polarized at thermal equilibrium, with strategies such as adding paramagnetic oxygen (via strontium peroxide decomposition), silica gel, and gadolinium-loaded silica gel to reduce the otherwise long longitudinal relaxation time (T1), enabling faster sensor readout rates. Experimental results demonstrate that these ^3He NMR magnetometers achieve high signal-to-noise ratios and relative magnetic field sensitivities between 10^−11 and 10^−7 in single-pulse measurements, with performance maintained at cryogenic temperatures. The study highlights the suitability of these compact, reliable probes for applications including superconducting magnet shimming and magnetic field stability monitoring in cryogenic environments.