Gaseous ³He nuclear magnetic resonance probe for cryogenic environments

Normal nuclear magnetic resonance (NMR) probes cannot be used to make high frequency resolution measurements in a cryogenic environment because they lose their frequency resolution when the liquid sample in the probe freezes. A gaseous ³He NMR probe, designed and constructed to work naturally in such cryogenic environments, is demonstrated at 4.2 K and 5.3 T to have a frequency resolution better than 0.4 ppb. As a demonstration of its usefulness, the cryogenic probe is used to shim a superconducting solenoid with a cryogenic interior to produce a magnetic field with a high spatial homogeneity and to measure the magnetic field stability.