Cryogenic system for a high temperature superconductor NMR probe

We have developed a cryogenic NMR probe using HTS detection coils for high resolution chemical spectroscopy and have demonstrated a signal-to-noise improvement by more than a factor of four over conventional technology. The probe is cooled by a remotely located closed-cycle refrigeration system and coil temperatures below 20 K have been attained. The probe is designed to be inserted into a 37 mm diameter bore of a high homogeneity superconducting magnet with the coils located less than 2 mm from a room temperature NMR sample. The samples can be loaded using the standard pneumatic loading system, and sample temperatures can be regulated using the standard gas flow method. Standard sample spinning can also be performed. The closed-cycle refrigeration system consists of a closed loop of circulating helium gas cooled by a heat exchange network on a Gifford-McMahon refrigerator. A vacuum insulated transfer line is used to flow the helium from the cooling system to the probe. The probe has been optimized for minimal heat leak while maintaining RF performance for the NMR experiments.