Nuclear magnetic resonance (NMR) probes using thin-film high temperature superconducting (HTS) resonators provide exceptional mass sensitivity in small-sample NMR experiments for natural products chemistry and metabolomics. We report improvements in sensitivity to our 1.5 mm ¹³C-optimized NMR probe based on HTS resonators. The probe has a sample volume of 35 microliters and operates in a 14.1 T magnet. The probe also features HTS resonators for ¹H transmission and detection and the ²H lock. The probe utilizes a ¹³C resonator design that provides a higher quality factor than our previous design. Initial NMR measurements verify that lineshape and excitation field uniformity are acceptable and similar to the previous design. The quality factor of the new resonator in the 14.1 T background field was measured to be 3,600, which is about twice the value of the previous design. Development of the new probe also helped validate a magnetic coupling model to account for interactions between the HTS resonators. In the future this model can be expected to reduce development time. Finally, we demonstrated the effect of adding a shorted transmission line stub to reduce the rise and fall time of ¹³C irradiation pulses. The probe will be used for applications in metabolomics.

Keywords: Nuclear Magnetic Resonance, High Temperature Superconductors, Superconducting Devices