Improved sensitivity of NMR spectroscopy probes by use of high-temperature superconductive detection coils

High resolution nuclear magnetic resonance (NMR) spectroscopy is an important technique for the determination of molecular structures and physical properties of liquid samples. A major drawback is its low signal-to-noise ratio compared with other spectroscopic methods. The dominant source of noise in a spectrometer is often Johnson noise in the detection coils. Conductus, a leading manufacturer of superconductive electronics, and Varian, a leading manufacturer of NMR spectrometers, have successfully developed NMR sample probes using detection coils fabricated from thin films of the high temperature superconductor, YBa/sub 2/Cu/sub 3/O/sub 7-/spl delta// (YBCO) which reduce that noise and provide a sensitivity enhancement of a factor of four compared with conventional coils. The detection coils are maintained at about 25 K while the sample, contained in a 5 mm diameter tube, is at room temperature. The coils must carry high radio frequency currents during the excitation phase of a pulsed NMR experiment and, in order to maintain spectral quality, should cause little perturbation of the polarizing magnetic field. Characteristics of these probes and examples of spectra obtained are shown.