Title :
Improved sensitivity of NMR spectroscopy probes by use of high-temperature superconductive detection coils
Author_Institution :
Varian NMR Instrum., Palo Alto, CA, USA
fDate :
6/1/1997 12:00:00 AM
Abstract :
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.
Keywords :
NMR spectroscopy; barium compounds; high-temperature superconductors; superconducting coils; yttrium compounds; Johnson noise; NMR spectroscopy probe; YBCO thin film; YBa/sub 2/Cu/sub 3/O/sub 7/; high-temperature superconductive detection coil; sensitivity; signal-to-noise ratio; Magnetic liquids; Magnetic noise; Magnetic properties; Manufacturing; Nuclear magnetic resonance; Probes; Signal resolution; Spectroscopy; Superconducting coils; Superconducting device noise;
Journal_Title :
Applied Superconductivity, IEEE Transactions on