A FAST FIELD-CYCLING NMR NQR SPECTROMETER

We describe a fast field-cycling NMR/NQR spectrometer with a switching time of only 0.7 ms between zero field and maximum field (1 T) which uses a novel air-cored magnet design in which the magnet is cut out of a solid copper tube by means of electric spark erosion. The pitch and cross section of the windings vary and have been optimized for small inhomogeneity of the field (6 parts in 10(5)) and the highest field for the available power (20 kW). The design of the power supply, which uses one capacitor as energy storage, and considerations concerning the safety of the instrument are also described as well as the probe and the more conventional parts of the NMR spectrometer. We conclude with examples of the performance and the main applications: field-dependent spin-lattice relaxation time measurement (T1 dispersion), cross relaxation and nuclear quadrupole double resonance (NQDR).