THE CONCENTRIC LOOP-GAP RESONATOR - A COMPACT, BROADLY TUNABLE DESIGN FOR NMR APPLICATIONS

A loop-gap resonator design is described for use in NMR applications. Previously reported versions have employed discrete capacitors at the "gap," which typically yields a very limited tuning range. The resonator described here uses one or more concentric tuning cylinders around the inner loop to permit tuning over a range of several hundred megahertz. Construction is straightforward, the Q is high, and the excellent inherent RF field homogeneity of the loop-gap resonator is retained. A simple theoretical model for the operation of this device is presented and verified experimentally. The performance of this concentric loop-gap resonator has proven excellent for 1H and 19F NMR imaging and spectroscopy at 4.7 T. © 1992.