Multipurpose loop-gap resonator

A three-loop-two-gap resonator is described that has properties that are similar to the widely used X-band rectangular TE102 multipurpose cavity. Both structures accommodate the same cavity accessories interchangeably: variable temperature Dewar insert, liquid nitrogen Dewar, electrochemical cell, tissue cell, and flat cell. However, optimum performance with the loop-gap resonator (LGR) is achieved with 1 mm flat cells rather than 0.4 mm cells used in the cavity. The lower Q of the LGR decreases the demodulation of phase noise when tuned to the dispersion. The geometry is flexible and it is suggested that it can serve as a convenient general purpose resonator for ESR spectroscopy.