A multilayered element resonator for CW-ESR and longitudinally detected ESR at radio frequency

The design and evaluation of a multilayered element resonator (MLR), which consists of multiple layers of half-loop conductor plates and insulator sheets, are presented. An MLR and a bridge shielded loop-gap resonator (BLGR), which have similar sizes and resonant frequencies, were fabricated to compare their performances. Using the MLR and the BLGR, the modulation field width and signal intensity of a phantom containing a nitroxide radical were measured by employing a continuous-wave electron spin resonance (CW-ESR) technique at a radio frequency of 300 MHz. Using the same resonators, the longitudinally detected ESR (LODESR) signal intensities of the phantom were also compared. The loadedQ values of the resonators were almost the same. The modulation widths in the MLR were significantly wider than those in the BLGR when the modulation coils were driven at the same voltage. The signal intensities of CW-ESR and LODESR from the phantom in the MLR were significantly greater than those from the BLGR. Since eddy currents disturb the penetration of the modulation field in CW-ESR or detection of changes in magnetization in LODESR observations, these results show that, in the MLR, the eddy currents were suppressed to a greater degree than in the BLGR.