Abstract:

This paper describes the development of an L-band resonator for ESR imaging, some problems encountered in the process of designing and manufacturing are discussed. The resonator is a 3-loop 2-gap re-entrant resonator with a physical size that can accommodate H₂O samples up to 20 mm in diameter and 30 mm in length. The resonance frequency of the unloaded resonator was 1.05 GHz. The Q factors of the resonator were measured under different sample (water) loading. The Q factor for the empty resonator was greater than >1 000. Matching between the resonator and the microwave bridge was obtained with a coupling loop inserted in one of the two lateral arms. The optimal diameter of the coupling loop was determined experimentally. For the unloaded cavity this value was about one third of the arm diameter, while for the loaded cavity it was nearly equal to that of the cavity arm. Using this resonator, we obtained the spatial distribution of TEMPO (2,2,6,6-tetramethylpiperidine-1-oxyl) nitroxide radicals in a sample tube.

Key words: ESR, re-entrant resonator, L-band, ESR Imaging