Determination of quality factor for highly overcoupled EPR resonators

Yasunori Ohba, Chika Watanabe, Shigeaki Nakazawa, Seigo Yamauchi

Research output: Contribution to journalArticlepeer-review

5 Citations (Scopus)


We reported determination of the loaded quality factor (Q) of highly overcoupled (dielectric, loop-gap, and cavity) resonators used in time-domain electron paramagnetic resonance. We introduced a microwave absorber into resonators and achieved critical-coupling. Due to the deep "Q-dip" of critical-coupling, we can easily determine the loaded Q as low as 10. The loaded Q of resonators with and without the microwave absorber was examined under various overcoupling conditions. We found that the radiation Q (Qr) can be calculated from the loaded Q of the resonator that contains the microwave absorber. We proposed a simple model that represents the loaded Q of the overcoupled resonator in terms of two parameters, Q0 and Qr. Q0 is the effective unloaded Q of the resonator determined for the critically coupled resonator without the microwave absorber and is independent of a degree of coupling. The model can be applied to overcoupling in which the coupling parameter (Q0/Qr) is in the range of 1 to ca. 20.

Original languageEnglish
Pages (from-to)781-794
Number of pages14
JournalApplied Magnetic Resonance
Issue number1
Publication statusPublished - 2010

ASJC Scopus subject areas

  • Atomic and Molecular Physics, and Optics


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