Wiedemann, Haakon T.A., Stefan Ruloff, Rudolf Richter, Christoph W. Zollitsch, and Christopher W.M. Kay. “Towards High Performance Dielectric Microwave Resonators for X-Band EPR Spectroscopy.” Journal of Magnetic Resonance, July 2023, 107519.
https://doi.org/10.1016/j.jmr.2023.107519.
Microwave (MW) resonators in Electron Paramagnetic Resonance (EPR) spectroscopy concentrate the MW magnetic field (B1) at the sample and separate the MW electric field component from the sample. There are numerous experimental methods in EPR spectroscopy which all impose di↵erent requirements on MW resonators (e.g. high or low quality factor, MW conversion, and B1-field homogeneity). Although commercial spectrometers o↵er standardized MW resonators for a broad application range, newly emerging and highly-specialized research fields push these spectrometers to or beyond their sensitivity limits. Optimizing the MW resonator o↵ers one direct approach to improve the sensitivity. Here we present three low-cost optimization approaches for a commercially available Xband (9-10 GHz) MW resonator for three experimental purposes (continuous-wave (CW), transient and pulse EPR). We obtain enhanced the MW conversion factors for all three optimized resonators and higher quality factors for two optimized resonators. The latter is important for CW and transient EPR. Furthermore, we fabricated a resonator which features an extended area of homogeneous B1-field and, hence, improved pulse EPR performance. Our results demonstrate that small changes to a commercial MW resonator can enhance its performance in general or for specific applications.