We present a novel design of loop-gap resonator, the loop-zag resonator, for sub-X-band electron-spin resonance spectroscopy. The loop-zag design can achieve improved coupling to small-sample spin systems through the improvement of sample filling factor and RF B1 field. By introducing ``zags'' to the resonator's gap path, the capacitance is increased, accommodating a smaller loop size and thereby a larger filling factor to maintain the requisite resonant frequency. We present experimental spectra on five different resonators, each with approximately the same resonant frequency of ∼2.9~GHz, showing that an increase in the number of zags and reduction in loop size gives rise to higher sensitivity. Finite-element simulations of these resonators provide estimates of the improved filling factors obtained through the addition of zags. The frequency range over which this loop-zag design is practical enables a breadth of future applications in microwave engineering, including ESR and ESR-like quantum information microwave techniques.
@article{arxiv.2307.11269,
title = {The loop-zag resonator: A loop-gap resonator design for improved sensitivity in electron-spin resonance experiments},
author = {Brendan C. Sheehan and Guanchu Chen and Sai Chauhan and Rilla McKeegan and Francisca Abdo Arias and William Henshon and Charles A. Collett and Jonathan R. Friedman},
journal= {arXiv preprint arXiv:2307.11269},
year = {2023}
}