The loop-zag resonator: A loop-gap resonator design for improved sensitivity in electron-spin resonance experiments

TL;DR

The paper introduces the loop-zag resonator, a novel design that enhances sensitivity in electron-spin resonance by increasing the filling factor and RF field through added zags, demonstrated with experimental spectra and simulations.

Contribution

A new loop-zag resonator design that improves coupling and sensitivity in ESR by increasing capacitance and filling factor, enabling smaller loops and higher performance.

Findings

Higher sensitivity with more zags and smaller loops

Experimental spectra confirm improved performance

Simulations estimate increased filling factors

Abstract

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 $B_1$ 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 $\sim2.9$~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.