Design of a loop-gap resonator with bimodal uniform fields using finite element analysis

TL;DR

This paper presents a finite element analysis-based design method for a loop-gap resonator capable of generating bimodal uniform fields at two frequencies, enhancing multi-frequency ESR experiments.

Contribution

It introduces a novel empirical design procedure for asymmetric LGRs with dual-frequency uniform fields, validated through comparison with a manufactured device.

Findings

Achieved uniform fields at two frequencies within the same sample volume.

Demonstrated tunability and high filling factors of the designed resonator.

Validated design through comparison with experimental measurements.

Abstract

The loop-gap resonator (LGR) was originally developed to provide a uniform microwave magnetic field on a sample for electron spin resonance (ESR) experiments. The LGR is composed of one or more loops and gaps acting as inductances and capacitances respectively. Typical LGR designs produce a uniform field on a sample at a single resonant frequency, but for certain experiments it is necessary to study the response of a material to uniform fields at multiple frequencies applied simultaneously. In this work we develop an empirical design procedure using finite element method calculations to design an asymmetric loop-gap resonator with uniform fields at two frequencies in the same sample volume and analyze the field uniformity, frequency tunability and filling factors, providing comparison to a manufactured device.