Faculty Collaboration Database

Uniform field loop-gap resonator and rectangular TE_U02 for aqueous sample EPR at 94GHz. J Magn Reson 2017 Sep;282:129-135

Date

08/15/2017

Pubmed ID

28803092

Pubmed Central ID

PMC5793860

DOI

10.1016/j.jmr.2017.08.001

Scopus ID

2-s2.0-85027276190 (requires institutional sign-in at Scopus site)   8 Citations

Abstract

In this work we present the design and implementation of two uniform-field resonators: a seven-loop-six-gap loop-gap resonator (LGR) and a rectangular TE_U02 cavity resonator. Each resonator has uniform-field-producing end-sections. These resonators have been designed for electron paramagnetic resonance (EPR) of aqueous samples at 94GHz. The LGR geometry employs low-loss Rexolite end-sections to improve the field homogeneity over a 3mm sample region-of-interest from near-cosine distribution to 90% uniform. The LGR was designed to accommodate large degassable Polytetrafluorethylen (PTFE) tubes (0.81mm O.D.; 0.25mm I.D.) for aqueous samples. Additionally, field modulation slots are designed for uniform 100kHz field modulation incident at the sample. Experiments using a point sample of lithium phthalocyanine (LiPC) were performed to measure both the uniformity of the microwave magnetic field and 100kHz field modulation, and confirm simulations. The rectangular TE_U02 cavity resonator employs over-sized end-sections with sample shielding to provide an 87% uniform field for a 0.1×2×6mm³ sample geometry. An evanescent slotted window was designed for light access to irradiate 90% of the sample volume. A novel dual-slot iris was used to minimize microwave magnetic field perturbations and maintain cross-sectional uniformity. Practical EPR experiments using the application of light irradiated rose bengal (4,5,6,7-tetrachloro-2',4',5',7'-tetraiodofluorescein) were performed in the TE_U02 cavity. The implementation of these geometries providing a practical designs for uniform field resonators that continue resonator advancements towards quantitative EPR spectroscopy.

Author List

Sidabras JW, Sarna T, Mett RR, Hyde JS

Authors

Richard R. Mett PhD Adjunct Professor in the Biophysics department at Medical College of Wisconsin
Jason W. Sidabras PhD Assistant Professor in the Biophysics department at Medical College of Wisconsin

MESH terms used to index this publication - Major topics in bold

Algorithms
Electromagnetic Fields
Electron Spin Resonance Spectroscopy
Equipment Design
Finite Element Analysis
Fluorescent Dyes
Indoles
Isoindoles
Microwaves
Polytetrafluoroethylene
Rose Bengal
Water