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Title: Hyperbolic-cosine waveguide tapers and oversize rectangular waveguide for reduced broadband insertion loss in W-band electron paramagnetic resonance spectroscopy. II. Broadband characterization

Abstract

Experimental results have been reported on an oversize rectangular waveguide assembly operating nominally at 94 GHz. It was formed using commercially available WR28 waveguide as well as a pair of specially designed tapers with a hyperbolic-cosine shape from WR28 to WR10 waveguide [R. R. Mett et al., Rev. Sci. Instrum. 82, 074704 (2011)]. The oversize section reduces broadband insertion loss for an Electron Paramagnetic Resonance (EPR) probe placed in a 3.36 T magnet. Hyperbolic-cosine tapers minimize reflection of the main mode and the excitation of unwanted propagating waveguide modes. Oversize waveguide is distinguished from corrugated waveguide, overmoded waveguide, or quasi-optic techniques by minimal coupling to higher-order modes. Only the TE{sub 10} mode of the parent WR10 waveguide is propagated. In the present work, a new oversize assembly with a gradual 90° twist was implemented. Microwave power measurements show that the twisted oversize waveguide assembly reduces the power loss in the observe and pump arms of a W-band bridge by an average of 2.35 dB and 2.41 dB, respectively, over a measured 1.25 GHz bandwidth relative to a straight length of WR10 waveguide. Network analyzer measurements confirm a decrease in insertion loss of 2.37 dB over a 4 GHz bandwidth andmore » show minimal amplitude distortion of approximately 0.15 dB. Continuous wave EPR experiments confirm these results. The measured phase variations of the twisted oversize waveguide assembly, relative to an ideal distortionless transmission line, are reduced by a factor of two compared to a straight length of WR10 waveguide. Oversize waveguide with proper transitions is demonstrated as an effective way to increase incident power and the return signal for broadband EPR experiments. Detailed performance characteristics, including continuous wave experiment using 1 μM 2,2,6,6-tetramethylpiperidine-1-oxyl in aqueous solution, provided here serve as a benchmark for other broadband low-loss probes in millimeter-wave EPR bridges.« less

Authors:
; ; ;  [1];  [1];  [1]
  1. Department of Biophysics, Medical College of Wisconsin, Milwaukee, Wisconsin 53226 (United States)
Publication Date:
OSTI Identifier:
22597094
Resource Type:
Journal Article
Journal Name:
Review of Scientific Instruments
Additional Journal Information:
Journal Volume: 87; Journal Issue: 3; Other Information: (c) 2016 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA); Journal ID: ISSN 0034-6748
Country of Publication:
United States
Language:
English
Subject:
46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND TECHNOLOGY; 75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; AQUEOUS SOLUTIONS; COMPARATIVE EVALUATIONS; ELECTRON SPIN RESONANCE; ELECTRONS; EXCITATION; GHZ RANGE 01-100; LENGTH; MAGNETS; MICROWAVE RADIATION; PARAMAGNETISM; POWER LOSSES; PROBES; SIGNALS; SPECTROSCOPY; WAVEGUIDES

Citation Formats

Sidabras, Jason W., Anderson, James R., Mainali, Laxman, Hyde, James S., Strangeway, Robert A., Department of Electrical Engineering and Computer Science, Milwaukee School of Engineering, Milwaukee, Wisconsin 53201, Mett, Richard R., and Department of Chemistry and Physics, Milwaukee School of Engineering, Milwaukee, Wisconsin 53201. Hyperbolic-cosine waveguide tapers and oversize rectangular waveguide for reduced broadband insertion loss in W-band electron paramagnetic resonance spectroscopy. II. Broadband characterization. United States: N. p., 2016. Web. doi:10.1063/1.4942642.
Sidabras, Jason W., Anderson, James R., Mainali, Laxman, Hyde, James S., Strangeway, Robert A., Department of Electrical Engineering and Computer Science, Milwaukee School of Engineering, Milwaukee, Wisconsin 53201, Mett, Richard R., & Department of Chemistry and Physics, Milwaukee School of Engineering, Milwaukee, Wisconsin 53201. Hyperbolic-cosine waveguide tapers and oversize rectangular waveguide for reduced broadband insertion loss in W-band electron paramagnetic resonance spectroscopy. II. Broadband characterization. United States. doi:10.1063/1.4942642.
Sidabras, Jason W., Anderson, James R., Mainali, Laxman, Hyde, James S., Strangeway, Robert A., Department of Electrical Engineering and Computer Science, Milwaukee School of Engineering, Milwaukee, Wisconsin 53201, Mett, Richard R., and Department of Chemistry and Physics, Milwaukee School of Engineering, Milwaukee, Wisconsin 53201. Tue . "Hyperbolic-cosine waveguide tapers and oversize rectangular waveguide for reduced broadband insertion loss in W-band electron paramagnetic resonance spectroscopy. II. Broadband characterization". United States. doi:10.1063/1.4942642.
@article{osti_22597094,
title = {Hyperbolic-cosine waveguide tapers and oversize rectangular waveguide for reduced broadband insertion loss in W-band electron paramagnetic resonance spectroscopy. II. Broadband characterization},
author = {Sidabras, Jason W. and Anderson, James R. and Mainali, Laxman and Hyde, James S. and Strangeway, Robert A. and Department of Electrical Engineering and Computer Science, Milwaukee School of Engineering, Milwaukee, Wisconsin 53201 and Mett, Richard R. and Department of Chemistry and Physics, Milwaukee School of Engineering, Milwaukee, Wisconsin 53201},
abstractNote = {Experimental results have been reported on an oversize rectangular waveguide assembly operating nominally at 94 GHz. It was formed using commercially available WR28 waveguide as well as a pair of specially designed tapers with a hyperbolic-cosine shape from WR28 to WR10 waveguide [R. R. Mett et al., Rev. Sci. Instrum. 82, 074704 (2011)]. The oversize section reduces broadband insertion loss for an Electron Paramagnetic Resonance (EPR) probe placed in a 3.36 T magnet. Hyperbolic-cosine tapers minimize reflection of the main mode and the excitation of unwanted propagating waveguide modes. Oversize waveguide is distinguished from corrugated waveguide, overmoded waveguide, or quasi-optic techniques by minimal coupling to higher-order modes. Only the TE{sub 10} mode of the parent WR10 waveguide is propagated. In the present work, a new oversize assembly with a gradual 90° twist was implemented. Microwave power measurements show that the twisted oversize waveguide assembly reduces the power loss in the observe and pump arms of a W-band bridge by an average of 2.35 dB and 2.41 dB, respectively, over a measured 1.25 GHz bandwidth relative to a straight length of WR10 waveguide. Network analyzer measurements confirm a decrease in insertion loss of 2.37 dB over a 4 GHz bandwidth and show minimal amplitude distortion of approximately 0.15 dB. Continuous wave EPR experiments confirm these results. The measured phase variations of the twisted oversize waveguide assembly, relative to an ideal distortionless transmission line, are reduced by a factor of two compared to a straight length of WR10 waveguide. Oversize waveguide with proper transitions is demonstrated as an effective way to increase incident power and the return signal for broadband EPR experiments. Detailed performance characteristics, including continuous wave experiment using 1 μM 2,2,6,6-tetramethylpiperidine-1-oxyl in aqueous solution, provided here serve as a benchmark for other broadband low-loss probes in millimeter-wave EPR bridges.},
doi = {10.1063/1.4942642},
journal = {Review of Scientific Instruments},
issn = {0034-6748},
number = 3,
volume = 87,
place = {United States},
year = {2016},
month = {3}
}