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Hyde JS, Strangeway RA, Sidabras JW. Dispersion EPR: Considerations for Low-Frequency Experiments. APPLIED MAGNETIC RESONANCE 2022; 53:193-206. [PMID: 35464635 PMCID: PMC9030583 DOI: 10.1007/s00723-021-01352-z] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/16/2021] [Revised: 04/28/2021] [Accepted: 05/12/2021] [Indexed: 06/14/2023]
Abstract
The hypothesis is made that the dispersion electron paramagnetic resonance (EPR) spectrum can yield a higher signal-to-noise ratio than the absorption spectrum in diagnostic examinations if phase noise in the bridge is under control. The rationale for this hypothesis is based on the observation that the dispersion spectrum becomes more intense than the absorption spectrum at high incident powers. The rationale is dependent on optimization of high microwave efficiency (Λ; mT/W1/2) and low quality factor (Q-value) resonators as well as the use of microwave sources with reduced phase noise. Microwave frequencies from 1.2 to 94 GHz are considered. Although the dispersion display appears to be observable with an adequate signal-to-noise ratio for most EPR research initiatives, a weakness of microwave bridges for studies at high incident microwave power was identified. Spurious leakage of incident microwave power through the circulator, thereby bypassing the probe leading to the resonator, can result in a decreased signal-to-noise ratio in both absorption and dispersion because of phase noise. For dispersion EPR with low Q-value sample resonators, this leakage is the primary contributor to phase noise at the receiver. In this work, we focus on the design of microwave reflection bridges and discuss possible methods to ameliorate this source of noise.
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Affiliation(s)
- James S. Hyde
- Medical College of Wisconsin, Department of Biophysics, Milwaukee, WI, USA
| | - Robert A. Strangeway
- Medical College of Wisconsin, Department of Biophysics, Milwaukee, WI, USA
- Milwaukee School of Engineering, Department of Electrical Engineering and Computer Science, Milwaukee, WI, USA
| | - Jason W. Sidabras
- Medical College of Wisconsin, Department of Biophysics, Milwaukee, WI, USA
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2
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Twig Y, Sorkin A, Cristea D, Feintuch A, Blank A. Surface loop-gap resonators for electron spin resonance at W-band. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2017; 88:123901. [PMID: 29289191 DOI: 10.1063/1.5000946] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Electron spin resonance (ESR) is a spectroscopic method used to detect paramagnetic materials, reveal their structure, and also image their position in a sample. ESR makes use of a large static magnetic field to split the energy levels of the electron magnetic moment of the paramagnetic species. A strong microwave magnetic field is applied to excite the spins, and subsequently the ESR system detects their faint microwave signal response. The sensitivity of an ESR system is greatly influenced by the magnitude of the static field and the properties of the microwave resonator used to detect the spin signal. In general terms, the higher the static field (microwave frequency) and the smaller the resonator, the more sensitive the system will be. Previous work aimed at high-sensitivity ESR was focused on the development and testing of very small resonators operating at moderate magnetic fields in the range of ∼0.1-1.2 T (maximum frequency of ∼35 GHz). Here, we describe the design, construction, and testing of recently developed miniature surface loop-gap resonators used in ESR and operating at a much higher frequency of ∼95 GHz (W-band, corresponding to a field of ∼3.4 T). Such resonators can greatly enhance the sensitivity of ESR and also improve the resulting spectral resolution due to the higher static field employed. A detailed description of the resonator's design and coupling mechanism, as well as the supporting probe head, is provided. We also discuss the production method of the resonators and probe head and, in the end, provide preliminary experimental results that show the setup's high spin sensitivity and compare it to theoretical predictions.
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Affiliation(s)
- Ygal Twig
- Schulich Faculty of Chemistry, Technion-Israel Institute of Technology, Haifa 32000, Israel
| | - Anton Sorkin
- Schulich Faculty of Chemistry, Technion-Israel Institute of Technology, Haifa 32000, Israel
| | - David Cristea
- Schulich Faculty of Chemistry, Technion-Israel Institute of Technology, Haifa 32000, Israel
| | - Akiva Feintuch
- Department of Chemical Physics, Weizmann Institute of Science, Rehovot 76100, Israel
| | - Aharon Blank
- Schulich Faculty of Chemistry, Technion-Israel Institute of Technology, Haifa 32000, Israel
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Hyde JS. Autobiography of James S. Hyde. APPLIED MAGNETIC RESONANCE 2017; 48:1103-1147. [PMID: 29962662 PMCID: PMC6022859 DOI: 10.1007/s00723-017-0950-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
The papers, book chapters, reviews, and patents by James S. Hyde in the bibliography of this document have been separated into EPR and MRI sections, and within each section by topics. Within each topic, publications are listed chronologically. A brief summary is provided for each patent listed. A few publications and patents that do not fit this schema have been omitted. This list of publications is preceded by a scientific autobiography that focuses on selected topics that are judged to have been of most scientific importance. References to many of the publications and patents in the bibliography are made in the autobiography.
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Affiliation(s)
- James S Hyde
- Department of Biophysics, Medical College of Wisconsin, 8701 Watertown Plan Road, Milwaukee, WI 53226; 414-955-4000; ; ORCID: 0000-0002-3023-1243
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Sidabras JW, Sarna T, Mett RR, Hyde JS. Uniform field loop-gap resonator and rectangular TE U02 for aqueous sample EPR at 94GHz. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2017; 282:129-135. [PMID: 28803092 PMCID: PMC5793860 DOI: 10.1016/j.jmr.2017.08.001] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/06/2017] [Revised: 08/03/2017] [Accepted: 08/04/2017] [Indexed: 05/03/2023]
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 TEU02 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 TEU02 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 TEU02 cavity. The implementation of these geometries providing a practical designs for uniform field resonators that continue resonator advancements towards quantitative EPR spectroscopy.
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Affiliation(s)
- Jason W Sidabras
- Max Planck for Chemical Energy Conversion, Department of Biophysical Chemistry, Mülheim an der Ruhr 45468, Germany; Medical College of Wisconsin, Department of Biophysics, Milwaukee, WI 53226-0509, United States.
| | - Tadeusz Sarna
- Department of Biophysics, Faculty of Biochemistry, Biophysics and Biotechnology, Jagiellonian University, Kraków, Poland
| | - Richard R Mett
- Medical College of Wisconsin, Department of Biophysics, Milwaukee, WI 53226-0509, United States; Milwaukee School of Engineering, Department of Physics and Chemistry, Milwaukee, WI 53202-3109, United States
| | - James S Hyde
- Medical College of Wisconsin, Department of Biophysics, Milwaukee, WI 53226-0509, United States
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Strangeway RA, Hyde JS, Camenisch TG, Sidabras JW, Mett RR, Anderson JR, Ratke JJ, Subczynski WK. Broadband W-band Rapid Frequency Sweep Considerations for Fourier Transform EPR. Cell Biochem Biophys 2017; 75:259-273. [PMID: 28555359 DOI: 10.1007/s12013-017-0804-7] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2017] [Accepted: 05/04/2017] [Indexed: 10/19/2022]
Abstract
A multi-arm W-band (94 GHz) electron paramagnetic resonance spectrometer that incorporates a loop-gap resonator with high bandwidth is described. A goal of the instrumental development is detection of free induction decay following rapid sweep of the microwave frequency across the spectrum of a nitroxide radical at physiological temperature, which is expected to lead to a capability for Fourier transform electron paramagnetic resonance. Progress toward this goal is a theme of the paper. Because of the low Q-value of the loop-gap resonator, it was found necessary to develop a new type of automatic frequency control, which is described in an appendix. Path-length equalization, which is accomplished at the intermediate frequency of 59 GHz, is analyzed. A directional coupler is favored for separation of incident and reflected power between the bridge and the loop-gap resonator. Microwave leakage of this coupler is analyzed. An oversize waveguide with hyperbolic-cosine tapers couples the bridge to the loop-gap resonator, which results in reduced microwave power and signal loss. Benchmark sensitivity data are provided. The most extensive application of the instrument to date has been the measurement of T1 values using pulse saturation recovery. An overview of that work is provided.
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Affiliation(s)
- Robert A Strangeway
- National Biomedical EPR Center, Department of Biophysics, Medical College of Wisconsin, 8701 Watertown Plank Road, Milwaukee, WI, 53226, USA.,Department of Electrical Engineering and Computer Science, Milwaukee School of Engineering, 1025 North Broadway, Milwaukee, WI, 53202, USA
| | - James S Hyde
- National Biomedical EPR Center, Department of Biophysics, Medical College of Wisconsin, 8701 Watertown Plank Road, Milwaukee, WI, 53226, USA.
| | - Theodore G Camenisch
- National Biomedical EPR Center, Department of Biophysics, Medical College of Wisconsin, 8701 Watertown Plank Road, Milwaukee, WI, 53226, USA
| | - Jason W Sidabras
- National Biomedical EPR Center, Department of Biophysics, Medical College of Wisconsin, 8701 Watertown Plank Road, Milwaukee, WI, 53226, USA
| | - Richard R Mett
- National Biomedical EPR Center, Department of Biophysics, Medical College of Wisconsin, 8701 Watertown Plank Road, Milwaukee, WI, 53226, USA.,Department of Physics and Chemistry, Milwaukee School of Engineering, 1025 North Broadway, Milwaukee, WI, 53202, USA
| | - James R Anderson
- National Biomedical EPR Center, Department of Biophysics, Medical College of Wisconsin, 8701 Watertown Plank Road, Milwaukee, WI, 53226, USA
| | - Joseph J Ratke
- National Biomedical EPR Center, Department of Biophysics, Medical College of Wisconsin, 8701 Watertown Plank Road, Milwaukee, WI, 53226, USA
| | - Witold K Subczynski
- National Biomedical EPR Center, Department of Biophysics, Medical College of Wisconsin, 8701 Watertown Plank Road, Milwaukee, WI, 53226, USA
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6
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Tipikin DS, Swarts SG, Sidabras JW, Trompier F, Swartz HM. POSSIBLE NATURE OF THE RADIATION-INDUCED SIGNAL IN NAILS: HIGH-FIELD EPR, CONFIRMING CHEMICAL SYNTHESIS, AND QUANTUM CHEMICAL CALCULATIONS. RADIATION PROTECTION DOSIMETRY 2016; 172:112-120. [PMID: 27522053 PMCID: PMC5225972 DOI: 10.1093/rpd/ncw216] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Exposure of finger- and toe-nails to ionizing radiation generates an Electron Paramagnetic Resonance (EPR) signal whose intensity is dose dependent and stable at room temperature for several days. The dependency of the radiation-induced signal (RIS) on the received dose may be used as the basis for retrospective dosimetry of an individual's fortuitous exposure to ionizing radiation. Two radiation-induced signals, a quasi-stable (RIS2) and stable signal (RIS5), have been identified in nails irradiated up to a dose of 50 Gy. Using X-band EPR, both RIS signals exhibit a singlet line shape with a line width around 1.0 mT and an apparent g-value of 2.0044. In this work, we seek information on the exact chemical nature of the radiation-induced free radicals underlying the signal. This knowledge may provide insights into the reason for the discrepancy in the stabilities of the two RIS signals and help develop strategies for stabilizing the radicals in nails or devising methods for restoring the radicals after decay. In this work an analysis of high field (94 GHz and 240 GHz) EPR spectra of the RIS using quantum chemical calculations, the oxidation-reduction properties and the pH dependence of the signal intensities are used to show that spectroscopic and chemical properties of the RIS are consistent with a semiquinone-type radical underlying the RIS. It has been suggested that semiquinone radicals formed on trace amounts of melanin in nails are the basis for the RIS signals. However, based on the quantum chemical calculations and chemical properties of the RIS, it is likely that the radicals underlying this signal are generated from the radiolysis of L-3,4-dihydroxyphenylalanine (DOPA) amino acids in the keratin proteins. These DOPA amino acids are likely formed from the exogenous oxidation of tyrosine in keratin by the oxygen from the air prior to irradiation. We show that these DOPA amino acids can work as radical traps, capturing the highly reactive and unstable sulfur-based radicals and/or alkyl radicals generated during the radiation event and are converted to the more stable o-semiquinone anion-radicals. From this understanding of the oxidation-reduction properties of the RIS, it may be possible to regenerate the unstable RIS2 following its decay through treatment of nail clippings. However, the treatment used to recover the RIS2 also has the ability to recover an interfering, mechanically-induced signal (MIS) formed when the nail is clipped. Therefore, to use the recovered (regenerated) RIS2 to increase the detection limits and precision of the RIS measurements and, therefore, the dose estimates calculated from the RIS signal amplitudes, will require the application of methods to differentiate the RIS2 from the recovered MIS signal.
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Affiliation(s)
- Dmitriy S Tipikin
- EPR Center at Dartmouth, Department of Radiology, Geisel School of Medicine at Dartmouth, Lebanon, NH 03766, USA
| | - Steven G Swarts
- Department of Radiation Oncology, University of Florida, Gainesville, FL 32610, USA
| | - Jason W Sidabras
- Department of Biophysics, Medical College of Wisconsin, Milwaukee, WI 53226, USA
| | - François Trompier
- Institut de Radioprotection et de Sûreté Nucléaire, BP 17, F-92265 Fontenay-aux-roses, France
| | - Harold M Swartz
- EPR Center at Dartmouth, Department of Radiology, Geisel School of Medicine at Dartmouth, Lebanon, NH 03766, USA
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Quine RW, Rinard GA, Shi Y, Buchanan L, Biller JR, Eaton SS, Eaton GR. UHF EPR spectrometer operating at frequencies between 400 MHz and 1 GHz. CONCEPTS IN MAGNETIC RESONANCE. PART B, MAGNETIC RESONANCE ENGINEERING 2016; 46B:123-133. [PMID: 28190987 PMCID: PMC5300075 DOI: 10.1002/cmr.b.21328] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
A spectrometer was designed and constructed to facilitate measurements of T1, T2, spin echo signal-to-noise, and resonator quality factor, Q, between about 400 and 1000 MHz. Pulse patterns are generated at 250 MHz and mixed with the output from a second source to perform excitation and detection. A cross-loop resonator was constructed in which the same sample could be measured in the same resonator over the full range of frequencies. An air-core, 4-coil, water-cooled electromagnet with a large experimental volume was built.
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Affiliation(s)
- Richard W. Quine
- Ritchie School of Engineering and Computer Science, University of Denver, Denver, Colorado 80210 USA
| | - George A. Rinard
- Ritchie School of Engineering and Computer Science, University of Denver, Denver, Colorado 80210 USA
| | - Yilin Shi
- Department of Chemistry and Biochemistry, University of Denver, Denver, Colorado, 80210 USA
| | - Laura Buchanan
- Department of Chemistry and Biochemistry, University of Denver, Denver, Colorado, 80210 USA
| | - Joshua R. Biller
- Department of Chemistry and Biochemistry, University of Denver, Denver, Colorado, 80210 USA
| | - Sandra S. Eaton
- Department of Chemistry and Biochemistry, University of Denver, Denver, Colorado, 80210 USA
| | - Gareth R. Eaton
- Department of Chemistry and Biochemistry, University of Denver, Denver, Colorado, 80210 USA
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Sidabras JW, Strangeway RA, Mett RR, Anderson JR, Mainali L, Hyde JS. Hyperbolic-cosine waveguide tapers and oversize rectangular waveguide for reduced broadband insertion loss in W-band electron paramagnetic resonance spectroscopy. II. Broadband characterization. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2016; 87:034704. [PMID: 27036800 PMCID: PMC4798996 DOI: 10.1063/1.4942642] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/29/2015] [Accepted: 02/11/2016] [Indexed: 06/05/2023]
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 TE10 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.
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Affiliation(s)
- Jason W Sidabras
- Department of Biophysics, Medical College of Wisconsin, Milwaukee, Wisconsin 53226, USA
| | - Robert A Strangeway
- Department of Biophysics, Medical College of Wisconsin, Milwaukee, Wisconsin 53226, USA
| | - Richard R Mett
- Department of Biophysics, Medical College of Wisconsin, Milwaukee, Wisconsin 53226, USA
| | - James R Anderson
- Department of Biophysics, Medical College of Wisconsin, Milwaukee, Wisconsin 53226, USA
| | - Laxman Mainali
- Department of Biophysics, Medical College of Wisconsin, Milwaukee, Wisconsin 53226, USA
| | - James S Hyde
- Department of Biophysics, Medical College of Wisconsin, Milwaukee, Wisconsin 53226, USA
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Webb A. Cavity- and waveguide-resonators in electron paramagnetic resonance, nuclear magnetic resonance, and magnetic resonance imaging. PROGRESS IN NUCLEAR MAGNETIC RESONANCE SPECTROSCOPY 2014; 83:1-20. [PMID: 25456314 DOI: 10.1016/j.pnmrs.2014.09.003] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/23/2014] [Revised: 09/30/2014] [Accepted: 09/30/2014] [Indexed: 06/04/2023]
Abstract
Cavity resonators are widely used in electron paramagnetic resonance, very high field magnetic resonance microimaging and also in high field human imaging. The basic principles and designs of different forms of cavity resonators including rectangular, cylindrical, re-entrant, cavity magnetrons, toroidal cavities and dielectric resonators are reviewed. Applications in EPR and MRI are summarized, and finally the topic of traveling wave MRI using the magnet bore as a waveguide is discussed.
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Affiliation(s)
- Andrew Webb
- C.J. Gorter Center for High Field MRI, Department of Radiology, Leiden University Medical Center, Leiden, The Netherlands.
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10
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Mett RR, Sidabras JW, Anderson JR, Hyde JS. Hyperbolic-cosine waveguide tapers and oversize rectangular waveguide for reduced broadband insertion loss in W-band electron paramagnetic resonance spectroscopy. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2011; 82:074704. [PMID: 21806211 PMCID: PMC3155584 DOI: 10.1063/1.3607432] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/07/2023]
Abstract
The two-way insertion loss of a 1 m length of waveguide was reduced by nearly 5 dB over a 4% bandwidth at W-band (94 GHz) for an electron paramagnetic resonance (EPR) spectrometer relative to WR10 waveguide. The waveguide has an oversize section of commercially available rectangular WR28 and a novel pair of tapers that vary in cross section with axial position according to a hyperbolic-cosine (HC) function. The tapers connect conventional rectangular WR10 waveguide to the WR28. For minimum loss, the main mode electric field is parallel to the long side of the WR28. Using mode coupling theory, the position of maximum flare (inflection point) in the taper was optimized with respect to the coupling to higher order modes and the reflection of the main mode. The optimum inflection point position is about one-tenth of the taper length from the small end of the taper. Reflection and coupling were reduced by about 20 dB relative to a pyramidal (linear) taper of the same length. Comb-like dips in the transmission coefficient produced by resonances of the higher order modes in the oversize section were about 0.03 dB. Specially designed high-precision, adjustable WR28 flanges with alignment to about 5 μm were required to keep higher order mode amplitudes arising from the flanges comparable to those from the HC tapers. Minimum return loss was about 30 dB. This paper provides a foundation for further optimization, if needed. Methods are not specific to EPR or the microwave frequency band.
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Affiliation(s)
- R R Mett
- Department of Biophysics, Medical College of Wisconsin, Milwaukee, Wisconsin 53226-0509, USA
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Hyde JS, Strangeway RA, Camenisch TG, Ratke JJ, Froncisz W. W-band frequency-swept EPR. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2010; 205:93-101. [PMID: 20462775 PMCID: PMC2885579 DOI: 10.1016/j.jmr.2010.04.005] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/16/2010] [Revised: 04/09/2010] [Accepted: 04/09/2010] [Indexed: 05/12/2023]
Abstract
This paper describes a novel experiment on nitroxide radical spin labels using a multiarm EPR W-band bridge with a loop-gap resonator (LGR). We demonstrate EPR spectroscopy of spin labels by linear sweep of the microwave frequency across the spectrum. The high bandwidth of the LGR, about 1 GHz between 3 dB points of the microwave resonance, makes this new experiment possible. A frequency-tunable yttrium iron garnet (YIG) oscillator provides sweep rates as high as 1.8x10(5) GHz/s, which corresponds to 6.3 kT/s in magnetic field-sweep units over a 44 MHz range. Two experimental domains were identified. In the first, linear frequency sweep rates were relatively slow, and pure absorption and pure dispersion spectra were obtained. This appears to be a practical mode of operation at the present level of technological development. The main advantage is the elimination of sinusoidal magnetic field modulation. In the second mode, the frequency is swept rapidly across a portion of the spectrum, and then the frequency sweep is stopped for a readout period; FID signals from a swept line oscillate at a frequency that is the difference between the spectral position of the line in frequency units and the readout position. If there is more than one line, oscillations are superimposed. The sweep rates using the YIG oscillator were too slow, and the portion of the spectrum too narrow to achieve the full EPR equivalent of Fourier transform (FT) NMR. The paper discusses technical advances required to reach this goal. The hypothesis that trapezoidal frequency sweep is an enabling technology for FT EPR is supported by this study.
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Affiliation(s)
- James S Hyde
- National Biomedical EPR Center, Department of Biophysics, Medical College of Wisconsin, Milwaukee, WI 53226, USA.
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12
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Quine RW, Czechowski T, Eaton GR. A Linear Magnetic Field Scan Driver. CONCEPTS IN MAGNETIC RESONANCE. PART B, MAGNETIC RESONANCE ENGINEERING 2009; 35B:44-58. [PMID: 19838315 PMCID: PMC2762224 DOI: 10.1002/cmr.b.20128] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Abstract
A linear magnetic field scan driver was developed to provide a rapidly scanning magnetic field for use in electron paramagnetic resonance (EPR) spectroscopy. The driver consists of two parts: a digitally synthesized ramp waveform generator and a power amplifier to drive the magnetic field coils. Additionally, the driver provides a trigger signal to a data collection digitizer that is synchronized to the ramp waveform. The driver can also drive an arbitrary current waveform supplied from an external source. The waveform generator is computer controlled through a serial data interface. Additional functions are controlled by the user from the driver front panel. The frequency and amplitude of the waveform are each separately controlled with 12-bit resolution (one part in 4,096). Several versions of the driver have been built with different frequency and amplitude ranges. Frequencies range from 500 to 20,000 Hz. Field sweep amplitudes range up to 80 G(pp). This article also gives a brief description of the field coils that are driven by the driver.
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Affiliation(s)
- Richard W Quine
- Department of Engineering, University of Denver, Denver, CO 80208
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13
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Froncisz W, Camenisch TG, Ratke JJ, Anderson JR, Subczynski WK, Strangeway RA, Sidabras JW, Hyde JS. Saturation recovery EPR and ELDOR at W-band for spin labels. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2008; 193:297-304. [PMID: 18547848 PMCID: PMC2561891 DOI: 10.1016/j.jmr.2008.05.008] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/07/2007] [Revised: 04/30/2008] [Accepted: 05/14/2008] [Indexed: 05/03/2023]
Abstract
A reference arm W-band (94 GHz) microwave bridge with two sample-irradiation arms for saturation recovery (SR) EPR and ELDOR experiments is described. Frequencies in each arm are derived from 2 GHz synthesizers that have a common time-base and are translated to 94 GHz in steps of 33 and 59 GHz. Intended applications are to nitroxide radical spin labels and spin probes in the liquid phase. An enabling technology is the use of a W-band loop-gap resonator (LGR) [J.W. Sidabras, R.R. Mett, W. Froncisz, T.G. Camenisch, J.R. Anderson, J.S. Hyde, Multipurpose EPR loop-gap resonator and cylindrical TE(011) cavity for aqueous samples at 94 GHz, Rev. Sci. Instrum. 78 (2007) 034701]. The high efficiency parameter (8.2 GW(-1/2) with sample) permits the saturating pump pulse level to be just 5 mW or less. Applications of SR EPR and ELDOR to the hydrophilic spin labels 3-carbamoyl-2,2,5,5-tetra-methyl-3-pyrroline-1-yloxyl (CTPO) and 2,2,6,6,-tetramethyl-4-piperidone-1-oxyl (TEMPONE) are described in detail. In the SR ELDOR experiment, nitrogen nuclear relaxation as well as Heisenberg exchange transfer saturation from pumped to observed hyperfine transitions. SR ELDOR was found to be an essential method for measurements of saturation transfer rates for small molecules such as TEMPONE. Free induction decay (FID) signals for small nitroxides at W-band are also reported. Results are compared with multifrequency measurements of T(1e) previously reported for these molecules in the range of 2-35 GHz [J.S. Hyde, J.-J. Yin, W.K. Subczynski, T.G. Camenisch, J.J. Ratke, W. Froncisz, Spin label EPR T(1) values using saturation recovery from 2 to 35 GHz. J. Phys. Chem. B 108 (2004) 9524-9529]. The values of T(1e) decrease at 94 GHz relative to values at 35 GHz.
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Affiliation(s)
- Wojciech Froncisz
- Department of Biophysics, Medical College of Wisconsin, Milwaukee, WI, USA
- Jagiellonian University, Krakow, Poland
| | | | - Joseph J. Ratke
- Department of Biophysics, Medical College of Wisconsin, Milwaukee, WI, USA
| | - James R. Anderson
- Department of Biophysics, Medical College of Wisconsin, Milwaukee, WI, USA
| | | | - Robert A. Strangeway
- Department of Biophysics, Medical College of Wisconsin, Milwaukee, WI, USA
- Milwaukee School of Engineering, Milwaukee, WI, USA
| | - Jason W. Sidabras
- Department of Biophysics, Medical College of Wisconsin, Milwaukee, WI, USA
| | - James S. Hyde
- Department of Biophysics, Medical College of Wisconsin, Milwaukee, WI, USA
- Author to whom correspondence should be addressed: James S. Hyde, Ph.D., Department of Biophysics, Medical College of Wisconsin, 8701 Watertown Plank Road, Milwaukee, WI 53226-0509, Phone: (414) 456-4005, Fax: (414) 456-6512, E-mail:
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Jang ZH, Suh BJ, Corti M, Cattaneo L, Hajny D, Borsa F, Luban M. Broadband electron spin resonance at low frequency without resonant cavity. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2008; 79:046101. [PMID: 18447559 DOI: 10.1063/1.2901382] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
We have developed a nonconventional broadband electron spin resonance (ESR) spectrometer operating continuously in the frequency range from 0.5 to 9 GHz. Dual antenna structure and the microwave absorbing environment differentiate the setup from the conventional one and enable broadband operation with any combination of frequency or magnetic field modulation and frequency or magnetic field sweeping. Its performance has been tested with the measurements on a 1,1-diphenyl-2-picrylhydrazyl (DPPH) sample and with the measurements on the single molecular magnet, V6, in solid state at low temperature.
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Affiliation(s)
- Z H Jang
- Department of Physics, Kookmin University, Seoul 136-702, Republic of Korea
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