Optimal dielectric and cavity configurations for improving the efficiency of electron paramagnetic resonance probes

Elnaggar, Sameh Y.; Tervo, R.; Mattar, Saba M.

doi:10.1016/j.jmr.2014.05.011

Cited by 10 publications

(13 citation statements)

References 28 publications

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“…The full potential of ring DRs is exploited for very small samples with a volume of a portion of a nanolitre (nl) as the DRs allow both for a good positioning of small samples within the hole (orientation maintaining with respect to sample tube) and a signal enhancement of about one order of magnitude and beyond: one advantage of DRs is the fact, that the higher C i =C ref only leads to stronger mw fields in the vicinity of the sample which has been calculated with CMT [19,20]. Mett et al and Elnaggar et al show that the field conversion constant C which is directly related to the probe's efficiency parameter K is crucial for the sensitivity of EPR spectrometers.…”

Section: Epr Performance Of Drs At Room and Low Temperaturesmentioning

confidence: 99%

“…1-3 this geometry requires relative permittivities of the DRs of 70 or more to serve for X-band frequencies. More sophisticated ways of predicting required dimensions employing finite element simulation or novel improvements of coupled mode theory (CMT) are presented by other authors [19][20][21]. Those theoretical investigations with Table 1.…”

Section: Introductionmentioning

confidence: 99%

“…Here, a thin capillary (ø = 200 lm) is positioned with grease inside the hole of K80 (ø = 1 mm). c Superposition of TE 01d -mode of a DR (thin, red) and TE 102 mode of the cavity resonator (dashed, blue) in the notation of [16] (color online) simulations and CMT of DRs coupled to cavity resonators found the TE 01d mode being able to couple in a parallel (symmetric, in phase) and antiparallel (antisymmetric, out of phase) configuration with respect to the TE 102 or TM 110 modes of the rectangular or cylindrical cavities, respectively [7,11,[19][20][21]. The parallel field superposition results in lower resonance frequencies and the antiparallel fields shows the opposite behavior with higher coupled microwave (mw) resonance frequencies.…”

Section: Introductionmentioning

confidence: 99%

“…A proportionality constant C for the incident mw power to B 1 -field conversion which is referred to as probe's efficiency parameter 2K by other authors [19,20] can be given as…”

Section: Introductionmentioning

confidence: 99%

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Dielectric Ceramic EPR Resonators for Low Temperature Spectroscopy at X-band Frequencies

Friedländer

Ovchar²,

Voigt

et al. 2014

Appl Magn Reson

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The performance of new dielectric ceramic resonators (DRs) for continuous wave (cw) X-band electron paramagnetic resonance (EPR) spectroscopy is investigated at room temperature and low temperatures (77, 6 K). The DRs with high dielectric constants of about e r ¼ 80, featuring low residual paramagnetic impurities, have been developed and produced on the basis of barium lanthanide titanates solid solutions with the general formula Ba 6Àx Ln 8þ2x=3 Ti 18 O 54 (Ln = Sm, Nd) that demonstrate at once low dielectric losses in the microwave range (tan d ¼ 7-14 9 10 -4 at 10 GHz) and appropriate temperature stability of the dielectric constant (s e ¼ AE5 ppm/K). They were optimized for samples with small dimensions and can be used in commercial Oxford instruments flow cryostats if the coupling is done via cavity resonators. We found a maximal EPR signal enhancement by a factor up to 74 at 6 K. The increases of quality and filling factors as well as that of the microwave (mw) B 1 -field in the resonator setup are discussed in dependence on temperature. We show that the absolute sensitivity gain must be related to that increase in the mw field and the remaining relative gain of the SNR is Electronic supplementary material The online version of this article (Applied Magnetic Resonanceabout 18 for small samples. The developed DRs have shown a good potential in EPR application as reliable and easy-to-use components allowing research of thin films and in particular small crystalline structures.

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Section: Epr Performance Of Drs At Room and Low Temperaturesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

“…A proportionality constant C for the incident mw power to B 1 -field conversion which is referred to as probe's efficiency parameter 2K by other authors [19,20] can be given as…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Dielectric Ceramic EPR Resonators for Low Temperature Spectroscopy at X-band Frequencies

Friedländer

Ovchar²,

Voigt

et al. 2014

Appl Magn Reson

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show abstract

“…cavity [5]- [9]. In all of these situations, the frequencies and fields of the resonators are affected by the presence of nearby conductors.…”

mentioning

confidence: 99%

Coupled Mode Theory Applied to Resonators in the Presence of Conductors

Elnaggar

Tervo

Mattar

2015

IEEE Trans. Microwave Theory Techn.

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Using the method of images, Energy Coupled Mode Theory (ECMT), a coupled mode equation in the frequency domain, is extended to deal with important cases where resonators are in close proximity to conducting surfaces. Depending on the type of conductors and the orientation of the resonators, the method of images determines the relative phases of the images. Using the formed images, the coupled frequencies and fields can be determined by applying ECMT. Two cases are studied. In the first case, it is shown that a dielectric resonator inserted in a cavity couples with both the mirror image and the cavity. The frequency behavior is described by the interaction with the image which counteracts that with the cavity. The second case is that of resonators sandwiched between conducting plates. It is shown that an infinite array of stacked images is formed. The coupling of the resonator with its images determines the coupled frequencies and fields. In this context, the main advantage of ECMT is its ability to separate the effects of the walls from the uncoupled system. This means that the system parameters are independent of the separation distances and/or the type of conductors, which renders the post processing analyses easier and predictable. Provided that the behaviors of the uncoupled resonators are known, ECMT is general and can be applied to more complex systems.

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Modes and Fields of Two Stacked Dielectric Resonators in a Cavity of an Electron Paramagnetic Resonance Probe

Mattar

Elnaggar

2017

Appl Magn Reson

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Optimal dielectric and cavity configurations for improving the efficiency of electron paramagnetic resonance probes

Cited by 10 publications

References 28 publications

Dielectric Ceramic EPR Resonators for Low Temperature Spectroscopy at X-band Frequencies

Dielectric Ceramic EPR Resonators for Low Temperature Spectroscopy at X-band Frequencies

Coupled Mode Theory Applied to Resonators in the Presence of Conductors

Modes and Fields of Two Stacked Dielectric Resonators in a Cavity of an Electron Paramagnetic Resonance Probe

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