Loop-Gap Resonators

Rinard, George A.; Eaton, Gareth R.

doi:10.1007/0-306-48533-8_2

Cited by 29 publications

(25 citation statements)

References 54 publications

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“…The other is to use more symmetric topologies for the resonators. For example, an MCPGR with two-or four-gap structures could generate a more homogeneous RF magnetic field than the MCPGR with a parallel-plate capacitor we used [21]. As well as the physical structure of the resonators, use of an MCPGR at a lower frequency decreases the lens effect due to a higher dielectric constant of the subject.…”

Section: Discussionmentioning

confidence: 98%

Use of multi-coil parallel-gap resonators for co-registration EPR/NMR imaging

Kawada¹,

Hirata²,

Fujii³

2007

Journal of Magnetic Resonance

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Section: Discussionmentioning

confidence: 98%

Use of multi-coil parallel-gap resonators for co-registration EPR/NMR imaging

Kawada¹,

Hirata²,

Fujii³

2007

Journal of Magnetic Resonance

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“…6, at the price of a larger shield radius. 9 Our design focused on the compactness of the structure, which provides an excellent working behavior because of its high ξ as shown in Sec. V. The resonator cavity has a compact volume of <0.045 dm 3 (with a cell of 0.012 dm 3 ), in comparison to a TE 011 cylindrical cavity that would have a volume of 0.14 dm 3 .…”

Section: A Simulated Performancesmentioning

confidence: 99%

“…In order to achieve a compact design fulfilling the electromagnetic requirements for our application, 8 the loop-gap resonator (LGR) 9 was selected as a first model. This typology has a broad field of applications including electron spin resonance (ESR), 10 electron paramagnetic resonance (EPR), 9 and nuclear magnetic resonance (NMR) 11 as it provides excellent EM characteristics within a volume three times more compact than a simple cylindrical cavity.…”

Section: Introductionmentioning

confidence: 99%

Compact microwave cavity for high performance rubidium frequency standards

Stefanucci

Bandi

Merli

et al. 2012

Review of Scientific Instruments

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Analysis of the mode composition of an X-band overmoded O-type Cerenkov high-power microwave oscillator Phys. Plasmas 19, 103102 (2012) Gap independent coupling into parallel plate terahertz waveguides using cylindrical horn antennas J. Appl. Phys. 112, 073102 (2012) A band-pass filter approach within molecular dynamics for the prediction of intrinsic quality factors of nanoresonators J. Appl. Phys. 112, 074301 (2012) A research of W-band folded waveguide traveling wave tube with elliptical sheet electron beam Phys. Plasmas 19, 093117 (2012) Additional information on Rev. Sci. Instrum. The design, realization, and characterization of a compact magnetron-type microwave cavity operating with a TE 011 -like mode are presented. The resonator works at the rubidium hyperfine ground-state frequency (i.e., 6.835 GHz) by accommodating a glass cell of 25 mm diameter containing rubidium vapor. Its design analysis demonstrates the limitation of the loop-gap resonator lumped model when targeting such a large cell, thus numerical optimization was done to obtain the required performances. Microwave characterization of the realized prototype confirmed the expected working behavior. Double-resonance and Zeeman spectroscopy performed with this cavity indicated an excellent microwave magnetic field homogeneity: the performance validation of the cavity was done by achieving an excellent short-term clock stability as low as 2.4 × 10 −13 τ −1/2 . The achieved experimental results and the compact design make this resonator suitable for applications in portable atomic high-performance frequency standards for both terrestrial and space applications.

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“…la) [1] and later extended to numerous other cross sections including those shown in Fig. lb-d. The literature has been reviewed by Hyde and Froncisz [2] and by Rinard and Eaton [3]. Although the literature is extensive, there has been no study of the dependence of EPR performance of LGRs on the length of the structure or on the microwave characteristics as this length approaches or exceeds the free-space (FS) wavelength.…”

Section: Introductionmentioning

confidence: 99%

Uniform radio frequency fields in loop-gap resonators for EPR spectroscopy

2007

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At high frequencies, e.g., Q-and W-bands, it is advantageous to make the axial length of loop-gap resonators (LGRs) at least as long asa free-space wavelength. The opposite scaling of capacitance and inductance with LGR length suggests that the length of an LGR can be increased without limit, with the axial radio frequency (rf) field profiles and resonance frequency independent of length. This scaling is accurate for resonator dimensions much less than one free-space wavelength. When the resonator length approaches one-tenth of a free-space wavelength, the rf field uniformity degrades. From one-tenth to one free-space wavelength, computer simulations and expe¡ measurements show that the axial magnetic field energy density profile is peaked in the eenter of the LGR, gradually decreases from 25-to 50% ata distance one radius from the end, and rapidly thereafter. The nonuniformity is of two types. One type, in the vicinity of one radius of the end, is caused by the flaring of the field as it curves from the central loop to the end region, into the larger retum loop(s). The other type, in the central part of the resonator, is caused by impedance mismatch at the ends of the LGR. The LGR may be viewed asa strongly reentrant (ridge) waveguide nearly open at both ends and supporting a standing wave. A transmission line model relates the central nonuniformity to the fringing capacitance and inductance at the ends of the resonator. This nonuniformity can be eliminated in several ways including modifying the ends of the LGR by adding a small metal bridge ora dielectric ring. These uniformity trimming elements increase the fringing capacitance and/or decrease the fringing inductance. With trimmed ends, LGRs can be made many free-space wavelengths long. The maximum resonator length is determined by the proximity in frequency of the fundamental LGR mode to the next highest frequency mode as well as the quality factor. Results of this theory ate compared and confirmed with finite-element simulations. This theory connects the uniform LGR with the uniform field cavity resonators previously introduced by this laboratory.

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Loop-Gap Resonators

Cited by 29 publications

References 54 publications

Use of multi-coil parallel-gap resonators for co-registration EPR/NMR imaging

Use of multi-coil parallel-gap resonators for co-registration EPR/NMR imaging

Compact microwave cavity for high performance rubidium frequency standards

Uniform radio frequency fields in loop-gap resonators for EPR spectroscopy

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