N. T. Cherpak

High sensitivity microwave characterization of organic molecule solutions of nanoliter volume

A microwave resonator composed of a sapphire cylinder and a quartz plate with a 400 nl cavity was developed for the determination of the complex permittivity of liquids at 10 GHz. This sensor was calibrated over a wide range of values for real and imaginary parts of permittivity. The measured resonator losses induced by the liquid were found to be proportional to the dipole relaxation time of the liquid molecules, as predicted by perturbation theory. Our analysis of weight concentration and temperature dependence of the measured inverse quality factor revealed a sensitivity of about 0.1% for aqueous solutions of glucose.

Behaviour of quasi-optical dielectric resonators excited with high Tc superconductors in the temperature range 10–300 K

Abstract The possibility of using quasi-optical dielectric resonators excited with higher type oscillations for the measurement of high T c superconductor surface impedance has been studied. The advantages of the resonators are evident, in that they allow investigation and non-destructive testing of HTSC made in disc form from materials of different compounds and structure over a wide frequency range. High reproducibility of the results was obtained using the chosen technique. Examples of complex studies of HTSC in the millimetre and radio-frequency ranges are given.

On the low-temperature microwave response of a YBa2Cu3O7−σ epitaxial film determined by a new measurement technique

The temperature dependence of the surface resistance RS(T) of a high-quality 600‐nm thick YBa2Cu2O7−σ epitaxial film, deposited on a MgO single-crystal substrate, has been investigated. The measurements were performed in the temperature range from Tc to 2K using a new technique—the application of a sapphire hemispherical resonator with whispering gallery mode in the 8‐mm wavelength range (Ka band). The new measurement technique makes it possible to reach high measurement sensitivity for RS(T) (to 10μΩ) at low temperatures. A linear dependence of RS(T) was obtained in the range 2–15K, in agreement with d-wave symmetry of the order parameter. The value found in the present work for the residual resistance Rres=RS(T→0) shows that the microwave properties of the film are close to those of single-crystals and, apparently, the internal properties of the superconductor determine Rres. Analysis of the published data shows that Rres(ω)∼ω3∕2 for YBa2Cu3O7−σ single crystals and films, and the nature of the residual ...

Q Factor of a Millimeter-Wave Sapphire Disk Resonator with Conductive End Plates

AbstractThe quality factor of a sapphire disk resonator with conductive end plates is studied theoreticallyand experimentally. The feasibity of measuring the sheet resistance of copper, titanium, and

Quasioptical dielectric resonators in millimeter-wave band experiments

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Conical quasioptical dielectric resonator

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Microwave-band reflection coefficient of high-temperature superconductor specimens in E-plane waveguide structures

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Giant radiofrequency magnetoabsorption in La0.5Sr0.5CoO3 cobaltite

high-temperature superconductor films in the 8-mm range is shown.