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Levitating, controlling, and detecting the motion of mesoscopic objects is useful for inertial sensing and fundamental studies in quantum physics. We report the first experimental measurements of Meissner-effect levitation for a sequence of identical millimeter-scale neodymium magnets having varying strengths within a cm-scale superconducting aluminum coaxial quarter-wave stub cavity. We experimentally, theoretically, and analytically characterized Meissner-effect levitation within a 10 GHz superconducting aluminum coaxial quarter-wave stub cavity for a sequence of identically shaped millimeter-scale neodymium magnets having varying strengths (1.22-1.47 T). Magnet levitation within the cavity is accompanied by both gradual and abrupt shifts in the resonance frequency (with a height sensitivity as large as 400 MHz/mm) as well as changes in the total quality factor (8%-17%) as a function of temperature during the superconducting transition of the aluminum cavity. The experimental observation is confirmed with a cylindrical and spherical magnet. The controlled heating and cooling of the cavity show hysteresis in the frequency shift. Furthermore, the experimental observation has shown excellent agreement with finite element simulations, room temperature measurements, and a lumped element model.

The defect chemistry of ceria has been studied using a microwave resonator. The dielectric properties of powder samples were investigated up to 600 °C and at different oxygen partial pressures pO2 (10-26 – 0.2 bar) and evaluated using the microwave cavity perturbation theory. For the ceria powder, an activation of the oxygen incorporation and release kinetics was observed from 480 °C onwards. The data suggest that the increased losses in non-stoichiometric ceria originate from the small polaron hopping mechanism, as known from literature. In addition, an increase in material polarization due to the formation of oxygen vacancies was experimentally observed. A comparison with sintered, coarse-grained samples of the same material and with literature data also demonstrated the importance of the microstructure for the defect chemistry of ceria. For the powder (ca. 80 nm grain size), significantly higher electronic conductivities (assumedly due to the higher concentration of small polarons) and lower activation energies were detected at 600 °C. On the other hand, lower conductivities, controlled by the concentration of acceptor cations in the material were reported for the sintered samples (1.1 µm) at this temperature. The findings are well in-line with existing defect chemical models of ceria. This study presents an analysis of the microwave behavior of ceria and provides insights into intrinsic and extrinsic mechanisms of oxygen exchange in ceria. The findings also contribute to a better understanding of microwave-based state diagnosis of three-way catalysts in automotive applications.

Sustainable exploration of the Moon could benefit from a microwave heating-based 3D Printing technology for In-Situ Resource Utilisation (ISRU) purposes such as for the fabrication of habitats and extraction of resources on the Moon. In this context, we have developed a Microwave Heating Demonstrator (MHD) payload concept, which can perform pre-defined ISRU experiments on the lunar surface. The MHD payload would also produce scientifically valuable data in its own right, which would help to establish fundamental criteria for developing a microwave heating-based 3D Printing technique, ultimately enabling lunar construction and other ISRU-derived mission activities.\ud \ud One of the major design criteria of the MHD payload was to enable sustainable heating performance at low microwave power, e.g., 250 W. This paper discusses some non-negligible phenomena during the microwave heating of lunar regolith, which need to be considered for future mission applications. We also present a design of the MHD payload development, focusing on the heating performance of the microwave cavity.

Cataloged from PDF version of article. Thesis (Master's): Bilkent University, Graduate Program in Materials Science and Nanotechnology, İhsan Doğramacı Bilkent University, 2023. Includes bibliographical references (leaves 52-56). Resonance energy dissipation mechanism has been gaining importance in the interest of sensing applications. As such, the capacity for precise and fast measurement of the transient phase of motion has been desirable. The development of optomechanics in recent years has enabled such a fast scheme. Here a design, setup, and measurement of a silicon nitride optomechanical system is explored. Fundamental parameters of the design are investigated with simulation analysis. Grating structures, waveguides, and resonator parameters are explored. A series of optical resonance responses are observed, and the resonance characteristics are analyzed for optomechanical devices of combinations of design parameters. Measurements on devices of different nanomechanical beam modulation schemes are performed. To translate the technique from the optical to microwave domain, an integration of a split ring resonator (SRR) cavity and NEMS device is explored. Mode simulation of the modified cavity design is done. A technique of alignment of EBL to an existing pattern on an insulating surface is optimized. The studied designs leave possibilities for applications in real-time mass sensing and fundamental studies on energy dissipation mechanisms. by ChulHyeong Lee M.S.

The tuning of microwave cavity filters (MCFs) is a complex process to improve the filtering performance. In practice, the tuning is mostly conducted in a manual way, and thus is time and resource intensive. Toward the demand for automatic tuning of MCFs with high accuracy and efficiency, this article proposes an intelligent tuning method for MCFs via modeling and optimization. The main contributions are threefold as follows: 1) A series of performance evaluation functions are defined to comprehensively characterize the tuning output; 2) a block modeling method is proposed to construct the electromechanical characteristic model to facilitate the calculation of the cost function; 3) an improved particle swarm optimization (PSO) algorithm, named granular multi-swarm PSO (GMS-PSO), is proposed to achieve quick search of optimal combinations of the tunable components. The effectiveness and practicality of the proposed method are demonstrated by experiments with a real intelligent tuning system.

Background: Nowadays the disposal or recycling of polyethylene terephthalate (PET) material is a real-world problem. The European Union’s DEM3TO project aims at recycling PET to return it to the main chemical components with which it was produced. In a specific reactor, microwave radiation is used to quickly depolymerise the initial polymer. At the end of the de-polymerization process, a filtering and drying process through an agitated Nutsche filter (ANF) is necessary. Methods: This study aims to design and develop a High Frequency (HF) cavity inside the ANF (plugin “HF-ANF”) to speed up and improve the drying process. The effects studied are the efficiency of the HF cavity as a function of the heating process, the evaporation/drying process, and the mechanical mixing (due to the blades) of the mixture. Results: During these studies it was possible to improve the efficiency of the HF plugin and allowing to absorb more than the 95% of the microwave energy into the mixture to increase the drying speed and the drying homogeneity of the ANF. In addition, the mixture was characterised to obtain the dielectric proprieties as a function of the temperature of the ANF and the concentration of the residual water. Conclusions: The study allowed us to develop some important methodology that usually cannot to be simulated in a non-multi physics simulator. The careful modelling of certain aspects that are not normally available in EM (Electro-Magnetic) simulators, like variable geometries, mixed material, heating effect and the dielectrics characterization process are difficult and critical process but are very important steps to be undertaken in order to obtain results that can be compared with real measurements.

In this paper we will describe the characterisation of a rf detection chain based on a travelling wave parametric amplifier (TWPA). The detection chain is meant to be used for dark matter axion searches and thus it is mounted coupled to a high Q microwave resonant cavity. A system noise temperature $T_{\rm sys} = (3.3 \pm 0.1$) K has been measured at a frequency of 10.77 GHz, using a novel scheme allowing measurement of $T_{\rm sys} $ exactly at the cavity output port., Comment: 8 pages

In this paper, we present the design and implementation methods of quarter-wavelength resonators accommodating Beltrami standing waves with parallel electric and magnetic (E‖H) fields. The resonator is bounded by the quarter-wavelength longitudinal electromagnetic conductor (LEMC), the circumferential electromagnetic conductor (CMEC), and the radial electromagnetic conductor (REMC). The LEMC, CEMC, and REMC boundaries are artificially implemented by the circumferentially aligned corrugation, concentrically aligned circular fins, and axisymmetrically aligned radial fins, respectively. The coupling control methods by introducing slots in the CEMC and REMC with the external TM01 and TE01 circular waveguides are presented. We design the quarter-wavelength resonators with the implemented LEMC, CEMC, and REMC boundaries with controlled external couplings and numerically demonstrate their E‖H properties, which confirms the validity of the proposed design method.

We propose an experimentally feasible scheme for generating genuinely tripartite entanglement in a hybrid quantum system which consists of topologically protected particle-like excitations (magnetic vortices), cavity microwave photons, and solid-state spins (NV centers in diamond). The magnetic vortices and solid-state spins are simultaneously coupled to the microwave cavity photons via magnetic dipole interaction. By introducing a microwave modulation to the collective spins and under appropriate parameter regimes, we find that the steady state of the system is a genuinely tripartite entangled state where vortices, cavity photons, and spins are entangled with each other. The effect of the introduced modulation on the produced entanglement is analyzed, and we also show that the entanglement is robust against dissipation. This work may offer a promising platform for studying macroscopic quantum effects and quantum information processing with the vortex–photon–spin system.

Selenium oxide thin films are highly transparent optical layers proper for optoelectronic technology. However, SeO2 films are rarely studied and observed suffering from clustery surface morphology, low light absorbability and low dielectric constant. For this reason herein, in an attempt to enhance its properties, platinum nanosheets (10–50 nm) are used as plasmonic substrates to grow transparent selenium oxide thin films. The films are deposited onto glass and Pt substrates using thermal evaporation technique under a vacuum pressure of 10−5 mbar. Both films of the glass/SeO2 and Pt/SeO2 are characterized by the techniques of x-ray diffraction, scanning electron microscopy, energy dispersive x-ray spectroscopy, optical spectrophotometry and impedance spectroscopy. While no significant effect of Pt nanosheets on the amorphous nature of structure of SeO2 is observed, remarkable enhancements in the light absorbability by 50 times and in dielectric constant by three times are achieved. In addition, Pt nanosheets form plasmonic interfaces resulting in improving the plasmon frequency, drift mobility and free carrier density of the films. Pt/SeO2 films showed plasmon frequency larger than 6.0 GHz and free carrier density of 1018 cm−3. Moreover, analysis of the terahertz cutoff frequency and impedance spectra have shown that the Pt/SeO2 interfaces can also be employed as terahertz receivers and as low pass filters suitable for 5G/6G technologies.

Carbon fibre-reinforced polymer composites are widely used in modern aircraft structures for the high stiffness-to-weight ratio. An aircraft's exterior is commonly applied with coatings for minimisation of aerodynamic drag, resistance to chemicals, hydraulic fluid and ultraviolet exposure. The issues with the coatings are the possible high thickness variations due to the manual painting adopted. The existing thickness measurement methods are mostly suited to metals and cannot be well employed for in-field tests of composites. Here a new microwave cylindrical cavity resonator sensor is developed for the non-destructive thickness evaluation of coatings on composite substrates. The open cavity and conductive carbon fibre composite form a resonant system, where the presence of coating affects the surface impedance, causing changes in the resonance frequency. Applying the wall impedance perturbation and transmission line theories, an analytical model is proposed. From the measured data, a linear relationship is obtained between the resonance frequency shift and thickness change, thereby simplifying the prediction process. The insensitivity to the dielectric properties of the coating and anisotropy of the composite substrate offers convenient calibration and implementation. The new sensor can provide efficient on-site assessment of paint coatings on carbon fibre composite surfaces used in modern aircraft construction and other engineering applications.

Current systems for metal detection in dry food processing are limited by relatively large foreign objects and high-cost implementation. These issues are resolved here using a non-contact, cylindrical microwave cavity resonator sensor where food passes through the cavity and metallic objects are detected by a shift in the resonant frequency. Classic perturbation theory is applied to the basic set-up and numerical simulations are used to verify the design of the sensor. A cavity sensor was fabricated with a quartz tube symmetrically located for dry food flow and metal detection. Good performance is demonstrated for a range of foods such as spaghetti, noodles, rice, wheat flour and soy milk powder. It is shown that the resonance frequency shift becomes larger when the foreign body gets closer to the cavity centre. The frequency variation is directly related to the volume of the object, and it is estimated that the minimum diameter of a detectable ball can be lower than 2 mm. For completeness it is also observed that the set-up can be used to detect dielectric objects. A graphical user interface is developed for practical applications. The method proposed is low-cost, convenient, scalable and complementary to other metallic contaminant detection approaches.

Microwaves provide alternative heating and allow process intensification due to their rapid, volumetric, and selective nature. Recognizing the central role of multiphase reactors in chemical industry, a recent surge in employing microwaves is observed. Here, we review the recent experimental and modeling investigations of microwave heating of multiphase reactors with emphasis on chemical engineering applications. We demonstrate that there is accumulated evidence for improved performance via microwave heating and a clear opportunity for further process intensification. In most of the cases, this improved performance stems from a temperature gradient between two phases. We discuss the ongoing debate on the mechanism by which microwaves affect chemical processes exacerbated by the inability of measuring the temperature distribution in a microwave cavity. We outline recent progress in this direction in monolith reactors and needs for future work. We underscore the lack of detailed modeling and simulation tools even for single-phase systems and emphasize the imperative for multiscale predictive modeling to bridge the experimental-modeling gap. Promising results are shown by a few recently published modeling studies that can predict the experimental measurements in complex multiphase reactors. A combination of experimental and modeling tools can provide a comprehensive picture of the microwave multiphase reactors as well as a means toward scale-up and optimization.

In order to simplify the conversion between slow light and fast light, we ameliorate the cavity-magnon coupling system and theoretically analyze the characteristics of group delay of the output field. The system under consideration consists of a microwave cavity and N yttrium iron garnets (YIGs), of which the quantity of YIG spheres is designed to be controlled by an external magnetic field. It is found, most importantly, that the conversion between fast and slow light can be realized by adjusting the number of YIG spheres that the external magnetic field acts on. Significantly, through adjusting the quantity N of magnons, the group delay can be stabilized at a required value even though the magnons are slightly detuned. Moreover, adjusting the quantity of YIG spheres can also alter the frequency corresponding to the fast-slow light effect, signifying that the conversion can be expanded to the frequency domain. Meanwhile, the cavity-magnon coupling strength required to generate the fast-slow light can be also effectively reduced by increasing the quantity of YIG spheres. Furthermore, we find that the cavity-magnon coupling strength and the cavity-field loss rate are complementary in terms of the group delay, which provides a feasible alternative for experimental design. The factors determining the slow-light limit have also been summarized based on their influence on the group delay. Our results have theoretical significance for the improvement of the generation and conversion of the fast-slow light, upgrading and innovating the information technology, especially in the field of all-optical networks.

Efficiency of microwave-enabled ex situ soil remediation can be improved by dielectric susceptors. Cost, and environmental burden of these susceptors can be minimized if they are used repeatedly in a permanent bed set-up. In this study, carbon nanofibers, activated carbon, magnetite, and silicon carbide were tested at the lab scale for repeated use in permanent microwave-induced thermal soil remediation. Despite their superior ability to convert microwaves into heat, carbon nanofibers experienced electrokinesis and activated carbon partially combusted in the microwave cavity, which complicates their pragmatic use in remediation applications. Magnetite was also able to convert microwaves into heat effectively and it was relatively more stable; however, repeated heating/and cooling cycles changed its physicochemical properties, which was attributed to oxidation of iron oxides at the air-soil interface. Silicon carbide, on the other hand, was an efficient heating agent and was stable during repeatable heating and cooling cycles. Through 25 heating/cooling cycles, an average peak temperature of 329 ± 55 °C was achieved for a 29 cm3 sample and analysis of dielectric properties after every 10th and 25th cycle indicated that there were no significant losses in thermal conductivity or permittivity of the material. Subsequent remediation experiments with silicon carbide demonstrated that between 89 and 97 % of the total petroleum hydrocarbons were removed from soil including a marked fraction of heavy hydrocarbons when 20.2 kJ g−1 of microwave energy was introduced. In addition, post-treatment experiments demonstrated that soil conditions were capable of supporting seed germination indicating that some conditions of soil were recovered after microwave remediation.

Microwave cavity resonators are crucial components of many quantum technologies and are a promising platform for hybrid quantum systems, as their open architecture enables the integration of multiple subsystems inside the cavity volume. To support these subsystems within the cavity, auxiliary structures are often required, but the effects of these structures on the microwave cavity mode are difficult to predict due to a lack of a priori knowledge of the materials' response in the microwave regime. Understanding these effects becomes even more important when frequency matching is critical and tuning is limited, for example, when matching microwave modes to atomic resonances. Here, we study the microwave cavity mode in the presence of three commonly-used machinable polymers, paying particular attention to the change in resonance and the dissipation of energy. We demonstrate how to use the derived dielectric coefficient and loss tangent parameters for cavity design in a test case, wherein we match a polymer-filled 3D microwave cavity to a hyperfine transition in rubidium., Comment: 5 pages, 3 figures