Microwave resonators for highly sensitive compositional analysis of solvents in microcapillary systems

The ability to precisely analyse the composition of liquid mixtures by non-contact techniques in both static and flow situations is extremely desirable for a diversity of industrial, analytical and quality control procedures. Microwave resonators allow very accurate and sensitive characterisation of the dielectric properties of polar liquids due to the strong interaction of the latter with microwave electric fields. They have the useful dual role of both exact characterisation of the complex permittivity of a dielectric sample when it is inserted within a region of high electric field of the resonator, and effective volumetric heating of the same sample if its dielectric loss is large enough to permit heating. They offer tremendous potential for investigation of very small amounts of polar solvents in non-polar hosts. In this regard they are superior to other traditional composition analysis techniques such as liquid chromatography, gas chromatography and mass spectrometry in the speed of analysis ( 1 s), non destructive nature and scope for miniaturisation of the resonator size to suit the system under test. For minute sample volumes, the resonator perturbation technique is extensively used for dielectric measurements on polar liquids. In this project, it has been employed for highly sensitive compositional analysis of two-component dielectric mixtures contained in microcapillary segments. The primary evaluation system used here was mixtures of acetonitrile and toluene, chosen because of the large difference in their molecular electric dipole moments. The results obtained from this first system provided the inspiration to assess mixtures made of acetonitrile and water, which are much more closely matched in terms of their electric dipole moments. Three different types of resonators namely hairpin resonator, split ring resonator and sapphire dielectric resonator were used to analyse both the aforementioned solution systems. The results show very sensitive characterisation and are in close agreement with the theoretical predictions governing perturbation of resonators by dielectric samples. In the last phase of this research, a miniaturised sapphire dielectric resonator was designed and fabricated that provided added enhancement in measured sensitivity of both evaluation mixtures

Ytterbium ion trapping and microfabrication of ion trap arrays

Over the past 15 years ion traps have demonstrated all the building blocks required of a quantum computer. Despite this success, trapping ions remains a challenging task, with the requirement for extensive laser systems and vacuum systems to perform operations on only a handful of qubits. To scale these proof of principle experiments into something that can outperform a classical computer requires an advancement in the trap technologies that will allow multiple trapping zones, junctions and utilize scalable fabrication technologies. I will discuss the construction of an ion trapping experiment, focussing on my work towards the laser stabilization and ion trap design but also covering the experimental setup as a whole. The vacuum system that I designed allows the mounting and testing of a variety of ion trap chips, with versatile optical access and a fast turn around time. I will also present the design and fabrication of a microfabricated Y junction and a 2- dimensional ion trap lattice. I achieve a suppression of barrier height and small variation of secular frequency through the Y junction, aiding to the junctions applicability to adiabatic shuttling operations. I also report the design and fabrication of a 2-D ion trap lattice. Such structures have been proposed as a means to implement quantum simulators and to my knowledge is the first microfabricated lattice trap. Electrical testing of the trap structures was undertaken to investigate the breakdown voltage of microfabricated structures with both static and radio frequency voltages. The results from these tests negate the concern over reduced rf voltage breakdown and in fact demonstrates breakdown voltages significantly above that typically required for ion trapping. This may allow ion traps to be designed to operate with higher voltages and greater ion-electrode separations, reducing anomalous heating. Lastly I present my work towards the implementation of magnetic fields gradients and microwaves on chip. This may allow coupling of the ions internal state to its motion using microwaves, thus reducing the requirements for the use of laser systems

Microwave Dielectrometry Adapted to Environments

Tesis por compendio[ES] La permitividad es una propiedad física de los materiales que describe su comportamiento en presencia de un campo electromagnético. Los sensores de microondas pueden desempeñar un papel esencial en las tareas de detección, supervisión o control de procesos, ya que algunos parámetros fisicoquímicos de los materiales producen cambios medibles en las propiedades dieléctricas. Además, la tecnología de calentamiento por microondas está adquiriendo una relevancia creciente para la transición ecológica y la descarbonización de los procesos industriales, y la permitividad es el parámetro esencial para el desarrollo exitoso de estos nuevos procesos. La permitividad depende de muchos factores, por lo que los métodos de medición de la permitividad deben adaptarse a las necesidades del material y del entorno de medición. El número de aplicaciones que requieren la monitorización o medida de las propiedades dieléctricas, las altas dependencias de esta magnitud bajo diferentes condiciones, y la necesidad de poner esta tecnología al alcance de un usuario más amplio y menos especializado, justifican el desarrollo de este trabajo. Esta tesis pretende desarrollar nuevos dispositivos para la monitorización y caracterización de dieléctricos adaptados a diferentes entornos, cubriendo un amplio rango de formatos, formas y propiedades de los materiales. Las dos primeras publicaciones incluidas en la tesis describen dos enfoques diferentes para abordar las mediciones de permitividad. El primer artículo describe un instrumento versátil, autónomo y fácil de usar para medir la permitividad de materiales dentro de tubos. El diseño de la cavidad logró una excelente sensibilidad, y el estudio de la red de acoplamiento permitió la caracterización de materiales de pérdidas bajas, moderadas y altas con una misma configuración. Este dispositivo incluye un reflectómetro vectorial portátil propio, lo que lo hace portátil y asequible. Las características del instrumento desarrollado permiten un uso sencillo por parte de personal no especializado y proporcionan versatilidad en muchas situaciones. La segunda publicación presenta el diseño específico de una sonda coaxial de extremo abierto con una mayor sensibilidad para determinar la permitividad de productos alimenticios de altas pérdidas en función de la temperatura a frecuencias de RF. Este artículo destaca la importancia de seleccionar la técnica de medición más adecuada, adaptada al entorno y a las particularidades del material, para la determinación apropiada de la permitividad. Los dos artículos siguientes describen el desarrollo y la utilización de un microscopio de microondas de campo cercano con resolución micrométrica para determinar mapas de permitividad de materiales planos heterogéneos a frecuencias de microondas. En ambos trabajos se describen los diferentes elementos que componen el instrumento del microscopio y las técnicas de análisis para determinar los valores de permitividad a partir de las medidas de los parámetros de la resonancia. En el primer trabajo se empleó por primera vez la tecnología de microondas en aplicaciones contra la falsificación, obteniendo la marca dieléctrica de la marca de agua de un billete. Además, este estudio demostró la capacidad de la energía de microondas para detectar marcas ocultas detrás de capas dieléctricas o metálicas, lo que abre nuevas posibilidades para el desarrollo de elementos de seguridad ópticamente opacos e imposibles de rastrear por medios ópticos. El segundo estudio demuestra la versatilidad de este sistema para determinar las propiedades dieléctricas de materiales planos heterogéneos midiendo la respuesta dieléctrica de especímenes de roca. Los métodos desarrollados en esta tesis aumentan la cartera de sistemas de caracterización dieléctrica y pueden ayudar a una amplia gama de sectores científicos e industriales en las tareas de monitorización y caracterización dieléctrica, haciendo estos trabajos más cómodos y accesibles.[CA] La permitivitat és una propietat física dels materials que descriu el seu comportament en presència d'un camp electromagnètic. Els sensors de microones poden exercir un paper essencial en les tasques de detecció, supervisió o control de processos, ja que alguns paràmetres fisicoquímics dels materials produeixen canvis mesurables en les propietats dielèctriques. A més, la tecnologia de calfament per microones està adquirint una rellevància creixent per a la transició ecològica i la descarbonització dels processos industrials, i la permitivitat és el paràmetre essencial per al desenvolupament reeixit d'aquests nous processos. La permitivitat depén de molts factors i, per tant, els mètodes de mesurament de la permitivitat han d'adaptar-se a les necessitats del material i de l'entorn de mesurament. El nombre d'aplicacions que requereixen el monitoratge o mesura de les propietats dielèctriques, les altes dependències d'aquesta magnitud sota diferents condicions, i la necessitat de posar aquesta tecnologia a l'abast d'un usuari més ampli i menys especialitzat, justifiquen el desenvolupament d'aquest treball. Aquesta tesi pretén desenvolupar nous dispositius per al monitoratge i caracterització de dielèctrics adaptats a diferents entorns, cobrint un ampli rang de formats, formes i propietats dels materials. Les dues primeres publicacions incloses en la tesi descriuen dos enfocaments diferents per a abordar els mesuraments de permitivitat. El primer article descriu un instrument versàtil, autònom i fàcil d'usar per a mesurar la permitivitat de materials dins de tubs. El disseny de la cavitat va aconseguir una excel·lent sensibilitat, i l'estudi de la xarxa d'acoblament va permetre la caracterització de materials de pèrdues baixes, moderades i altes amb una mateixa configuració. Aquest dispositiu inclou un reflectòmetre vectorial portàtil propi, la qual cosa el fa portàtil i assequible. Les característiques de l'instrument desenvolupat permeten un ús senzill per part de personal no especialitzat i proporcionen versatilitat en moltes situacions. La segona publicació presenta el disseny específic de una sonda coaxial d'extrem obert amb una major sensibilitat per a determinar la permitivitat de productes alimentaris d'altes pèrdues en funció de la temperatura a freqüències de RF. Aquest article destaca la importància de seleccionar la tècnica de mesurament més adequat, adaptada a l'entorn i a les particularitats del material, per a la determinació apropiada de la permitivitat. Els dos articles següents descriuen el desenvolupament i la utilització d'un microscopi de microones de camp pròxim amb resolució micromètrica per a determinar mapes de permitivitat de materials plans heterogenis a freqüències de microones. En tots dos treballs es descriuen els diferents elements que componen l'instrument del microscopi i les tècniques d'anàlisis per a determinar els valors de permitivitat a partir de les mesures dels paràmetres de la ressonància. En el primer treball es va emprar per primera vegada la tecnologia de microones en aplicacions contra la falsificació, obtenint la marca dielèctrica de la marca d'aigua d'un bitllet. A més, aquest estudi va demostrar la capacitat de l'energia de microones per a detectar marques ocultes darrere de capes dielèctriques o metàl·liques, la qual cosa obri noves possibilitats per al desenvolupament d'elements de seguretat òpticament opacs i impossibles de rastrejar per mitjans òptics. El segon estudi demostra la versatilitat d'aquest sistema per a determinar les propietats dielèctriques de materials plans heterogenis mesurant la resposta dielèctrica d'espècimens de roca. Els mètodes desenvolupats en aquesta tesi augmenten la cartera de sistemes de caracterització dielèctrica i poden ajudar a una àmplia gamma de sectors científics i industrials en les tasques de monitoratge i caracterització dielèctrica, fent aquests treballs més còmodes i accessibles.[EN] Permittivity is a physical property of materials describing their behavior in the presence of an electromagnetic field. Microwave sensors can play an essential role in detecting, monitoring, or process control tasks as some physicochemical parameters of materials produce measurable changes in dielectric properties. Besides, microwave heating technology is gaining increasing relevance for the ecological transition and decarbonization of industrial processes, and permittivity is the essential parameter for the successful development of these new processes. Permittivity depends on many factors and thus, permittivity measurement methods must be adapted to the needs of the material and the measurement environment. The number of applications that require the monitoring or measurement of dielectric properties, the high dependencies of this magnitude under different conditions, and the need to make this technology available to a broader and less specialized user justify the development of this work. This thesis aims to develop new devices for the monitoring and characterization of dielectrics adapted to different environments, covering a wide range of materials' formats, shapes, and properties. The first two publications included in the thesis describe two different approaches to address permittivity measurements. The first paper describes a versatile, stand-alone, and easy-to-use instrument for measuring the permittivity materials inside tubes. The design of the cavity achieved an excellent sensitivity, and the study of the coupling network allowed the characterization of low, moderate, and high-loss materials with the same setup. This device included an in-house portable vector reflectometer, making it portable and cost-affordable. The features of the developed instrument allow straightforward use by non-specialized personnel and provide versatility in many situations. The second publication presents a specific open-ended coaxial design with increased sensitivity to determine the permittivity of lossy food products as a function of temperature at RF frequencies. This paper highlight the relevance of selecting the most suitable measurement technique, adapted to the environment and particularities of the material, for the appropriate determination of permittivity. The following two papers describe the development and use of a near-field scanning microwave microscope with micrometric resolution to determine permittivity maps of heterogeneous planar materials at microwave frequencies. The different elements comprising the microscope instrument and the analysis techniques to determine permittivity values from the resonance measurements were described throughout both works. In the first paper, microwave technology was employed for the first time in anti-counterfeiting applications by obtaining the dielectric mark of a banknote watermark. Besides, this study showed the ability of microwave energy to detect hidden marks behind dielectric or metallic layers, opening new possibilities for developing optically opaque security features untraceable by optical means. The second study demonstrates the versatility of this system in determining the dielectric properties of heterogeneous planar materials by measuring the dielectric response of rock specimens. The methods developed in this thesis dissertation increase the portfolio of dielectric characterization systems and can help a wide range of scientific and industrial sectors in dielectric monitoring and characterization tasks, making these works more convenient and accessible.Financial support through the grant reference BES-2016-077296 of the call Convocatoria de las ayudas para contratos predoctorales para la formación de doctores de 2016 by Ministerio de Economía y Competitividad (MINECO) and by European Social Funds (ESF) of European Union is also gratefully acknowledgedGutiérrez Cano, JD. (2022). Microwave Dielectrometry Adapted to Environments [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/186351TESISCompendi

Cylindrical microwave resonator sensors for measuring materials under flow

In this thesis the various possibilities of implementing microwave sensors for measureing materials flowing in pipes are studied, with special emphasis on full-bore resonator sensors. With such resonator sensors a method to confine the electro-magnetic energy in the sensor must be used. Two main principles are studied in detail, the principle of resonance below cut-off, and the design using end grids. The first principle is shown to allow sensors with fairly open, or even completely nonintrusive structures to be designed. The second often involves sectorial or semisectorial structures. The waveguide modes in sectorial and semisectorial waveguides are therefore analyzed. From the analysis of the sectorial waveguides came the idea for a new type of resonator sensor based on the principle of resonance below cut-off, the cylindrical fin resonator sensor (CFR). Various design aspects of this sensor are studied based on calculations, measurements, and simulations using the Hewlett-Packard HFSS software. A sensor suitable for measuring the composition of mixtures of hydro-carbons and water is developed based on the discussion. The sensor has a simple mechanical structure and is less expensive to manufacture than the end grid sensors. Various designs of end grids are compared based on theoretical considerations, simulations, and measurements, and recommendations for optimized designs are given. The ring grid with eight sectors and a ratio of radii of roughly 40% is shown to provide the best isolation for a given thickness of the grid. A new type of resonator sensor based on semisectorial resonance modes, is developed for measuring the mixture ratio of oil and water in an oil well deep in the ground, where the temperature and pressure are high. The sensor is designed for installation in the annulus (i.e. the annular space between the casing or liner and the production tubing in a well), where it can be used for measuring the inflow from a specific zone in a smart well. The emphasis is on matching the spatial constraints and achieving the desired frequency response, which is analyzed theoretically, simulated with the HFSS, and finally measured. A humidity sensor for harsh environments is developed. The emphasis is on the choice of resonance mode to achieve the best immunity to contamination, and on the design of the end grids. Both calculations and field tests are presented. Predicting the height of the resonance peak under changing measurement conditions is treated also on a general level in the thesis. This issue is important, when the coupling probes are designed based on results from simulations with HFSS. The accuracy of the results obtained with HFSS is studied based on observations of scatter in the results, the dependence of the results on the convergence parameter ΔS, and by comparing the calculated and measured results. It is shown that the cut-off frequency and the resonant frequency are predicted with a higher accuracy than the quality factor.reviewe

Submillimetre scattering antennas

Early attempts at constructing point contact detectors for submillimetre radiation led to the conclusion that the whisker itself exhibited long wire antenna properties. This discovery initiated the design of more advanced travelling wave antenna structures in a number of laboratories. The objective of the present study has been to investigate an alternative approach to electromagnetic transduction, namely the standing wave antenna. In the context of this work the antenna is to be regarded not merely as a coherent flux collector, but as a device for efficiently converting the Poynting flux in a Gaussian beam waist into a conduction current. A basic study of coupled dipole arrays has been undertaken by a scattering technique that obviates the need for extracting power from the antenna terminals. A microcomputer controlled open resonator has been developed for making absolute measurements of the total scattering cross-section of arrays and the optical constants of various ultra thin substrate materials. Back-scattering measurements under travelling wave conditions were also undertaken to verify that these arrays exhibited useful radiation patterns in both the E and H-planes. The electrical properties of the antenna arrays were found to be predictable using established theory. A photolithographic technique was employed to reproduce the antenna structures on thin mylar substrates previously metallized with silver. Once antennas can be fabricated, there is a requirement for compatible transmission line structures which should ideally match the feed point impedances of the antennas so as to achieve maximum power transfer. In order to investigate the matching conditions, backscattering measurements were made on arrays of identical dipoles each connected to a length of coplanar transmission line. Travelling wave vee-antennas have also been employed in an investigation of the dependence of the line velocity factor on substrate thickness. The electrical properties of the coplanar transmission lines were found to be in agreement with conventional theory and the ability of standing wave antennas to efficiently couple energy to them at a frequency of 891 GHz was verified.<p

Electromagnetic Waves

This book is dedicated to various aspects of electromagnetic wave theory and its applications in science and technology. The covered topics include the fundamental physics of electromagnetic waves, theory of electromagnetic wave propagation and scattering, methods of computational analysis, material characterization, electromagnetic properties of plasma, analysis and applications of periodic structures and waveguide components, and finally, the biological effects and medical applications of electromagnetic fields