Introduction: This thesis is an account of the design, construction and testing of a particle accelerator which represents a minor variation on the now-familiar theme of the tandem van de Graaff. The machine has been very briefly described elsewhere (Naylor 1968).

Introduction: This thesis is an account of the design, construction and testing of a particle accelerator which represents a minor variation on the now-familiar theme of the tandem van de Graaff. The machine has been very briefly described elsewhere (Naylor 1968).

Introduction: This thesis is an account of the design, construction and testing of a particle accelerator which represents a minor variation on the now-familiar theme of the tandem van de Graaff. The machine has been very briefly described elsewhere (Naylor 1968).

Introduction: This thesis is an account of the design, construction and testing of a particle accelerator which represents a minor variation on the now-familiar theme of the tandem van de Graaff. The machine has been very briefly described elsewhere (Naylor 1968).

The Bayer process for the production of alumina (A1203) from bauxite involves a perennial gibbsite (y-Al(OH)3) precipitation step, relating to an inherently slow crystal growth from supersaturated sodium aluminate solutions (pregnant Bayer liquors). The kinetics and mechanisms involved in the transformation of the tetrahydroxo, Al(III)-containing species in solution into octahedrally-coordinated Al(OH)3 crystals in the presence of NA+ and excess of ions, are as yet not fully known. To gain further knowledge and better understanding of the nature of solution species, their specific interaction and participation in the gibbsite crystallization mechanisms, the role alkali ions play in the kinetic behaviour and mechanisms of nucleation, growth and aggregation/agglomeration from caustic aluminate solutions of industrial strength has been investigated.

The Bayer process for the production of alumina (A1203) from bauxite involves a perennial gibbsite (y-Al(OH)3) precipitation step, relating to an inherently slow crystal growth from supersaturated sodium aluminate solutions (pregnant Bayer liquors). The kinetics and mechanisms involved in the transformation of the tetrahydroxo, Al(III)-containing species in solution into octahedrally-coordinated Al(OH)3 crystals in the presence of NA+ and excess of ions, are as yet not fully known. To gain further knowledge and better understanding of the nature of solution species, their specific interaction and participation in the gibbsite crystallization mechanisms, the role alkali ions play in the kinetic behaviour and mechanisms of nucleation, growth and aggregation/agglomeration from caustic aluminate solutions of industrial strength has been investigated.

<p>Multiple industry applications, including combustion, flow control, and medicine, have leveraged nanosecond pulsed plasma (NPP) discharges to create plasma generated reactive species (PGRS). The PGRS are essential to induce plasma-assisted mechanisms, but the rate of generation and permanence of these species remains complex. Many of the mechanisms surrounding plasma discharge have been discovered through experiments, but a consistent challenge of time scales limits the plasma measurements. Thus, a well-constructed model with experimental research will help elucidate complex plasma physics. The motivation of this work is to construct a feasible physical model within the additional numerical times scale limitations and computational resources. This thesis summarizes the development of a one-moment fluid model for NPP discharges, which are applied due to their efficacy in generating ionized and excited species from vacuum to atmospheric pressure. </p><p>From a pulsed power perspective, the influence of pulse parameters, such as electric field intensity, pulse shape and repetition rate, are critical; however, the effects of these parameters on PGRS remain incompletely characterized. Here, we assess the influence of pulse conditions on the electric field and PGRS computationally by coupling a quasi-one-dimensional model for a parallel plate geometry, with a Boltzmann solver (BOLSIG+) used to improve plasma species characterization. We first consider a low-pressure gas discharge (3 Torr) using a five-species model for argon. <a>We then extend to a 23 species model with a reduced set of reactions for air chemistry remaining at low pressure.</a> The foundations of a single NPP is first discussed to build upon the analysis of repeating pulses. Because many applications use multiple electric pulses (EPs) the need to examine EP parameters is necessary to optimize ionization and PGRS formation. </p><p>The major goal of this study is to understand how the delivered EP parameters scale with the generated species in the plasma. Beginning with a similar scaling study done by Paschen we examine the effects of scaling pressure and gap length when the product remains constant for the two models. This then leads to our study on the relationship of pulsed power for different voltages and pulse widths of EPs. By fixing the energy delivered to the gap for a single pulse we determine that the electron and ion number densities both increased with decreasing pulse duration; however, the rate of this increase of number densities appeared to reach a limit for 3 ns. These results suggest the feasibly of achieving comparable outputs using less expensive pulse generators with higher pulse duration and lower peak voltage. Lastly, we study these outcomes when increasing the number of pulses and discuss the effects of pulse repetition and the electron temperature.</p><p>Future work will extend this parametric study to different geometries (i.e. pin-to-plate, and pin-to pin) and ultimately incorporate this model into a high-fidelity computational fluid dynamics (CFD) model that may be compared to spectroscopic results under quiescent and flowing conditions will be discussed.<br></p>

<p dir="ltr">This thesis deals with optical cavity-coupled two-dimensional (2D) materials. First, we describe a new theoretical approach to model the properties of cavity-coupled plasmons in 2D conductors. Next, we propose an optical cavity architecture for enhanced light-matter interaction with potential for performance and functionality beyond that of traditional approaches and describe an initial investigation of one example of such a system. Finally, we provide a thorough description of the fabrication techniques used to produce the previously mentioned optical cavities.</p><p dir="ltr">The advent of 2D materials has opened exciting possibilities for controlling light-matter interactions at the nanoscale. The first major contribution of this work is the investigation of coupling between patterned 2D Van der Waals materials and Fabry-Perot cavities, focusing on how system parameters like pattern shape and material properties influence these interactions. Using a quasistatic eigenmode expansion approach, we develop a theoretical framework to predict and manipulate optical behavior in these systems. Our work opens new pathways for engineering light-matter interactions within patterned 2D material platforms, paving the way for the engineering of novel optical phenomena.</p><p dir="ltr">The second major contribution of this work is the development of a versatile platform for light-matter coupling experiments in Van der Waals materials. It is well-known that light-matter interaction can be used to realize unprecedented functionality in the coupled materials. However, few---if any---approaches to date utilize this phenomenon to its fullest extent. We have provided a platform that can be used to realize light-matter coupling efficiencies beyond what is possible in conventional systems, can be easily integrated with 2D materials, and provides new opportunities to engineer the photonic environment of the coupled material. In particular, we focus on silicon dielectric bowtie cavities (DBCs) coupled to few-layer flakes of $\rm WSe_2$. This approach leverages topology-optimized cavity architectures to achieve simultaneous spatial and spectral confinement, yielding Purcell factors exceeding 2500, mode volumes as small as $\sim10^{-3}(\lambda/2n)^3$, and quality factors up to $\sim200$---performance metrics limited only by material losses. The lithographically defined DBCs enable deterministic emission hotspot placement and tunability across a broad wavelength range with minimal performance impact. Photoluminescence imaging and spectroscopy reveal comparable $\rm WSe_2$ exciton emission enhancement to plasmonic structures. This platform surpasses the limitations of conventional cavity architectures by enabling unprecedented coupling efficiencies and unique functionality while maintaining sufficient mechanical robustness for 2D material transfer.</p><p dir="ltr">The final chapter outlines the fabrication process for the cavities described in the previous chapter. The fabrication involves advanced nanolithography techniques to define patterns with high resolution, addressing challenges such as proximity effects and process blur. Techniques such as proximity effect correction (PEC) are used to enhance pattern accuracy, while careful optimization of exposure and development parameters ensures minimal distortion. The process utilizes high-anisotropy reactive ion etching to transfer the patterns onto the substrate, where precise optimization of the etching parameters has been performed to achieve high resolution and selectivity. The final optimized process yields structures with a minimum feature size of approximately 20 nm and minimum radius of curvature of approximately 10 nm, allowing for the repeatable fabrication of complex inverse-designed cavities.</p>

<p dir="ltr">Decades of semiconductor technology scaling and breakthroughs in communication technology have miniaturized computing, embedding it everywhere, enabling the development of smart things connected to the internet, forming the Internet of Things. Further miniaturization of devices has led to an exponential increase in the number of devices in and around the body in the last decade, forming a subset of IoT which is increasingly becoming popular as the Internet of Bodies (IoB). The gradual shift from the current form of human-electronics coexistence to human-electronics cooperation, is the vision of Internet of Bodies (IoB). This vision of a connected future with devices in and around our body talking to each other to assist their day-to-day functions demands energy efficient means of communication. Electro-Quasistatic Human Body Communication (EQS-HBC) has been proposed as an exciting alternative to traditional Radio Frequency based methodologies for communicating data around the body. In this dissertation, we expand the boundaries of wearable and implantable IoB nodes using Electro-Quasistatic Human Body Communication and Powering by developing advanced channel models and demonstrating novel applications.</p><p dir="ltr">Leveraging the advanced channel models developed for wearable EQS-HBC, we demonstrate wearable applications like ToSCom which extend the use cases of touchscreens to beyond touch detection and location to enable high-speed communication strictly through touch. We further demonstrate an application of EQS Resonant Human Body Powering to demonstrate Step-to-Charge, allowing mW-scale wireless power transfer to wearable devices. With increasing connected implanted healthcare devices becoming a part of the IoB space, we benchmark RF-based technologies for In-Body to Out-of-Body (IBOB) communication using novel in-vivo experiments. We then explore EQS-HBC in the realm of IBOB communication using advanced channel modeling, revealing its potential for low-power and physically secure data transfer from implantable devices to wearable nodes on the body, demonstrating its potential in extending the battery life span of implantable nodes. Finally, an overview of the potential of IoB devices is analyzed with the use of EQS-HBC where we propose a human-inspired distributed network of IoB nodes which brings us a step closer to the potential for perpetually operable devices in and around the body.</p>