Ion cyclotron emission from energetic ion populations in fusion plasmas

In this thesis I present particle in cell (PIC) simulations of ion cyclotron emission (ICE). ICE comprises suprathermal radiation in the ion cyclotron frequency range, whose spectrum peaks at successive local cyclotron harmonics of the emitting energetic ion population. ICE has previously been observed in all large toroidal MCF plasmas [Dendy and McClements, 2015; McClements et al., 2015]. ICE is caused by a collective instability, which in its linear phase corresponds to the magnetoacoustic cyclotron instability (MCI). The passive, non-invasive character of ICE measurements, suggest ICE is an attractive way forward for future energetic ion measurements in ITER. In the simulations in this thesis we use the EPOCH particle-in-cell code to solve the self-consistent Maxwell-Lorentz system of equations for fully kinetic electrons and thermal background ions, together with the minority energetic ion distribution that drives the primary ICE. We first perform a detailed quantitative comparison between fusion born proton driven chirping ICE observed during KSTAR ELM crashes and fully nonlinear direct numerical simulations of the MCI. We find good quantitative agreement between the simulated and observed spectra, to the extent that the simulations can be used to infer fast (-μs) time scale dynamics of the local electron number density in the emitting region. We then extend this study to determine the origin of a faint, time delayed proton chirping feature observed in one of the KSTAR plasma pulses. We do this using bicoherence analysis of both experimental and simulation data. We then run MCI PIC simulations of the pre ELM crash \steady state" ICE observed on KSTAR, which is believed to be driven by neutral beam injected (NBI) deuterons. PIC simulations of MCI excited ICE in JET and ASDEX Upgrade (AUG) plasmas are then discussed, and we show that AUG observations of the fundamental ICE harmonic can only be explained in terms of the MCI if nonlinear wave-wave interactions between higher harmonics are taken into account. Motivated by recent observations of ICE in the core region of several tokamaks, including AUG and DIIID, we then compare MCI simulations using two types of energetic ion distribution function, a spherical shell of varying thickness, and a ring beam of varying width. It is found that both distribution functions lead to MCI excited waves, and their nonlinear properties are discussed

Solar energy in Latin America: A review of the of the four leading markets

One method countries around the world are employing to transition away from fossil fuels is through increasing the share of renewable energy in electricity generation. Wind and solar energy projects are the least expensive option for electricity generation in many parts of the world due to costs falling significantly over the past several years. Solar energy is especially cost effective in places with high solar radiation such as Latin America. These lower costs have led to solar energy being an attractive option for satisfying the growing electricity demand in the region. Capacity in photovoltaic solar plants therefore grew significantly over the past five years specifically in Brazil, Mexico Chile and Argentina. This growth can be partially attributed to the government support through various regulatory policies and other mechanisms such as renewable energy auctions. This work seeks to provide an overview of the solar industry in Latin America, focusing on the four largest markets listed above, looking at their electricity sectors, the current state of the industry, evaluating the most effective support mechanisms used to help establish the market, and discussing common barriers. The report will end with a comparative analysis of the four markets, elaborating on why Brazil and Chile have been relatively more successful in developing the solar industry, the reasons for the slow progress witnessed in Argentina, and the issues Mexico is facing due to the current administration.Um método que os países de todo o mundo estão a utilizar para fugir aos combustíveis fósseis é através do aumento da quota de energias renováveis na produção de eletricidade. Investir em projetos de energia eólica e solar é a opção menos dispendiosa para a produção de eletricidade em muitas partes do mundo, devido à queda significativa dos custos nos últimos anos. A energia solar é especialmente rentável em locais com grande radiação solar, como a América Latina. Estes custos mais baixos levaram a que a energia solar fosse uma opção atraente para geração de eletricidade na região. Assim, a capacidade dos painéis solares fotovoltaicos cresceu significativamente nos últimos cinco anos especificamente no Brasil, México, Chile e Argentina. Este crescimento pode ser atribuído ao apoio dos governos através de várias políticas regulatórios e outros mecanismos, como os leilões de energias renováveis. Este trabalho procura fornecer uma visão geral da indústria solar na América Latina, focando-se nos quatro maiores mercados acima listados. Analisará os sectores de eletricidade, o estado atual da indústria, avaliará os mecanismos de apoio utilizados para ajudar a estabelecer o mercado e discute barreiras e obstáculos comuns. A dissertação terminará com uma análise comparativa dos quatro mercados elaborando as razões pelas quais o Brasil e o Chile têm tido relativamente mais sucesso no desenvolvimento da indústria solar, as razões dos lentos progressos verificados na Argentina e as questões que o México enfrenta devido à atual administração

Multiscale reaction-diffusion algorithms: PDE-assisted Brownian dynamics

Two algorithms that combine Brownian dynamics (BD) simulations with mean-field partial differential equations (PDEs) are presented. This PDE-assisted Brownian dynamics (PBD) methodology provides exact particle tracking data in parts of the domain, whilst making use of a mean-field reaction-diffusion PDE description elsewhere. The first PBD algorithm couples BD simulations with PDEs by randomly creating new particles close to the interface which partitions the domain and by reincorporating particles into the continuum PDE-description when they cross the interface. The second PBD algorithm introduces an overlap region, where both descriptions exist in parallel. It is shown that to accurately compute variances using the PBD simulation requires the overlap region. Advantages of both PBD approaches are discussed and illustrative numerical examples are presented.Comment: submitted to SIAM Journal on Applied Mathematic

Characterization of Functionally Graded Materials

The purpose of this study was to characterize the behavior of a functionally graded material through experimentation and analytical modeling. Functionally graded materials are a ceramic metal composite which transitions from metal on one face to ceramic on the opposite face. Creating reliable models required verifying the material properties. This was accomplished through the use of a static modulus of elasticity test as well as a dynamic ping test. The natural frequencies from the dynamic test were compared with finite element models to determine which material properties most accurately represented the functionally graded material. It was found that the material properties established experimentally by Hill and Lin produced the best models. A fracture surface was examined to determine the failure criteria for the prediction of failure in a cyclic loading scenario. It was determined that the material would fail in a brittle manner and the maximum principle stresses should be used to predict failure. Finally, a model was generated to analyze the through-the-thickness stresses in the material under a sinusoidal forcing function. It was determined that the majority ceramic upper layer was the critical layer for failure and required an amplitude of 5.83 KN to reach failure in the specimen

Perception of Parental Conflict as a Predictor of Attachment and Caregiving Styles in the Romantic Relationships of Young Adults

Attachment styles and caregiving styles have provided a useful framework for conceptualizing romantic relationships. The present study seeks to examine whether perceptions of high parental conflict will predict less secure attachment and caregiving styles in the romantic relationships of young adults. It is hypothesized that higher perceptions of parental conflict, as measured by the Family Structure Survey and the Conflict Tactics Scale, will correlate positively with more insecure ratings on a dimensional attachment measure, and will correlate positively with maladaptive extremes of caregiving styles, measured using the Caregiving Questionnaire. Low correlations between dimensional attachment and parental conflict were found. Results are discussed in the context of a social-learning hypothesis for attachment and caregiving styles in the romantic relationships of young adults, with the parents\u27 marriage being the primary model of romantic relationships

The Effect of Foreground Mitigation Strategy on EoR Window Recovery

The removal of the Galactic and extragalactic foregrounds remains a major challenge for those wishing to make a detection of the Epoch of Reionization 21-cm signal. Multiple methods of modelling these foregrounds with varying levels of assumption have been trialled and shown promising recoveries on simulated data. Recently however there has been increased discussion of using the expected shape of the foregrounds in Fourier space to define an EoR window free of foreground contamination. By carrying out analysis within this window only, one can avoid the foregrounds and any statistical bias they might introduce by instead removing these foregrounds. In this paper we discuss the advantages and disadvantages of both foreground removal and foreground avoidance. We create a series of simulations with noise levels in line with both current and future experiments and compare the recovered statistical cosmological signal from foreground avoidance and a simplified, frequency independent foreground removal model. We find that while, for current generation experiments, foreground avoidance enables a better recovery at $k_{perp} > 0.6 \mathrm{Mpc}^{-1}$, foreground removal is able to recover significantly more signal at small $k_{los}$ for both current and future experiments. We also relax the assumption that the foregrounds are smooth by introducing a Gaussian random factor along the line-of-sight and then also spatially. We find that both methods perform well for foreground models with line-of-sight and spatial variations around $0.1\%$ however at levels larger than this foregrounds removal shows a greater signal recovery.Comment: 14 pages, 10 figures, accepted by MNRA