Diamagnetic measurements of poloidal beta have been performed in the STOR-M tokamak by a flux loop placed exterior to the vacuum chamber. Poloidal beta is defined as the ratio of plasma kinetic pressure to poloidal magentic field pressure. Compensation for the vacuum toroidal field has been performed using a non-enclosing co-planar coil, and vibrational compensation from auxiliary coils. It was found that in STOR-M conditions (20\% toroidal magnetic field decay over discharge) there is significant influence on the diamagnetic flux measurements from strong residual signals, presumably from image currents being induced by the toroidal field coils, requiring further compensation. A blank (non-plasma) shot is used specifically to eliminate the residual component which is not proportional to the toroidal magnetic field. Data from normal ohmic discharge operation is presented and calculations of poloidal beta from coil data ($eta_ heta simeq 0.5$) is found to be in reasonable agreement with the values of poloidal beta obtained from measurements of electron density and Spitzer temperature with neoclassical corrections for trapped electrons. Contributions present in the blank shot (residual) signal and the limitations of this method are discussed. A pulse with Compact Toroid Injection was examined and compared to a normal ohmic discharge, and one where the Compact Toroid Injector was used to supply the tokamak with neutral gas. Soft X-Ray (SXR) measurements were taken and compared. There is a strong agreement between the profiles of the poloidal beta and the SXR measurements. The bulk plasma thermal energy was measured and found to increase by 5.6 J following the injection of a CT. The diamagnetic measurements appear to be affected by image currents induced in the chamber walls by the plasma current, and also by plasma position fluctuations. Future work outlining the possibilty of compensating these currents and improving the measurements is presented.

Diamagnetic measurements of poloidal beta have been performed in the STOR-M tokamak by a flux loop placed exterior to the vacuum chamber. Poloidal beta is defined as the ratio of plasma kinetic pressure to poloidal magentic field pressure. Compensation for the vacuum toroidal field has been performed using a non-enclosing co-planar coil, and vibrational compensation from auxiliary coils. It was found that in STOR-M conditions (20\% toroidal magnetic field decay over discharge) there is significant influence on the diamagnetic flux measurements from strong residual signals, presumably from image currents being induced by the toroidal field coils, requiring further compensation. A blank (non-plasma) shot is used specifically to eliminate the residual component which is not proportional to the toroidal magnetic field. Data from normal ohmic discharge operation is presented and calculations of poloidal beta from coil data ($eta_ heta simeq 0.5$) is found to be in reasonable agreement with the values of poloidal beta obtained from measurements of electron density and Spitzer temperature with neoclassical corrections for trapped electrons. Contributions present in the blank shot (residual) signal and the limitations of this method are discussed. A pulse with Compact Toroid Injection was examined and compared to a normal ohmic discharge, and one where the Compact Toroid Injector was used to supply the tokamak with neutral gas. Soft X-Ray (SXR) measurements were taken and compared. There is a strong agreement between the profiles of the poloidal beta and the SXR measurements. The bulk plasma thermal energy was measured and found to increase by 5.6 J following the injection of a CT. The diamagnetic measurements appear to be affected by image currents induced in the chamber walls by the plasma current, and also by plasma position fluctuations. Future work outlining the possibilty of compensating these currents and improving the measurements is presented.

<p> The effect of a C-7 substituent on the position of the cycloheptatriene/ norcaradiene equilibrium has been investigated. For this purpose a series of monosubstituted cycloheptatrienes was prepared in which the C-7 substituent was a carbonium ion grouping. From the spectral properties of these systems, it has been concluded that proportion of the norcaradiene valence tautomer present increases as the electron withdrawing ability of the carbonium ion substituent is enhanced.</p> <p> From a comparison of the pmr spectra of 7-norcaradienylmethyl cations with suitable model systems it is suggested that these norcaradienes are aromatic and that they support an induced diamagnetic ring current when in a magnetic field. It would appear that this type of cyclic delocalization is enhanced by the presence of an electron defficient substituent at C-7 of a norcaradiene and possible reasons for this are discussed.</p> <p> The 7-norcaradienylmethyl cations underwent a thermal isomerization to give benzenoid materials at relatively low temperatures. A mechanism for this rearrangement has been proposed and the implication of these results to the general pathways involved in the rearrangements of the C8H9+ family of cations discussed.</p> <p> Several synthetic routes to 9-substituted-3,4-homotropylidenes were investigated. A number of new compounds were isolated and a new synthetic approach to this class of compounds is suggested.</p> <p> Diamagnetic susceptibility exaltations of a series of substituted cycloheptatrienes were determined and used as a criterion of aromaticity. It was concluded that cycloheptatrienes are best regarded as homoaromatic molecules. Moreover it would appear that the substantial diamagnetic susceptibility exaltations observed with these compounds are related to the bulk of a C-7 substituent. One neutral norcaradiene was examined by this technique and was found to be nonaromatic.</p> / Thesis / Doctor of Philosophy (PhD)

Recent trends in energy production have led to a renewed interest in improving grid level energy storage solutions. Flywheel energy storage is an attractive option for grid level storage, however, it suffers from high parasitic loss. This study investigates the extent to which passive diamagnetic bearings, a form of electromagnetic bearing, can help reduce this parasitic loss. Such bearings require three main components: a weight compensation mechanism (lifter-floater), a stabilizing mechanism and an electrical machine. This study makes use of a new radial modification of an existing linear multi-plattered diamagnetic bearing. Here a prototype is built and analytical expressions derived for each of the three main components. These expressions provide a method of estimating displacements, fields, forces, energy and stiffness in the radial diamagnetic bearing. The built prototype solution is found to lift a 30 [g] mass using six diamagnetic platters for stabilization (between ring magnets) with a disc lifter and spherical floater for weight compensation. The relationship between mass and number of platters was found to be linear, suggesting that, up to a point, increases in mass are likely possible and indicating that significant potential exists for these bearings where high stiffness is not needed – for instance in flywheel energy storage. The study examines methods of reducing bearing (parasitic) losses and demonstrates that losses occur in three main forms during idling: air-friction losses, electrical machine losses, stabilizing machine losses. Low speed (158 [rpm]) air-friction losses are found to be the dominant loss at 0.1 [W/m3]. The focus of this study, however, is on loss contributions resulting from the bearing’s electrical machine and stabilizing machine. Stabilizing machine losses are found to be very low at: 1 × 10−6 [W/m3] – this leaves electrical machine losses as the dominant loss. Such electrical machine losses are analysed and divided into eddy current loss and hysteresis loss. Two components of hysteresis loss are remanent field related cogging loss and remagetization loss. Eddy current losses in silicon steel laminations in an electrical machine are quite high, especially at high speeds, with losses in the order of 1 × 105 [W/m3]. Noting the further high cost of producing single unit quantities of custom lamination-based electrical machine prototypes, this high loss prompts a look at potentially lower cost ferrite materials for building these machines. A commercial sample of soft magnetite ferrite is shown to have equivalent eddy current losses of roughly 1 × 10−13 [W/m3]. The study notes that micro-structured magnetite has significant hysteresis loss. Such loss is in the order of 1 × 10−3 [W/m3] when referring to both remanence related cogging and remagnetization. This study, thus, extends its examination of loss to nano-structured magnetite. Magnetite nano-particles have shown superparamagnetic (no hysteresis) behaviour that promises the elimination of hysteresis losses. A co-precipitation route to the synthesis of these nano-particles is examined. A detailed examination involving a series of 31 experiments is shown to demonstrate only two pathways providing close-to-superparamagnetic behaviour. After characterization by Scanning Electron Microscope (SEM), X-Ray Diffractometer (XRD), Superconducting Quantum Interference Device (SQUID) and crude colorimetry, the lowest coercivity and remanence found in any given sample falls at −0.17 [Oe] (below error) and 0.00165 [emu/g] respectively. These critical points can be used to estimate hysteresis related power loss, however, to produce bulk ferrite a method of sintering or bonding synthesized powder is needed. A microwave sintering solution promises to preserve nano-structure when taking synthesized powders to bulk material. A set of proof-of-concept experiments provide the ground work for proposing a future microwave sintering approach to such bulk material production. The study uses critical points measured by way of SEM, XRD, SQUID characterization (e.g. remanence and coercivity) to implement a modified Jiles-Atherton model for hysteresis curve fitting. The critical points and curve fitting model allow estimation of power loss resulting from remanent related cogging and remagnetization effects in nano-structured magnetite. Such nano-structured magnetite is shown to exhibit hysteresis losses in the order of 1 × 10−4 [W/m3] from remagnetization and 1 × 10−7[W/m3] from remanence related cogging drag. These losses are lower than those of micro-structured samples, suggesting that nano-structured materials have a significant positive effect in reducing electrical machine losses for the proposed radial multi-plattered diamagnetic bearing solution. The lower parasitic loss in these bearings suggests excellent compatibility with flywheel energy storage applications.

Les modes de déchirement sont connus pour détériorer le confinement et limiter les performances dans les machines de fusion. Plusieurs études sur les modes de déchirements ont été menées, en incluant un degré croissant de complexité dans le modèle physique afin de mieux comprendre les observations expérimentales. Une de ces extensions est l'introduction d'une description du plasma comme un fluide à deux espèces, ions et électrons, dont les dynamiques sont fortement différentes. Un autre mécanisme physique connu pour être important est la courbure du champ magnétique non perturbé. Dans cette thèse, nous étudions les questions de la stabilité linéaire et de l'évolution non linéaire des îlots magnétiques, en présence de la courbure des lignes de champ et de la rotation diamagnétique, avec le code MHD non linéaire XTOR-2F, qui inclut le transport anisotrope de chaleur et les effets géométriques. Cette analyse est appliquée à une décharge entièrement non-inductive de Tore Supra. Ce mode d'opération est crucial pour démontrer la possibilité d'un fonctionnement continu sur un réacteur de type tokamak. Dans cette thèse, la possibilité d'une stabilisation complète des modes de déchirement par la rotation diamagnétique, en présence de la courbure toroidale des lignes de champ magnétique, est démontrée. Dans le domaine linéairement stable, le mode est métastable: le niveau de saturation dépend de la taille de l'îlot initial. Dans le domaine non linéaire, la saturation de l'îlot est fortement réduite par la rotation diamagnétique et par le nombre de Lundquist. La question de l'extrapolation des résultats obtenus vers la future generation de machines de fusion est également abordée / Tearing modes are known to deteriorate the confinement and limit plasma performance in fusion devices. Various studies of this mode have been performed lately including an increasing level of complexity in the physical description which is required for understanding of experimental observations. One of such extensions is the introduction of diamagnetic rotation into the system. Another physical mechanisms known to be important for tearing mode dynamics is the curvature of unperturbed magnetic field lines and neoclassical physics. In this thesis we investigate the issues of linear stability of the tearing modes in a presence of both curvature and diamagnetic rotation using the non linear full-MHD toroidal code XTOR-2F, which includes anisotropic heat transport, diamagnetic and geometrical effects. This analysis is applied to one of the fully non-inductive discharges on Tore-Supra. Such experiments are crucially important to demonstrate reactor scale steady state operation for the tokamak. In this thesis, the possibility of full linear stabilization of the tearing modes by diamagnetic rotation in the presence of toroidal curvature is shown. In the linearly stable domain, the mode is metastable: saturation level depends on the seed island size. In the non linear regime, the saturation of n=1, m=2 mode is found to be strongly reduced by diamagnetic rotation and by Lundquist number. The question of extrapolation of the obtained results towards future generation of fusion devices is also addressed. In particular, for ITER size machines, the toroidal curvature is expected to be more important due to higher performance factor &#946;.

京都大学 / 0048 / 新制・課程博士 / 博士(農学) / 甲第19038号 / 農博第2116号 / 新制||農||1031(附属図書館) / 学位論文||H27||N4920(農学部図書室) / 31989 / 京都大学大学院農学研究科森林科学専攻 / (主査)教授 木村 恒久, 教授 西尾 嘉之, 教授 髙野 俊幸 / 学位規則第4条第1項該当 / Doctor of Agricultural Science / Kyoto University / DFAM

No presente trabalho foram estudadas, inicialmente, distorções periódicas \"bend\" provocadas por campo magnético em amostra nemática calamítica da mistura: decilsulfato de sódio, decanol e água. Com base na teoria elástica continua, medidas do comprimento de onda das distorções periódicas permitiram obter a razão K IND. 9 / X IND. em função da temperatura, onde K IND. 9 é a constante elástica de \"bend\" e X IND. a anisotropia de susceptibilidade diamagnética. Em seguida, amostras nemáticas foram dopadas com ferrofluído em diferentes concentrações, o que possibilitou, através da comparação entre os resultados (com e sem o \"doping\"), determinar K IND. 9 e X IND. , respectivamente. Num segundo momento, a mesofase nemática calamítica obtida da mistura liotrópica de laurato de potássio, decanol e água, é submetida a gradiente térmico vertical em configuração planar. Uma nova instabilidade térmica foi observada envidenciando uma estrutura de rolos com os seus eixos perpendiculares à configuração inicial do diretor. O comprimento de onda da instabilidade tem valores em torno de 10 vezes menores que a espessura da amostra. A instabilidade, cujo processo de formação e relaxação é estudado, aparece com a diminuição do gradiente térmico próximo à transição de fase nemático-isotrópica. Considerando-se estes fatos, sugere-se um mecanismo em função da variação das dimensões dos objetos micelares com a temperatura. / In this work were primarily studied the periodic distortions \"bend\" provoked by magnetic field on calamitic nematic sample of the mixture: sodium decylsulfate, decanol and water. Based on the continuum elastic theory, measures of the wave lenght of periodic distortions permitted to obtain the ratio K9 /X in function of the temperature, where k9 is the elastic constant of \"bend\" and x the anisotropic of diamagnetic susceptibility. Afterwards, nematic samples were doped with ferrofluid in different concentrations, which made possible, through a comparison between the results (with and without the \"doping\"), to determine x and K9 respectively. In a second moment, the calamitic nematic mesophase obtained from the liotropic mixture of potassium laurate, decanol and water is submitted to a vertical thermic gradient in plane configuration. A new thermic instability was observed showing evidences of a roll structure with its perpendicular axis to the initial configuration of the director. The lenght of the instability wave has values around ten times smaller than the thickness of the sample. The instability, whose process of formation with the decrease of the thermic gradient next to the transition of isotropic-nematic phase. Considering these facts, we would suggest a mechanism related to the variation of the micelar objects dimensions in function of the temperature.

No presente trabalho foram estudadas, inicialmente, distorções periódicas \"bend\" provocadas por campo magnético em amostra nemática calamítica da mistura: decilsulfato de sódio, decanol e água. Com base na teoria elástica continua, medidas do comprimento de onda das distorções periódicas permitiram obter a razão K IND. 9 / X IND. em função da temperatura, onde K IND. 9 é a constante elástica de \"bend\" e X IND. a anisotropia de susceptibilidade diamagnética. Em seguida, amostras nemáticas foram dopadas com ferrofluído em diferentes concentrações, o que possibilitou, através da comparação entre os resultados (com e sem o \"doping\"), determinar K IND. 9 e X IND. , respectivamente. Num segundo momento, a mesofase nemática calamítica obtida da mistura liotrópica de laurato de potássio, decanol e água, é submetida a gradiente térmico vertical em configuração planar. Uma nova instabilidade térmica foi observada envidenciando uma estrutura de rolos com os seus eixos perpendiculares à configuração inicial do diretor. O comprimento de onda da instabilidade tem valores em torno de 10 vezes menores que a espessura da amostra. A instabilidade, cujo processo de formação e relaxação é estudado, aparece com a diminuição do gradiente térmico próximo à transição de fase nemático-isotrópica. Considerando-se estes fatos, sugere-se um mecanismo em função da variação das dimensões dos objetos micelares com a temperatura. / In this work were primarily studied the periodic distortions \"bend\" provoked by magnetic field on calamitic nematic sample of the mixture: sodium decylsulfate, decanol and water. Based on the continuum elastic theory, measures of the wave lenght of periodic distortions permitted to obtain the ratio K9 /X in function of the temperature, where k9 is the elastic constant of \"bend\" and x the anisotropic of diamagnetic susceptibility. Afterwards, nematic samples were doped with ferrofluid in different concentrations, which made possible, through a comparison between the results (with and without the \"doping\"), to determine x and K9 respectively. In a second moment, the calamitic nematic mesophase obtained from the liotropic mixture of potassium laurate, decanol and water is submitted to a vertical thermic gradient in plane configuration. A new thermic instability was observed showing evidences of a roll structure with its perpendicular axis to the initial configuration of the director. The lenght of the instability wave has values around ten times smaller than the thickness of the sample. The instability, whose process of formation with the decrease of the thermic gradient next to the transition of isotropic-nematic phase. Considering these facts, we would suggest a mechanism related to the variation of the micelar objects dimensions in function of the temperature.

Au cours de ce travail, nous nous sommes particulièrement intéressés à une classe de molécules électroactives précurseurs de matériaux moléculaires conducteurs à composant unique, les complexes bis(1,2-dithiolène) d'or et de nickel neutres. Nous avons tout d'abord développé une série originale de complexes radicalaires d'or [Au(R-thiazYdt)2] à partir de ligands dithiolène, riches en électron, les N-alkyl-1,3-thiazoline-2-chalcogénone-4,5-dithiolate (R-thiazYdt)2 avec Y = O, S, Se et R = Pr, iPr, cycloPr, NMe2. Le substituant R de l'hétérocycle joue un rôle majeur sur les propriétés des matériaux, résultant des interactions électroniques intermoléculaires entre ces complexes paramagnétiques. Les complexes de nickel diamagnétiques, [Ni(R-thiazSdt)2], des mêmes ligands dithiolène, présentent quant à eux une organisation à l'état solide très différente, conséquence de leur caractère à "couche fermée". Enfin, la réactivité originale des dérivés avec R = tBu conduit à des ligands dithiolène portés par un cycle aromatique 2-alkylthio-thiazole (RS-tzdt). Leurs complexes d'or neutres [Au(RS-tzdt)2] forment des empilements fortement dimérisés et semi-conducteurs. / During this work, we particularly focused on one type of electroactive molecules, precursors of single component molecular conductors, the neutral gold and nickel bis(1,2-dithiolene) complexes. First we developed a series of radical gold complexes [Au(R-thiazYdt)2] derived from electron rich dithiolene ligands, the N-alkyl-1,3-thiazoline-2-chalcogenone-4,5-dithiolate (R-thiazYdt)2 with Y = O, S, Se and R = Pr, iPr, cycloPr, NMe2. The R substituent plays an important role on the properties of these materials resulting from the intermolecular electronic interactions between these paramagnetic complexes. Besides, diamagnetic nickel complexes, [Ni(R-thiazSdt)2], with the same dithiolene ligands exhibit a different organization in the solid state, a consequence of their closed shell nature. Finally, the original reactivity of the derivatives with R = tBu leads to dithiolene ligands with an aromatic 2-alkylthio-1,3-thiazole ring (RS-tzdt). Their neutral gold complexes [Au(RS-tzdt)2] form semi-conducting strongly dimerized stacks.

Devido à sua importância em turbulência causada por ondas de deriva e à aplicação com propósitos em diagnósticos de plasma, a investigação de fluxos zonais (ZF) e modos acústicos geodésicos (GAM) tem atraído bastante atenção na literatura em física de plasmas. Nesta tese, primeiramente consideramos efeitos de equilíbrio com rotação poloidal e toroidal nestes modos, posteriormente investigamos efeitos diamagnéticos em GAM a partir de um modelo de dois fluido, no qual incluímos viscosidade paralela de íons e, na parte final, consideramos amortecimento de Landau e efeitos diamagnéticos simultaneamente no estudo de GAM, porém, a partir do modelo girocinético. Efeitos diamagnéticos são causados por termos que envolvem gradientes de densidade e de temperatura provenientes da função Maxwelliana de equilíbrio. O acoplamento entre os harmônicos poloidais, $m = \\pm1$, e as derivadas radiais de quantidades macroscópicas do plasma é responsável pelo aumento no valor da frequência no GAM de alta frequência e pela instabilidade no GAM de baixa frequência. Este tipo de instabilidade, que é proporcional à frequência diamagnética de elétrons e à razão entre os gradientes de temperatura e de densidade, é mais propenso a ocorrer em posições radiais em que o fator segurança é alto. Modos geodésicos são fracamente amortecidos devido a um mecânismo não colisional conhecido por amortecimento de Landau, o qual é causado pela interação entre a onda eletrostática e partículas carregadas, íons no caso, e a taxa de amortecimento é maior próximo ao centro da coluna de plasma, onde o fator de segurança assume valores mais baixos. O equilíbrio MHD com rotação foi investigado em três regimes com relação às superfícies magnéticas: isotérmico, adiabático e isométrico. Foi observado que o gradiente de temperatura possui sentido oposto em relação à velocidade de rotação poloidal apenas no regime isométrico. Ao considerar equilíbrio com rotação e superfícies magnéticas isotérmicas e incluir fluxo de calor na equação da energia, observamos que ZF apresentam frequência não-nula, a qual é proporcional à velocidade de rotação poloidal e inversamente proporcional ao fator de segurança. Como direções futuras ressaltamos que é importante considerar efeitos eletromagnéticos, estudar automodos geodésicos e incluir o efeito de partículas aprisionadas para o desenvolvimento da física de ZF e GAM. Tal desenvolvimento beneficiará tanto a área de transporte em tokamaks como a área de diagnósticos, na qual a obtenção do perfil radial da temperatura de íons e do fator de segurança é um dos objetivos. Nesta área, um novo tipo de diagnóstico conhecido como espectroscopia em modos acústicos geodésicos está sendo desenvolvido baseado no estudo de automodos. / Due to the important role in drift wave turbulence and applications for plasma diagnostic purposes, the investigation of zonal flows (ZF) and associated geodesic acoustic modes (GAM) has arisen much attention in the plasma physics literature. In this thesis, first we consider equilibrium poloidal and toroidal rotation effects on these modes using the ideal MHD model, then we investigate diamagnetic effects on GAM using a two fluid model that includes parallel ion viscosity, and, in the final step, we include both Landau damping and diamagnetic effects on the study of GAM within the framework of the gyrokinetic model. By diamagnetic effects we mean the density and temperature radial gradients terms coming from the equilibrium Maxwellian distribution function. The effects caused by the coupling between the $m = \\pm1$ poloidal harmonics and the radial derivatives of equilibrium macroscopic quantities are responsible for an increase in the frequency value of the high frequency GAM and for an instability in the low frequency GAM. This instability, which is proportional to the electron drift frequency and the ratio between ion temperature and density gradients, are more likely to occur in radial positions where the safety factor is high. We observe that geodesic modes are slowly damped by a collisionlees mechanism known as Landau damping which is caused by the wave particle interaction between the eletrostatic potential and the íons. This damping is enhanced near the center of the plasma column, where the safety factor has lower values. Equilibrium MHD with plasma rotation were investigated in three regimes regarding the magnetic surfaces: isotherm, adiabatic and isometric. It is found that the temperature gradient has opposite directions compared to the poloidal rotation only for the isometric regime. By considering equilibrium rotation with isotherm magnetic surfaces and including heat flux we observed that ZF has a non-zero frequency which is proportional to the poloidal velocity and the inverse of the safety factor. For future directions we point out that electromagnetic effects, geodesic eigenmodes and trapped particles physics should be important for the development of the ZF and GAM physics, either in the area of anomalous transport caused by drift wave turbulence or for diagnostic purposes for obtaining the radial profile of the ion temperature and the safety factor. In this area, a new kind of diagnostic known as geodesic acoustic mode spectroscopy is being developing based on the study of eigenmodes.