<p>Thermonuclear fusion is a promising energy source for the future. If an economically efficient thermonuclear reactor would be built it has to be a cheap, safe, and highly productive electric power plant, or, a heating plant.</p><p>The emphasis of this thesis is on the single cell mirror trap with a marginally stable minimum B vacuum magnetic field, the straight field line mirror field, which provides MHD stability of the system, absence of the radial drift even to the first order in plasma β , and a reduced magnetic flux tube ellipticity. Strong density depletion at the mirrors is proposed as a mean to build up a strong potential barrier for the electrons and thereby increase the electron temperature. Conditions to obtain an energy gain factor Q>10 are briefly analyzed. Current coils which could generate the derived magnetic field are proposed. A sloshing ion distribution function is constructed for the three dimensional ‘straight line mirror field’. The gyro centre Clebsch coordinates are found to be a new pair of motional invariants for this magnetic field. The gyro centre Clebsch coordinate invariants can be used to obtain complete solutions of the Vlasov equation, including the diamagnetic drift. These solutions show that the equilibria satisfy the locally omniginuity criterion to the first order in β .</p><p>Contributions of the plasma diamagnetism to the magnetic flux tube ellipticity are studied for the straight field line mirror vacuum magnetic field and a sloshing ion distribution. Computations employing ray tracing have shown that there is a modest increase in the ellipticity, but the effect is small if β <0.2 .</p><p>Adiabatic charged particle motion in general field geometry has been studied. A set of four independent stationary invariants, the energy, the magnetic moment, the radial drift invariant, and the bounce average parallel velocity is proposed to describe adiabatic equilibria. </p>

The optical efficiency of a commercially available sputter deposited spectrally selective solar absorber was improved. The main purposes were to decrease the thermal emittance, increase the solar absorbtance of the absorber and to protect the substrate from degradation due to environmental influence. The adhesion properties between the corrosion-protecting barrier and the substrate were also studied. This project was focused on process improvements that are realistic to implement in industrial production. The thermal emittance of the absorber was decreased from 0.12 to 0.06 by changing the material of the corrosion-protecting layer from nickel-chromium to copper-nickel. Copper-nickel was less sensitive to variations in the sputter parameters than nickel-chromium. A novel method that could simplify the search for alternative corrosion resistant materials with a low thermal emittance has been purposed. Since resistivity data usually exist or can easily be measured and infrared measurements require more sophisticated measurements, the Hagen-Rubens relation was investigated for copper-nickel and nickel-chromium alloys. The dc-resistivity was found to be related to the infrared emittance or the integrated thermal emittance for alloys in their solid soluble fcc phase. The solar absorbtance was increased when a graded index absorbing coating was tailored for a crossover of the reflectance from low to high reflectance at about 2.5 µm. The solar absorber graded index coating was optimized for nickel metal content in nickel oxide and a solar absorptance of 0.89-0.91 was achieved. The solar absorptance was further increased to 0.97 when an antireflection coating was added on top of the absorbing layer. Finally, extrapolation algorithms were developed to assure correct determination of the thermal emittance for coatings on glass since modern spectrometers that do not cover the complete wavelength interval required to calculate the thermal emittance of surfaces at room temperatures accurately. The error arising from the extrapolation algorithms were smaller than the noise from the optical measurements. Similar strategies can be used for other surfaces.

Ceramics constitute an important group of low-density armour materials. Their high intrinsic strength makes it possible to design ceramic armour systems capable of defeating projectiles directly on the ceramic surface. This capability, named interface defeat, signifies that the projectile material is forced to flow radially outwards on the surface of the ceramic without penetrating significantly. This thesis presents impact experiments between long-rod projectiles and ceramic targets. The projectile/target interaction was studied using flash X-ray technique. Transition velocities (the impact velocity at which interface defeat can no longer be maintained and penetration starts) were estimated for different combinations of metallic projectiles and ceramic targets and compared to critical velocities estimated on a theoretical basis. Replica scaling experiments were also performed in order to investigate the possible influence of scale. All ceramic materials tested showed a distinct transition from interface defeat to penetration. Experiments with different silicon carbides showed that the transition velocity correlated better with the fracture toughness than with the hardness of the ceramic materials. For conical projectiles, penetration occurred along a conical surface crack and at a lower transition velocity than that observed for cylindrical projectiles. Experiments with unconfined alumina targets in different scales showed only a slight increase in dimensionless final penetration with length scale. A unique transition velocity seems to exist for each combination of projectile, target material and target configuration. This velocity was found to depend on both the strength (hardness) and the brittleness (fracture toughness) of the ceramic. The lower transition velocity of conical projectiles compared with cylindrical ones is mainly due to the radially expanding load and the penetration of projectile material into surface cracks. The results of the experiments in different scales indicate that replica scaling is valid for penetration in ceramics.

Microengineering has developed a broad range of production techniques to reduce size, increase throughput, and reduce cost of electrical and mechanical devices. The miniaturisation has also entailed entirely new opportunities. In this work, a piezoresistive silicon sensor measuring mechanical deformation has been designed and fabricated with the help of microengineering. Due to the large variety of used processes, this device can serve as a survey of techniques in this field. Four basic process categories are recognised: additive, subtractive, modifying, and joining methods. The last category, joining methods, has previously been the least investigated, especially when it comes to compatibility with the other categories. The adaptability of wet chemical etching to established silicon wafer bonding technique has been investigated. Further, phenomena related to oxygen plasma pre-treatment for direct bonding has been investigated by blister bond adhesion tests, X-ray photoelectron spectroscopy, and atomic force microscopy. Wafer bonding has been adapted to monocrystalline quartz. For wet chemical pre-treatment, characteristics specific for quartz raise obstacles. Problems with limited allowable annealing temperature, low permeability of water released in the bond at annealing, and electrostatic bonding of particles to the quartz surface, have been studied and overcome. The influence of internal bond interfaces on resonators has been investigated. Chemical polishing of quartz by ammonium bifluoride has been experimentally investigated at high temperatures and concentrations. Chemometrical methods were used to search for optimum conditions giving the lowest surface roughness. These extreme conditions showed no extra advantages. Adhesion quantification methods for wafer bonding have been comprehensively reviewed, and augmentations have been suggested. The improved techniques’ usefulness for three areas of use has been forecasted: general understanding, bonding scheme optimisation, and quality control. It was shown that the quality of measurements of all commonly used methods could be dramatically improved by small means.

In recent years portable electronic devices, such as mobile phones and personal digital assistants, have increased the demand for high performance displays with low power consumption. An interesting candidate with the potential of fulfilling these demands is the reflective single-polarizer surface controlled bistable twisted nematic liquid crystal display. The main focus of this work involves the optical properties of displays based on these bistable structures. In the investigations, the display is considered as an integrated optical system, containing not only the liquid crystal cell, but also components such as polarizers and retardation films. The specific aim of the thesis was to derive new optical modes of the reflective single-polarizer bistable twisted nematic device using the Jones matrix method to study the interaction between the polarization of light and the optically anisotropic media. The electro-optical properties of the derived modes have been studied and evaluated both theoretically and experimentally. The modes possess excellent brightness and high contrast ratio. By introducing a quarter-wave retardation film into the optical configuration, the contrast ratio can be significantly increased by preventing spectral leakage of light in the dark state. To experimentally realize the derived optical modes, special layers for the alignment of the liquid crystal molecules on the cell substrate surface have been proved needed. Therefore, also the photo-alignment technology of nematic liquid crystals on novel alignment materials has been studied with the aim to control liquid crystal cell parameters such as pretilt angle and anchoring energy, both critical for the bistable switching. The results of this thesis will increase the understanding of the optical properties of the reflective single-polarizer bistable twisted nematic liquid crystal display and will be valuable when considering this type of device for practical applications.

Complex moduli and Poisson’s ratio have been estimated using extensional and torsional wave experiments. The data were used for assessment of linearity and isotropy of two polymers, polymethyl methacrylate (PMMA) and polypropylene (PP). The responses of both materials were found to be close to linear and isotropic. A statistical analysis of different estimation approaches for complex modulus and Poisson’s ratio was conducted. It was shown that a joint estimation of complex modulus and Poisson’s ratio improves the estimated results. Considerable improvement was achieved in the frequency range 5-15 kHz for Poisson’s ratio. A non-equilibrium split Hopkinson pressure bar (SHPB) procedure for identification of complex modulus has been developed. Two simplified procedures were also established. Both overestimated the magnitude of the complex modulus. The complex modulus of PP was identified using PMMA and aluminium bars, and the estimated complex modulus was in good agreement with published results. The procedure was found to be accurate regardless of the specimen size or the specimen-to-bar impedance ratio. The procedure was also used to analyze the mechanical response of four compacted pharmaceutical tablet materials. A Debye-like relaxation was observed for all tested materials. Utilizing SHPB effectively requires knowledge about the impact process that is normally used for excitation. Therefore the impact between a cylindrical striker and a long cylindrical bar of viscoelastic material was studied theoretically and experimentally. Strains measured at three locations along a PMMA bar impacted by strikers of the same material agreed well with the theoretical results. A method for identification of complex shear modulus from measured shear strains on a disc subjected to a transient torque at its centre has been established. The two-dimensional wave solutions used are exact in the sense of three-dimensional theory. The results from experimental tests with different load amplitudes and durations agree well with each other.

Thermonuclear fusion is a promising energy source for the future. If an economically efficient thermonuclear reactor would be built it has to be a cheap, safe, and highly productive electric power plant, or, a heating plant. The emphasis of this thesis is on the single cell mirror trap with a marginally stable minimum B vacuum magnetic field, the straight field line mirror field, which provides MHD stability of the system, absence of the radial drift even to the first order in plasma β , and a reduced magnetic flux tube ellipticity. Strong density depletion at the mirrors is proposed as a mean to build up a strong potential barrier for the electrons and thereby increase the electron temperature. Conditions to obtain an energy gain factor Q&gt;10 are briefly analyzed. Current coils which could generate the derived magnetic field are proposed. A sloshing ion distribution function is constructed for the three dimensional ‘straight line mirror field’. The gyro centre Clebsch coordinates are found to be a new pair of motional invariants for this magnetic field. The gyro centre Clebsch coordinate invariants can be used to obtain complete solutions of the Vlasov equation, including the diamagnetic drift. These solutions show that the equilibria satisfy the locally omniginuity criterion to the first order in β . Contributions of the plasma diamagnetism to the magnetic flux tube ellipticity are studied for the straight field line mirror vacuum magnetic field and a sloshing ion distribution. Computations employing ray tracing have shown that there is a modest increase in the ellipticity, but the effect is small if β &lt;0.2 . Adiabatic charged particle motion in general field geometry has been studied. A set of four independent stationary invariants, the energy, the magnetic moment, the radial drift invariant, and the bounce average parallel velocity is proposed to describe adiabatic equilibria.

Type Ia supernovae (SNe Ia) are excellent tools in cosmology. Their intrinsic luminosities are found to vary systematically with the light-curve widths, providing an empirical calibration. This property, called the width-luminosity relation (WLR), is the basis of modern SN Ia cosmology and led to the unexpected discovery of the current accelerated rate of cosmic expansion. By examining the spectroscopic diversity of SNe Ia, this thesis aims to improve both the use of SNe Ia in cosmology and the physical understanding of the observed properties. Spectra of SNe Ia contain a wealth of information, but are difficult to organize. In this thesis, new methods are developed to consistently quantify and analyze the spectral features of supernovae. The efficacy of the methods is tested on a large library of observed spectra encompassing a wide range of properties. The spectroscopic diversity of SNe Ia enters cosmology through K-correction calculations. Before this work, K-correction was a major contributor of the systematic errors in cosmology. It is shown here that the systematic errors can be largely diminished by carefully quantifying the mean spectroscopic properties of SNe Ia. The remaining statistical errors are also quantified and shown to be redshift dependent. With the aid of principal component analysis (PCA), the multidimensional spectral information is reduced to a few components describing the largest variations in the spectral library. Using this tool, it is shown here that SN Ia intrinsic luminosity is the main driver of the spectroscopic diversity at maximum light, for every spectral feature from the ultraviolet to the near-infrared. These spectroscopic sequences can potentially account for a large fraction of the K-correction statistical errors and even enable the use of SN Ia spectra as independent indicators of intrinsic luminosity and colors. The established relations will also disentangle the effects of demographic shift and true evolution in high-redshift SN Ia spectra. The temporal evolution of the spectral features is shown to exhibit the persistence of the spectroscopic sequences throughout other epochs. The effect is attributed to the more rapid spectroscopic temporal evolution of fainter SNe Ia. This conclusion supports the theory that WLR is primarily a spectroscopic effect, rather than a bolometric one.

The search for lepton flavour violation is significant to our understanding of the standard model of particle physics. This measurement uses the muon decay data collected by the TWIST experiment at TRIUMF to search for lepton flavour violation between charged lepton species. Specifically, I searched for the decay µ+→e+X0, where X° is an unknown, undetected, neutral boson, against a background of stan¬dard muon decays, µ+→e+vevµ I set branching ratios for these decays such that B(µ+→e+X0)< 2 x 10-5 - 5 x 10-5, for X0 of various masses accessable by the momenta of the muon decay spectrum, to a confidence level of 95%. This improves upon the previous best limits by a. factor of three. A correction to the spectrum was required to set a limit on a massless X0 of B(µ+→e+X0)< 6.3 x 10-5.

In the last decade, adaptive optics systems have been implemented on all the major ground based telescopes and have proven reliable tools for correcting the image to near the diffraction limit. However, the correction from these systems is limited to a narrow field of view. This dissertation address the challenges of widening the corrected field of single conjugate adaptive optics by properly using statistical information on the optical turbulence profile of the atmosphere above the telescope, and by optimizing the trade-off between image quality and field of view. Altair is the facility adaptive optics system for the 8-meter Gemini North telescope and marks the historical beginning of wide field adaptive optics. Its performance evaluation in Part One is the first on-sky comparison of sparse field images from an altitude-conjugated and a ground-conjugated deformable mirror. All of the other basic aspects of Altair's performance are characterized for use by the Gemini community to plan observations. We also study and report. on techniques for extrapolating the edge of the deformable mirror, a critical step in altitude-conjugated mode. In Part Two we develop a point spread function model for Ground Layer Adaptive Optics (GLAO) that is based on analytic forms of the phase power spectral density. This model has been used for feasibility studies of GLAO on Gemini, and the Thirty Meter Telescope (TMT), currently the most advanced extremely large telescope project. The TMT will be an adaptive telescope that has science goals for the huge 81 square arcminute field of the Wide Field Optical Spectrograph (WFOS). We will show that WFOS-GLAO provides useful gains and will operate in the very wide GLAO (VWGLAO) regime, which has no additional overhead for seeing improved operation. To identify the VWGLAO regime we use statistical turbulence profile models and examine anisoplanatism in terms of image quality metrics relevant to the science that GLAO will likely assist. The VWGLAO regime is where there are useful gains over the theoretical seeing limit for wide field science that measure data collection efficiency as proportional to the product of image quality and the field of view (solid angle). We also show that for many cases VWGLAO will not be impacted by lag anisoplanatism nor by wavefront sensor noise.