Powerful lasers are needed to generate artificial guide stars for astronomical adaptive optics. Continuous wave (CW) lasers yield the most efficient excitation of the D2 line in the mesopheric sodium layer. Data is presented from early systems which used commercially available CW dye lasers. Building on these results, a dye laser was designed and constructed which incorporates a sodium Faraday filter (SFF) to select and lock the laser frequency to the peak of the D2 sodium resonance. This laser was the first ring dye laser made using an intra-cavity SFF, and also the first incorporating a SFF to produce a significant amount of power in a single longitudinal mode. A major part of this thesis concerns the design and construction of the SFF. The theory of operation is developed and then used to design a SFF with a high throughput at the D2 line of sodium. The two main elements of a SFF are a sodium cell and a magnet. The design and construction of these two elements is discussed in detail. The design and construction of a wavefront sensor for the Multiple Mirror Telescope's unique geometry is presented. This wavefront sensor and a CW dye laser were used to generate the first astronomical images sharpened by an adaptive optics system incorporating a sodium laser guide star.

Backside illuminated thinned CCDs have the highest response in the UV and blue spectral region. Their use in detectors is limited due to the instability of the CCD. A low temperature oxide nearly 30 Å thick is grown on the acid thinned backside to tie up dangling bonds. The oxide carries fixed positive charges that attract and trap photogenerated electrons. A permanent and stable backside charging procedure is necessary to create a negative bias that will drive electrons to the frontside collection wells. We have shown chemisorption charging to be a novel method to permanently charge CCDs. The catalytic nature of certain metals are exploited to chemisorb oxygen as negative atomic species at the metal/oxide interface. Charging is shown to occur by depositing a thin film 10 Å of platinum on the backside. No tunneling occurs because of the thick oxide. The Passivated Platinum Film (PPtF) which utilizes a hafnium oxide antireflection coating to passivate the platinum is an effective process, but it is sensitive to the environment and discharges quickly upon hydrogen exposure. A silver catalytic coating is shown to be far superior to other charging techniques. Silver irreversibly chemisorbs oxygen and hydrogen is not dissociatively adsorbed except at temperatures < 100°K. High quantum efficiencies have been recorded for the UV-blue ranges. A slight drop is seen at cold temperatures due to interaction of water with oxygen to form hydroxyl ions. No change in QE is seen upon exposure to hydrogen or during outgassing. Silver is also one of the most transparent metals and easily deposited by evaporation. We therefore have developed a charging process which is nearly ideal for CCD imaging.

A complete Stokes imaging spectropolarimeter has been developed based on the principles of computed-tomography, spectrometry and polarimetry. The Computed-Tomography Imaging SpectroPolarimeter (CTISP) is a polarization extension to the Computed Tomography Imaging Spectrometer (CTIS)¹. Imaging spectrometers estimate the object cube (x,y, λ), whose smallest subdivision is a voxel, while Stokes imaging spectrometers estimate four Stokes object cubes (x,y, Sp(λ); p = 0,1,2,3), one for each Stokes parameter. CTISP uses a two-dimensional disperser to diffract the image in the field stop into a 5-by-5 array of diffraction orders. As in computed tomography, each focal plane array (FPA) pixel effectively integrates a different path through the object cube, and when all pixels are recorded, a significant portion of the object cube's information is obtained. The frequency space representation of the object cube, however, indicates that two conical regions of information are not recorded, thereby limiting the reconstruction accuracy. CTISP scans only in the polarization domain (not spectral or spatial domains), acquiring four FPA frames, one behind each of the four polarization analyzers. Currently, CTISP's resolution is 33 by 33 spatially over a 3.5 degrees full angle field of view with 16 spectral bands of 20nm width covering 440nm-740nm. CTISP acquisition is modeled using the linear imaging equation gₐ=Hₐfₐ+ξₐ, which is inverted using the iterative expectation-maximization algorithm to solve for fₐ, the object cube as seen through analyzer a. The recorded diffraction images gₐ and the empirically determined calibration matrices Hₐ, are each acquired using analyzer a. The nth voxel reconstruction result is extracted from each of the four fₐ vectors to form a four element vector f(n) which is then multiplied by the inverse of the voxel characteristic matrix W(n) to obtain the estimate of the Stokes vector S(n). W(n) is derived from the four Hₐ matrices. A fully computer-controlled calibration facility and a suite of programs are used to calibrate CTISP. CTISP was validated using synthetically generated and real objects. Spectral agreement is consistent with CTIS, while Stokes parameter polarization errors were typically 0.04-0.07 for this instrument. Errors are most significant at the spectral limits of CTISP. An object dependent correction reduces these errors to below one percent.

A novel approach is proposed for studying the ν(μ) → ν(τ) oscillation and detection of extragalactic neutrinos. Active Galactic Nuclei (AGN), Gamma Ray Bursters (GRB) and Topological Defects are believed to be sources of ultrahigh energy ν(μ) and νₑ. These astrophysical sources provide a long baseline of 100Mpc, or more, for possible detection of ν(μ) → ν(τ) oscillation with mixing parameter Δm² down to 10⁻¹⁷ eV², many orders of magnitude below the current accelerator experiments. The propagation characteristics of upward going muon and tau neutrinos is studied to show that high energy tau neutrinos cascade down in energy as they propagate through the Earth, producing an enhancement of the incoming tau neutrino flux in the low energy region. By contrast, high energy muon neutrinos get attenuated as they traverse the Earth. It is observed that the relative steepness of the incoming neutrino flux spectrum and the nadir angle of the Earth are two important factors that influence the enhancement and cascade of nutau flux. This effect provides a novel way to search for tau neutrino appearance by measuring the angular dependence of tau neutrino induced upward muons; and upward hadronic and electromagnetic showers. A Monte Carlo evaluation of tau survival probability and its range shows that at energies below 10⁷ - 10⁸ GeV, depending on the material, only tau decays are important. However, at higher energies the tau energy losses are significant, hence reducing the survival probability of tau. Here, tau energy loss for energies up to 10⁹ GeV have been calculated taking into consideration the decay of tau. An understanding of tau energy loss at very high energies could help with the interpretation of long tracks produced by charged particles in large underground detectors.

Lightning, a familiar phenomenon on Earth, may also occur at other times and locations in our solar system. It has been suggested as a mechanism for forming chondrules, millimeter-sized beads of glassy silicate found in primitive meteorites formed in the early solar system 4.5 billion years ago. It has also been detected in Voyager images of Jupiter, and there is evidence that it may occur on other planets as well, including Venus, Saturn and Neptune. The mechanism believed to produce lightning discharges on Earth, and possibly other planets, is charge production by collisions of ice particles, followed by gravitational separation of oppositely-charged large and small particles. This work examines the possibility of the occurrence of lightning discharges in the atmospheres of Jupiter and Neptune as well as in the protoplanetary nebula (PPN) of the early solar system by modeling charge separation and growth of the electric field. The model is also applied to the Earth as a test of its predictive power. It is found that the model can reproduce the correct timescale, particle charge and electric field magnitude seen in terrestrial lightning. The model also predicts lightning on Jupiter at the 3-5 bar level provided that the local water abundance is greater than the solar value. This is a much higher abundance than measured by the Galileo probe into Jupiter's atmosphere, which suggests that the water content measured by the probe does not apply to the entire planet. An application of the model to Neptune's water and NH₄SH clouds finds that lightning is unlikely in these clouds due to the large electric field required for electrical breakdown. Lightning may be possible in the overlying H₂S-NH₃ cloud provided that these substances can undergo collisional charge exchange with a magnitude at least 1% of that found in water ice. In the protoplanetary nebula, it appears that large-scale precipitation-induced lightning could not have occurred, due to the small mass density, low temperature and high electrical conductivity of the surroundings. This is a robust conclusion that does not depend sensitively on the values of the parameters involved.

In this thesis, we shall consider a particularly important metric known as the AdS soliton through the context of brane worlds in an arbitrary number of extra dimensions. In this regard, we take as our motivation two of the most exciting recent developments in theoretical physics; namely the AdS/CFT correspondence and the RS and ADD brane world scenarios. We examine how our understanding of branes originally developed, both as fundamental extended objects from string theory and as a phenomenologically viable description of the universe, where we are thought to reside on a brane located in a higher dimensional bulk. We then discuss the AdS/CFT correspondence in which branes are used to study a conjectured duality between gravity in D dimensions and gauge theories in (D - 1) dimensions. It is in this context that the AdS soliton geometry first arises, as it proves quite useful for studying ordinary QCD-like gauge theories from the point of view of supergravity. We follow this by a discussion of how to make a viable brane world in six dimensions using the AdS soliton. We further discuss the cosmology of this and other related six dimensional models. After this, we generalize the AdS soliton to an arbitrary number of dimensions, greater than six, and compactify the extra dimensions so as to have a realistic low-energy effective theory in the standard four dimensions. We examine several realizations of the AdS soliton in higher dimensions, both analytically and numerically, and touch upon how it can nicely solve the hierarchy problem of scales in physics. Finally, we also briefly consider the cosmology of an AdS soliton brane world.

The Rice Magnetospheric Specification and Forecast Model (MSFM) will be upgraded to remove the need for the ground based parameters Kp and Dst through the use of solar wind driven analytical and artificial neural network (ANN) models that specify and predict these parameters. The ground based parameters require long processing times before they are made available to the U.S. Air Force 55$\sp{\rm th}$ Space Weather Squadron and the installed version of the MSFM. This delay hinders the usefulness of the specification of the magnetosphere and subsequent forecasts. By replacing these parameters with values specified by solar wind driven models this processing time can be reduced and the MSFM can achieve a true forecast. The effects of a higher time resolution quasi-Kp index from the MEB inversion and solar wind ANN algorithms on the MSFM equatorial particle fluxes will also be investigated.

The combination of excellent space-based remote sensing, and image reconstruction techniques, as well as improvements in numerical modeling, help enhance our understanding of particle transport in solar flares. We conduct a rigorous analysis of flare hard X-ray emission using the unprecedented spectral and spatial resolution of the RHESSI telescope data in order to better understand the spectral properties of the emitting electron population in solar flares. We complete our study with a forward-fit to the data using a Fokker-Planck kinetic code, to numerically model the particle transport in phase-space in realistic magnetic geometries and for different particle injection profiles.

Electrostatic and Monte Carlo Simulations of the Xenon-10 Dark Matter Detector were carried out. Electrostatic simulations led to optimization of the charge sensitive region through proper determination of resistor chain values for the field shaping wires and through maximization of the charge sensitive region by reducing areas of charge loss. These simulations also led to identification of problem regions which would otherwise hindered detector calibration and data analysis. Monte Carlo simulations of the light response for both primary and secondary scintillation light were instrumental in position reconstruction in the gas phase of the detector and in the identification of events occurring inside the problem regions found in the electrostatic simulations. Data comparison with Activated Xenon (131Xe) with its gamma ray feature at 164 keV and isotropic event distribution showed good agreement with simulated data.

Satellite observations have shown that fluxes of relativistic electrons in the earth's radiation belts can vary by orders of magnitude during periods of high solar activity. Understanding the dynamic behavior of these particles is very important because they can disrupt wireless communication, impair space exploration and affect GPS navigation. We use two numerical methods to simulate the variations of energetic particles in the radiation belts. First, we develop a radial diffusion model with time-dependent boundary conditions and a Kp-dependent electron lifetime model. Using this model, we simulate a series of high-speed-stream declining-phase magnetic storm events. The results are consistent with spacecraft observations and show that radial diffusion can propagate the enhancement of phase space density from the outer boundary into the center of the outer radiation belt. The second part of the work adapts Nunn's Vlasov Hybrid Simulation method to an existing MHD-Particle simulation code, resulting in an efficient new method to calculate phase space density of energetic particles. We use the 1995 January storm event as a test case. Good agreement is obtained between the simulation results and measured phase space densities for this event. Simulating the dynamics of the radiation belts is one important part of global space weather modeling. The advance in radiation belt modeling can help us to better understand the physics behind these interesting and important phenomena.