Ore-Body Delineation using Borehole Seismic Techniques for Hard Rock Exploration

Very often, economically viable ore deposits are low in volume and located at depth within extremely complex geological environments. Such deposits are difficult to explore. Borehole seismic methods, particularly crosshole reflection imaging, could be utilized to detect and delineate such resources. This study aims to evaluate the true potential of crosshole seismic reflection method for mineral exploration. One of the most promising applications of this method is in finding down-dip extensions of the existing resources

Single-Atom Resolved Imaging and Manipulation in an Atomic Mott Insulator

This thesis reports on new experimental techniques for the study of strongly correlated states of ultracold atoms in optical lattices. We used a high numerical aperture imaging system to probe 87Rb atoms in a two-dimensional lattice with single-site resolution. Fluorescence imaging allows to detect single atoms with a large signal to noise ratio and to reconstruct the atom distribution on the lattice. We applied this new technique to a two-dimensional Mott insulator and directly observed number squeezing and the emerging shell structure. A comparison of the radial density and variance distributions to theory provides a precise in situ temperature and entropy measurement from single images. We find entropies around the critical value for quantum magnetism. In a second series of experiments, we demonstrated two-dimensional single-site spin control in the optical lattice. The differential light shift of a tightly focused laser beam shifts selected atoms into resonance with a microwave field driving a spin flip. In this way, we reach sub-diffraction limited spatial resolution well below the lattice spacing. Starting from a Mott insulator with unity filling we were able to create arbitrary spin patterns. We used this ability to prepare atom distributions to study one-dimensional single-particle tunneling dynamics in a lattice. By discriminating the dynamics of the ground state and of the first excited band, we find that our addressing scheme leaves most atoms in the vibrational ground state. Moreover, we studied coherent light scattering from the atoms in the optical lattice and found diffraction maxima in the far-field. We showed that an antiferromagnetic order leads to additional diffraction peaks which can be used to detect this order also when single-site resolution is not available. The new techniques described in this thesis open the path to a wide range of novel applications from quantum dynamics of spin impurities, entropy transport, implementation of novel cooling schemes, and engineering of quantum many-body phases to quantum information processing.In dieser Arbeit werden neue experimentelle Techniken für die Untersuchung von stark korrelierten Zuständen von ultrakalten Atomen in optischen Gittern vorgestellt. Wir untersuchen 87Rb Atome in einem zwei-dimensionalen Gitter und erreichen dabei eine Auflösung der einzelnen Gitterplätze mit Hilfe eines hochauflösenden Abbildungssystems. Fluoreszenzabbildung erlaubt es, einzelne Atome mit großem Signal-zu-Rausch-Verhältnis zu detektieren und die Verteilung der Atome auf dem Gitter zu rekonstruieren. Wir wenden diese neue Technik auf einen zwei-dimensionalen Mott-Isolator an and beobachten direkt das number squeezing und die Schalenstrukur. Ein Vergleich der radialen Dichte- und Varianzverteilung mit der Theorie ermöglicht eine präzise Temperatur- und Entropiemessung an einzelnen Bildern und wir finden Entropien um den kritischen Wert für Quantenmagnetismus. In einer zweiten Reihe von Experimenten zeigen wir, dass wir gezielt einzelne atomare Spinzustände im Gitter manipulieren können ohne die benachbarten Atome zu beeinflussen. Wir benutzen den differentiellen light shift eines stark fokussierten Laserstrahls, um einzelne Atome in Resonanz mit einem Mikrowellenfeld zu bringen, das den Spin umklappt. Auf diese Weise erreichen wir eine Ortsauflösung unter der Beugungsgrenze. Wir beginnen mit einem Mott-Isolator mit einem Atom pro Gitterplatz und können darin beliebige Spinmuster erzeugen. Diese neuen Möglichkeiten zur Präparation atomarer Verteilungen nutzen wir, um die eindimensionale Einteilchen-Tunneldynamik in einem Gitter zu untersuchen. Wir unterscheiden die Dynamik von Atomen im Grundzustand und im ersten angeregten Band und zeigen so, dass unser Adressierschema die meisten Atome im Grundzustand lässt. Darüber hinaus untersuchen wir kohärente Lichtstreuung an den Atomen im Gitter und finden Beugungsmaxima im Fernfeld. Wir zeigen, dass eine antiferromagnetische Ordnung der Atome zu zusätzlichen Beugungsmaxima führt, die man auch ohne unsere hohe Auflösung zum Nachweis dieser Ordnung nutzen könnte. Die neuen Techniken, die in dieser Arbeit vorgestellt werden, öffnen den Weg für viele neue Anwendungen von der Quantendynamik von Spin-Defekten, Entropietransport, der Umsetzung neuer Kühlschemata sowie der Realisierung von Quanten-Vielteilchenphasen bis hin zur Quanteninformationsverarbeitung

Model for quantitative tip-enhanced spectroscopy and the extraction of nanoscale-resolved optical constants

Near-field infrared spectroscopy by elastic scattering of light from a probe tip resolves optical contrasts in materials at dramatically sub-wavelength scales across a broad energy range, with the demonstrated capacity for chemical identification at the nanoscale. However, current models of probe-sample near-field interactions still cannot provide a sufficiently quantitatively interpretation of measured near-field contrasts, especially in the case of materials supporting strong surface phonons. We present a model of near-field spectroscopy derived from basic principles and verified by finite-element simulations, demonstrating superb predictive agreement both with tunable quantum cascade laser near-field spectroscopy of SiO$_2$ thin films and with newly presented nanoscale Fourier transform infrared (nanoFTIR) spectroscopy of crystalline SiC. We discuss the role of probe geometry, field retardation, and surface mode dispersion in shaping the measured near-field response. This treatment enables a route to quantitatively determine nano-resolved optical constants, as we demonstrate by inverting newly presented nanoFTIR spectra of an SiO$_2$ thin film into the frequency dependent dielectric function of its mid-infrared optical phonon. Our formalism further enables tip-enhanced spectroscopy as a potent diagnostic tool for quantitative nano-scale spectroscopy.Comment: 19 pages, 9 figure

The aerodynamics of curved jets and breakaway in Coanda flares

An investigation was carried out into external-Coanda Effect flares designed by British Petroleum International plc. The phenomenon of interest was breakaway of an under expanded axisymmetric curved wall jet from the guiding surface due to high blowing pressure. A survey of investigations of similar flows suggested very complex jet fluid dynamics. Strong cell structure including shock waves was present giving bulk and discrete compression and bulk dilatation. More expansion was imposed by the radial velocity components. Wall curvature and a rear-facing step added further significant influences. The combination of these factors is known to produce highly non-linear turbulence, and this constitutes a major difficulty for the application of computational methods to the flare. In view of the amount of resources required to eliminate the problems of using a Navier-Stokes code, an economical approach was adopted, matching the Method of Characteristics to various simplified models and an integral boundary layer. In the experimental work, a planar model of the flare was contructed and studied using a wide range of methods in order to achieve accuracy and provide comparability with other work. An axisymmetric model was designed and investigated in a similar manner, so that the influence of this geometry could be clearly distinguished. A full-scale flare was subjected to a restricted range of tests to compare the laboratory results with the industrial application. The results from all the experiments demonstrated good correspondence. The main conclusion was that amalgamation of separation bubbles is crucial for breakaway. These are present long before breakaway, and are strongly reduced by decreasing the cell scale, adding a rear-facing step and axisymmetry, which leads to improved breakaway performance. Although the computational methods did not prove robust enough for all design purposes, they did permit significant insights into the mechanism of breakaway

In-situ measurement and characterization of cloud particles using digital in-line holography

Satellite measurement validations, climate models, atmospheric radiative transfer models and cloud models, all depend on accurate measurements of cloud particle size distributions, number densities, spatial distributions, and other parameters relevant to cloud microphysical processes. And many airborne instruments designed to measure size distributions and concentrations of cloud particles have large uncertainties in measuring number densities and size distributions of small ice crystals. HOLODEC (Holographic Detector for Clouds) is a new instrument that does not have many of these uncertainties and makes possible measurements that other probes have never made. The advantages of HOLODEC are inherent to the holographic method. In this dissertation, I describe HOLODEC, its in-situ measurements of cloud particles, and the results of its test flights. I present a hologram reconstruction algorithm that has a sample spacing that does not vary with reconstruction distance. This reconstruction algorithm accurately reconstructs the field to all distances inside a typical holographic measurement volume as proven by comparison with analytical solutions to the Huygens-Fresnel diffraction integral. It is fast to compute, and has diffraction limited resolution. Further, described herein is an algorithm that can find the position along the optical axis of small particles as well as large complex-shaped particles. I explain an implementation of these algorithms that is an efficient, robust, automated program that allows us to process holograms on a computer cluster in a reasonable time. I show size distributions and number densities of cloud particles, and show that they are within the uncertainty of independent measurements made with another measurement method. The feasibility of another cloud particle instrument that has advantages over new standard instruments is proven. These advantages include a unique ability to detect shattered particles using three-dimensional positions, and a sample volume size that does not vary with particle size or airspeed. It also is able to yield two-dimensional particle profiles using the same measurements

Design and implementation of a digital holographic microscope with fast autofocusing

Holography is a method for three-dimensional (3D) imaging of objects by applying interferometric analysis. A recorded hologram is required to be reconstructed in order to image an object. However one needs to know the appropriate reconstruction distance prior to the hologram reconstruction, otherwise the reconstruction is out-of-focus. If the focus distance of the object is not known priori, then it must be estimated using an autofocusing technique. Traditional autofocusing techniques used in image processing literature can also be applied to digital holography. In this thesis, eleven common sharpness functions developed for standard photography and microscopy are applied to digital holograms, and the estimation of the focus distances of holograms is investigated. The magnitude of a recorded hologram is quantitatively evaluated for its sharpness while it is reconstructed on an interval, and the reconstruction distance which yields the best quantitative result is chosen as the true focus distance of the hologram. However autofocusing of highresolution digital holograms is very demanding in means of computational power. In this thesis, a scaling technique is proposed for increasing the speed of autofocusing in digital holographic applications, where the speed of a reconstruction is improved on the order of square of the scale-ratio. Experimental results show that this technique offers a noticeable improvement in the speed of autofocusing while preserving accuracy greatly. However estimation of the true focus point with very high amounts of scaling becomes unreliable because the scaling method detriments the sharpness curves produced by the sharpness functions. In order to measure the reliability of autofocusing with the scaling technique, fifty computer generated holograms of gray-scale human portrait, landscape and micro-structure images are created. Afterwards, autofocusing is applied to the scaleddown versions of these holograms as the scale-ratio is increased, and the autofocusing performance is statistically measured as a function of the scale-ratio. The simulation results are in agreement with the experimental results, and they show that it is possible to apply the scaling technique without losing significant reliability in autofocusing