The objective of this study was to provide an optical technique allowing full-field in-plane deformation measurements at high temperature by using high-sensitivity moiré interferometry. This was achieved by a new approach of performing deformation measurements at high temperatures in a vacuum oven using an achromatic interferometer. The moiré system setup was designed with particular consideration for the stability, compactness, flexibility, and ease of control. A vacuum testing environment was provided to minimize the instability of the patterns by protecting the optical instruments from the thermal convection currents. Also, a preparation procedure for the high-temperature specimen grating was developed with the use of the plasma-etched technique. Gold was used as a metallic layer in this procedure. This method was demonstrated on a ceramic block, metal/matrix composite, and quartz. Thermal deformation of a quartz specimen was successfully measured in vacuum at 980 degrees Celsius, with the sensitivity of 417 nm per fringe. The stable and well-defined interference patterns confirmed the feasibility of the developments, including the high-temperature moiré system and high-temperature specimen grating. The moiré system was demonstrated to be vibration-insensitive. Also, the contrast of interference fringes at high temperature was enhanced by means of a spatial filter and a narrow band interference filter to minimize the background noise from the glow of the specimen and heater. The system was verified by a free thermal expansion test of an aluminum block. Good agreement demonstrated the validity of the optical design. The measurements of thermal deformation mismatch were performed on a graphite/epoxy composite, a metal/matrix composite equipped with an optical fiber, and a cutting tool bit. A high-resolution data-reduction technique was used to measure the Strain distribution of the cutting tool bit. / Ph. D.

Although contact problems with friction have received considerable attention in recent years, analytical as well as experimental limitations have tended to obscure some of their essential features. All the experimental techniques employed in the past lacked either required sensitivity or adequate spatial resolution for local measurements of deformation near the contact surface. Further, most techniques also did not allow the use of prototype material which is crucial for investigation of contact stress problems with friction. In the present study, a relatively new experimental method, which has been developed at VPI & SU, is employed: high-sensitivity moiré interferometry. Using a clearance pin-joint model made of prototype structural material, Aluminum 7071-T6, studies on frictional phenomena between the pin and plate are conducted to provide a comprehensive treatment of the following subjects: slip-stick phenomena, variation of contact zone, distribution of frictional force at the contact region, effects of frictional shear stress on stress concentration, and identification of slip amplitude. Experimental techniques and algorithms of analysis necessary for the research are further developed. The results showed a strong influence of friction, including significant differences in the load-increasing and load-decreasing phases. / Ph. D.

The elastohydrodynamic lubrication regime (EHD) is found in many machine elements, such as rolling element bearings, gears, cam/tappet, where a combination of hydrodynamic effect, elastic deformation of the surfaces and an increase of the lubricant’s viscosity with pressure create a continuous lubricant film which is capable of supporting pressures of the order of tens of thousands of atmospheres. One of the most important features of these films is their thickness, as this determines whether the bounding surfaces are completely separated, thus avoiding premature wear and failure of the contact. Consequently for many years scientists were interested in finding methods for measuring the lubricant film thickness in elastohydrodynamic conditions. One of the most versatile and widely used techniques for measuring lubricant film thickness in EHD contacts is the optical interferometry method. Apart from numerous advantages, this method has the limitation in the fact that one of the contacting surfaces must be transparent, usually glass or sapphire, thus it does not replicate real conditions found in machine elements contacts. On the other hand, the other group of methods used for studying the behaviour of elastohydrodynamic films includes a variety of electrical methods. Historically, these appeared before the optical methods, but gradually lost importance with the success of the later. Most capacitive, resistive, inductance methods developed so far use specially designed sensors for monitoring the lubricant film thickness. In the case of electrical techniques, both elements of the contact are metallic, which means that these can be used for measuring film thickness in real machine elements. One of the main disadvantages of electrical methods though, is the difficulty with which the calibration of various electrical quantities, against lubricant film thickness is obtained. This thesis describes the work carried out by the author on the application of a capacitive method for studying lubrication of elastohydrodynamic contacts. The novelty of the method used consists in the calibration of the capacitance of the contact with optical interferometry. This project started from the premises that a thicker Chromium layer will supply the phase change needed to precisely measure the lubricant film thickness by eliminating the fragile silica layer, and it has been shown that an increase in Cr thickness results in a increase in reflection of the glass–Cr interface making the resulting images hard to process. Modifications to the existing experimental rig were carried out in order to apply/collect an electrical signal from both the disc and the ball. Signal collection from the disc was quite straightforward and a graphite brush paired with a copper nut was used, as this is the oldest method of collecting/applying and electrical signal from a rotating element. Collecting an electrical signal from the ball presented quite a challenge as the ball is submerged in oil. A number of brushes was designed, made and tested and the one that provided the most stable results chosen. For calibration purposes a base oil and two additives were chosen, the additives were chosen in such a way that the improvement made to the lubrication process to be very different from one additive to the other. The chosen additives were a Viscosity Index Improver [VII] and an Organic Friction Modifier [OFM]. The VII is used by many researchers in order to obtain multigrade lubricants using the same base oil by varying its percentage in the mix. The OFM is used to provide protection between the two contacting bodies when EHD film fails and EHD lubrication is replaced by mixed lubrication by forming a boundary layer on the contacting surfaces. Optical measurements were carried out on the base oil and the two resulting lubricants from the additive mixes using the Ultra Thin Film Interferometry [UTFI] method. The measurements were used as a benchmark against which the capacitive measurements were calibrated. Tests were conducted in a number of controlled conditions for speed, temperature, load and sliding conditions. Results showed that the highest influence on the lubrication process was given by the speed, an increase in speed results in an increase in optically measured film thickness and a decrease in electrically measured film thickness. Phenomenon explained by a large amount of lubricant pushed into the contact. Another parameter that influenced the results quite significantly was temperature, a rise in temperature supplies a decrease in optically measured film thickness and an increase in capacitive measured film thickness which was explained by lubricant viscosity dropping with a rise in temperature. Three different sliding conditions were employed and a small drop in optically measured film thickness followed by a small rise in electrically measured film thickness was recorded due to a local increase in contact temperature when sliding was employed. The capacitive method developed in this project is precise enough to accurately measure lubricant film thickness down to 100nm; a model for thicknesses lower that 100nm was proposed Results from the optical and capacitive methods were compared and a good correlation was found, indicating that the developed capacitive method can be used as a tool for measuring metal on metal contacts without further calibration.

NASA has funded a project called the Hunt for Observable Signatures of Terrestrial Systems (HOSTS) to survey nearby solar type stars to determine the amount of warm zodiacal dust in their habitable zones. The goal is not only to determine the luminosity distribution function but also to know which individual stars have the least amount of zodiacal dust. It is important to have this information for future missions that directly image exoplanets as this dust is the main source of astrophysical noise for them. The HOSTS project utilizes the Large Binocular Telescope Interferometer (LBTI), which consists of two 8.4-m apertures separated by a 14.4-m baseline on Mt. Graham, Arizona. The LBTI operates in a nulling mode in the mid-infrared spectral window (8-13 mu m), in which light from the two telescopes is coherently combined with a 180 degree phase shift between them, producing a dark fringe at the location of the target star. In doing so the starlight is greatly reduced, increasing the contrast, analogous to a coronagraph operating at shorter wavelengths. The LBTI is a unique instrument, having only three warm reflections before the starlight reaches cold mirrors, giving it the best photometric sensitivity of any interferometer operating in the mid-infrared. It also has a superb Adaptive Optics (AO) system giving it Strehl ratios greater than 98% at 10 mu m. In 2014 into early 2015 LBTI was undergoing commissioning. The HOSTS project team passed its Operational Readiness Review (ORR) in April 2015. The team recently published papers on the target sample, modeling of the nulled disk images, and initial results such as the detection of warm dust around eta Corvi. Recently a paper was published on the data pipeline and on-sky performance. An additional paper is in preparation on beta Leo. We will discuss the scientific and programmatic context for the LBTI project, and we will report recent progress, new results, and plans for the science verification phase that started in February 2016, and for the survey.

This Thesis proposes phase modulating interferometry as an alternative to phase stepping and phase-shifting interferometry for use in the shape and displacement characterization of microelectromechanical systems (MEMS) [Creath, 1988; de Groot, 1995a; Furlong and Pryputniewicz, 2003]. A phase modulating interferometer is developed theoretically with the use of a stroboscopic illumination source and implemented on a Linnik configured interferometer using a software control package developed in the LabVIEWâ„¢ programming environment. Optimization of the amplitude and phase of the sinusoidal modulation source is accomplished through the investigation and minimization of errors created by additive noise effects on the recovered optical phase. A spatial resolution of 2.762 µm over a 2.97x2.37 mm field of view has been demonstrated with 4x magnification objectives within the developed interferometer. The measurement resolution lays within the design tolerance of a 500Ã… ±2.5% thick NIST traceable gold film and within 0.2 nm of data acquired under low modulation frequency phase stepping interferometry on the same physical system. The environmental stability of the phase modulating interferometer is contrasted to the phase stepping interferometer, exhibiting a mean wrapped phase drift of 40.1 mrad versus 91 mrad under similar modulation frequencies. Shape and displacement characterization of failed µHexFlex devices from MIT's Precision Compliant Systems Laboratory is presented under phase modulating and phase stepping interferometry. Shape characterization indicates a central stage displacement of up to 7.6 µm. With a linear displacement rate of 0.75 Ã…/mV under time variant load conditions as compared to a nominal rate of 1.0 Ã…/mV in an undamaged structure [Chen and Culpepper, 2006].

This thesis concerns the study of time reversal and plane-wave decomposition in various geophysical applications. Time reversal is a key step in seismic interferometry, reverse time migration and full waveform inversion. The plane-wave transform, also known as the tau-p transform or slant-stack, can separate waves based on their ray parameters or their emergence angles at the surface. I propose a new approach to retrieve virtual full-wave seismic responses from crosscorrelating recorded seismic data in the plane-wave domain. Unlike a traditional approach where the correlogram is obtained from crosscorrelating recorded data, which contains the full range of ray parameters, this method directly chooses common ray parameters to cancel overlapping ray paths. Thus, it can sometime avoid spurious arrivals when the acquisition requirement of seismic interferometry is not strictly met. I demonstrate the method with synthetic examples and an ocean bottom seismometer data example. I show a multi-scale application of plane-wave based full waveform inversion (FWI) with the aid of frequency domain forward modeling. FWI uses the two-way wave-equation to produce high-resolution velocity models for seismic imaging. This technique is implemented by an adjoint-state approach, which viii involves a time-reversal propagation of the residual wavefield at receivers, similar to seismic interferometry. With a plane-wave transformed gather, we can decompose the data by ray parameters and iteratively update the velocity model with selected ray parameters. This encoding approach can significantly reduce the number of shots and receivers required in gradient and Hessian calculations. Borrowing the idea of minimizing different data residual norms in FWI, I study the effect of different scaling methods to the receiver wavefield in the reverse time migration. I show that this type of scaling is able to significantly suppress outliers compared to conventional algorithms. I also show that scaling by its absolute norm generally produces better results than other approaches. I propose a robust stochastic time-lapse seismic inversion strategy with an application of monitoring Cranfield CO2 injection site. This workflow involves two steps. The first step is the baseline inversion using a hybrid starting model that combines a fractal prior and the low-frequency prior from well log data. The second step is to use a double-difference inversion scheme to focus on the local areas where time-lapse changes have occurred. Synthetic data and field data show the effectiveness of this method. / text

Jouvence of FLUOR (JouFLU) is a major overhaul of the FLUOR (Fiber Linked Unit for Optical Recombination) beam combiner built by the Laboratoire d’études spatiales et d’instrumentation en astrophysique (LESIA) and installed at the CHARA Array. These upgrades improve the precision, observing efficiency, throughput, and integration of FLUOR with the CHARA Array as well as introduce new modes of operation to this high-precision instrument for interferometry. Such high precision observations with FLUOR have provided the first unambiguous detections of hot dust around main sequence stars, showing an unexpectedly dense population of (sub)micrometer dust grains close to their sublimation temperature, 1400 K. Competing models exist to explain the persistence of this dust; some of which suggest that dust production is a punctuated and chaotic process fueled by asteroid collisions and comet infall that would show variability on timescales of a few years. By re-observing stars from the exozodiacal disks survey we have searched for variations in the detected disks. We have found evidence that for some stars the amount of circumstellar flux from these previously detected exozodiacal disks, or exozodis, has varied. The flux from some exozodis has increased, for some the flux has decreased, and for a few the amount has remained constant. These results are intriguing and will be no doubt useful for future modeling of this phenomenon. Furthermore, long-term monitoring is suggested for some of these objects to confirm detections and determine the rate of variation.

The most promising technique for the direct, ground-based detection of gravitational waves is the use of advanced interferometric gravitational wave detectors. These detectors use long-baseline Michelson interferometers, where the critical enabling component is the laser. The laser required for these interferometers must provide a low noise, single frequency, diffraction limited, high power TEM₀₀ beam. Very importantly, the laser beam must be available continuously and without the need for operator intervention. In this thesis I describe the development and characterisation of injection-locked 10 W Nd:YAG lasers, designed specifically for use at the Australian Consortium for Interferometric Gravitational Astronomy (ACIGA) High Power Test Facility (HPTF) in Western Australia, and on the Japanese TAMA 300 gravitational wave interferometer (GWI). The starting point was a 5 W laboratory laser that had demonstrated the proof-of-principle; however this laser had insufficient power, inadequate reliability, and was not suitable for deployment to a remote site. I describe the development of this laser technology and design to realise reliable, longterm operation and field deployability, while satisfying the requirements for a GWI, with the final laser system bearing little resemblance to the proof-of-principle system. Injection-locked lasers were successfully installed at the ACIGA HPTF and at TAMA 300 in June 2004 and September 2005 respectively. The 10 W laser uses a Nd:YAG Coplanar Pumped Folded Slab (CPFS) gain medium. The slab is side-pumped using a temperature controlled, fast-axis collimated, custom laser diode array, and conduction cooled in the orthogonal direction. Interferometry is used to measure the thermal lensing within the gain medium; these measurements are used to design a single-mode, travelling-wave slave resonator. The entire slave laser is temperature controlled and mounted on an integrated, air-cooled base. The thermal design is validated by extensive thermal testing. Long-term and robust injection-locking is achieved by using a servo system based on the Pound-Drever-Hall technique. I describe the development of a split feedback servo system to provide increased frequency stabilisation loop bandwidth and show that long-term injection-locking of the slave laser to a low power non-planar ring oscillator (NPRO) master laser produces a single frequency output at ~ 10 W with M²[subscript]x.y approx ≤ 1.1. Finally, the noise of the injection-locked laser is characterised. Relative intensity noise measurements demonstrate stability comparable to current GWI laser sources, while the results of a heterodyne beat measurement show that the 10 W injectionlocked laser output has frequency noise limited by the NPRO input. The laser installed at the ACIGA HPTF has been used to investigate the effects of increased intracavity laser powers on next-generation interferometers, with the laser described in this thesis being the key enabling component of this research. / http://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1349763 / Thesis (Ph.D.) - University of Adelaide, School of Chemistry and Physics, 2009

The most promising technique for the direct, ground-based detection of gravitational waves is the use of advanced interferometric gravitational wave detectors. These detectors use long-baseline Michelson interferometers, where the critical enabling component is the laser. The laser required for these interferometers must provide a low noise, single frequency, diffraction limited, high power TEM₀₀ beam. Very importantly, the laser beam must be available continuously and without the need for operator intervention. In this thesis I describe the development and characterisation of injection-locked 10 W Nd:YAG lasers, designed specifically for use at the Australian Consortium for Interferometric Gravitational Astronomy (ACIGA) High Power Test Facility (HPTF) in Western Australia, and on the Japanese TAMA 300 gravitational wave interferometer (GWI). The starting point was a 5 W laboratory laser that had demonstrated the proof-of-principle; however this laser had insufficient power, inadequate reliability, and was not suitable for deployment to a remote site. I describe the development of this laser technology and design to realise reliable, longterm operation and field deployability, while satisfying the requirements for a GWI, with the final laser system bearing little resemblance to the proof-of-principle system. Injection-locked lasers were successfully installed at the ACIGA HPTF and at TAMA 300 in June 2004 and September 2005 respectively. The 10 W laser uses a Nd:YAG Coplanar Pumped Folded Slab (CPFS) gain medium. The slab is side-pumped using a temperature controlled, fast-axis collimated, custom laser diode array, and conduction cooled in the orthogonal direction. Interferometry is used to measure the thermal lensing within the gain medium; these measurements are used to design a single-mode, travelling-wave slave resonator. The entire slave laser is temperature controlled and mounted on an integrated, air-cooled base. The thermal design is validated by extensive thermal testing. Long-term and robust injection-locking is achieved by using a servo system based on the Pound-Drever-Hall technique. I describe the development of a split feedback servo system to provide increased frequency stabilisation loop bandwidth and show that long-term injection-locking of the slave laser to a low power non-planar ring oscillator (NPRO) master laser produces a single frequency output at ~ 10 W with M²[subscript]x.y approx ≤ 1.1. Finally, the noise of the injection-locked laser is characterised. Relative intensity noise measurements demonstrate stability comparable to current GWI laser sources, while the results of a heterodyne beat measurement show that the 10 W injectionlocked laser output has frequency noise limited by the NPRO input. The laser installed at the ACIGA HPTF has been used to investigate the effects of increased intracavity laser powers on next-generation interferometers, with the laser described in this thesis being the key enabling component of this research. / http://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1349763 / Thesis (Ph.D.) - University of Adelaide, School of Chemistry and Physics, 2009

The measurement and monitoring of glacial surface velocity is important for many aspects of glaciology, such as determining the mass balance, for characterising the stability or instability of glaciers, or the identification of potential hazards from surging glaciers or Jökulhlaups, a type of glacial outburst flood. Predominately measurements of glacial surface velocity have been produced using either differential interferometry (DInSAR) applied to radar data, or offset-tracking applied to either optical or radar data. Both of these methods have their own set of limitations, notably the one-dimensional nature of DInSAR measurements, and the relatively low accuracy of offset-tracking. Instead using DInSAR and multiple-aperture interferometry (MAI) applied to ERS-1/2 Tandem SAR data, measurements of glacial surface displacements were obtained in the line-of-sight (LOS) and along-track directions respectively. Then using a weighted-least squares adjustment, the method for producing the full three-dimensional surface velocity field is presented and applied to the Svartisen glacial system, Norway and the Petermann Glacier, Greenland. The advantages and disadvantages of applying such a method were explored, of which interferometric coherence is found to be the largest factor in retrieving accurate measurements using MAI. Low interferometric coherence due to temporal decorrelation resulted in the inability to extract the full three-dimensional surface velocity field over the Bagley Icefield, Alaska, and the Mýrdalsjökull & Eýjafjallajökull ice caps, Iceland. A feasibility analysis into the use of Sentinel-1 data, revealed that the current revisit period is too large to maintain interferometric coherence between acquisitions, preventing the application of either DInSAR or offset-tracking in order to measure the surface velocity of the Blåmannsisen Glacier, Norway. Despite the limitations encountered, in part due to the selection of source data, MAI in tandem with DInSAR has been shown to be capable of measuring the three-dimensional surface velocity to a higher accuracy than offset-tracking when coherence is high. The methods used within have been developed to work with pre-processed single look complex (SLC) SAR data rather than raw unfocused SAR data, in an effort to improve their adoption and enable more accurate estimates of glacial surface velocity.