Langmuir Circulation is a common phenomenon driven by wind in oceans and lakes and was first studied by Langmuir in 1927. According to various ocean observations, this kind of phenomenon plays an important role in many phenomena such as the aggregation of bubbles, the distribution of plankton as well as the mixing of spilled oil and sediment in the ocean. To study this, an experimental facility has been developed in the lab which creates a small scale version of Langmuir Circulation. This thesis is about the design and testing of this tank and surrounding aluminum frame, as well as the design and construction of the illumination equipment (the Green Lantern 2.0) needed for Particle Image Velocimetry measurements within the tank. ANSYS will be used to show whether the tank is structurally strong enough to support the fluid. An enhancement is found that prevents a frontward bend of tank wall, which is analyzed by ANSYS to find an optimized construction to minimize tank deformation. Then, the Light-Emitting Diode (LED) and collimating lens selection for the Green Lantern 2.0 will also be shown in this paper. Besides, this thesis also presents preliminary flow measurement data acquired using the illumination equipment (the Green Lantern).

Introduction In order to address the increasing demand for Fluorine-18 and the rising cost per mL of 18O enriched water, IBA developed improvements to their 18F- production systems. For this new design we started from scratch, with the main objectives of reducing the required enriched water volume and improving the cooling of the insert. A better cooling allows increasing the target current and thus the produced activity. Finally, we aimed to reduce the number of parts and improve the design of auxiliary components. Material and Methods Six Niobium conical inserts with different target chamber volumes were machined and tested. Only 4 of these were selected to create the new range of IBA 18F− targets shown in TABLE 1. The new Niobium target inserts have a complex shape with drilled channels on the outside of the chamber and a deep channel next to the beam strike area (FIG. 1, green circle) to ensure efficient cooling. The 18O water inlet lines are now directly inserted in the Niobium body (FIG. 1, blue circle) to improve 18F- quality (no more contact with small o-rings). In operation, a 35µm Havar® target window is used. All tests were performed using IBA Cyclone® 18 cyclotron. The targets were filled with different volumes of enriched 18O water (enrichment > 92 %) and irradiated with 18 MeV protons on target with beam currents up to 145 μA for 30 to 150 minutes, while the internal pressure rise of the target was recorded. For each target, a pressure-current curve was plotted and an optimum balance between target water fill volume, pressure and current has been determined, which maximises available activity after two hours, in each case. Results and Conclusion Radionuclidic impurities were measured and more than 100 FDG syntheses on various synthesizers confirmed the effectiveness of the new design. Increasing the current up to 145µA in Conical 16, the production reached 18 Ci in 2 hours, single beam, with a target pressure under 43 bar. Today, the use of these new targets for daily commercial production is increasing within the IBA Cyclone® installed base.

Introduction Technetium-99m, supplied in the form of 99Mo/99mTc generators, is the most widely used radioisotope for nuclear medical imaging. The parent isotope 99Mo is currently produced in nuclear reactors. Recent disruptions in the 99Mo supply chain [1] prompted the development of methods for the direct accelerator-based production of 99mTc. Our approach involves the 100Mo(p,2n)99mTc reaction on isotopically enriched molybdenum using small medical cyclotrons (Ep ≤ 20 MeV), which is a viable method for the production of clinically useful quantities of 99mTc [2]. Multi-Curie production of 99mTc requires a 100Mo target capable of dissipating high beam intensities [3]. We have reported the fabrication of 100Mo targets of both small and large area tar-gets by electrophoretic deposition and subsequent sintering [4]. As part of our efforts to further enhance the performance of molybdenum targets at high beam currents, we have developed a novel target system (initially de-signed for the GE PETtrace cyclotron) based on a pressed and sintered 100Mo plate brazed onto a dispersion-strengthened copper backing. Materials and Methods In the first step, a molybdenum plate is produced similarly to the method described in [5] by compacting approximately 1.5 g of commercially available 100Mo powder using a cylindrical tool of 20 mm diameter. A pressure between 25 kN/cm2 and 250 kN/cm2 is applied by means of a hydraulic press. The pressed molybdenum plate is then sintered in a reducing atmosphere (Ar/2% H2) at 1,700 oC for five hours. The resulting 100Mo plates have about 90–95 % of the molybdenum bulk density. The 100Mo plate is furnace brazed at ~750 oC onto a backing manufactured from a disperse on strengthened copper composite (e.g. Glidcop AL-15) using a high temperature silver-copper brazing filler. This process yields a unique, mechanically and thermally robust target system for high beam power irradiation. Irradiations were performed on the GE PETtrace cyclotrons at LHRI and CPDC with 16.5 MeV protons and beam currents ≥ 100 µA. Targets were visually inspected after a 6 hour, 130 µA bombardment (2.73 kW/cm2, average) and were found fully intact. Up to 4.7 Ci of 99mTc have been produced to date. The saturated production yield remained constant between 2 hour and 6 hour irradiations. Results and Conclusion These results demonstrate that our brazed tar-get assembly can withstand high beam intensities for long irradiations without deterioration. Efforts are currently underway to determine maximum performance parameters.

Le développement de sources laser générant des impulsions femtoseconde à très haut taux de répétition est l'un des axes de recherche les plus porteur de ces 10 dernières années, et ouvre la voie pour de nombreuses applications industrielles et scientifiques. Les lasers à fibres permettent d'obtenir des sources de forte puissance moyenne, mais le fort confinement de la lumière générant de fortes non-linéarités, limite l'énergie des impulsions de sortie. Les amplificateurs à cristaux quant à eux, ne permettent généralement pas d'obtenir des impulsions aussi courtes que dans les lasers à fibres principalement à cause des propriétés spectroscopiques des cristaux, mais cependant ils permettent d'obtenir des énergies bien plus élevées. La post-compression par effets non-linéaires est une des solutions permettant de réduire la durée de ces impulsions. Cependant, les non-linéarités sont généralement préjudiciables, et limitent les performances des lasers (principalement en terme de qualité temporelle des impulsions). Une technique mise en oeuvre pour contrôler et exploiter positivement ces non-linéarités afin d'obtenir des impulsions courtes et de bonne qualité, tout en atteignant des énergies élevées dans les amplificateurs régénératifs à cristaux, est présentée dans cette thèse.L'application d'un étirement négatif à l'impulsion avant amplification, permet de compenser dans certaines conditions, la dispersion positive des composants de l'amplificateur ainsi que la phase non-linéaire accumulée durant l'amplification . Nous avons donc étudié théoriquement et expérimentalement les différents régimes d'amplification non-linéaire, afin de trouver les paramètres optimaux. Ceci à permis de démontrer des impulsions ultracourtes et d'excellentes qualités temporelles même avec de fortes intégrales B. En considérant le couplage de la dispersion et des effets non-linéaires, ainsi que la bande de gain des milieux à gain, nous avons pu générer des impulsions sub-100 fs pour des puissances crêtes de plusieurs centaines de MW. Ces résultats obtenus dans des amplificateurs à très fort gain (50 dB) nous ont permis d'établir de nouveaux records de durées pour ce type d'architectures.Une autre étude sur la montée en puissance a permis de dimensionner une nouvelle gamme d'amplificateurs à cristaux, exploitant la géométrie pavé (usuellement appelée "slab") pour optimiser l'évacuation thermique. Une source de plus de 60 W a été réalisée, démontrant le potentiel de montée en puissance de ce type d'amplificateurs. Nous avons également mis en évidence les limites de cette architecture, en montrant des dégradations spatiales liées aux effets thermiques, problèmes majeurs lors de la montée en puissance.5 articles ont été rédigés grâce à ces résultats théoriques et expérimentaux. Ces travaux ont été présentés dans dix conférences. Enfin, ils ont permis à la société Amplitude Systèmes de procéder à la mise sur le marché de deux nouvelles gammes de produits : un laser compact et intégré et le TANGOR 100 W. / The development of laser sources delivering femtosecond pulses at high repetition rate is one of the main axe of reaserch of these 10 past years and is a key for many industrial and scientific applications. In one hand, fiber lasers allow to reach high average power sources, but the strong confinment of the light leads to high nonlinearities limiting output pulse energy. In the other hand, bulk amplifiers cannot provide as short pulse duration as fiber lasers because of crystals spectroscopic properties. However they can reach higher energy. Usually nonlinear effects are deletarious and limit output temporal pulse quality. A technic to tailor and exploid positively these nonlinearities in order to obtain shorter pulses together with high pulse energy in bulk regenerative amplifier is presented in this thesis.Negative dispersion managment prior amplification permits to precompensate the amplifier positive dispersion together with the accumulated nonlinear phase aquired during amplification. In order to deliver ultrashort pulses with an excellent temporal quality theoritical studies have been carried out to optimise the paramaters. By considering dispersion, nonlinearities and limited gain bandwidth, we could demonstrated sub-100 fs pulses with a peak power of hundreds of MW. These results established new pulse duration record in high gain (50 dB) bulk amplifiers.Another study allowed to design new amplifier geometries for power scaling. This has been done by using slab crystal geometry to improved heat dissipation. More than 60W average power has been demonstrated, highlighting the potential of such architecture for high power lasers. We also studied limitations of such design, especially thermal degradation effects, which are one of the main issues of high power bulk amplifier.5 articles have been written thanks to these theoritical and experimental results and have been presented in 10 conferences. As industrial results Amplitude Systemes has lunched into market two new lines of products: a compact and all integrated laser and a TANGOR 100 W.

No description available.

High Power Impulse Magnetron Sputtering (HiPIMS) comes as a new and promising PVD method for the development of high-performance coatings for cutting applications. This technique utilizes high energy and ionization which can produce a denser and stronger ceramic in comparison to traditional deposition techniques. Important coating characteristics that arise from this method such as enhanced hardness, adhesion, and less defects, can be applied when machining hard-to-cut materials. In this study, investigation of tool life and wear mechanisms, mechanical and physical properties of AlTiN coatings deposited on carbide tools by HiPIMS and Cathodic Arc Evaporation (CAE) were analyzed when machining Inconel 718 and Stainless Steel 304. Experimental turning tests were performed to evaluate tool life, and the wear mechanisms were analyzed by optical and scanning electron microscopy. Nanohardness, scratch test, fracture toughness and other methods were carried out to evaluate the coating properties. Impedance experiments were performed to determine the coating porosity and resistance to corrosion. The results showed that HiPIMS coating presented higher hardness, toughness to fracture and adhesion to the substrate in comparison to CAE coatings. The HiPIMS coated tool substantially improved tool life when machining Inconel. The dominant wear mechanism found was abrasion, which is induced by the presence of hard carbides. The main wear patterns observed were flank, notch, and crater wear. The tool performance of HiPIMS was found to have enhanced mechanical properties, lower porosity, and form a larger amount of tribo-oxides when machining, in comparison to CAE. / Thesis / Master of Applied Science (MASc)

A new fully integrated wavelength stabilization scheme based on grating-coupled surface-emitting lasers is explored. This wavelength stabilization scheme relies on two gratings. The first grating is fabricated on the p-side of the semiconductor laser in close proximity to the laser waveguide such that it couples light out of the guided mode of the waveguide into a propagating mode in the substrate; this grating is known as the grating coupler. The second grating is fabricated on the n-side of the substrate such that for the stabilization wavelength, this second grating operates in the Littrow condition and is known as the feedback grating. Furthermore with the proper design of the two gratings, the feedback grating will operate under total internal reflection conditions allowing a near unity retro-reflection of the light of the stabilization wavelength. The grating coupler and feedback grating together comprise a dual grating reflector (DGR). The DGR wavelength stabilization scheme is investigated both theoretically by means of numerical modeling and experimentally by integration of a DGR as a wavelength selective reflector into a single quantum well semiconductor laser with a gain peak centered at 975nm. Numerical modeling predicts a peak reflection of approximately 70% including losses and a spectral width of 0.3nm. The integration of a DGR into a semiconductor laser proved both the efficacy of the scheme and also allowed us to experimentally determine the effective reflectivity to be on the order of 62%; the spectral width of light output from these devices is typically on the order of 0.2nm. Furthermore, these devices had light-current characteristic slopes greater than 0.84W/A operating under continuous wave conditions. The DGR was then modified to provide a reflection with two spectral peaks. A semiconductor device incorporating this dual wavelength DGR was fabricated and tested. These devices showed a peak optical power of in excess of 5.5W and a light-current characteristic slope of 0.86W/A in quasi continuous wave operation; these devices also exhibit a large operating current range in which both wavelengths have comparable output powers. Another modified DGR design was investigated for the purpose of providing an even narrower spectral reflection. Devices incorporating this modified design provided an output with a spectral width as narrow as 0.06nm. DGRs were also integrated into an extremely broad area device of an unorthodox geometry; square devices that lase in two orthogonal directions were fabricated and tested. The last idea investigated was combining a DGR wavelength stabilized laser with a tapered semiconductor optical amplifier into a master oscillator power amplifier device, with the optical coupling between the two components provided by identical grating couplers disposed on the p-side surfaces of each of the devices. These master oscillator power amplifiers provide a peak power of 32W when operating under quasi continuous wave operation.

The topic of this proposal is the development of high peak power laser sources with a focus on linearly chirped pulse laser sources. In the past decade chirped optical pulses have found a plethora of applications such as photonic analog-to-digital conversion, optical coherence tomography, laser ranging, etc. This dissertation analyzes the aforementioned applications of linearly chirped pulses and their technical requirements, as well as the performance of previously demonstrated parabolic pulse shaping approaches. The experimental research addresses the topic of parabolic pulse generation in two distinct ways. First, pulse shaping technique involving a time domain approach is presented, that results in stretched pulses with parabolic profiles with temporal duration of 15 ns. After pulse is shaped into a parabolic intensity profile, the pulse is compressed with DCF fiber spool by 100 times to 80 ps duration at FWHM. A different approach of pulse shaping in frequency domain is performed, in which a spectral processor based on Liquid Crystal on Silicon technology is used. The pulse is stretched to 1.5 ns before intensity mask is applied, resulting in a parabolic intensity profile. Due to frequency to time mapping, its temporal profile is also parabolic. After pulse shaping, the pulse is compressed with a bulk compressor, and subsequently analyzed with a Frequency Resolved Optical Gating (FROG). The spectral content of the compressed pulse is feedback to the spectral processor and used to adjust the spectral phase mask applied on the pulse. The resultant pulse iv after pulse shaping with feedback mechanism is a Fourier transform, sub-picosecond ultrashort pulse with 5 times increase in peak power. The appendices in this dissertation provide additional material used for the realization of the main research focus of the dissertation. Specification and characterization of major components of equipments and devices used in the experiment are present. The description of Matlab algorithms that was used to calculate required signals for pulse shaping are shown. A brief description of the Labview code used to control the spectral processor will also be illustrated.

Recent developments in holographic recording of volume Bragg gratings (VBGs) in photo-thermo-refractive (PTR) glass have demonstrated their utility as components in high power laser systems for spectral narrowing, transverse mode control, beam combining, and pulse stretching/compression. VBG structures are capable of diffracting incident light into a single diffraction order with high efficiency given the Bragg condition is met. The Bragg condition depends on both the wavelength and angle of the incident light making VBGs useful for filtering and manipulating both the wavelength and angular spectrum of a source. This dissertation expands upon previous research in PTR VBGs by investigating multiplexed VBGs and their applications in laser systems. Multiplexing involves the integration of several VBGs into the same volume of PTR glass. This process enables the fabrication of splitting and combining elements which have been used for high power beam combining with significantly reduced complexity as compared to other combining schemes. Several configurations of multiplexed beam combiners were demonstrated for both spectral and coherent combining systems with high power results yielding a combined power of 420 W with 96% efficiency. Multiplexing was also used to produce unique phase structures within VBGs. This effect was exploited to create extremely narrowband spectral filters called moire Bragg gratings. The technical challenges of producing moire gratings in bulk glass have revealed new insights into the use of PTR glass as a recording medium and produced devices capable of narrowband filtering of only 15 pm in the near infrared. Experiments were performed using such devices as intra-cavity laser elements for longitudinal mode selection. Investigations have also been made into increasing the level of multiplexing possible within PTR glass. These explorations included scaling the number of beam combining channels, fabrication of integrated multi-notch filters, and generated several other potentially interesting devices for future research. The summation of this work indicates a promising future for multiplexed VBGs in PTR glass.

No description available.