Revestimentos de zinco obtidos por imersão a quente têm sido amplamente utilizados em estruturas expostas em solos, águas naturais e atmosfericamente, devido a excelente resistência em meios de baixa agressividade. Nessas aplicações, as arestas de corte ficam expostas e estão mais susceptíveis à corrosão. Objetivando relacionar a microestrutura dos revestimentos com técnicas de microssondas eletroquímicas, para melhor entender os processos corrosivos de aços galvanizados, buscou-se uma nova metodologia para ampliar as fases e obter uma estrutura em camadas. Para a caracterização da morfologia dos revestimentos obtidos pelo processo de galvanização por imersão a quente (galvanized, galvannealed e galvalume) utilizou-se microscopia óptica e eletrônica de varredura com microanálise. Para verificar e analisar os mecanismos de corrosão das fases presentes nos revestimentos de zinco de forma localizada empregou-se a técnica de varredura por eletrodo vibratório (SVET) e microcélula capilar (MEC), e de forma complementar, para identificar os produtos de corrosão formados utilizou-se micro difração de raios X (μ-DRX). Os resultados demonstraram que a metodologia empregada neste estudo é adequada para avaliar as fases de forma individual ou conectadas galvanicamente, e assim identificar as fases mais ativas durante os processos corrosivos. Os resultados obtidos por microcélula complementam os mapeamentos de densidade de corrente obtidos por eletrodo vibratório, mostrando que os intermetálicos permanecem estáveis após os ensaios e a região mais ativa é o revestimento não intemperizado (polido) próximo à interface aço/revestimento. O revestimento que apresentou melhor resistência à corrosão em soluções contendo cloreto foi o Zn55Al. O espectro μ-XRD para o revestimento galvanized, indica a presença das fases zincita e Fe-α sobre o aço IF (interstitial free), mostrando que sob condições de OCP a superfície de aço IF foi protegida pelo revestimento apesar da sua grande área. Esta precipitação pode ainda proteger áreas de aço expostas aonde o revestimento foi danificado por arranhões ou na aresta de corte. / Hot-dip zinc coatings have been widely used in structures exposed to soils, natural water and atmosphere due to their excellent resistance in low aggressive media. In such applications, the cutting edges are exposed and more susceptible to corrosion. In order to correlate the microstructure of the coating with electrochemical microprobe techniques, a new methodology was developed to amplify the size of the phases and to obtain a layered structure. Optical microscopy and scanning electron microscopy were used to characterize the morphology of the coatings obtained by the hot dip galvanization process (galvanized, galvannealed e galvalume). Scanning vibrating electrode technique (SVET) and capillary microcell (MEC) were used to identify and study the corrosion mechanisms of the phases present in zinc coatings. The corrosion products were identified by X-ray micro-diffraction (μ-XRD). The results demonstrated that the methodology employed in this study is adequate to evaluate the phases individually or galvanically connected, thus identifying the most active phases during the corrosive processes. The results obtained by microcell complement the current density mappings obtained by vibrating electrode, showing that the intermetallics remain stable after the analysis and the most active region is the not wedered coating near the steel/coating interface. The coating that showed the best corrosion resistance in solutions containing chloride was the Zn55Al. The μ-XRD spectrum for the galvanized coating indicates the presence of zincite and Fe-α on the IF steel (interstitial free), showing that under OCP conditions the IF steel surface was protected by the coating despite its large area. This precipitation can further protect exposed steel areas where the coating has been damaged by scratches or at the cutting edge.

Neste trabalho, foi utilizado o método de deposição assistida por feixe de íons (IBAD na sigla em inglês) para produção de filmes finos de nitreto de índio em substratos de silício (111) e Safira-C. Variando as condições de deposição e utlilizando a técnica de difração de raios-X, investigou-se com o intuito de obter os parâmetros que resultam em filmes finos com melhor grau de cristalinidade. Os filmes produzidos a 380C apresentaram alta cristalinidade, superior àqueles a 250C. Temperaturas muito superiores a 380C não ocasionam a formação de filme cristalino de InN, como foi observado ao utilizar a temperatura de 480C; o mesmo se observa ao utilizar temperatura ambiente. Na temperatura considerada adequada ,de 380C, obteve-se que a utilização de Ra, ou seja, a razão de fluxo de partículas entre o nitrogênio e índio, em torno de 2,3 permite obter um melhor grau de cristalinização, o qual decresce conforme se diverge desse valor. A comparação entre difratogramas de amostras produzidas com e sem a evaporação prévia de titânio, o qual é possível observar um deslocamento dos picos do InN, indicam que o efeito Gettering permite a redução de impurezas no filme, principalmente de oxigênio. Utilizou-se a técnica de Retroespalhamento de Rutherford para obtenção da composição dos elementos e o perfil de profundidade. Notou-se uma forte mistura dos elementos do substrato de silício e safira com o nitreto de índio mesmo próximos a superfície. A presença indesejável de impurezas, principalmente o oxigênio, durante a deposição de filmes finos é praticamente inevitável. Desta forma, cálculos ab initio baseados na Teoria do Funcional da Densidade (DFT) foram realizados para investigar defeitos isolados e complexos de oxigênio no nitreto de índio e a sua influência nas propriedades óticas. Considerou-se diferentes concentrações de oxigênio (x=2,76, 8,32, 11,11 e 22,22%) aplicando-se o método PBEsolGGA e TB-mBJ para o tratamento da energia e potencial de troca e correlação. Obteve-se que é energeticamente favorável o oxigênio existir principalmente como defeito carregado e isolado. Os resultados utilizando a aproximação de TB-mBJ indicam um estreitamento do bandgap conforme a concentração de oxigênio aumenta. Entretanto, a alta contribuição do efeito de Moss-Burstein resulta num efetivo alargamento do band gap, gerando valores de band gap ótico maiores que no do bulk de nitreto de índio. / In the present work, the ion beam assisted deposition (IBAD) method was used for the production of thin films of indium nitride in silicon (111) and sapphire (001) substrates. Through variation of deposition conditions and by using X-ray diffraction technique, the parameters which resulted in thin films with the best crystallinity were investigated. The film produced at 380C showed good crystallinity, which was better than the one produced at 250C. Temperatures much higher than 380C doesn\'t lead to the formation of crystalline films of InN; the same is observed by using room temperature. In the temperature of 380C considered as adequate, it was obtained that using Ra, that is, the flux ratio of nitrogen and indium, around 2.3 allows getting a better crystallinity, which decreases as deviates from this value. The comparison between diffractograms of samples produced with and without the previous titanium evaporation, where a dislocation of indium nitride peak was observed, indicates that the Gettering effect reduces the impurities on the films, especially oxygen. The Rutherford Backscattering technique was applied in order to obtain the elements composition and the depth profile. It was noticed a strong mixture between substrates elements with the indium nitride even close to the surface. The presence of unintentional impurities, mainly oxygen, are almost inevitable during thin films deposition. Thus, Density Functional Theory based on \\textit calculations was employed to investigate single and complex defects of oxygen in Indium Nitride and their influence on the optical properties. Different oxygen contents (x=2.76, 8.32, 11.11 and 22.22%) were considered in our study by using PBEsolGGA and TB-mBJ for the treatment of exchange-correlation energy and potential. It was found that oxygen is energetically favorable to exist mainly as singly charged isolated defect. The results using TB-mBJ approximation predicts a narrowing of the bandgap as oxygen content increases. Nevertheless, the larger contribution of the Moss-Burstein effect leads to an effective band-gap increase, yielding absorption edge values larger than that of the intrinsic bulk indium nitride.

A thesis submitted to the Faculty of Science, University of the Witwatersrand, Johannesburg, in fulfilment of the requirements for the degree of Doctor of Philosophy. Johannesburg, 2015.

Dentre as espécies de moscas que causam miíases, destaca-se a Cochliomyia hominivorax (Coquerel, 1858) (Diptera: Calliphoridae), a qual se encontra distribuída em alguns locais do Caribe e nos países da América do Sul. Por ser um parasita obrigatório, é considerada um dos maiores problemas da pecuária mundial, acarretando prejuízos da ordem de milhões de dólares por ano em vários países. Dentro do manejo integrado das miíases, as principais estratégias de controle são o uso de agrotóxicos e a chamada Técnica do Inseto Estéril (TIE). A implementação desta última, em particular, permitiu a erradicação de C.hominivorax da América do Norte e de toda a América Central entre 1957 e 2004, sendo agora mantida uma barreira biológica na fronteira entre Panamá e Colômbia. Os esforços para erradicação ainda continuam na Jamaica e várias ilhas do Caribe, e diversos países da América do Sul já expressaram interesse pela TIE. Visando apoiar os projetos de controle de C. hominivorax com o uso da TIE nos países do MERCOSUL, foram realizados estudos de criação, esterilização com raios X e compatibilidade reprodutiva de linhagens. A colônia de C. hominivorax foi estabelecida com sucesso no CENA/USP e na Biofábrica MOSCAMED Brasil, e entre as gerações F1 e F18 chegou a ser produzido um volume de 30,9 L de pupas ( 257.200 pupas). Os valores dos parâmetros de controle de qualidade da criação foram semelhantes aos da biofábrica do México e do laboratório do USDA-ARS. Para escolha do melhor substrato de oviposição, foram testados 4 tratamentos à base de carne, fígado e dieta larval podre, sendo que o de dieta larval podre+coágulo e sangue bovino citratado foi o que permitiu maior oviposição e viabilidade de ovos. A temperatura base estimada para o desenvolvimento embrionário foi de 13,1 ºC, com uma constante térmica de 9,17 GD. Foram testadas 6 diferentes dietas para adultos à base de mel, rapadura, ovo spray dried, melaço e hemácias spray dried, sendo que todas permitiram alta fecundidade e fertilidade. Nos bioensaios de dieta larval, foram testadas duas dietas líquidas, com bagaço de cana ou fibra de coco, a dieta padrão de carne e uma dieta de gel. Não houve diferença significativa entre os parâmetros de controle de qualidade das dietas e a dieta de gel provou ser viável e de menor custo. Para determinação das doses esterilizantes, pupas com 24 h antes da emergência dos adultos foram irradiadas com 10, 25 e 60 Gy de raios X. As doses que induzem 99% de esterilidade foram estimadas em 43,7 e 47,5 Gy para machos e fêmeas, respectivamente. Para estudar a compatibilidade reprodutiva e competitividade entre linhagens, foram realizados 4 testes com cruzamentos entre uma linhagem do Caribe (Jamaica-06) e a brasileira. Como não foi encontrada incompatibilidade reprodutiva nem problemas de competitividade entre as linhagens, campanhas de supressão da mosca da bicheira no MERCOSUL poderiam utilizar moscas estéreis tanto da região do Caribe quanto do Brasil / The New World Screwworm (NWS), Cochliomyia hominivorax (Coquerel, 1858) (Diptera: Calliphoridae), is a fly species that provokes myiasis and is currently distributed at some Caribbean islands and South American countries. As an obligate parasite, this fly is one of the most serious threats to livestock industry, causing economic losses of millions of dollars per year in many countries. The main control strategies in the integrated management of myiasis rely on the use of chemicals and the so called Sterile Insect Technique (SIT). This technique, in particular, allowed the eradication of the NWS from the entire North and Central America between 1957 and 2004, and a biological buffer zone was set at the Panama-Colombia border. The eradication efforts still continue in Jamaica and several Caribbean islands. Some South American countries also declared interest for the use of the SIT against the NWS. Aiming to support projects to control the NWS through the SIT in MERCOSUR countries, several studies on rearing, sterilization with X rays and reproductive compatibility between strains were performed. The NWS colony was successfully established at CENA/USP and the MOSCAMED Brazil facility. Between the generations F1 and F18, a volume of 30.9 L of pupae ( 257,200 pupae) was produced. The values of the quality control parameters from the rearing were similar to those from the screwworm mass-rearing facility in Mexico and the USDA-ARS laboratory. To evaluate the best oviposition substrate, four treatments made of raw meat, liver or wasted larval diet were tested, and the one made of wasted larval diet + citrated bovine blood and clot allowed the highest oviposition and egg hatch. The estimated basal temperature for the embryonic development was 13.1 ºC, with a thermal constant of 9.17 GD. Six different adult diets made of honey, rapadura, spray dried egg, molasses or spray dried blood were tested and all allowed high fecundity and fertility. For the bioassays with larval diets, two liquid diets (with sugarcane bagasse or coconut fiber as bulking agents), the standard meat diet and a gelled diet were tested. There was no significant difference among the quality control parameters from the diets and the use of the gelled diet proved to be feasible and cheaper. In order to estimate the sterilization doses, pupae 24 h before the adult emergence were irradiated at 0 (control), 10, 25 and 60 Gy of X rays. The doses that induce 99% sterility were 43.7 and 47.5 Gy for males and females, respectively. To assess the reproductive compatibility and competitiveness between strains, four tests with crosses between a Caribbean strain (Jamaica-06) and the Brazilian one were performed. As no reproductive incompatibility nor competitiveness problems were found, suppression campaigns against the NWS in MERCOSUR could use sterile flies either from the Caribbean basin as from Brazil

Thesis (Ph. D.)--University of Washington, 2006. / Vita. Includes bibliographical references (p. 145-151).

Astrophysikalische Jets sind stark kollimierte Materieströmungen hoher Geschwindigkeit. Sie stehen im Zusammenhang mit einer Fülle verschiedener astrophysikalischer Objekte wie jungen Sternen, stellaren schwarzen Löchern ('Mikro-Quasare'), Galaxien mit aktivem Kern (AGN) und wahrscheinlich auch mit dem beobachteten intensiven Aufblitzen von Gamma-Strahlung (Gamma Ray Bursts). Insbesondere hat sich gezeigt, dass die Jets der Mikro-Quasare wahrscheinlich als kleinskalige Version der Jets der AGN anzusehen sind. <br /> <br /> Neben den Beobachtungen haben vor allem auch theoretische Überlegungen gezeigt, dass Magnetfelder bei der Jetentstehung, -beschleunigung und -kollimation eine wichtige Rolle spielen. Weiterhin scheinen Jets systematisch verknüpft zu sein mit dem Vorhandensein einer Akkretionsscheibe um das zentrale Objekt. Insbesondere wenn ein schwarzes Loch den Zentralkörper darstellt, ist die umgebende Akkretionsscheibe der einzig mögliche Ort um Magnetfeld erzeugen zu können. <br /> <br /> Wir sind speziell interessiert am Entstehungsprozess hoch relativistischer Jets wie sie bei Mikro-Quasaren und AGN beobachtet werden. Insbesondere untersuchen wir die Region, in der der Jet kollimiert, eine Region, deren räumliche Ausdehnung extrem klein ist selbst im Vergleich zur Auflösung der Radioteleskope. Dies ist ein Grund, wieso zum heutigen Zeitpunkt für die meisten Quellen die theoretische Modellierung die einzige Möglichkeit darstellt, um Information über die physikalischen Prozesse in der innersten Region der Jetentstehung zu erhalten. <br /> <br /> Uns ist es zum ersten Mal gelungen, die globale zwei-dimensionale Magnetfeldstruktur stationärer, axialsymmetrischer, relativistischer und stark magnetisierter (kräfte-freier) Jets zu berechnen, die zum einen asymptotisch in einen zylindrischen Jet kollimieren, zum anderen aber in einer differential rotierenden Akkretionsscheibe verankert sind. Damit erlaubt dieser Ansatz eine physikalische Verkn&#168;upfung zwischen Akkretionsscheibe und dem asymptotischen Jet. Nimmt man also an, dass die Fußpunkte der Magnetfeldlinien mit Keplergeschwindigkeit rotieren, so kann man eine direkte Skalierung der Jetmagnetosphere mit der Größe des Zentralobjektes erhalten. Unsere Resultate zeigen eine gute Übereinstimmung zwischen unserem Modell und Beobachtungen des Jets von M87. <br /> <br /> Für das Beispiel eines relativistischen Mikroquasarjets haben wir die Röntgenemission im Bereich von 0.2-10.1 keV berechnet. Dafür haben wir in der Literatur aus den relativistischen magnetohydrodynamischen Gleichungen berechnete Jetgrößen (Dichte-, Geschwindigkeits-, und Temperaturprofil) verwendet und das Spektrum für jeden Punkt entlang der Jetströmung abgeleitet. Das theoretische thermische Röntgenspektrum des innersten, heißen Teils des Jets erhalten wir zusammengesetzt aus den spektralen Anteilen der einzelnen Volumenelemente entlang des Jets. Um relativistische Effekte wie Dopplerverschiebung und -verstärkung (boosting) aufgrund der Jetbewegung zu untersuchen, haben wir für verschiedene Inklinationswinkel des Jets zur Sichtlinie berechnet, wie die erhaltenen Spektren davon beeinflusst werden. <br /> <br /> Unsere Spektren zeigen deutlich die hochionisierten Eisen-Emissionslinien, die in den galaktischen Mikroquasaren GRS 1915+105 und XTE J1748-288 andeutungsweise beobachtet wurden.<br /> Eine Dopplerverschiebung dieser Linien ist in unseren Spektren deutlichzu sehen. Da die innerste, Röntgenstrahlung emittierende Region des magnetohydrodynamischen Jets allerdings noch unkollimiert ist, spielt Dopplerboosting in unseren Spektren, abhängig vom Sichtwinkel, keine große Rolle. Mit unseren Resultaten konnte zum ersten Mal ein Röntgenspektrum gewonnen werden, das auf der numerischen Lösung eines magnetohydrodynamischen Jets beruht. / Jets are highly collimated flows of matter. They are present in a large variety of astrophysical sources: young stars, stellar mass black holes (microquasars), galaxies with an active nucleus (AGN) and presumably also intense flashes of gamma-rays. In particular, the jets of microquasars, powered by accretion disks, are probably small-scale versions of the outflows from AGN. <br /> <br /> Beside observations of astrophysical jet sources, also theoretical considerations have shown that magnetic fields play an important role in jet formation, acceleration and collimation. Collimated jets seem to be systematically associated with the presence of an accretion disk around a star or a collapsed object. If the central object is a black hole, the surrounding accretion disk is the only possible location for a magnetic field generation. <br /> <br /> We are interested in the formation process of highly relativistic jets as observed from microquasars and AGN. We theoretically investigate the jet collimation region, whose physical dimensions are extremely tiny even compared to radio telescopes spatial resolution. Thus, for most of the jet sources, global theoretical models are, at the moment, the only possibility to gain information about the physical processes in the innermost jet region.<br /> <br /> For the first time, we determine the global two-dimensional field structure of stationary, axisymmetric, relativistic, strongly magnetized (force-free) jets collimating into an asymptotically cylindrical jet (taken as boundary condition) and anchored into a differentially rotating accretion disk. This approach allows for a direct connection between the accretion disk and the asymptotic collimated jet. Therefore, assuming that the foot points of the field lines are rotating with Keplerian speed, we are able to achieve a direct scaling of the jet magnetosphere in terms of the size of the central object. We find a close compatibility between the results of our model and radio observations of the M87 galaxy innermost jet.<br /> <br /> We also calculate the X-ray emission in the energy range 0.2--10.1,keV from a microquasar relativistic jet close to its source of 5 solar masses. In order to do it, we apply the jet flow parameters (densities, velocities, temperatures of each volume element along the collimating jet) derived in the literature from the relativistic magnetohydrodynamic equations. We obtain theoretical thermal X-ray spectra of the innermost jet as composition of the spectral contributions of the single volume elements along the jet. Since relativistic effects as Doppler shift and Doppler boosting due to the motion of jets toward us might be important, we investigate how the spectra are affected by them considering different inclinations of the line of sight to the jet axis. <br /> <br /> Emission lines of highly ionized iron are clearly visible in our spectra, probably also observed in the Galactic microquasars GRS 1915+105 and XTE J1748-288. The Doppler shift of the emission lines is always evident. Due to the chosen geometry of the magnetohydrodynamic jet, the inner X-ray emitting part is not yet collimated. Ergo, depending on the viewing angle, the Doppler boosting does not play a major role in the total spectra. This is the first time that X-ray spectra have been calculated from the numerical solution of a magnetohydrodynamic jet.

This thesis treats the reflective and structural properties of multilayer structures. Soft X-ray multilayer mirrors intended as near-normal incidence reflective optics and polarizers in the water window (λ=2.4-4.4 nm) are the main focus. Such mirrors require multilayer periodicities between 1.2-2.2 nm, a large number ~600of multilayer periods (N), and atomically flat interfaces. Bi-metallic multilayers were deposited by dual-target magnetron sputtering on Si(001) Geometrical roughness and intermixing/interdiffusion at the interfaces were investigated in connection with the impact of ion-surface interactions during growth of Cr/Ti, Cr/Sc, and Ni/V multilayers. This was achieved by comparing multilayers grown with or without high-flux low energy (Eion&lt;30 eV) ion assistance. The use of modulated ion assistance resulted in a substantial improvement of interface flatness and abruptness in each of theAb-initio calculations indicate that the stabilization of the amorphous layer structure is due to a lowering of the total energy of the system by eliminating high energy incoherent interfaces between crystalline Sc and Cr. Light element incorporation in Cr/Sc multilayers was investigated through residual gas pressure variation. It is shown that multilayers retain their structural and optical properties within the high vacuum range of 2×10-7-to-2×10-6 Torr. The incorporation of 34 at.% nitrogen at a higher residual gas pressure ( ~2×10-5 Torr) resulted in highly textured understoichiometricx/ScNy multilayers. As a result of nitrogen incorporation, interface widths as small as 0.29 nm, and near-normal incidence reflectivity enhancement (at λ=3.11 nm) by 100 % (compared to pure Cr/Sc multilayers) was achieved. Light element incorporation was also found to be advantageous for the thermal stability of the multilayers. In-situ hard X-ray reflectivity measurements performed during isothermal annealing in thex/ScNy are stable up to 350 °C. As an alternative route to metallic multilayers, single crystal CrN/ScN superlattices, grown by reactive sputtering in N atmosphere onto MgO(001), were also investigated. The superlattice synthesis at 735 °C, resulted in highly abrupt interfaces with minimal interface widths of 0.2 nm. As-deposited superlattices with only 61 periodsλ=3.11 nm as well as very high thermal stability up to 850 °C. / Denna avhandling behandlar syntes, analys, och materialvetenskap rörande så kallade multilagerspeglar för mjuk röntgenstrålning. Speglarna är lämpade som optiska komponenter för instrument såsom röntgenmikroskop i våglängdsområdet 2,4 nm till 4,4 nm, även kallat vattenfönstret. Tack vare de senaste decenniernas stora teknologiska och vetenskapliga framsteg i att framställa mycket intensiva källor för mjuk röntgenstrålning, såsom tex synkrotronljuskällor, frielektronlasrar, och plasmagenererade källor, är det nu tänkbart att utnyttja denna strålning till nya tillämpningar som tidigare inte varit möjliga. Några exempel är; röntgenmikroskopi av biologiska preparat med upplösning ca 1/100 av det som är möjligt med synligt ljus, fotolitografi av Det finns flera stora utmaningar för att lyckas tillverka multilagerspeglar. Först och främst måste man hitta materialkombinationer som ger upphov till reflektion i mellanytorna mellan materialen men som inte samtidigt absorberar all röntgenstrålning. Dessutom måste materialen gå att belägga på varandra i flera hundra tunna lager, vart och ett endast ca 1 nanometer tjockt, med en ytojämnhet om endast några tiondels nanometer. Den absoluta tjockleks precision i varje I det här arbetet har fyra olika typer av multilagerbeläggningar undersökts: krom/titan (Cr/Ti), krom/skandium (Cr/Sc), nickel/vanadin (Ni/V) samt kromnitrid/skandiumnitrid (CrN/ScN). Materialvalen har baserats på teoretiska beräkningar som visat att dessa materialsystem genererar mycket god reflektans i vattenfönstret. Varje kombination av metaller är optimal för en specifik våglängd och de individuella lagertjocklekarna måste optimeras teoretiskt för varje enskilt För Cr/Sc multilager har vi visat att lagren som beläggs har en oordnad, så kallad amorf, struktur mellan metallatomerna som har sitt ursprung i att multilagrets totala energi kan sänkas om mellanytor mellan kristallint Cr och kristallint Sc kan undvikas. Studier av effekterna av kväveupptag hos Cr/Sc multilagerspeglar under sputtringsprocessen har lett till ökad förståelse av materialsystemet. Till exempel har vi visat att kvävet framförallt binder till de inre regionerna av Sc och inte så mycket till Cr-lagren eller i mellanytorna. Med kväve i strukturen har vi gjort speglar som tål höga temperaturer, vilket är av stor betydelse för tillämpningar baserade högintensiva ljuskällor. Så kallade supergitter, dvs multilager

Hard x-ray free-electron lasers are novel sources of coherent x-rays with unprecedented brightness and very short pulses. The radiation from these sources enables a wide range of new experiments that were not possible with previous x-ray sources. Many of these experiments require the possibility to focus the intense x-ray beam onto small samples. This Thesis investigates the possibility to use diffractive zone plate optics to focus the radiation from hard x-ray free-electron lasers. The challenge for any optical element at free-electron laser sources is that the intensity in a single short pulses is high enough to potentially damage the optics. This is especially troublesome for zone plates, which are typically made of high Z elements that absorb a large part of the incident radiation. The first part of the Thesis is dedicated to simulations, where the temperature behavior of zone plates exposed to hard x-ray free-electron laser radiation is investigated. It is found that the temperature increase in a single pulse is several hundred Kelvin but still below the melting point of classical zone plate materials, such as gold, tungsten, and iridium. Even though the temperature increases are not high enough to melt a zone plate it is possible that stresses and strains caused by thermal expansion can damage the zone plate. This is first investigated in an experiment where tungsten gratings on diamond substrates are heated to high temperatures by a pulsed visible laser. It is found that the gratings are not damaged by the expected temperature fluctuations at free-electron lasers. Finally, a set of tungsten zone plates are tested at the Linac Coherent Light Source where they are exposed to a large number of pulses at varying fluence levels in a prefocused beam. Damage is only observed at fluence levels above those typically found in an unfocused x-ray free-electron laser beam. At higher fluences an alternative is to use a diamond zone plate, which has significantly less absorption and should be able to survive much higher fluence. Damage in diamond structures is investigated during the same experiment, but due to a remaining tungsten etch mask on top of the diamond the results are difficult to interpret. Additionally, we also demonstrate how the classical Ronchi test can be used to measure aberrations in focusing optics at an x-ray free-electron laser in a single pulse. The main result of this Thesis is that tungsten zone plates on diamond substrates can be used at hard x-ray free-electron laser sources. / <p>QC 20130514</p>

The physical properties of visible light and its interaction with matter create obstructions the human eye cannot explore. High energy radiation has been used as an alternative to visible light to penetrate these concealed regions and reveal their contents. However, traditional imaging techniques require a two-sided apparatus with a radiation source and a detector on opposite sides of the concealed object. One-sided imaging of concealed objects is made possible by a technique called backscatter imaging, utilizing high energy radiation. However, the signal produced by backscatter imaging is inherently weak, which makes in- terpretation di cult. One of the most promising techniques for recovering the weak signal is the coding and decoding provided by Coded Aperture Imaging (CAI). The purpose of this study was to create and test a coded aperture imaging system using backscattered x-rays. This would enable one-sided imaging of concealed objects and demonstrate whether a portable imaging system was feasible. The results obtained from conducting a computer simulation, visi- ble light experiments, and x-ray experiments proved that the process works, however, the x-ray ux levels required were too high for a portable system, based upon the current equipment available at UOIT. / UOIT

AbstractThe number and distances of metal-oxygen and metal-metal interactions were determined for various concentrations of aqueous metal nitrate solutions by modified x-ray diffraction techniques. The number of M-O interactions ranges from four to five in the 0.8 M and 1.2 M AgNO3 solutions and from six to nine in the 0.8 M, 1.2 M, and 1.6 M Pb(N03)2 solutions. The 1.6 M Ce(N03)3 solution has eight to nine Ce-O interactions, while one Hg-Hg interaction is found for the H92 (N03)2 solutions. For the silver and lead nitrate solutions, the number of M-0 interactions decreases with an increase in concentration. The cations also effect the number of interactions. Based on the nature of their RDF's, the lead and cerium ions are classified as positively hydrated and the silver ion is negatively hydrated.Ball State UniversityMuncie, IN 47306