Dissertations / Theses: 'X-rays generator'

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Colson, Louis. "Conception et réalisation d'un dosimètre opérationnel pour la chirurgie interventionnelle assistée par radioscopie X." Thesis, Normandie, 2021. http://www.theses.fr/2021NORMC208.

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Cette thèse concerne la conception d’un dosimètre opérationnel pour les chirurgiens opérant sous rayonnement X. Les rayons X ont été découverts en 1895 par Wilhelm Röntgen. Depuis, ils sont très largement employés que ce soit pour les contrôles effectués dans les aéroports ou dans le domaine médical. Très utiles pour soigner les personnes, ils ne sont pas sans danger que ce soit pour les patients ou les praticiens hospitaliers. Normalement, les patients sont soumis de manière ponctuelle à des irradiations. En revanche, certains praticiens hospitaliers sont confrontés aux irradiations au quotidien. On distingue ici, les personnels orientés « radiographie », qui sont normalement protégés lors de l’irradiation du patient, de certains chirurgiens qui utilisent les rayons X comme moyen de contrôle durant l’opération et pour laquelle ils sont à proximité de la zone irradiée. C’est à cette problématique que s’intéresse cette thèse. L’étude que nous proposons en partenariat avec le laboratoire de recherche en science du numérique GREYC et l’Ecole des Applications Militaires de l’Energie Atomique (EAMEA) située à Cherbourg, est donc destinée à concevoir et réaliser un détecteur de rayons X pour applications médicales visant à donner une information pour une faible dose et des faibles énergies. La partie simulation et validation (irradiation) s’est faite à l’EAMEA. Le reste du travail s’est déroulé au sein du laboratoire GREYC qui a acquis, depuis plusieurs années, une réelle expérience dans le domaine des capteurs.Pour cela, nous avons commencé par réaliser des simulations Monte-Carlo à l’aide du code de calcul GEANT4 afin de définir la géométrie optimale du détecteur. A la suite de ces résultats de simulation, nous avons réalisé le capteur par pulvérisation cathodique rf magnétron par dépôt successif de couches minces. La couche sensible du capteur a fait l’objet d’une caractérisation Raman dont les résultats sont comparés à la littérature. Une fois le capteur réalisé, nous avons procédé à une caractérisation sous un flux de rayonnement X émis depuis un générateur continu de rayons X. Les différents essais avec le générateur continu ont permis de développer une chaine d’acquisition du signal pour ensuite tester le capteur sous un champ de rayonnement pulsé au Centre Hospitalier Public du Cotentin
This thesis concerns the design of an operational dosimeter for surgeons operating under X-rays. X-rays were discovered in 1895 by Wilhelm Röntgen. Since then, they have been very employed, whether for checks carried out at airports or in the medical field. Very useful for treating people, they are not without danger whether it is for patients or hospital practitioners. Normally, patients are subjected occasionally to irradiation. On the other hand, some hospital practitioners are confronted with daily irradiation. A distinction is made here between “radiography” for diagnostic, who are normally protected during irradiation of the patient, and certain surgeons who use X-rays as a control during the operation and for whom they are close to the irradiated area. This is the issue that this thesis is interested in. The study that we are proposing in partnership with the digital science research laboratory GREYC and the School of Military Applications of Atomic Energy (EAMEA) both located in Cherbourg, is therefore intended to design and produce an X-ray detector for medical applications aimed at giving information for low dose and low energies. The simulation and validation (irradiation)part was done at EAMEA. The rest of the work took place within the GREYC laboratory which has acquired, for several years, real experience in the field of sensors.We started by performing Monte-Carlo simulations using the GEANT4 calculation code in order to define the optimal geometry of the sensor. Following these simulation results, we produced the sensor by rf magnetron sputtering by successive deposition of thin layers. The sensitive layer of the sensor was subject to Raman characterization, the results of which were compared with the literature. Once the sensor had been produced, we carried out a characterization under a flow of X-rays emitted from a continuous X-ray generator. The various tests with the generator continued made it possible to develop a signal acquisition chain in order to test the sensor under a pulsed radiation field in the Centre Hospitalier Public du Cotentin

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Sow, Amadou Tidiane. "Evaluation de la fiabilité d'un générateur à rayons X pour application médicale." Thesis, Bordeaux, 2014. http://www.theses.fr/2014BORD0120/document.

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Les systèmes d’imagerie médicale, principalement les systèmes à rayons X, sont devenus incontournables dans le diagnostic et le traitement des maladies complexes. Le générateur à rayons X fait partie des sous-systèmes critiques d’un système à rayons X. La technologie des générateurs à rayons X se complexifie et les contraintes vues par les composants augmentent. L’évaluation de la fiabilité du générateur à rayons X est par conséquent nécessaire afin d’optimiser la durée de vie de ce dernier. Dans ces travaux de thèse, une méthodologie d’évaluation de la fiabilité d’un générateur à rayons X est proposée. La méthodologie repose sur l’évaluation de la fiabilité allant du composant au système. Des essais de vieillissement sont d’abord réalisés au niveau des composants critiques du générateur afin d’identifier les mécanismes de défaillance et de construire les courbes de durée de vie permettant d’effectuer une prévision de fiabilité. Les paramètres du recueil de fiabilité FIDES ont aussi été utilisés pour construire les courbes de durée de vie des composants critiques. Une méthode de prévision de la fiabilité basée sur l’hypothèse du dommage cumulé avec la règle de Miner est proposée pour évaluer la durée de vie des composants critiques sous contraintes thermomécaniques. Cette méthode utilise les règles de comptage rainflow pour obtenir une distribution des différences de température vues par les composants critiques. Une association de fiabilité permet enfin d’estimer la durée de vie de chaque sous système du générateur à rayons X à travers ses composants critiques
Medical imaging systems, mainly X-rays imaging systems, have become essential in the diagnosis and treatment of complex diseases. X-rays generator is one of the critical subsystems of a medical system. Its technology became more complex and constraints seen by the components increase. An assessment of X-rays generator reliability is therefore necessary to optimize its lifetime. In this thesis, a reliability assessment method of an X-rays generator is proposed. The methodology is based on the assessment of the reliability from component to system. Aging tests are first performed for X-rays generator critical components in order to identify failure mechanisms and build lifetime curves for performing reliability prediction. FIDES guide parameters were also used to construct critical components lifetime curves. A reliability prediction method based on the assumption of cumulative damage with Miner's rule is proposed to evaluate critical components lifetime under thermomechanical stresses. This method uses rainflow counting rules for the temperature cycles distribution of critical components. A reliability block diagram is finally used to estimate the lifetime of each X-ray generator subsystem through its critical components

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Parmee, Richard. "X-ray generation by field emission." Thesis, University of Cambridge, 2018. https://www.repository.cam.ac.uk/handle/1810/284924.

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Since the discovery of X-rays over a century ago the techniques applied to the engineering of X-ray sources have remained relatively unchanged. From the inception of thermionic electron sources, which, due to simplicity of fabrication, remain central to almost all X-ray applications at this time, there have been few fundamental technological advances. The emergence of new materials and manufacturing techniques has created an opportunity to replace the traditional thermionic devices with those that incorporate Field Emission electron sources. One of the most important attributes of Field Emission X-ray sources is their controllability, and in particular the fast response time, which opens the door to applying techniques which have formerly been the preserve of optical systems. The work in this thesis attempts to bridge the gap between the fabrication and optimisation of the vacuum electronic devices and image processing aspects of a new approach to high speed radiographic imaging, particularly with a view to addressing practical real-world problems. Off the back of a specific targeted application, the project has involved the design of a viable field emission X-ray source, together with the development of an understanding of the failure modes in such devices, both by analysis and by simulation. This thesis reviews the capabilities and the requirements of X-ray sources, the methods by which nano-materials may be applied to the design of those devices and the improvements and attributes that can be foreseen. I study the image processing methods that can exploit these attributes, and investigate the performance of X-ray sources based upon electron emitters using carbon nanotubes. Modelling of the field emission and electron trajectories of the cathode assemblies has led me to the design of equipment to evaluate and optimise the parameters of an X-ray tube, which I have used to understand the performance that is achievable. Finally, I draw conclusions from this work and outline the next steps to provide the basis for a commercial solution.

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Atkins, C. "Active X-ray optics for the next generation of X-ray space telescopes." Thesis, University College London (University of London), 2010. http://discovery.ucl.ac.uk/19312/.

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Described within is the design, manufacture, metrology and X-ray testing of an active X-ray prototype intended for the next generation of X-ray telescopes. One of the challenges faced by the X-ray telescope community is how to combine high resolution and high sensitivity into one system, as weight limitations place constraints on the optics that can be launched. Therefore the mandate of the active X-ray prototype is to provide high sensitivity through the ability of the optics to be nested and to deliver high angular resolution through the active control of the optic’s form. Piezoelectric unimorph actuators provide the active component: it is intended that they will correct for figure errors within the optic and therefore increase the angular resolution capability. The prototype’s design is based upon an ellipsoidal segment which provides point-to-point focussing of an X-ray source. The prototype itself is composed of an electroformed nickel optic where the non-reflective surface is populated with 30 piezoelectric actuators and it is the production of the prototype that is the core of the presented research. Metrology of the actuators’ influence functions is presented and highlight the prototype’s ability to deform its optic surface by microns. In addition, the measured influence functions are compared against finite element models and a distinct similarity between the functions is observed. The prototype was tested at an X-ray beamline facility in November 2008 and the results showed the prototype’s ability to correct the optic to achieve an improved angular resolution: from 0.786 arc-minutes to 0.686 arc-minutes in terms of full width half maximum. Finally, difficulties in the manufacture of the prototype and X-ray testing shall be presented alongside future work in conclusion to this thesis.

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Turcu, Ion Cristian Edmond. "Generation and application of x-rays from excimer laser produced plasmas." Thesis, University of London, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.265966.

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Zhang, Xiaoshi. "Extreme nonlinear optics for coherent x-ray generation." Connect to online resource, 2007. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:3256470.

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Bloom, Michael Samuel. "Studies on the relativistic electrons and X-rays generated by laser wakefield accelerators." Thesis, Imperial College London, 2014. http://hdl.handle.net/10044/1/29132.

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Laser wakefield accelerators (LWFAs) operate through a high intensity ultra short laser pulse exciting a relativis- tic density wave in a plasma. I carried out experiments constructing LWFAs using lasers of a wide range of powers. Thereby allowing me to examine the generation of electrons and x-rays under these different conditions. The compar- ison of these results with my own and existing analytical models and computational modelling is discussed. In fulfilment of this, I developed novel techniques to measure hard x-rays in the tens of KeV energy range. In measure- ment of the relativistic electrons I found it possible to de- velop techniques to not only accurately measure the energy but also discern the three momentum vectors of electrons measured on a multiscreen electron spectrometer. As LWFAs open up the ability to produce high energy elec- tron beams without the need of tens of meters of RF accel- eration cavities and the lasers used to drive them can also be made relatively compact perhaps one of the most excit- ing application of this is the production of hard x-rays for imaging. As the source size of a LWFA betatron source is typically of micron scale, I investigated using LWFA derived x-rays for phase contrast imaging.

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Galarowicz, Dale. "Instrumentation requirements for TREE Effects Data Collection at the Naval Postgraduate School Flash X-ray facility." Thesis, Monterey, California : Naval Postgraduate School, 1990. http://handle.dtic.mil/100.2/ADA237681.

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Thesis (M.S. in Electrical Engineering)--Naval Postgraduate School, June 1990.
Thesis Advisor(s): Maruyama, X.K. Second Reader: Michael, S.N. "June 1990." Description based on title screen as viewed on March 24, 2010. DTIC Descriptor(s): Data Acquisition, Electronics, Facilities, Instrumentation, Integrated Systems, Noise (Electrical And Electromagnetic), Photons, Pulse Generators, Pulses, Radiation, Requirements, Scale, Transient Radiation Effects, Transients, Trees, Wafers, X Rays. DTIC Identifier(s): Transient radiation effects, Data acquisition, X ray apparatus, Electromagnetic pulses, Theses. Author(s) subject terms: EMP, IEMP, Flash X-Ray Instrumentation. Includes bibliographical references (p. 105-106). Also available in print.

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Smith, Craig. "Efficient generation of bright, collisionally pumped X-ray lasers." Thesis, University of Oxford, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.318474.

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Martin, Ian Peter Stephen. "Short pulse x-ray generation in synchrotron radiation sources." Thesis, University of Oxford, 2011. http://ora.ox.ac.uk/objects/uuid:9ac0bcc2-bedb-46d0-b95c-22f4741f45a0.

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This thesis describes an investigation into the performance of different schemes for generating short x-rays pulses via synchrotron radiation emission. A review is given of the methods that have been previously proposed for this task. From this review, three leading schemes are selected for in-depth investigations, each of which explores the boundary of what is presently achievable in accelerator-based light sources. The first scheme generates short x-ray pulses by operating an electron storage ring in a quasi-isochronous state using a ‘low-alpha’ lattice. High and low emittance lattices are developed, studied through simulation and then implemented on the Diamond storage ring. Beam dynamics and bunch length measurements are presented for a variety of machine conditions, and an assessment is made of the minimum practically achievable bunch length for stable user operation. Radiation pulses of 1 ps r.m.s. are demonstrated using this scheme. The second and third schemes investigate performance limits for a linac-based light source through numerical simulations. The first of these generates ultra-short pulses by passing a highly compressed electron bunch through a long undulator to radiate in the ‘single-spike’ regime. A comparison is made with theoretical predictions for the required electron bunch length to operate in this way, which highlights the need for accurate start-to-end simulations. The final scheme generates ultra-short x-ray pulses through laser manipulation of the electron bunches. The modulated electrons pass through a long undulator with tapered gap, such that only the centre of the modulated portion experiences high free-electron laser (FEL) gain. A method to enhance the FEL output from this scheme using a wavelength filter and grating-compressor is investigated. The sensitivity of the two schemes to jitter sources is determined, and it is demonstrated both schemes are capable of generating GW-level, fully coherent sub-fs soft x-ray pulses. Such pulses would open up the development of time-resolved science to new regimes.

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Fletcher, Julian Hooton. "Soft X-ray contact microscopy using laser generated plasma sources." Thesis, University of Oxford, 1993. http://ora.ox.ac.uk/objects/uuid:444fa0f3-d9b7-40ff-a8e0-1e4fd5ce03c5.

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The ultimate objective of this project was to develop a small, transportable X-ray microscope which would be able to view a wide range of biological specimens without the need for any type of sample preparation at a resolution greater than that obtainable by conventional light microscopy (ie. about 250nm). Of the various possible implementations of X-ray microscopy currently being investigated, contact microscopy was chosen as being the most suitable for the development of such a small-scale instrument, while at the same time minimizing the effects on image quality of radiation damage to the biological specimen. The requirement for a high brightness pulsed X-ray source of less than 50ns duration for illumination of the specimen was met by the production of laser generated plasmas. These were formed by focusing a 2.2J KrF laser beam, of wavelength 248nm and duration 20ns, onto the surface of one of a number of different target materials. In order to obtain the large intensities required for the production of a sufficiently high temperature plasma, a doubly pre-ionized, discharge-pumped amplifier KrF laser was developed. This was seeded by a smaller oscillator laser by means of a coupled unstable resonator configuration. A number of different cavity arrangements were investigated and an output beam divergence of 2.5 times the diffraction limit was achieved. The plasmas generated by focusing the laser beam to an intensity of 10¹⁴W/cm² onto carbon, titanium, molybdenum and tungsten targets were characterized as fully as was necessary for their use in the X-ray microscope. Preliminary investigations on the use of a grazing incidence ellipsoidal mirror to focus the emitted X-rays onto the specimen of the microscope were made and such an optical component was manufactured and tested. Finally, numerous images of a number of different biological specimens were made and resolutions of better than 100nm were achieved. Images were read out using a Park Scientific Instruments atomic force microscope, which enabled the entire microscopy process to be carried out in a single working day. The system is now in routine use and can produce more than ten images per session.

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Fioretti, Valentina <1982&gt. "Background minimization issues for next generation hard X-ray focusing telescopes." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2011. http://amsdottorato.unibo.it/3858/.

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The hard X-ray band (10 - 100 keV) has been only observed so far by collimated and coded aperture mask instruments, with a sensitivity and an angular resolution lower than two orders of magnitude as respects the current X-ray focusing telescopes operating below 10 - 15 keV. The technological advance in X-ray mirrors and detection systems is now able to extend the X-ray focusing technique to the hard X-ray domain, filling the gap in terms of observational performances and providing a totally new deep view on some of the most energetic phenomena of the Universe. In order to reach a sensitivity of 1 muCrab in the 10 - 40 keV energy range, a great care in the background minimization is required, a common issue for all the hard X-ray focusing telescopes. In the present PhD thesis, a comprehensive analysis of the space radiation environment, the payload design and the resulting prompt X-ray background level is presented, with the aim of driving the feasibility study of the shielding system and assessing the scientific requirements of the future hard X-ray missions. A Geant4 based multi-mission background simulator, BoGEMMS, is developed to be applied to any high energy mission for which the shielding and instruments performances are required. It allows to interactively create a virtual model of the telescope and expose it to the space radiation environment, tracking the particles along their path and filtering the simulated background counts as a real observation in space. Its flexibility is exploited to evaluate the background spectra of the Simbol-X and NHXM mission, as well as the soft proton scattering by the X-ray optics and the selection of the best shielding configuration. Altough the Simbol-X and NHXM missions are the case studies of the background analysis, the obtained results can be generalized to any future hard X-ray telescope. For this reason, a simplified, ideal payload model is also used to select the major sources of background in LEO. All the results are original contributions to the assessment studies of the cited missions, as part of the background groups activities.

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Marlowe, Hannah Rebecca. "Polarimetric and spectrographic instrumentation to enable next generation x-ray observatories." Diss., University of Iowa, 2016. https://ir.uiowa.edu/etd/3136.

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Ultraluminous X-ray (ULX) sources are non-nuclear extragalactic accreting compact objects whose X-ray luminosities exceed the Eddington limit for stellar mass black hole binaries (BHB). Their high luminosities suggest they are either intermediate mass black holes, that their emission is beamed, or that they are emitting at super-Eddington rates. We observed the ULX IC 342 X-1 simultaneously in X-ray and radio with Chandra and the VLA to investigate previously reported unresolved radio emission coincident with the ULX. The Chandra spectrum appears to be consistent with an accretion disc-dominated thermal state and suggests a mass of the black hole using the modeled inner disc temperature to be 157Mʘ ≤ M √ (cosi) ≤ 200 Mʘ. No significant radio emission was observed, consistent with the source being in a thermal disc-dominated state. Reanalysis of previous X-ray observations of the source shows that high energy curvature often interpreted as evidence for supercritical accretion cannot confidently be identified using the 2-10 keV energy band. Black hole systems such as BHBs, ULXs, and AGN represent the greatest test labs in the universe for the study of extreme gravity. Emission from the accretion disk and scattering from the surrounding corona allow study of the ultra-strong gravity and magnetic fields very near the central BH engine. However, many of these effects are imprinted as polarization of the emission and are invisible to spectral and timing studies alone. The outflows from AGN are also thought to play a key role in galaxy shaping and cluster formation. High efficiency and spectral resolution are required to measure ionization-velocities and density parameters from these sources to constrain the outflow structure. Beamline studies and theoretical modeling were carried out to characterize the throughput and spectral resolving power of off-plane gratings for use in future x-ray observatories which will make these measurements. Additionally, synchrotron measurements were carried out to test theoretical predictions of strong polarization response for off-plane diffraction gratings. The empirical results of this study are the first to demonstrate a lack of polarization sensitivity for grazing-incidence off-plane gratings and support more complex modeling results than used previously.

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Viotti, Anne-Lise. "Efficient generation and characterization of soft x-ray by laser-driven high-order harmonic generation." Thesis, KTH, Tillämpad fysik, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-185796.

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Kim, Jong Ryul. "Dose analysis of the Model 112A Pulserad Pulsed X-Ray Generator by ITS/CYLTRAN." Thesis, Monterey, California. Naval Postgraduate School, 1989. http://hdl.handle.net/10945/25856.

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Pietruszka, Renee B. "Operation and characteristics of the Flash X-Ray Generator at the Naval Postgraduate School." Thesis, Monterey, California. Naval Postgraduate School, 1989. http://hdl.handle.net/10945/26130.

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Installation of the Model 112A Pulserad Pulsed X ray Generator at the Naval Postgraduate School Flash X ray Facility was completed in August of 1988. Characterization of the Pulserad 112A is essential to its effective use in future radiation effects study. This study will describe the basic system components, the principles of beam generation, an the characteristics of the radiation output. Fundamentals of radiation dosimetry and their application to flash X-ray sources will be discussed. Finally, the results of initial mapping of the radiation field generated by the Model 112A Pulserad Pulsed X-Ray Generator will be presented

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Gullayanon, Rutchanee. "A calibration methodology for energy dispersive X-ray fluorescence measurements based upon synthetically generated reference spectra." Diss., Georgia Institute of Technology, 2011. http://hdl.handle.net/1853/42771.

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This research developed an on-line measurement systemfor determining the amount of fluorochemicals on carpet fibers using energy-dispersive X-ray fluorescence (EDXRF).This system is designed as a complementary tool to an existingchemical burn test certified by the American Association ofTextile Chemists and Colorists (AATCC), which is performed off-line on randomly selected carpet samples and time consuming.This research reviewed XRF principles and determined parameters that affect XRF spectra such as measurement time, measurement number, X-ray tube voltage, X-ray tube current, primary beam filter, and carpet characteristics. For this application, XRF calibrations must be performed for carpets of all styles and types. However, preparing actual carpet calibration samples is expensive. This research introduced a methodology to synthetically generate reference spectra using XRF spectra from standard fluorochemical stock solution samples and from base carpet samples for each carpet type to be tested. Thus, actual, physical standards are not required for each carpet type or style. This study showed that the synthetically generated XRF spectra alone were not always sufficient to guarantee the confidence interval required by the certified AATCC test. Thus, it is recommended that for on-line implementation, burn test results should be used to create a historical data base for each carpet type to reduce margin of error for calibrations generated from the synthetic spectra.

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Geiser, Gabrielle Jennifer. "Irradiation of intracerebral rat gliosarcoma using a microplanar beam of synchrotron-generated X rays : histopathologic findlings /." [S.l.] : [s.n.], 1998. http://www.ub.unibe.ch/content/bibliotheken_sammlungen/sondersammlungen/dissen_bestellformular/index_ger.html.

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Corbett, Richard Ewing. "Studies of laser generated plasmas relevant to soft X-ray laser research." Thesis, Queen's University Belfast, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.254182.

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Kazemi, Shada. "Design, development and fabrication of a new generation semiconductor X-ray detector." Thesis, University of Surrey, 2010. http://epubs.surrey.ac.uk/843693/.

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X-ray detectors are used in a number of areas, namely in astronomy, microscopy, medical imaging diagnostic, biological science and material analysis. Demand is rising significantly within the industry for X-ray detectors that do not require a cooling system, e.g. pin-diode detectors. The elimination of the cooling system will facilitate the design of portable detectors. Development of this technology opens opportunities for the design of new instruments and the manufacture of more specialist detectors for customised applications. The rapid progress of the semiconductor industry has enabled the construction of more sophisticated electronic devices. This progress has also resulted in the creation of simulation tools, which enable researchers to simulate the processing of their devices. This method is more time and cost efficient as different models can be tested before actually investing in device processing in a laboratory. For this project we have used Silvaco simulation tools and packages to design nine different pin-diode X-ray detectors and evaluated their electrical performance before manufacturing them. Microfabrication technology has also been employed to make the pin-diode X-ray detectors that are capable of simultaneously detecting low X-ray energies (< 10 keV) and measure the radiation energies with high sensitivity, speed and resolution. The X- ray detectors have been manufactured using the University of Surrey's cleanroom and laboratories. This project is run as a Knowledge Transfer Partnership scheme in partnership with e2V Scientific Instruments (e2Vsi). To improve efficiency and productivity in industry, recent years have seen increased collaboration between industry and academia. New technologies have been commercialised with varying degrees of success and new applications have emerged, also benefiting academic research. e2Vsi is a manufacturing company specialising in the design, development and production of high resolution semiconductor X-ray detectors and the project objectives are therefore closely aligned with industry's needs.

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Ma, Qing. "High-Resolution X-Ray Image Generation from CT Data Using Super-Resolution." Thesis, Université d'Ottawa / University of Ottawa, 2021. http://hdl.handle.net/10393/42782.

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Synthetic X-ray or digitally reconstructed radiographs (DRRs) are simulated X-ray images projected from computed tomography (CT) data that are commonly used for CT and real X-Ray image registration. High-quality synthetic X-ray images can facilitate various applications such as guiding images for virtual reality (VR) simulation and training data for deep learning methods such as creating CT data from X-Ray images. It is challenging to generate high-quality synthetic X-ray images from CT slices, especially in various view angles, due to gaps between CT slices, high computational cost, and the complexity of algorithms. Most synthetic X-ray generation methods use fast ray-tracing in a situation where the image quality demand is low. We aim to improve image quality while maintaining good accuracy and use two steps; 1) to generate synthetic X-ray images from CT data and 2) to increase the resolution of the synthetic X-ray images. Our synthetic X-ray image generation method adopts a matrix-based projection method and dynamic multi-segment lookup tables, which shows better image quality and efficiency compared to conventional synthetic X-ray image generation methods. Our method is tested in a real-time VR training system for image-guided intervention procedures. Then we proposed two novel approaches to raise the quality of synthetic X-ray images through deep learning methods. We use a reference-based super-resolution (RefSR) method as a base model to upsampling low-resolution images into higher resolution. Even though RefSR can produce fine details by utilizing the reference image, it inevitably generates some artifacts and noise. We propose texture transformer super-resolution with frequency domain (TTSR-FD) which introduces frequency domain loss as a constraint to improve the quality of the RefSR results with fine details and without apparent artifacts. To the best of our knowledge, this is the first work that utilizes frequency domain as a part of loss functions in the field of super-resolution (SR). We observe improved performance in evaluating TTSR-FD when tested on our synthetic X-ray and real X-ray image datasets. A typical SR network is trained with paired high-resolution (HR) and low-resolution (LR) images, where LR images are created by downsampling HR images using a specific kernel. The same downsampling kernel is also used to create test LR images from HR images. As a result, most SR methods only perform well when the testing image is acquired using the same downsampling kernel used during the training process. We also propose TTSR-DMK, which uses multiple downsampling kernels during training to generalize the model and adopt a dual model that trains together with the main model. The dual model can form a closed-loop with the main model to learn the inverse mapping, which further improves the model’s performance. Our method works well for testing images produced by multiple kernels used during training. It can also help improve the model performance when testing images are acquired with kernels not used during training. To the best of our knowledge, we are the first to use the closed-loop method in RefSR. We have achieved: (i) synthetic X-ray image generation from CT data, which is based on a matrix-based projection and lookup tables ; (ii) TTSR-FD: synthetic X-ray image super-resolution using a novel frequency domain loss ; (iii) TTSR-DMK: an adaptation network to overcome the performance drop for testing data which do not match to downsampling kernels used in training. Our TTSR-FD results show improvements (PSNR from 37.953 to 39. 009) compared to the state-of-the-art methods TTSR. Our experiment with real X-Ray images using TTSR-FD can remove visible artifacts in the qualitative study even though PSNR is similar. Our proposed adaptation network, TTSR-DMK, improved model performance for multiple kernels even with unknown kernel situations.

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Silva, Francisco José Maia da. "Generation of intense few-cycle phase-stable electric fields: from the mid-IR to soft X-rays." Doctoral thesis, Universitat Politècnica de Catalunya, 2016. http://hdl.handle.net/10803/387809.

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Devising new tools that expand our capabilities to sense and manipulate the world enables much of the scientific and technological progress around us. For example, light is increasingly more important as a tool for humanity. Not all light is equal, however - the light that we normally interact on a daily basis (e.g. the sun), despite its serene and directional appearance, exists in a state of ever changing disorder. What one would perceive as a smooth beam of white light is actually an ever changing pattern of colours. However, As the scale over which the colour changes is spatially too small and temporarily too rapid to be resolved by the human eye we perceive it as a smooth white beam. This lack of a clear spatio-temporal structure in naturally occurring light - coherence - limits what can be done with it. If one were to overlap all the frequencies in a temporally coherent beam of light, one could generate an extremely short and powerful pulse. For example, by compressing in time all the colours in sunlight one would generate a light pulse with just a few femtoseconds duration. If such pulse would have a very modest energy (e.g., a Joule), it would have a peak power approaching the PetaWatt - several orders of magnitude more than the total energy production on earth at a given time. When focused on a minuscule spot, the electric field oscillations of this wave would have amplitudes greatly surpassing the electric fields that bind electrons to atoms, or even atoms together in molecules. This implies that by focusing these pulses into matter one can destroy chemical bonds, free the electrons from the influence of the atom's nucleus and even further accelerate these particles away from the interaction region. It follows that with the correct electric field shape, one could control and manipulate matter in new and interesting ways.In this thesis we have dedicated ourselves to the creation and characterisation of intense, few-cycle pulsed sources of light, using several different approaches. In this thesis a light source with more than 3 octaves (450-4500 nm) has been developed through filamentation of intense mid-IR pulses in solids. This source has high repetition rate (100 kHz), high spectral density and absolute carrier-envelope phase stability. Additionally, numerical simulations suggest that the nonlinear propagation dynamics induce self-compression, possibly leading to single-cycle pulses. The scaling of strong field processes such as electron acceleration highly depends on the period or wavelength of the driving electrical field. This has implications for High harmonic generation (HHG) - the longer the wavelength of this field, the higher the energy of the generated photons. In this thesis we have built a high energy pulsed parametric light source at 2100 nm, a wavelength that enables one to generate soft-x-ray photons with energies exceeding 300 eV through phase-matched HHG ¿ and further demonstrated HHG cutoff extension up to 190 eV in Argon, when compared to HHG from 800 nm pulses.When doing HHG, in order to restrict the soft-X-ray emission to a single isolated attosecond pulse one needs to employ a gating technique. In this thesis we have extended the attosecond lighthouse technique up to the Water window (284-543 eV) which is of fundamental interest to study biological processes with unprecendent spatio-temporal resolution and elemental specificity. The routine generation and characterisation of pulses in the single-cycle regime has historically been a challenge. As such sources invariably require extreme nonlinear spectral broadening, the optimisation of the output pulse has always been a limitation. In this thesis we extend the dispersion-scan technique to the single-cycle regime and demonstrate its use as a straightforward way to compress, characterise and phase-stabilise 3.2 fs pulses with >50 GW peak power. We illustrate the steps done to optimise this source to reach the single-cycle regime.
Concebir nuevas herramientas que expandan nuestras capacidades para medir y manipular el mundo habilita gran parte del progreso cientifico y tecnologico que nos rodea. Por ejemplo, la luz es cada vez más importante como herramienta para la humanidad. Sin embargo, no toda la luz es igual - la luz con la cual normalmente interactuamos a diario (por ejemplo, la luz del sol), a pesar de su aspecto sereno y direccional, existe en un estado de constante cambio y disorden. Lo que se podria percibir como un rayo homogeneo de luz blanca es en realidad un patron en constante cambio de color e forma. Sin embargo, como la escala de los cambios de color es espacialmente demasiado pequeña y temporalmente demasiado rapida para ser resuelta por el ojo humano lo percibimos como un rayo blanco homogeneo. Esta falta de una estructura espacio-temporal en la luz natural - coherencia - limita lo que se puede hacer con ella. Si uno superpone todas las frecuencias en un rayo temporalmente coherente de luz, uno genera un pulso de luz extremadamente corto y potente. Por ejemplo, mediante la superposicio¿n en el tiempo de todos los colores en la luz del sol se generaria un pulso de luz con una duracion de pocos femtosegundos. Si tal pulso tiene una energia muy modesta (por ejemplo, un Julio), tendria una potencia de pico alrededor del Petawatt - ordenes de magnitud mas grande que la produccio¿n de energia en la Tierra en un determinado momento. Cuando enfocadas en un punto minusculo, las oscilaciones del campo electrico de esta onda tendran amplitudes superando los campos electricos que unen los electrones a los atomos, o incluso los atomos unos a los otros en moleculas. Esto implica que enfocando estos pulsos en la materia uno puede destruir enlaces quimicos, liberar los electrones de la influencia del nucleo del atomo y acelerar estas particulas. En consecuencia, con la forma de campo electrico correcta, se podria controlar y manipular la materia en formas nuevas e interesantes. En esta tesis nos hemos dedicado a la creacion y caracterizacion de fuentes de pulsos de luz intensos de pocos ciclos, utilizando diversas tecnicas. En esta tesis una fuente de luz con mas de 3 octavas (450-4500 nm) ha sido desarrollada a traves de filamentacion en solidos de impulsos mid-IR intensos. Esta fuente tiene una alta tasa de repeticion (100 kHz), alta densidad espectral y estabilidad de fase. Ademas, simulaciones numericas sugieren que la dinamica de propagacion no lineal induce auto-compresion temporal. El escalamiento de los procesos de campo fuerte, como la aceleracion de electrones, depende en gran medida de la longitud de onda del campo electrico interveniente. Esto tiene grandes implicaciones para la generacion de harmonicos altos (HHG) - mas larga sea la longitud de onda del campo, mayor es la energia de los fotones generados. En esta tesis hemos construido una fuente de luz de alta energia a 2100nm, una longitud de onda que nos permite generar fotones con energi¿as superiores a 300 eV a traves de HHG con phase-matching - y ademas demostrado extension de corte HHG hasta 190 eV en argon, en comparacion con HHG a partir de pulsos a 800 nm. Al hacer HHG, para limitar la emision de rayos-X blandos a un solo pulso de attosegundos aislado, uno necesita emplear una tecnica de gating. En esta tesis hemos extendido la te¿cnica del faro de attosegundos hasta la ventana de la agua (284-543 eV) lo cual posee interes fundamental para estudiar procesos biologicos con resolucio¿n espacio-temporal y especificidad elemental. Como esas fuentes invariablemente requieren un ensanchamiento espectral no lineal extremo, la optimizacion del pulso siempre presenta un problema. En esta tesis hemos extendido la tecnica de dispersion-scan, hasta el regimen de un solo ciclo optico y demostramos su uso como una forma de comprimir, caracterizar y estabilizar la fase de pulsos de 3.2 fs.

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23

Debnath, Sree Bash Chandra. "New generation X-ray detector for radiation therapy and instrumentation for surface physics." Thesis, Aix-Marseille, 2020. http://www.theses.fr/2020AIXM0252.

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Le traitement moderne par radiothérapie est motivé par la demande constante d'un détecteur dosimétrique approprié. Plus récemment, seuls quelques détecteurs se sont montrés prometteurs dans ce sens, mais ils présentent plusieurs obstacles lors de leur mise en œuvre, tant pour les applications à forte dose de rayonnement que pour celles à faible dose. Les dosimètres à rayons X développés industriellement sont encore limités par l'exigence de taille importante, l'effet de moyennage de volume, le manque de sensibilité et le faible rapport signal/bruit, etc. Dans ce contexte, ce travail de thèse est consacré à la conception et à la fabrication d'un nouveau détecteur de rayons X extrêmement compact, en temps réel et très sensible. Le principe du dispositif est basé sur des clusters scintillantes qui sont greffées à l'extrémité d'une petite fibre centrale. Sous irradiation aux rayons X, les clusters émettent de la lumière visible qui est collectée par un compteur de photons à travers la fibre optique. Le détecteur développé a été testé pour la caractérisation de petits champs (inférieurs à 0,5 x 0,5 cm²) en radiothérapie et également en brachythérapie. Dans les deux cas, le détecteur présente d'excellentes performances.En outre, un détecteur similaire à tête nanométrique a été mis en œuvre pour la physique des surfaces au moyen d'une nouvelle technique à double sonde (STM/Fibre). Ainsi, les résultats de cette recherche explorent la dosimétrie des rayonnements miniaturisés avec l'amélioration des traitements des tumeurs de stade précoce. En outre, dans le domaine de l'imagerie des surfaces, une nouvelle technique de caractérisation des matériaux sera mise au point
The modern radiation therapy treatment is driven by the everlasting demand of a suitable dosimetric detector. Most recently, only a few detectors have shown promise in this direction, but exhibiting several barriers while implementing both in high and low radiation dose applications. The industrially developed X-ray dosimeters/detectors are still limited by the significant size requirement, volume averaging effect, lack of sensitivity, and low signal-to-noise ratio, etc. In this context, this thesis work is devoted to the design and fabrication of a novel extremely compact, small-scale, real-time, dynamic, and highly sensitive X-ray detector. The device principle is based on scintillating clusters that are grafted at the extremity of a small core fiber. Under X-ray irradiation, clusters emit visible light that is collected by a photon counter through the optical fiber. The developed detector was tested for small (lower than 0.5 x 0.5 cm²) field characterization in radiotherapy. It also allows characterizing radiation dosimetry in brachytherapy. In both cases, the detector demonstrates excellent performances when compared to the existing dosimeters and MC simulation.In addition, a similar detector with nano-metric head was implemented for the application in surface physics by means of a novel dual-probe (STM/Fiber) technique. Thus, the outcomes of this research explore miniaturized radiation dosimetry and will disclose the path of enhancing early-stage tumor treatments through real-time dosimetry. Moreover, the performance of the probe in surface imaging will open the path of novel material characterization technique allowing simultaneous sample imaging

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24

Wende, Henning [Verfasser], and Andrea [Akademischer Betreuer] Santangelo. "Next Generation Data Processing for Future X-ray Observatories / Henning Wende ; Betreuer: Andrea Santangelo." Tübingen : Universitätsbibliothek Tübingen, 2015. http://d-nb.info/1197058303/34.

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Al, Husseini Abdul Mohsen Z. (Abdul Mohsen Zuheir). "Design and modeling of a third generation slumping tool for X-ray telescope mirrors/." Thesis, Massachusetts Institute of Technology, 2011. http://hdl.handle.net/1721.1/67607.

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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2011.
Cataloged from PDF version of thesis.
Includes bibliographical references (p. 141-144).
Glass sheets with high surface quality and angular resolution of 5 arcsec are in demand for the International X-Ray Observatory. Several glass flattening techniques are presented in this thesis, including a method of thermally shaping individual sheets of glass using porous mandrels as air bearings developed at the Space Nanotechnology Lab. This method, a second generation slumping tool, eliminates the problems of sticking and dust particle-induced distortion that plague traditional slumping methods. A detailed mathematical model of the slumping process is developed, allowing prediction of final glass shape based on process parameters that include air supply pressure, imperfections on the mandrel surface, glass total thickness variations and gravity vector orientation. Simulations were conducted for a variety of scenarios to study the impact of apparatus tilt and pressure asymmetries on glass shape. Experiments to verify model findings are conducted under closed-loop control of pressure and apparatus tilt. Little improvement in repeatability is seen, suggesting that the error is due to unmodeled forces such as contact forces from the glass holding technique. Finally, the design process and fabrication of a third generation slumping tool is presented. In addition to scaling the design to accommodate larger flats, slumps are done horizontally to float the glass and minimize contact during the process. New capabilities of the tool also include active gap measurement and control, as well as plenum air temperature monitoring.
by Abdul Mohsen Z. Al Husseini.
S.M.

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26

Lai, Chien-Jen Ph D. Massachusetts Institute of Technology. "Tabletop coherent extreme ultraviolet and soft X-ray sources based on high harmonic generation." Thesis, Massachusetts Institute of Technology, 2014. http://hdl.handle.net/1721.1/91106.

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Thesis: Ph. D., Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science, 2014.
Cataloged from PDF version of thesis.
Includes bibliographical references (pages 105-115).
High harmonic generation (HHG) is a fascinating strong-field physics phenomenon that occurs when a laser pulse with a moderate intensity interacts with atoms and partially ionizes the atoms. A series of harmonics are generated at similar efficiencies and extend to a few tenth, even thousandth, order harmonics at the extreme ultraviolet (EUV) and soft X-ray range. Such an unprecedented broadband and coherent spectrum thus has many novel applications, one of which is to build tabletop coherent EUV and soft X-ray sources. The development of EUV and soft X-ray lasers is very challenging because of the strong absorption of these wavelengths in almost all materials and the lack of appropriate reflection optics. So far, bright coherent EUV and soft X-ray sources are only available at several large-scale facilities, like free-electron lasers. However, the demands for coherent EUV sources is growing due to the advances in atomic physics, chemistry, and material science. Therefore, lab-scale EUV sources are highly desirable for these novel applications and research opportunities, and HHG emerges as a promising technology toward this goal. This thesis will present my PhD work on HHG. It includes the numerical models developed to simulate HHG either on single-atom scale or for a macroscopic medium, the modification to the current theoretical model, the analysis of the influence of plasma defocusing on HHG, the study of the wavelength scaling of HHG efficiency and cutoff with visible and near-infrared (IR) lasers, and the generation of multi-mJ ultrashort mid-IR (2.6 mJ, 39 fs, and 2 tm central wavelength) pulses at kHz repetition rate in the aim of extending the cutoff of HHG. With the kHz mid-IR pulses, an EUV source providing up to 108 photons/sec at 160 eV has been demonstrated, and photons in the water window range have also been detected. At the end, a chapter will summarize these research works and propose some possible future directions.
Ph. D.

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Lloyd, David T. "Characterizing the spatial properties of high harmonic generation." Thesis, University of Oxford, 2014. http://ora.ox.ac.uk/objects/uuid:4c51a956-b3a9-4172-ad17-0e9584a4ffa3.

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This thesis is concerned with describing a novel technique for characterizing the (spectrally resolved) spatial properties of light. The new approach, known as Scanning Interference Method for Integrated Transverse Analysis of Radiation (SCIMITAR), is a specific implementation of a variable-separation two-pinhole interferometer. Evaluation of the series of interference patterns produced by a SCIMITAR measurement allows the transverse profiles of intensity and spatial phase to be retrieved, while at the same time characterizing the spatial coherence of light. Including a diffraction grating in the simple experimental arrangement permits the spectral dependence of the aforementioned quantities to be measured. The SCIMITAR technique was demonstrated by characterizing the spatial properties of high harmonic generation (HHG). Excellent agreement with an alternate characterization technique known as SWORD was observed. The spectral dependence of the harmonic spatial properties was also investigated. Evidence suggesting absorption may play a role in shaping the harmonic intensity and spatial coherence was presented. Treating the harmonic radiation as either a fully coherent or partially coherent beam allowed the intensity width, spatial phase curvature and coherence width of the harmonic radiation source to be deduced. Measurement of the fine variation of the harmonic complex coherence factor (CCF) with pinhole separation revealed distinctive modulations. The Van Cittert-Zernike theorem was modified by including a Gerchberg-Saxton inspired improvement, allowing data missing from the SCIMITAR measurement to be inferred. The harmonic equivalent incoherent source intensity profile was found to be asymmetric with low intensity features isolated away from the optical axis. Calculations of the diffraction pattern produced by illumination of a non-redundant array of pinholes showed that the modulated harmonic properties could adversely influence lensless imaging-type experiments.

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28

Partridge, Tony. "Self-adaptation and rule generation in a fuzzy system for X-ray rocking curve analysis." Thesis, University of Warwick, 1994. http://wrap.warwick.ac.uk/88863/.

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X-ray rocking curve analysis is an example of a changing application domain. The salient characteristic of such a domain is that situations and facts can change over time. This means that the domain cannot be modelled by a fixed set of fuzzy rules. Instead, the rules must change over time and these changes must model actual changes that occur in the application domain. Three new techniques have been developed for altering a set of fuzzy rules: altering the credibility weight of an expert and using connection matrices to shift the focus of attention between different sets of rules; fine-tuning and changing the membership functions of fuzzy premise variables and thereby altering the meaning of the rules; and generating new fuzzy rules by inductive learning from examples. A fuzzy system for X -ray rocking curve analysis has been developed and used to test each of these techniques. This fuzzy system uses frames, logic-based variables, connection matrices and credibility weights, fuzzy rules and a record of previous decisions in order to model X-ray rocking curve analysis. Question and answer sessions with the user are used to describe experimental rocking curves and structural parameters are deduced from this description. These structural parameters are then used to simulate a theoretical curve, which is compared with the experimental one. A performance measure is derived to calculate the degree of matching between the two curves. This performance measure is used to test each of the three techniques in turn. Tests have shown that the fuzzy system optimises its performance to suit new situations and facts.

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29

Sik, Ayhan Serkan. "X-ray Physics And Computerized Tomography Simulation Using Java And Flash." Master's thesis, METU, 2003. http://etd.lib.metu.edu.tr/upload/3/756239/index.pdf.

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For the education of X-ray imaging, having a detailed knowledge on the interaction of radiation with matter is very important. Also the generation and detection concepts of the X-ray have to be grasped well. Sometimes it is not easy to visualize the interactions and assess the scheme in quantum physics level for the medical doctors and the engineers who have not studied on the modern physics in an appropriate level. This thesis aims to visualize these interactions, X-ray generation and detection, and computerized tomographic imaging. With these simulations, the user can 1) observe and analyze which type of interaction occurs under which condition, 2) understand the interaction cross sections and interaction results, 3) visualise X-ray generation and detection features, 4) clarify the method of image reconstruction, and the features affecting the image quality in computerized tomography system. This is accomplished by changing the controllable variables of the radiation and the systems with the provided interfaces. In this thesis, JAVA/FLASH based simulation interfaces are designed to easily assess the subject. The benefits of these software are their ability to execute the programs prepared on the World Wide Web media. The interfaces are accessible from anywhere, at any time.

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30

Plogmaker, Stefan. "Techniques and Application of Electron Spectroscopy Based on Novel X-ray Sources." Doctoral thesis, Uppsala universitet, Yt- och gränsskiktsvetenskap, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-168799.

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The curiosity of researchers to find novel characteristics and properties of matter constantly pushes for the development of instrumentation based on X-radiation. I present in this thesis techniques for electron spectroscopy based on developments of X-ray sources both in time structure and energy. One part describes a laser driven High-Harmonic Generation source and the application of an off-plane grating monochromator with additional beamlines and spectrometers. In initial experiments, the source is capable of producing harmonics between the 13th and 23rd of the fundamental laser 800 nm wavelength. The intensity in the 19th harmonic, after monochromatization, was measured to be above 1.2·1010 photons/second with a repetition rate of 5 kHz. The development of a chopper system synchronized to the bunch clock of an electron storage ring is also presented. The system can be used to adjust the repetition rate of a synchrotron radiation beam to values between 10 and 120 kHz, or for the modulation of continuous sources. The application of the system to both time of flight spectroscopy and laser pump X-ray probe spectroscopy is shown. It was possible to measure triple ionization of Kr and in applied studies the valence band of a laser excited dye-sensitized solar cell interface. The combination of the latter technique with transient absorption measurements is proposed. The organic molecule maleic anhydride (MA) and its binding configuration to the three anatase TiO2 crystals (101), (100), (001) has been investigated by means of Xray Photoelectron Spectroscopy (XPS) and Near Edge X-ray Absorption Fine structure Spectroscopy (NEXAFS). The results provide information on the binding configuration to the 101 crystal. High Kinetic Energy Photoelectron Spectroscopy was used to investigate multilayers of complexes of iron, ruthenium and osmium. The benefit of hard X-rays for ex-situ prepared samples is demonstrated together with the application of resonant valence band measurements to these molecules.

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Rackstraw, David Simon. "Opacity and saturable absorption in solid-density plasmas generated by an X-ray free-electron-laser." Thesis, University of Oxford, 2015. https://ora.ox.ac.uk/objects/uuid:38596abc-a7ad-4a2a-ba58-50e8f3df2bc6.

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The arrival of 4th generation light-sources has opened up new regimes in X-ray-matter interactions. A billion times spectrally brighter than the preceding X-ray sources, free-electron-lasers (FELs) can deposit large amounts of energy into a system in less than 100 fs. Since the absorption of x-rays is reasonably well understood and the pulse length is so short, the plasma conditions created are well characterized. The work presented in this thesis relates to a series of experiments where solid aluminium foils were heated with the focussed FEL radiation. The way that the opacity of the FEL heated foil would affect the observed emission spectrum is investigated. The extent to which the opacity influences the emission spectra is found to have intensity and photon energy dependencies. The transmission of the x-ray pulse used to generate a solid-density aluminium plasma is studied in both simulation work using the collisional-radiative code SCFLY and experiment. The phenomenon of saturable absorption is seen to occur, caused by the system being ionized to such an extent that none of the ions present can absorb the x-ray photons through K-shell photoionization. The use of the FEL beam in a split and delay scheme was also explored. Simulations of the time dependent changes in transmission and what may be observed were performed.

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Ciricosta, Orlando. "Plasma evolution and continuum lowering in hot dense matter generated by X-ray free electron lasers." Thesis, University of Oxford, 2014. http://ora.ox.ac.uk/objects/uuid:2f872e7c-80dd-43d5-b171-b1d14957c0e6.

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The advent of the 4th generation X-ray sources paves the way for a new phase of experimental investigation of Hot-Dense plasmas. At the Linac Coherent Light Source (LCLS), pulses of keV X-rays, shorter than 100 fs, and with intensities up to 10¹⁸ W·cm^-2, are routinely produced, allowing for the production of uniform samples of solid-density plasmas. The simple single-photon X-ray absorption mechanism can be easily modelled, so that the plasma conditions can be accurately retrieved, without relying on diagnostic techniques that are not benchmarked in this high density regime. The work presented here describes the results of the first experiment where the LCLS interacts with a solid Al target, isochorically heating it at temperatures up to 190 eV. The system is described by the SCFLY non-LTE model, where the density and temperature are computed self consistently, as a consequence of the detailed atomic processes, rather than imposed by the user. The approximations affecting the simulations are discussed in detail. The code is first validated, by modelling the charge state distribution measured in a previous experiment (L. Young et. al), where the LCLS interacts with a Ne gas, a simplified (collisionless) problem. Then it is used to model the K-alpha spectroscopic data obtained for Al. The plasma evolution, explained by SCFLY simulations, is found to be primarily determined by collisions, whose visible effects on the experimental spectra are discussed. By varying the wavelength of the laser and observing the change in the K-alpha fluorescence, the K-edges for different ions in the plasma were determined, leading to a charge resolved measurement of continuum lowering in the HDM system. The results disagree with the widely used Stewart-Pyatt model, with the disagreement increasing for higher charge states, but are consistent with the older Ecker-Kroell model. These results have profound implications for dense plasma modelling.

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Alpuche, Aviles Jorge Edmundo. "The Development and Validation of a First Generation X-Ray Scatter Computed Tomography Algorithm for the Reconstruction of Electron Density Breast Images Using Monte Carlo Simulation." Journal of X-ray Science and Technology, IOS Press, 2011. http://hdl.handle.net/1993/4970.

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Breast CT is a promising modality whose inherent scatter could be used to reconstruct electron density (rho_e) images. This has led us to investigate the benefits of reconstructing linear attenuation coefficient (mu) and (rho_e) images of the breast. First generation CT provides a cost-effective and simple approach to reconstruct (rho_e) images in a laboratory but is limited by the anisotropic probability of scatter, attenuation, noise and contaminating scatter (coherent and multiple scatter). These issues were investigated using Monte Carlo (MC) simulations of a first generation breast scatter enhanced CT (B-SECT) system. A reconstruction algorithm was developed for the B-SECT system and is based on a ring of detectors which eliminates the scatter dependence on the relative position of the scattering centre. The algorithm incorporates an attenuation correction based on the (mu) image and was tested against analytical and MC simulations. MC simulations were also used to quantify the dose per scan. The ring measures a fraction of the total single incoherent scatter which is proportional to ray integrals of (rho_e) and can be quantified even when electron binding is non negligible. The algorithm typically reconstructs accurate (rho_e) images using a single correction for attenuation but has the capability for multiple iterations if required. MC simulations show that the dose coefficients are similar to those of cone beam breast CT. Coherent and multiple scatter can not be directly related to (rho_e) and lead to capping artifacts and overestimated (rho_e) by a factor greater than 2. This issue can be addressed using empirical corrections based on the radiological path of the incident beam and result in (rho_e) images of breast soft tissue with 1% accuracy, 3% precision and a mean glandular dose of 4 mGy for a 3D scan. The reconstructed (rho_e) image was more accurate than the (rho_e) estimate derived from the (mu) image. An alternative correction based on the thickness of breast traversed by the beam provides an enhanced contrast image reflecting the breast scatter properties. These results demonstrate the feasibility of detecting small (rho_e) changes in the intact breast and shows that further experimental evaluation of this technique is warranted.

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Cassin, Rémy. "Imagerie nanométrique ultra-rapide par diffraction cohérente de rayonnement XUV produit par génération d'harmoniques d'ordre élevés." Thesis, Université Paris-Saclay (ComUE), 2017. http://www.theses.fr/2017SACLS591/document.

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L'objectif de ce mémoire est dedévelopper de nouvelles méthodes d'imageriesans lentille en simple tir 2D et 3D avec dessources harmoniques XUV. Un intérêt particulierest porté aux techniques d'imageries permettantl'imagerie des objets biologiques et de phase.Dans un premier temps, on introduit la théorie del'imagerie dans lentille et on détaille lesméthodes utilisées au cours de cette thèse pourreconstruire le champ diffracté par l'objet quel'on souhaite imager. Les techniques d'imageriessont séparées en deux catégories : itératifs etholographiques. On discute des conditionsexpérimentales nécessaires à la reconstruction del'image de l'objet et on compare les avantagesrespectifs des deux types de méthodes. Puis, ondétaille les aspects expérimentaux du faisceauXUV obtenu par HHG et on couvre brièvementla théorie associée à ce processus. La sectionsuivante traite des paramètres et des techniquesde traitement des données influant sur la qualitéde l'image reconstruite en imagerie sans lentille.On montre comment améliorer lesreconstructions HERALDO dans un régime defaible flux de photons. On présente ensuite lesrésultats d'une technique de caractérisationcomplète de la cohérence spatiale d’un faisceauXUV en simple tir. Cette dernière est unparamètre critique de l'imagerie sans lentille. Al'aide d'un tableau non redondant de référencesponctuelles, on mesure la cohérence spatialepour chaque distance entre les références, sansaucune mesure du profil spatial du faisceau. Onmontre que la distribution de la cohérence estgaussienne et que son diamètre dépend desconditions de génération du faisceauharmonique. On étudie aussi quantitativementcomment l'accumulation de plusieurs tirs dediffraction diminue la cohérence apparente dufaisceau. Une expérience d'imagerie d'objets dephase avec une source harmonique pouvant êtreappliquée à des objets biologiques est ensuiteprésentée.A notre connaissance c'est la premièrereconstruction par méthode CDI d'objets dephase avec une source harmonique. La suite dumanuscrit présente les résultats de deuxexpériences visant à réaliser de l'imagerie 3D àl'échelle nanométrique avec une sourceharmonique. Tout d’abord, on présente unetechnique d'imagerie 3D simple tir. C'est lapremière expérience permettant unereconstruction 3D à partir d'une seuleacquisition, avec une résolution spatialenanométrique et une résolution temporellefemtoseconde, sans utiliser de connaissances apriori sur l'objet étudié. Cette technique possèdeun vaste spectre d'application, particulièrementpour l'étude structurelle d'échantillonsbiologiques sensibles aux dégâts d'irradiation.De plus, cette technique peut être facilementapplicable à des FELs et des synchrontrons pourobtenir de meilleures résolutions. La deuxièmeexpérience d'imagerie 3D est une preuve deconcept validant la faisabilité de lacryptomographie avec une source harmonique.Pour reconstruire le volume 3D de l'échantillon,la cryptotomographie utilise des figures dediffraction qui sont acquises pour desorientations de l'échantillon inconnues. Lerégime de faible flux dans lequel on se place nouspermet de simuler les paramètres d'une sourceharmonique fonctionnant dans la fenêtre de l'eau.On conclut que, le niveau du signal de diffractionest suffisant pour pouvoir identifier l'orientationde l'objet à partir des figures de diffractionenregistrées, dans des conditions expérimentalesoptimisées. Ainsi, avec suffisamment de figuresde diffraction enregistrées et assez d'orientationsde l'objet, on peut reconstruire le volume 3D del'objet. Ces résultats impliquent qu'uneexpérience de cryptotomographie d'objetsbiologiques avec une source harmoniquefonctionnant dans la fenêtre de l'eau seraitréalisable
The aim of this dissertation is todevelop new lensless single shot imagingtechnique in 2D and 3D with XUV harmonicsources which can be applied to study biologicalobjects and phase objects. Firstly, we introducethe theory underlying lensless imagingtechniques and we describe the methods usedduring this thesis to reconstruct the light fielddiffracted by the studied object. The imagingtechniques are split in two categories: iterativeand holographic. The iterative methodsreconstruct the phase of the diffracted wavefront using constraints in the Fourier space andthe reel space. With the holographic techniques,the phase is encoded directly in the interferencefringes between the reference and the objectwithin the diffraction pattern. We discuss theexperimental parameters required to achieve animage reconstruction and we compare therespective advantages of the two types ofmethod. Then, we describe the experimentalparameters of the XUV beam produced by highharmonic generation (HHG) and we brieflyexplain the theory of the HHG. The next sectiondiscusses the parameters the quality of thereconstructed image. We show how to improvethe resolution and the signal to noise ratio usingthe HERALDO technique in the low fluxregime.We then show the result of a new technique forthe single shot characterization of the spatialcoherence of XUV beams. Indeed, the spatialcoherence is a critical parameter for coherentdiffractive imaging techniques. Using a NRA ofreference holes, we measure the spatialcoherence for each distance between each pairof holes, without the knowledge of the intensitydistribution on the sample. We show that thespatial coherence has a gaussian distribution andthat its diameter varies according to thegeneration parameters of the harmonic beam.We also study quantitatively the effect of multishotsaccumulation of the diffraction pattern onthe apparent coherence of the beam. We alsoshow the result of phase object imaging usingcoherent diffractive imaging with a harmonicsource. To our knowledge, this if the first timesuch result has been achieved. The rest of thedissertation present new lensless imaging 3Dtechniques using harmonic sources. The first ofthe last two experiments shown is a lenslesssingle shot stereo 3D technique. It is the first oneallowing a 3D reconstruction from a singleacquisition, with a nanometer spatial resolutionand a femtosecond temporal resolution, withoutusing \textit{a priori} knowledge of the samplestudied. This method has a vast spectrum ofapplication and is particularly interesting for thestructural study of biological sample sensitive toradiation damage and for the study of nonreversibledynamical phenomena in 3D.Furthermore, this can easily be implemented inFELs and synchrotrons to reach even betterspatial resolution. The second 3D experimentshown in this thesis is a proof of concept ofcryptotomography using a high harmonic sourcein a low flux regime. To reconstruct the 3Dvolume of the sample, cryptotomographie usesdiffraction pattern acquired for unknown sampleorientations and therefore non-classified. Thelow flux regime used here simulate the flux of aharmonic source generated in the water window.We conclude from this experiment that, with theproper experimental conditions, the diffractionsignal is sufficient to allow the classification byorientation of the diffraction patterns. Withenough diffraction pattern and angles of thesample recorded, we can achieve a 3Dreconstruction of the sample. This result impliesthat the cryptotomography of biological objectsusing a water window harmonic source ispossible

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Carstens, Henning [Verfasser], and Ferenc [Akademischer Betreuer] Krausz. "Enhancement cavities for the generation of extreme ultraviolet and hard x-ray radiation / Henning Carstens ; Betreuer: Ferenc Krausz." München : Universitätsbibliothek der Ludwig-Maximilians-Universität, 2016. http://d-nb.info/1163949116/34.

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Dirks, Bob Petrus Franciscus. "Study and modelling of the new generation Cd(Zn)Te X and gamma-ray detectors for space applications." Paris 7, 2006. http://www.theses.fr/2006PA077048.

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La communauté scientifique d'astrophysique a besoin d'un nouvel instrument pour approfondir sa connaissance sur l'origine du fond cosmique de rayon X, la physique des trous noirs et les mécanismes d'accélération de particules dont l'énergie s'étend entre 0. 5 et 80 keV. Les instruments existants comme Chandra et XMM-Newton montrent des résultats excellents jusqu'à -10 keV, mais la sensibilité n'est plus suffisante au-dessus de cette valeur. Afin de conserver les mêmes performances jusqu'à -80 keV, ou de les améliorer, des miroirs en incidence rasante avec une grande longueur focale (>20 m) devraient être employés. Etant donné que des satellites de cette taille ne peuvent pas être mis en orbite avec les lanceurs existants, le miroir et le détecteur doivent être placés sur deux satellites différents volant en formation. La mission spatiale, Simbol-X, sera le premier projet de ce type. Une sensibilité élevée à 80 keV exige non seulement une grande longueur focale, mais également une unité de détection avec une résolution spatiale élevée, ainsi que des détecteurs encore efficaces à ces énergies relativement élevées. Le CEA/Saclay/DAPNlA développe cet élément crucial pour Simbol-X. L'imageur se compose de plusieurs modules. Ceux-ci sont composés de différentes mini-caméras X, qui sont une hybridation de l'électronique de lecture dédiée et des cristaux Cd(Zn)Te semiconducteurs. L'ensemble doit pouvoir détecter efficacement des photons jusqu'à 80 keV avec une résolution d'énergie de ~1. 3 keV (FWHM) à 68 keV. En outre, le cristal doit être équipé de petits pixels (0. 5x0. 5 mmA2) pour atteindre la résolution spatiale désirée de 15 arcsec. Afin d'atteindre une bonne sensibilité et résolution d'énergie, il est obligatoire de combiner une électronique de lecture en bruit ultra-bas, avec des cristaux semi-conducteurs de haute qualité. L'électronique de lecture, baptisée IDeF-X (Imaging Détecter Front-end for X-rays), est également développée par le CEA/Saclay. Une connaissance complète de son fonctionnement ainsi que sa caractérisation font parties de ce travail. Les performances spectroscopiques du détecteur sont directement liées au bruit de l'électronique. Les caractéristiques du bruit de l'ASIC sont donc examinées en détail en fonction de la capacité d'entrée et du courant, deux sources importantes de bruit. Puisque l'ASIC est fait pour être couplé de façon DC aux cristaux, la connaissance des courants de fuite des détecteurs Cd(Zn)Te multi-pixels est très importante. J'ai développé un circuit électronique qui permet une mesure précise des courants de fuite très faibles, par pixel (~10A-12 A) dans les détecteurs Cd(Zn)Te 64 pixels. Des cartes de courants sont présentées pour différents détecteurs dans des conditions diverses de fonctionnement. D'ailleurs, la relation entre le courant et la température permet également d'obtenir des cartes d'énergie d'activation des impuretés à l'intérieur du cristal. En outre, le circuit est un outil pour étudier les propriétés mécaniques des contacts entre pixel et substrat. Des spectres d'énergie sont acquis avec quatre puces IDeF-X V1. 0 (16 canaux) complètement opérationnelles, connectées à différents cristaux CdTe et CdZnTe (64 pixels). Les résultats donnent les conditions opérationnelles optimales pour obtenir la meilleure résolution d'énergie à 60 keV (source 241 Am). Pour un détecteur CdTe avec un pixel (360 V bias, 22°C) une excellente résolution d'énergie de 1 keV (FWHM) est obtenue. Cette valeur a également été réalisée par plusieurs pixels d'un détecteur CdTe avec 64 pixels en indium découpé (400 V bias, -18°C). Afin de mieux comprendre le comportement et de prévoir la performance des détecteurs, j'ai construit une chaîne de simulation complète. Elle commence par les interactions de particules à l'intérieur du cristal et la simulation continue jusqu'à la sortie de l'électronique de lecture. Je combine GEANT4 pour simuler différentes interactions à l'intérieur du Cd(Zn)Te et MGS-CdTe V1. 0 pour simuler la création des porteurs de charge, le transport, les effets de piégeage et l'induction des signaux sur les électrodes. Par convolution de ces signaux avec la fonction de réponse d'impulsion numérique d'IDeF-X V1. 0, une réponse complète du détecteur est produite. La comparaison entre les spectres simulés et les mesures montre un excellent accord. GEANT4 et MGS-CdTe sont également employés individuellement pour étudier les différents paramètres du détecteur. Ceux-ci incluent la taille du nuage de charge après une interaction, la multiplicité des interactions et l'efficacité de la détection. La chaîne de simulation est un outil puissant pour prévoir la forme du signal, les interférences entre les pixels et la stratégie de lecture pour la mission Simbol-X
The scientific astrophysics community needs a new instrument to gain more insight in the origin of the cosmic X-ray background, the physics of black holes and particle acceleration mechanisms in the energy range between 0. 5 to 80 keV. Existing instruments like Chandra and XMM-Newton show very good results up to -10 keV but lack sufficient sensitivity above this value. In order to keep or improve the same performances up to -80 keV, grazing incidence mirrors with a large focal length of at least 20 m should be used. Since satellites this big cannot be launched with existing launchers, the mirror and detecter must be placed on two different satellites flying in formation. The Simbol-X space mission will be the first project of this type. A high sensitivity at 80 keV requires not only a long focal length but also a detection unit with high spatial resolution, using detectors that are still efficient at these relatively high energies. CEA/Saclay/DAPNIA is developing this crucial element for the Simbol-X space mission. The imager consists of several modules, each built from individual X-ray mini-cameras. A single camera is a hybridization of custom read-out electronics connected to a Cd(Zn)Te semiconductor crystal. The ensemble must be able to efficiently detect photons of up to 80 keV with an energy resolution of -1. 3 keV (FWHM) at 68 keV. Furthermore it must be equipped with small pixels (0. 5x0. 5 mmA2) to attain the desired spatial resolution of 15 arcsec. In order to reach a good sensitivity and energy resolution, ultra-low noise read-out electronics in combination with high-quality semiconductor crystals are mandatory. The read-out electronics, baptized IDeF-X (Imaging Detector Front-end for X-rays), is also developed by CEA/Saclay. A thorough understanding of its functioning as well as its testing forms a part of this work. The spectroscopic performances of the detecter are directly related to thé electronics noise. The noise characteristics of the ASIC are therefore examined in detail as a function of the input capacitance and current, two important sources of noise. Since the chip is designed to be DC coupled to the crystals, knowledge of the leakage current (per pixel) inside multi-pixel Cd(Zn)Te detectors is very important. I developed an electronic circuit which allows an accurate measurement of the very low leakage currents per pixel (~10A-12 A), in 64 pixels Cd(Zn)Te detectors. Current maps are presented of different detectors at various operating conditions. Moreover, the relation between the current and temperature also allows obtaining activation energy maps of the impurities inside the crystal. In addition, the circuit is a tool to study the mechanical properties of the pixel-substrate contacts. With four fully operational 16-channels IDeF-X V1. 0 ASICs connected to different 64 pixels CdTe and CdZnTe crystals, energy spectra are taken. From the results, optimal operation conditions (bias voltage, peaking time, temperature) are obtained to get the best energy resolution of thé 60 keV energy peak of 241 Am. For a single pixel CdTe Schottky detecter (360 V bias, 22°C) an excellent energy resolution of 1 keV (FWHM) is obtained. This value has also been achieved by several individual pixels of a 64 pixels indium diced CdTe detecter (400 V bias, -18°C). In order to better understand thé detecter behaviour and to predict detecter performances, I constructed a full simulation chain. It starts with the particle interactions inside the crystal and continues the simulation up to the output of the read-out electronics. I combine GEANT4, to simulate individual interactions inside Cd(Zn)Te, and MGS-CdTe V1. 0 to simulate charge carrier creation, transport, trapping effects and signal induction on the electrodes. By convolving these signals with the (numerical) impulse response function of IDeF-X V1. 0, a complète detecter response is generated. Simulated spectra are compared with measurements and show excellent agreement. GEANT4 and MGS-CdTe are also used separately to study different parameters related to the detecter functioning. These include the size of the charge cloud after an interaction, event multiplicity and detection efficiency. The simulation chain serves as a powerful tool to predict signal shape, cross-talk between pixels and read-out strategy for the Simbol-X mission

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Zhang, Biao. "Generation of biohybrid (poly(ionic liquid)/guar)-based materials." Thesis, Lyon, 2016. http://www.theses.fr/2016LYSEI049.

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Ce travail de thèse a visé la préparation de matériaux biohybrides à base de poly (liquide ionique)s (PIL) et de polysaccharide, en l’occurrence la gomme de guar. Les chaînes de poly (1- [2-acryloyl éthyl] -3 bromure-méthylimidazolium (poly (AEMIBr)) ont été synthétisées par polymérisation contrôlée de type RAFT. Des homopolymères de DP élevé (jusqu'à 300) et de faible dispersité (inférieur à 1,19) ont été obtenus seulement en quelques heures dans l'eau. Ces PIL ont par ailleurs été utilisés comme macroagents de transfert pour générer différents copolymères à blocs en milieu homogène et en émulsion dans le but d’accéder à des nano objets autoassemblés. En effet, différentes morphologies ont été obtenues en s’appuyant sur lesconcepts de la PISA. De plus, des copolymères greffés de type guar-g-PIL ont finalement été construits en milieu liquide ionique.en utilisant des dérivés de guar macroagents de transfert Les PIL combinent à la fois les propriétés des IL (non-volatile, stabilité thermique et chimique, haute conductivité...) et celles des polymères en termes de renforcement mécanique, c’est pourquoi ils ont été exploités pour élaborer des matériaux biohybrides de haute performance. La stratégie envisagée dans ce travail réside sur l’exploitation de trois composants: (i) les chaînes de poly (AEMIBr), (ii) le guar et (iii) un liquide ionique: le chlorure de butylméthylimidazolium (BMIMCl). La voie expérimentale permettant l’obtention de tels matériaux est très simple et non dégradante puisqu’elle n’implique que des étapes de solubilisation de polymères en milieu IL. Les propriétés rhéologiques et thermiques de ces matériaux ont été évaluées. En outre, la morphologie interne, par des mesures de WAXS et SAXS, ainsi que le transport ionique ont été étudiés. Il en ressort que de multiples interactions synergiques sont formées entre le guar et les chaînes de PIL, en parallèle des interactions de type PIL/IL et guar/IL. Des ionogels possédant un haut module élastique (jusqu'à 30 000 Pa) et une stabilité thermique élevée (jusqu'à 310 °C) ont ainsi été obtenus. En particulier, la présence de PIL a permis d’améliorer de façon considérable la stabilité dimensionnelle des gels, en limitant complétement les phénomènes d’exudation rencontrés dans les systèmes binaires guar/IL. Il s’avère, de plus, que ces matériaux sont parfaitement homogènes à l’échelle d’observation des analyses SAXS et WAXS. Ces gels ioniques présentent d'excellentes propriétés de transport ionique (10-4 S/cm à 30 °C) grâce notamment à leur structuration interne continue. Cette famille des matériaux multicomposants à base de guar, présente un fort potentiel, notamment pour une utilisation en tant que gel électrolyte dans le domaine de l’énergie
This Ph.D work focuses on the preparation of biohybrid materials based on poly(ionic liquid)s (PIL) and a polysaccharide, guar gum. Poly(1-[2-acryloylethyl]-3-methylimidazolium bromide (poly(AEMIBr)) chains were synthesized through RAFT polymerization. Homopolymers with DP up to 300 and dispersity below 1.19 were obtained within hours in water. High chain-end fidelity further allowed for PIL chain extension with various monomers and stable PIL-based nanoparticles with various morphologies using the PISA concept were achieved. A series of guar-g-PIL graft copolymers were finally constructed in IL using guar macroRAFT agents. As PILs combine the attributes emanating from IL molecules (non-volatile, thermally stable, conducting…) with the ones of polymers in terms of mechanical reinforcement, the resulting polymers were exploited to elaborate high performance biohybrid materials. The cornerstone of this subsequent work was based on the straightforward formation of three-component blends: (i) poly(AEMIBr), (ii) guar and (ii) ionic liquid: butylmethylimidazolium chloride (BMIMCl). The pathway to obtain such ternary blends is very simple, since it only implies successive polymer solubilisation steps in IL. The rheological and thermal properties of the resulting materials were investigated. Also, the internal morphology by WAXS and SAXS measurements as well as the ionic transport were studied. It appeared that strong synergistic hydrogen bonding are developed between guar and PIL chains in addition to PIL/IL and guar/IL interactions. Ionogels with high elastic modulus (up to 30 000 Pa) and high thermal stability (up to 310°C) were prepared. Importantly, addition of PIL significantly enhanced the dimensional stability of the resulting ionogels and overcame IL exudation encountered in IL/guar binary systems. SAXS and WAXS revealed a homogeneous morphology and the ionogels were proven to exhibit excellent conductive properties (10-4 S/cm at 30°C) thanks to their highly continuous morphology. The resulting sustainable multicomponent materials may find applications as gel electrolyte for biobattery systems or supercapacitors

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Shakya, Mahendra Man. "Generation of intense high harmonics : i) to test and improve resolution of accumulative x-ray streak camera ii) to study the effects of carrier envelope phase on XUV super continuum generation by polarization gating." Diss., Manhattan, Kan. : Kansas State University, 2007. http://hdl.handle.net/2097/408.

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Grattoni, Vanessa [Verfasser], and Wolfgang [Akademischer Betreuer] Hillert. "Advanced seeding methods for generation of fully-coherent ultra-short soft x-ray pulses / Vanessa Grattoni ; Betreuer: Wolfgang Hillert." Hamburg : Staats- und Universitätsbibliothek Hamburg, 2020. http://d-nb.info/1218688424/34.

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40

Pearson, Stephen. "The 'Generation X' paradigm in Spanish culture of the 1990s (LuciÌa Etxebarria, Ray Loriga, JoseÌ AÌngel ManÌƒas)." Thesis, Manchester Metropolitan University, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.412831.

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Huijts, Julius. "Broadband Coherent X-ray Diffractive Imaging and Developments towards a High Repetition Rate mid-IR Driven keV High Harmonic Source." Thesis, Université Paris-Saclay (ComUE), 2019. http://www.theses.fr/2019SACLS154/document.

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Des sources des rayons XUV (1-100 nm) sont des outils extraordinaires pour sonder la dynamique à l’échelle nanométrique avec une résolution femto- voire attoseconde. La génération d’harmoniques d’ordre élevé (GH) est une des sources majeures dans ce domaine d’application. La GH est un processus dans lequel une impulsion laser infrarouge femtoseconde est convertie, de manière cohérente, en fréquences élevées dans le domaine EUV par interaction hautement non-linéaire dans un atome, une molécule et plus récemment, dans un cristal. La GH possède une excellente cohérence spatiale qui a permis de réaliser des démonstrations impressionnantes en imagerie sans lentille. Pour accroître le potentiel de ces sources, des défis sont à relever : leur brillance et énergie de photon maximum doivent augmenter et les techniques d’imagerie sans lentille doivent être modifiées pour être compatibles avec l’importante largeur spectrale des impulsions attosecondes émise par ces sources. Cette thèse présente une nouvelle approche dans laquelle des figures de diffraction large bande, i.e. potentiellement attosecondes, sont rendues monochromatiques numériquement. Cette méthode est basée uniquement sur la mesure du spectre de la source et la supposition d’un échantillon spatialement non-dispersif. Cette approche a été validée tout d’abord dans le visible, à partir d’un supercontinuum. L’échantillon binaire est reconstruit par recouvrement de phase pour une largeur spectrale de 11 %, là où les algorithmes usuels divergent. Les simulations numériques montrent aussi que la méthode de monochromatisation peut être appliquée au domaine des rayons X, avec comme exemple un masque semi-conducteur utilisé en de lithographie EUV. Bien que la brillance « cohérente » de la source actuelle (qui progresse) reste insuffisante, une application sur l’inspection de masques sur source Compton est proposée. Dans une extension de ces simulations un masque de lithographie étendu est reconstruit par ptychographie, démontrant la versatilité à d’autres techniques d’imagerie sans lentille. Nous avons également entamé une série d’expérience dans le domaine des X-durs sur source synchrotron. Les figures de diffraction après monochromatisation numérique semblent prometteuses mais l’analyse des données demandent des efforts supplémentaires. Une partie importante de cette thèse est dédiée à l’extension des sources harmoniques à des brillances et énergies de photon plus élevées. Ce travail exploratoire permettrait la réalisation d’une source harmonique compacte pompée par un laser OPCPA dans le moyen infrarouge à très fort taux de répétition. Les longueurs d’onde moyen infrarouge (3.1 μm dans ce travail de thèse) sont favorables à l’extension des énergies des photons au keV et aux impulsions attosecondes. Le but est de pouvoir couvrir les seuils d’absorption X et d’améliorer la résolution spatio-temporelle. Cependant, deux facteurs rendent cette démonstration difficile: le nombre de photons par impulsion de la source OPCPA est très limité et la réponse du dipôle harmonique à grande longueur est extrêmement faible. Pour relever ces défis plusieurs configurations expérimentales sont explorées : génération dans un jet de gaz ; génération dans une cellule de gaz ; compression solitonique et la génération d’harmoniques combinées dans une fibre à cristal photonique ; compression solitonique dans une fibre à cristal photonique et génération d’harmoniques dans une cellule de gaz. Les premiers résultats expérimentaux sur la compression solitonique jusqu’à 26 femtosecondes et des harmoniques basses jusqu’à l’ordre sept sont présentésEn résumé, ces résultats représentent une avancée vers l’imagerie nanométrique attoseconde sans lentille basée sur des algorithmes « large bande » innovants et une extension des capacités de nouvelles sources harmoniques ‘table-top’ au keV pompées par laser OPCPA
Soft X-ray sources based on high harmonic generation are up to now unique tools to probe dynamics in matter on femto- to attosecond timescales. High harmonic generation is a process in which an intense femtosecond laser pulse is frequency upconverted to the UV and soft X-ray region through a highly nonlinear interaction in a gas. Thanks to their excellent spatial coherence, they can be used for lensless imaging, which has already led to impressive results. To use these sources to the fullest of their potential, a number of challenges needs to be met: their brightness and maximum photon energy need to be increased and the lensless imaging techniques need to be modified to cope with the large bandwidth of these sources. For the latter, a novel approach is presented, in which broadband diffraction patterns are rendered monochromatic through a numerical treatment based solely on the spectrum and the assumption of a spatially non-dispersive sample. This approach is validated through a broadband lensless imaging experiment on a supercontinuum source in the visible, in which a binary sample was properly reconstructed through phase retrieval for a source bandwidth of 11 %. Through simulations, the numerical monochromatization method is shown to work for hard X-rays as well, with a simplified semiconductor lithography mask as sample. A potential application of lithography mask inspection on an inverse Compton scattering source is proposed, although the conclusion of the analysis is that the current source lacks brightness for the proposal to be realistic. Simulations with sufficient brightness show that the sample is well reconstructed up to 10 % spectral bandwidth at 8 keV. In an extension of these simulations, an extended lithography mask sample is reconstructed through ptychography, showing that the monochromatization method can be applied in combination with different lensless imaging techniques. Through two synchrotron experiments an experimental validation with hard X-rays was attempted, of which the resulting diffraction patterns after numerical monochromatization look promising. The phase retrieval process and data treatment however require additional efforts.An important part of the thesis is dedicated to the extension of high harmonic sources to higher photon energies and increased brightness. This exploratory work is performed towards the realization of a compact high harmonic source on a high repetition rate mid-IR OPCPA laser system, which sustains higher average power and longer wavelengths compared to ubiquitous Ti:Sapphire laser systems. High repetition rates are desirable for numerous applications involving the study of rare events. The use of mid-IR wavelengths (3.1 μm in this work) promises extension of the generated photon energies to the kilo-electronvolt level, allowing shorter pulses, covering more X-ray absorption edges and improving the attainable spatial resolution for imaging. However, high repetition rates come with low pulse energies, which constrains the generation process. The generation with longer wavelengths is challenging due to the significantly lower dipole response of the gas. To cope with these challenges a number of experimental configurations is explored theoretically and experimentally: free-focusing in a gas-jet; free-focusing in a gas cell; soliton compression and high harmonic generation combined in a photonic crystal fiber; separated soliton compression in a photonic crystal fiber and high harmonic generation in a gas cell. First results on soliton compression down to 26 fs and lower harmonics up to the seventh order are presented.Together, these results represent a step towards ultrafast lensless X-ray imaging on table-top sources and towards an extension of the capabilities of these sources

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Chirla, Razvan Cristian. "Attosecond Pulse Generation and Characterization." The Ohio State University, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=osu1313429461.

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Ndipingwi, Miranda Mengwi. "Designing next generation high energy density lithium-ion battery with manganese orthosilicate-capped alumina nanofilm." University of the Western Cape, 2015. http://hdl.handle.net/11394/5136.

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>Magister Scientiae - MSc
In the wide search for advanced materials for next generation lithium-ion batteries, lithium manganese orthosilicate, Li₂MnSiO₄ is increasingly gaining attention as a potential cathode material by virtue of its ability to facilitate the extraction of two lithium ions per formula unit, resulting in a two-electron redox process involving Mn²⁺/Mn³⁺ and Mn³⁺/Mn⁴⁺ redox couples. This property confers on it, a higher theoretical specific capacity of 333 mAhg⁻¹ which is superior to the conventional layered LiCoO₂ at 274 mAhg⁻¹ and the commercially available olivine LiFePO₄ at 170 mAhg⁻¹. Its iron analogue, Li₂FeSiO₄ has only 166 mAhg⁻¹ capacity as the Fe⁴⁺ oxidation state is difficult to access. However, the capacity of Li₂MnSiO₄ is not fully exploited in practical galvanostatic charge-discharge tests due to the instability of the delithiated material which causes excessive polarization during cycling and its low intrinsic electronic conductivity. By reducing the particle size, the electrochemical performance of this material can be enhanced since it increases the surface contact between the electrode and electrolyte and further reduces the diffusion pathway of lithium ions. In this study, a versatile hydrothermal synthetic pathway was employed to produce nanoparticles of Li₂MnSiO₄, by carefully tuning the reaction temperature and the concentration of the metal precursors. The nanostructured cathode material was further coated with a thin film of aluminium oxide in order to modify its structural and electronic properties. The synthesized materials were characterized by microscopic (HRSEM and HRTEM), spectroscopic (FTIR, XRD, SS-NMR, XPS) and electrochemical techniques (CV, SWV and EIS). Microscopic techniques revealed spherical morphologies with particle sizes in the range of 21-90 nm. Elemental distribution maps obtained from HRSEM for the novel cathode material showed an even distribution of elements which will facilitate the removal/insertion of Li-ions and electrons out/into the cathode material. Spectroscopic results (FTIR) revealed the vibration of the Si-Mn-O linkage, ascertaining the complete insertion of Mn ions into the SiO₄⁴⁻ tetrahedra. XRD and ⁷Li MAS NMR studies confirmed a Pmn21 orthorhombic crystal pattern for the pristine Li₂MnSiO₄ and novel Li₂MnSiO₄/Al₂O₃ which is reported to provide the simplest migratory pathway for Li-ions due to the high symmetrical equivalence of all Li sites in the unit cell, thus leading to high electrochemical reversibility and an enhancement in the overall performance of the cathode materials. The divalent state of manganese present in Li₂Mn²⁺SiO₄ was confirmed by XPS surface analysis. Scan rate studies performed on the novel cathode material showed a quasi-reversible electron transfer process. The novel cathode material demonstrated superior electrochemical performance over the pristine material. Charge/discharge capacity values calculated from the cyclic voltammograms of the novel and pristine cathode materials showed a higher charge and discharge capacity of 209 mAh/g and 107 mAh/g for the novel cathode material compared to 159 mAh/g and 68 mAh/g for the pristine material. The diffusion coefficient was one order of magnitude higher for the novel cathode material (3.06 x10⁻⁶ cm2s⁻¹) than that of the pristine material (6.79 x 10⁻⁷ cm2s⁻¹), with a charge transfer resistance of 1389 Ω and time constant (τ) of 1414.4 s rad⁻¹ for the novel cathode material compared to 1549 Ω and 1584.4 s rad-1 for the pristine material. The higher electrochemical performance of the novel Li₂MnSiO₄/All₂O₃ cathode material over the pristine Li₂MnSiO₄ material can be attributed to the alumina nanoparticle surface coating which considerably reduced the structural instability intrinsic to the pristine Li₂MnSiO₄ cathode material and improved the charge transfer kinetics.

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44

SAMPATH, KUMAR RAGHAV. "NUMERICAL, EXPERIMENTAL AND ANALYTICAL STUDY OF THERMAL HEATING OF SPHERE AND DISK SHAPED BIOCRYSTALS EXPOSED TO 3 ^RDGENERATION SYNCHROTON SOURCES." University of Cincinnati / OhioLINK, 2006. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1155103284.

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45

Nilsson, Marita. "Hydrogen generation from dimethyl ether by autothermal reforming." Licentiate thesis, Stockholm : Kemi, Kungliga Tekniska högskolan, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-4434.

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46

Sutherland, Julia Robin Miller. "Phase-Matching Optimization of Laser High-Order Harmonics Generated in a Gas Cell." Diss., CLICK HERE for online access, 2005. http://contentdm.lib.byu.edu/ETD/image/etd880.pdf.

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47

Siebert, Andreas [Verfasser], Marcus [Akademischer Betreuer] Bär, and Jörg [Gutachter] Libuda. "Insights into Operation-Induced Changes of Next Generation Post-Lithium Battery Electrodes Revealed by X-Ray Spectroscopic Operando Measurements / Andreas Siebert ; Gutachter: Jörg Libuda ; Betreuer: Marcus Bär." Erlangen : Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), 2020. http://d-nb.info/1221370391/34.

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48

Dacasa, Pereira Hugo. "Spatial and temporal metrology of coherent ultrashort pulses inthe extreme-ultraviolet domain." Thesis, Université Paris-Saclay (ComUE), 2017. http://www.theses.fr/2017SACLX041/document.

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Les impulsions ultra-brèves de rayonnement ultraviolet extrême (UVX) ont un grand champ d’application dans les domaines tels que le diagnostic de plasmas, la spectroscopie ou l’étude de la dynamique ultrarapide dans les atomes et les molécules.Aujourd’hui, il existe trois sources délivrant ce genre d’impulsions. Les harmoniques d’ordre élevé (HHG, en anglais) générés dans les gaz rares ou sur les solides peuvent fournir des impulsions attosecondes. Cependant, leur énergie, le plus souvent de l’ordre du nanojoule, limite les applications. L’amplification des impulsions harmoniques dans les plasmas créés par laser (SXRL, en anglais) a démontré pouvoir fournir des énergies de plusieurs dizaines de microjoules. Des énergies plus élevées peuvent être obtenues avec les lasers à électrons libres (LEL) UVX injectés, mais ce sont des Très Grandes Infrastructures ayant un accès limité.Ces dernières années, des progrès significatifs ont été réalisé avec chacune des ces sources, avec pour objectif la génération d’impulsions plus brèves. Il est devenu nécessaire de développer des nouvelles techniques de métrologie temporelle des impulsions UVX ultra-brèves. De plus, beaucoup d’expériences, comme ceux impliquant des phénomènes non-linéaires, nécessitent de hautes intensités UVX. La focalisation efficace des impulsions de faibles énergies peut significativement augmenter le domaine d’application. De bons fronts d’onde sont nécessaires pour focaliser les impulsions UVX à haute intensité, et les optiques doivent aussi être de bonne qualité et alignées avec précision.Dans cette thèse, les propriétés spatiales des harmoniques d’ordre élevé ont été extensivement étudiées grâce à un senseur de front d’onde UVX. Cet appareil couplé à une source HHG a démontré être utile pour la caractérisation de table et à la longueur d’onde ainsi que pour l’optimisation de systèmes optiques UVX.Le problème de la mise en place de la complète caractérisation temporelle d’impulsions UVX est aussi discuté en détail, et deux nouveaux schémas pour la reconstruction d’impulsions de LEL injectés et de lasers X à plasma sont présentés. Finalement, la première implantation d’un système d’amplification à dérive de fréquence (CPA, en anglais) sur un LEL UVX est présentée et son implantation pour les lasers X à plasmas est aussi discutée
Ultrashort pulses of extreme-ultraviolet (XUV) radiation have a wide range of applications in fields such as plasma probing, spectroscopy, or the study of ultrafast dynamics in atoms and molecules.Nowadays, there are three main sources of such pulses. High-order harmonic generation (HHG) in rare gases or solid surfaces is able to provide attosecond pulses. However, their limited energy, of the order of nanojoules, limits its number of applications. The amplification of high-harmonic pulses in laser-driven plasmas (SXRL) has been demonstrated to provide energies of tens of microjules. Higher pulse energies can be obtained from seeded XUV free-electron lasers (FELs), large-scale facilities with more limited accessibility.In recent years, significant progress has been made with each of these sources towards the generation of shorter pulses. It is thus necessary to develop new techniques for full temporal metrology of ultrashort XUV pulses. Additionally, many experiments, such as those involving nonlinear phenomena, require high XUV intensities. Efficient focusing of low-energy pulses can significantly increase their range of application. Good wavefronts are required in order to focus XUV pulses to high intensities, and the optics must be of high quality and precisely aligned.In this thesis, the spatial properties of high-harmonic pulses are extensively explored thanks to the use of an XUV Hartmann wavefront sensor. This device is also proven here to be useful for tabletop, at-wavelength characterization and optimization of XUV optical systems with HHG sources.The problem of performing full temporal characterization of XUV pulses is also discussed in detail, and two new schemes for complete pulse reconstruction for seeded XUV FELs and seeded SXRLs are presented. Finally, the first implementation of chirped pulse amplification (CPA) in a seeded XUV FEL is reported, and its implementation in seeded SXRLs is discussed as well

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Kalenský, Ondřej. "Design přenosného veterinárního rentgenového přístroje." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2017. http://www.nusl.cz/ntk/nusl-318804.

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This diploma thesis is focused on the design of a product family of portable veterinary x-ray generators. The thesis deals with the possibilities of using parameterization when designing products which are part of a product series. The main body of the thesis lies in the design of a parametric script which generates variations of portable veterinary x-ray generators depending on the size and position of the inner components. The outer surfaces are defined by algorithms from the input parameters. It is possible to alter the individual attributes (e.g. the progresion of curves, the dimensions of component parts and the proportions between the individual parts). The output from the parametric script is three size-variations of the product.

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50

Araújo, Raiane Sodré de. "Geração de segundo harmônico em compostos hidrazônicos." Universidade Federal de Sergipe, 2016. https://ri.ufs.br/handle/riufs/5376.

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES
In this work, we investigated the phenomenon of second harmonic generation in hydrazone compounds. Based on optical absorption measurements, we determined the energy bands corresponding to the first excited state and the energy gap of the compound. Using the X-ray powder diffraction method, we verified the crystalline nature of the samples. The process of second harmonic generation exhibited by these compounds was characterized by the Kurtz and Perry powder method. We noted that these materials have good efficiency at second harmonic generation, being comparable to KDP. The results indicate that these are promising compounds for the development of photonic applications based on second-order nonlinear optical effects.
No presente trabalho, investigamos o fenômeno de geração de segundo harmônico em compostos hidrazônicos. A partir de medidas de absorção ´optica, determinamos as bandas de energia correspondentes aos primeiros estados excitados e a energia do gap dos compostos. Usando a difra¸c˜ao de raio-X m´etodo do p´o, verificamos a natureza cristalina das amostras estudadas. O processo de gera¸c˜ao de segundo harmˆonico exibidos por esses compostos foi caracterizado pelo m´etodo do p´o de Kurtz e Perry. Observamos que esses materiais apresentam boa eficiˆencia de gera¸c˜ao de segundo harmˆonico compar´aveis ao KDP. Os resultados obtidos indicam que esses compostos s˜ao promissores para o desenvolvimento de aplica¸c˜oes fotˆonicas baseado em efeitos ´opticos n˜ao lineares de segunda ordem.

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Dissertations / Theses on the topic 'X-rays generator'

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