Analysis of scattered, or diffraction energy (the seismic response of small-scale objects) in the seismic data from Canterbury Basin, New Zealand reveals additional geological information about depositional patterns in sedimentary deposits. Diffrac- tion images from the seismic response for Canterbury Basin provide complementary interpretation tools to the conventional specular reflection images. To image diffrac- tions for a dataset from Canterbury Basin, I take the following steps: First, I attenuate multiples using a surface multiple prediction algorithm to predict multiples and apply regularized nonstationary regression to adaptively subtract the predicted multiples. Next, I separate diffractions using the plane-wave destruction method. The plane- wave destruction method removes conventional reflected energy in order to enhance the diffracted energy. I then apply a velocity continuation method on diffraction data to estimate migration velocities and then migrate the data using Kirchhoff migration in the dip-angle-gather domain. The resultant conventional and diffraction images are improved images suitable for geological interpretation of prograding sediment drifts. / text

The field of X-ray imaging and X-ray diffraction have been combined in a new technique called Tomographic Energy Dispersive Diffraction Imaging (TEDDI). This diffraction imaging technique allows 3D sample images to be obtained, non-destructively, where each imaged point contains the atomic structural information associated with its diffraction pattern. The main drawback of the TEDDI technique is the long collection times needed to produce the images. In order to overcome this obstacle the rapid TEDDI (rTEDDI) system has been developed at the University of Manchester's Material Science Centre. The research and development of rTEDDI has been the focus of this PhD thesis. A proof of concept for the rTEDDI imaging technique was obtained using thin samples on station 7.6 SRS Daresbury. In this case a first generation array collimator was used in conjunction with an energy resolving Si pixelated detector. Structural information such as lattice parameters, crystal system and phase identiffcation were obtained for metal, polymer and deer antler bone samples. The use of high Z semiconductor detector material was investigated in order to increase the potential of TEDDI for larger and more dense samples. To enable penetration of larger samples high energy X-rays needed to be utilized. In order to detect these higher energies with a good efficiency the detector media was changed from Si to CdZnTe (CZT).The second generation rTEDDI, using CZT as the detection media, was intended to be used under high flux/high energy synchrotron radiation conditions. Testing of the system under these conditions on station 16.3 SRS Daresbury showed an inability to produce diffraction imaging. An in depth investigation into detector and collimator array performance showed a two fold cause. The ERD2004 detector was unable to handle the high countrates experienced during high flux/high energy synchrotron radiation conditions. The MK1.2 collimator array was found to become partially transparent to X-ray energies around the absorption edge of W resulting in the swamping of the diffraction signal under high flux/high energy synchrotron radiation conditions. A new detector Application Specific Integrated Circuit (ASIC) design, developed by the detector division and the Rutherford Appleton Laboratory, and Data Aquisition (DAQ) system, developed by Aspect Systems, as well as a number of new collimator array designs were developed and tested. Testing of the new collimator array structures have shown positive results and the new HEXITECdetector which was designed to be able to handle high countrates, have shown an unprecedented inter pixel uniformity and energy resolution which have been attributed to the ASIC performance and the use of better quality CZT material.

To understand the function of macromolecules like proteins it helps to know the structure of the molecule. Coherent diffraction imaging is an emerging method that might be used to figure out the structures of macromolecules. In this method diffraction patterns of the macromolecule are recorded by shining light on the molecule from many unknown orientations and detecting the pattern of the diffracted photons. By assembling the diffraction patterns in a specific way and finding the phase of the photons that gave rise to the diffraction patterns, it is theoretically possible to obtain the electronstructure of the molecule and thus the molecular structure. The assembling of several thousand diffraction patterns representing unknown orientations of the molecule is hard to do by hand, but there are several methods that can be used. The EMC (Expand-Maximize-Compress) algorithm is one of those methods. It is an iterative algorithm that tries to create a model describing the Fourier Transform of the electron density of the molecule by maximizing each diffraction patterns fit to the model. This work examines how sensitive the EMC algorithm is to datasets with few diffraction patterns or a low intensity of the light being diffracted by the molecule, for the proteins phytochrome and lysozyme. The result of the work could be used to make sure enough data in collected in real experiments. Diffraction patterns simulated with the program Condor is used in this work, instead of diffraction patterns from real experiments.EMC finds the correct model when the data set contains about 1/3 fewer photons for the smaller more symmetrical molecule lysozyme than it does for phytochrome. This might be because the shapes in lysozymes diffraction patterns are larger than in phyochrome’s patterns. For phytochrome the EMC algorithm assembled the diffraction patterns correctly, with fewest photons for the light intensity 0.764 J/μm2 and 1250 diffraction patterns. For lysozyme it was with an intensity 1.910 J/μm2 and 1425 diffraction patterns. More investigation of the data is needed to understand what factors that affect the EMC algorithms ability to assemble the diffraction patterns correctly. / För att förstå makromolekylers kemiska eller biologiska funktion so underlättar det om man känner till molekylens kemiska struktur. Med den nya tekniken “coherent diffraction imaging” ska det vara möjligt att lista ut makromolekylers struktur. I denna teknik detekterar man diffraktionsmönster av molekylen genom att belysa molekylen med ljus från många olika okända vinklar and registrera mönstret som skapas av det diffrakterade ljuset. Genom att sätta ihop alla dessa diffraktionsmönster på rätt sätt och sen återskapa fasen för ljuset i diffraktionsmönstret så kan man generera molekylens elektronstruktur och från elektronstrukturen kan man få tag i molekylens struktur. Att sätta ihop tio tusentals diffraktionsmönster med okända vinklar på rätt sätt är väldigt svårt att göra, men det finns flera olika metoder som kan användas. EMC (Expand-Maximize-Compress) är en sådan metod. EMC är en iterativ algoritm som skapar en modell av (Fourier transformen av) molekylens elektronstruktur genom att maximera hur bra diffraktionsmönstren passar med modellen. Detta arbete utreder hur bra EMC algoritmen är på att hitta rätt (Fourier transform av) elektronstruktur när väldigt få diffraktionsmönster används eller när intensiteten på ljuset som sprids av molekylen är lågt. Programmet Condor används för att generera teoretiska diffraktionsmönster för de 2 molekylerna lysozym och fytokrom. EMC används sedan med olika uppsättningar av intensitet och antal diffraktionsmönster för att skapa en modell av elektronstrukturen. EMC behövde ca 1/3 färre antal fotoner i sin modell för att hittar den rätta modellen av elektronstrukturen för den lilla symmetriskt formade molekylen lysozym än för fytokrom. Att det är lättare för EMC algoritmen att hitta den korrekta modellen för lysozym än fytokrom kan bero på att lysozyms diffraktionsmönster har större former/features eller på lysozyms storlek och form. EMC körningen som behövde minst antal fotoner för att hitta den korrekta elektronstrukturen för fytokrom hade intensiteten 0,764 J/μm2 på det inkommande ljuset och behövde 1250 diffraktionsmönster. För lysozym behövdes det 1,910 J/μm2 och 1425 diffraktionsmönster för att EMC algoritmen skulle hitta rätt modell av elektronstrukturen.

The main focus of this thesis is on the phase retrieval problem. This problem has a broad range of applications in advanced imaging systems, such as X-ray crystallography, coherent diffraction imaging, and astrophotography. Thanks to its broad applications and its mathematical elegance and sophistication, phase retrieval has attracted researchers with diverse backgrounds. Formally, phase retrieval is the problem of recovering a signal 𝔁 ∈ ℂⁿ from its phaseless linear measurements of the form |𝛼ᵢ∗𝔁| + 𝜖ᵢ where sensing vectors 𝛼ᵢ, 𝑖 = 1, 2, ..., 𝓶, are in the same vector space as 𝔁 and 𝜖ᵢ denotes the measurement noise. Finding an effective recovery method in a practical setup, analyzing the required sample complexity and convergence rate of a solution, and discussing the optimality of a proposed solution are some of the major mathematical challenges that researchers have tried to address in the last few years. In this thesis, our aim is to shed some light on some of these challenges and propose new ways to improve the imaging systems that have this problem at their core. Toward this goal, we focus on the high-dimensional setting where the ratio of the number of measurements to the ambient dimension of the signal remains bounded. This regime differs from the classical asymptotic regime in which the signal's dimension is fixed and the number of measurements is increasing. We obtain sharp results regarding the performance of the existing algorithms and the algorithms that are introduced in this thesis. To achieve this goal, we first develop a few sharp concentration inequalities. These inequalities enable us to obtain sharp bounds on the performance of our algorithms. We believe such results can be useful for researchers who work in other research areas as well. Second, we study the spectrum of some of the random matrices that play important roles in the phase retrieval problem, and use our tools to study the performance of some of the popular phase retrieval recovery schemes. Finally, we revisit the problem of structured signal recovery from phaseless measurements. We propose an iterative recovery method that can take advantage of any prior knowledge about the signal that is given as a compression code to efficiently solve the problem. We rigorously analyze the performance of our proposed method and provide extensive simulations to demonstrate its state-of-the-art performance.

Electron Ptychography is a technique to retrieve the phase information of the medium through which the electron wave travels in a Transmission Electron Microscope (TEM). Phase calculation is carried out by acquiring an oversampled dataset of diffraction patterns from the sample and execution of a Fourier-based mathematical solution or algorithm using the collected dataset of intensity patterns. The phase of the electron wave contains valuable information about the structure of the material under study. In this contribution, we provide a scientific background necessary for understanding the phase calculation method, examine the capabilities and limitations of the Electron Ptychography in experimental setup and introduce two novel methods to increase the signal to noise ratio by using the same dose budget used in a classic Ptychography experiment. / Thesis / Master of Applied Science (MASc)

We are developing a tabletop extreme-ultraviolet source using high harmonic generation at Brigham Young University. The thesis goes over the theory of high harmonic generation using the three-step model. This tabletop source was designed for probing magnetic domains of iron nanoparticles. We present optimization of the 42 eV and 52 eV harmonics through phase matching. Phase matching consists of tuning the intensity of the IR beam and pressure of the gas medium. The target gas medium used for this thesis is argon. The 42 eV harmonic was optimized to 8.2 billion photons per second. This was used with a 1500 mm focal-length lens, 15 mm medium length, laser power of 1.53 Watts, and a pressure of 12 Torr of argon gas. The 52 eV harmonic was optimized to 1.5 billion photons per second with a 1500 mm focal-length lens, 20 mm medium length, laser power of 3.29 W, and 14.9 Torr of argon gas. There are two designs for selection of harmonics: 1) a tunable design consisting of a toroidal mirror and flat diffraction grating and 2) a set of normal-incidence extreme-ultraviolet mirrors designed for 42 or 52 eV photons. Magnetic imaging uses x-ray magnetic circular dichroism to obtain magnetic contrast and use it to visualize magnetic nanosystems. Therefore, the high harmonic source also needs to generate circularly polarized light. Generating circularly polarized high harmonics is possible with a bichromatic beam. This is achieved using an apparatus called the MAZEL-TOV designed by Oren Cohen’s group at Technion University in Israel. The MAZEL-TOV consists of a BBO crystal for second harmonic generation, a pair of pulse delay compensation plates, and a quarter-wave plate. These optics are placed inline with the laser beam. We have successfully optimized the circularly polarized extreme-ultraviolet harmonics with the MAZEL-TOV. A spectrometer was made to calibrate the harmonics in the MAZEL-TOV spectrum. The tabletop source was then used to demonstrated coherent diffraction imaging of two pinholes.

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.

Non-destructive imaging modalities for evaluating the internal properties of materials can be formulated as physics-driven inverse problems. Model-based Iterative reconstruction (MBIR) methods that integrate a forward model of the imaging system and a prior model of the object being imaged can provide superior reconstruction quality relative to conventional methods. However, making MBIR feasible for practical applications faces two key challenges. First, we require efficient computational methods for MBIR that allow large-scale reconstructions in real-time. Second, we must develop forward models that accurately capture the physics and geometry of the imaging system, and, support the use of advanced denoisers that enhance image quality as prior models.<br><br>This thesis attempts to address the aforementioned challenges and is divided into three main chapters, each corresponding to a different inverse imaging application. <br><br>In the first chapter of this thesis, we propose a novel 4D model-based iterative reconstruction (MBIR) algorithm for low-angle coherent-scatter X-ray Diffraction (XRD) tomography that can substantially increase the SNR. Our forward model is based on a Poisson photon counting model that incorporates a spatial point-spread function, detector energy response and energy-dependent attenuation correction. Our prior model uses a Markov random field (MRF) together with a reduced spectral bases set determined using non-negative matrix factorization. Our algorithm efficiently computes the Bayesian estimate by exploiting the sparsity of the measurement data. We demonstrate the ability of our method to achieve sufficient spatial resolution from sparse photon-starved measurements and also discriminate between materials of similar densities with real datasets.<br><br>In the second chapter of this thesis, we propose a multi-agent consensus equilibrium (MACE) algorithm for distributing both the computation and memory of <br>MBIR for Computed Tomographic (CT) reconstruction across a large number of parallel nodes. In MACE, each node stores only a sparse subset of views and a small portion of the system matrix, and each parallel node performs a local sparse-view reconstruction, which based on repeated feedback from other nodes, converges to the global optimum. Our distributed approach can also incorporate advanced denoisers as priors to enhance reconstruction quality. In this case, we obtain a parallel solution to the serial framework of Plug-n-play (PnP) priors, which we call MACE-PnP. In order to make MACE practical, we introduce a partial update method that eliminates nested iterations and prove that it converges to the same global solution. Finally, we validate our approach on a distributed memory system with real CT data. We also demonstrate an implementation of our approach on a massive supercomputer that can perform large-scale reconstruction in real-time. <br><br>In the third chapter of this thesis, we propose a method that makes MBIR feasible for real-time single-shot holographic imaging through deep turbulence. Our method uses surrogate optimization techniques to simplify and speedup the reflectance and phase-error updates in MBIR. Further, our method accelerates computation of the surrogate-updates by leveraging cache-prefetching and SIMD vector processing units on a single CPU core. We analyze the convergence and real CPU time of our method using simulated datasets, and demonstrate its dramatic speedup over the original MBIR approach. <br>

NiTi-based shape memory alloys (SMAs) offer a good combination of high-strength, ductility, corrosion resistance, and biocompatibility that has served them well and attracted the attention of many researchers and industries. The alloys unique thermo-mechanical ability to recover their initial shape after relatively large deformations by heating or upon unloading due to a characteristic reversible phase transformation makes them useful as damping devices, solid state actuators, couplings, etc. However, there is a need to increase the temperature of the characteristic phase transformation above 150 °C, especially in the aerospace industry where high temperatures are often seen. Prior researchers have shown that adding ternary elements (Pt, Pd, Au, Hf and Zr) to NiTi can increase transformation temperatures but most of these additions are extremely expensive, creating a need to produce cost-effective high temperature shape memory alloys (HTSMAs). Thus, the main objective of this research is to examine the relatively unstudied NiTiZr system for the ability to produce a cost effective and formable HTSMA. Transformation temperatures, precipitation paths, processability, and high-temperature oxidation are examined, specifically using high energy X-ray Diffraction (XRD) measurements, in NiTi-20 at.% Zr. This is followed by an in situ XRD study of the phase growth kinetics of the favorable H-phase nano precipitates, formed in NiTiHf and NiTiZr HTSMAs, based on prior thermo-mechanical processing in a commercial NiTi-15 at.% Hf HTSMA to examine the final processing methods and aging characteristics. Through this research, knowledge of the precipitation paths in NiTiZr and NiTiHf HTSMAs is extended and methods for characterization of phases and strains using high energy XRD are elucidated for future work in the field.

Koherent Diffraktionsavbildning med en intensiv röntgenpuls från en Frielektronlaser har möjliggjort strukturbestämning av isolerade nanopartiklar som inte går att studera med hjälp av konventionella metoder, så som elektronmikroskopi. En mycket kort pulslängd tillsammans med spridningssignalens beroende av objektets elektroniska struktur medför också möjligheten att studera inducerad ultrasnabb dynamik med denna teknik. I detta projekt studerades joniseringspåverkan av Xe hos Xe-Ar core-shell-nanokluster. Enligt teorin har neutral Xe lägre spridningstvärsnitt under dess 3d-resonans än det motsvarande för fotonenergier över 3d-resonansen. Därför var en hög kontrast i klustren förväntad vid energier över dess 3d-resonans. I stället observerades mörkare regioner liknande hål i rekonstruktioner från de experimentella resultaten vid energier över 3d-resonansen hos Xe. En möjlig förklaring var jonisering av neutral Xe. För att undersöka detta skapades 3D modeller av Xe-Ar nanokluster för att simulera den interaktionen mellan intensiva röntgenpulser och nanokluster. Diffraktionsmönstren som genererades med hjälp av 3D-modellerna användes sedan för att utföra Iterativ fasrekonstruktion och rekonstruera partikeldensiteten. Brytningsindex av neutral Xe och de första tio jontillstånden hos Xe beräknades med hjälp av en modell konstruerad i detta projekt, kallad för step-model. Följaktligen introducerades samtliga jontillstånden hos Xe från 0 till 10 in i 3D modeller av Xe-Ar nanoklustren med brytningsindexen av jontillstånden uppskattade med hjälp av Kramers-Kronig-relationerna. Här antogs det att samtidigt som resonansen för varje Xe-jon förflyttas visar 𝛽 (det vill säga den imaginära komponenten i det komplexa brytningsindexet) som en funktion av fotonenergin, ett icke-monotoniskt beteende med en förändring i fotonenergin. Simuleringsresultaten erhållna med hjälp av Kramers-Kronig-relationerna visade en avtagande trend för 𝛽 i Xe-joner med en laddning&gt; 4+ till skillnad från en ökning i 𝛽 för joner med en laddning &lt;4+ relativt dess motsvarande för neutral Xe. Denna metod ansågs tillräcklig för att användas som en första approximation. Dessa resultat visade att ju mer Xe joniseras (och därför minskar 𝛽) desto mer transparenta blir Xe-jonerna under en laserpuls och därför ser de mörkare ut jämfört med Ar som har sin resonans långt ifrån fotonenergierna relevanta för detta projekt (660–760 eV). Vidare simulerades temporära förändringar i Xe-jonpopulationer för att bekräfta de erhållna simuleringsresultaten via step-model. En massiv energideposition då den intensiva röntgenpulsen träffar Xe-kärnorna initierar en serie av joniseringsmekanismer under de första få femtosekunderna av pulsen. Simuleringar för de jonpopulationer som uppstår och försvinner under förloppet av en 100 femtosekunder-lång röntgenpuls visade att jontillstånd mellan 1+ och 10+ är redan förbrukade efter några få femtosekunder vid 1016 W/cm2. Vid slutet av pulsen observerades endast högt laddade Xe-joner (upp till 35+). Den slutsats som drogs var därför att mörkare regioner som liknade hål och observerades i rekonstruktioner från experimentella data var en konsekvens av en förflyttning av resonansen hos de högt laddade Xe-joner (&gt;4+) relativt dess motsvarande i en neutral Xe så att deras spridning minskar. / Coherent Diffraction Imaging with intense x-ray pulses from X-ray Free-Electron Lasers has enabled structure determination of isolated nanoparticles, that cannot be studied with conventional methods, such as electron microscopy. The very short pulse durations and the intrinsic dependence of the scattering signal on the electronic structure of the scattering object also allow studying ultrafast light-induced dynamics with this technique. In this project, the ionization impact of Xe on Xe-Ar core-shell nanoclusters was studied. Theory predicts that neutral Xe has a lower scattering cross-section below its 3d resonance than that at photon energies above its 3d resonance. Therefore, a high contrast in clusters above the neutral Xe’s 3d resonance is expected. However, in the experimental data, unusual dark features resembling holes were observed at energies above Xe’s 3d resonance. As possible explanation, ionization of neutral Xe was suggested. To investigate this, 3D models of Xe-Ar nanoclusters were created to simulate the interaction of intense x-ray pulses and nanoclusters. The diffraction patterns generated by these 3D models were used to perform Iterative Phase Retrieval to reconstruct the particle densities. The refractive indices of neutral Xe and Xe’s first ten ionic states were computed using a model designed in this project, called the step-model. Hence, each and every ionic state of Xe from 0 to 10 were introduced into the 3D models of the Xe-Ar nanoclusters with refractive indices of the ionic states estimated based on the Kramers-Kronig relations. Here, it was assumed that as the resonance is shifting for every ionic state of Xe, 𝛽 (i.e the imaginary component of the complex refractive index) as a function of photon energy shows a nonmonotonic behavior as the photon energy is varied. The simulation results by Kramers-Kronig relations showed a decrease in 𝛽 for ionic states &gt; 4+ in contrast to an increase in 𝛽 for ions with charges &lt; 4+ relative to that of neutral Xe. This approach was sufficient to be used as a first approximation. The results showed that Xe ions become more transparent to the laser pulse as their charge increases (and 𝛽 thereby decreases) and therefore they appear darker than Ar, which has its resonance far away from photon energies relevant for this project (660–760 eV). Furthermore, temporal changes in ionic populations of Xe were simulated to confirm the simulation results obtained by the step-model. The massive energy deposition upon interaction with the intense laser pulse launches a series of ionization events in the Xe cores during the first few fs of the x-ray pulse. The simulation of ionic populations emerging and depleting during the 100-fs-long 1016 W/cm2 x-ray pulse showed that ionic states 1+ to 10+ are depleted already after a few fs. By the end of the pulse, only highly charged (up to 35+) Xe ions are observed. Therefore, it was concluded that the dark features resembling holes in reconstructions from the experimental data were a consequence of a shift in the resonance of highly charged Xe ions (&gt;4+) relative to that of neutral Xe so that their scattering decreases.