This thesis describes the development of soft x-rayreflective optics, instrumentation and applications for compactsoft x-ray microscopy. The microscope is based on a table-topliquid-jet-target laser-plasma source in combination with aspherical normal-incidence multilayer condenser mirror andnanofabricated diffractive optics for imaging. High-resolutionimaging is performed at the wavelength 3.374 nm in thewater-window (2.3 - 4.4 nm), where natural contrast betweencarbon and oxygen allows imaging of unstained biologicalmaterial in their natural aqueous environment. The design and implementation of a compact soft x-rayreflectometer based on a laser-plasma source is described. Thereflectometer allows rapid and accurate characterization ofnormal-incidence multilayer coatings used at water-windowwavelengths. This instrument, which measures absolutereflectivity and multilayer period, is now used in thefabrication process, aiming to improve the soft x-raynormal-incidence multilayer condenser system of the compactsoft x-ray microscope. Latest results from the developmentprocess are presented. A new design of the compact soft x-ray microscope, withimprovements in mechanical and thermal stability, providesuser-friendly and daily operation. This includes also a newnozzle design for the liquid-jet-target laser-plasma source,which enables higher source stability and operation withcryogenic liquids. In addition, a new experimental arrangementunder construction is briefly described. It will utilize acondenser zone plate and operate at the wavelength 2.478nm. Finally, performance test of the compact soft x-raymicroscope is presented and discussed. In addition, a projectto explore the use of soft x-ray microscopy for imaging sensorycells is described. The high-resolution imaging of these cellswas performed at the synchrotron-based soft x-ray microscope atLawrence Berkeley National Laboratory (LBNL).

This thesis describes the development of a sub-60-nm full-period resolution compact soft x-ray microscope operating in the water-window region (2.3-4.4 nm). Soft x-ray water-window microscopy is a powerful technique for high-resolution imaging of organic materials exploiting the natural contrast mechanism between carbon and oxygen, cf. Sect. 4.1. The thesis discusses the components of, as well as the integration of the microscope, including liquid-jet laser-plasma x-ray sources, optics, simulations, and image-processing tools. Liquid-jet-target laser-plasma sources for generation of soft x-rays and extreme-ultraviolet radiation are compact sources with high brightness. The work focused on improved target stability, decreased debris, and accurate source characterization. For x ray microscopy applications a liquid-jet target delivery system allowing cryogenic liquids was developed. Source characterization was performed for two different liquid-jet targets: Methanol and liquid nitrogen. For extreme-ultraviolet lithography applications, the potential use of a liquid-tin-jet laser-plasma source was explored including conversion efficiency and debris measurements. High quality optics are essential in the development of compact x-ray microscopes. For soft x-ray wavelengths, zone plates and multilayer mirrors are used to focus or redirect radiation. This thesis describes the development and characterization of a condenser zone plate suitable for use in a compact soft x-ray microscope operating at λ = 2.478 nm. It also investigates the possibility to perform differential interference contrast microscopy in the water window using a single diffractive optical element. An arrangement for rapid and accurate determination of absolute and local diffraction efficiency of soft x-ray zone plates using a compact laser-plasma source has been developed. The instrument is used to characterize the zone plates fabricated at the Biomedical & X-Ray Physics division at KTH. Through a collaboration with the Fraunhofer-Institut in Jena, Germany, a large diameter spherical Cr/Sc multilayer mirror, suitable as condenser in the compact x-ray microscope, was developed and characterized. The mirror is designed for λ = 3.374 nm and shows a high, and uniform reflectivity of 3%. This increases the photon flux by an order of magnitude compared to the W/B4C mirrors previously used. The thesis describes the development of a compact soft x-ray microscope with sub-60-nm full-period resolution. It can operate at two different wavelengths in the water window using the soft x-ray laser-plasma sources combined with the condenser optics described above. Imaging is performed by zone plate objectives. The microscope is capable of imaging hydrated biological samples with thicknesses up to ~10 μm. Improvements made to the mechanical design has turned it into a user friendly instrument allowing daily operation. A numerical method was developed to study the effects of partially coherent illumination on 2D imaging. To stimulate experiments on functional imaging in x-ray microscopy an image-analysis algorithm for identifying colloidal-gold particles was developed. Size selective identification and localization of single gold particles down to a diameter of 50 nm was demonstrated. / QC 20100819

<p>This thesis describes the development of soft x-rayreflective optics, instrumentation and applications for compactsoft x-ray microscopy. The microscope is based on a table-topliquid-jet-target laser-plasma source in combination with aspherical normal-incidence multilayer condenser mirror andnanofabricated diffractive optics for imaging. High-resolutionimaging is performed at the wavelength 3.374 nm in thewater-window (2.3 - 4.4 nm), where natural contrast betweencarbon and oxygen allows imaging of unstained biologicalmaterial in their natural aqueous environment.</p><p>The design and implementation of a compact soft x-rayreflectometer based on a laser-plasma source is described. Thereflectometer allows rapid and accurate characterization ofnormal-incidence multilayer coatings used at water-windowwavelengths. This instrument, which measures absolutereflectivity and multilayer period, is now used in thefabrication process, aiming to improve the soft x-raynormal-incidence multilayer condenser system of the compactsoft x-ray microscope. Latest results from the developmentprocess are presented.</p><p>A new design of the compact soft x-ray microscope, withimprovements in mechanical and thermal stability, providesuser-friendly and daily operation. This includes also a newnozzle design for the liquid-jet-target laser-plasma source,which enables higher source stability and operation withcryogenic liquids. In addition, a new experimental arrangementunder construction is briefly described. It will utilize acondenser zone plate and operate at the wavelength 2.478nm.</p><p>Finally, performance test of the compact soft x-raymicroscope is presented and discussed. In addition, a projectto explore the use of soft x-ray microscopy for imaging sensorycells is described. The high-resolution imaging of these cellswas performed at the synchrotron-based soft x-ray microscope atLawrence Berkeley National Laboratory (LBNL).</p>

L’observation d’échantillons biologiques à une échelle nanométrique est actuellement un thème majeur pour la biologie. En particulier, la microscopie à rayons X dans la fenêtre de l’eau (entre les seuils d’absorption K-alpha de l’oxygène et du carbone, soit entre 2,4 et 4,4 nm de longueur d’onde) présente un intérêt remarquable car elle permet à la fois l’observation d’échantillons biologiques avec un fort contraste d’absorption naturel, mais également une haute résolution grâce à la courte longueur d’onde d’utilisation. Plusieurs microscopes basés sur des composants diffractifs ont d’ores et déjà été développés et ont montré une résolution allant jusqu’à 12 nm. Dans ce contexte, nous développons au Laboratoire Charles Fabry un microscope X plein champ à miroirs en incidence proche de la normale. Le schéma optique du microscope a dans un premier temps été étudié et optimisé. Il est basé sur un objectif de Schwarzschild, et dispose donc d’une longue distance de travail ce qui permettra de faciliter l’installation de l’échantillon à observer. Les miroirs doivent être traités avec un revêtement multicouche à très faible période à base de chrome et de scandium. Plusieurs systèmes multicouches à couches sub nanométrique ont été étudiés pour maximiser la réflectivité des revêtements à une longueur d’onde proche de 3,14 nm, parmi lesquels : Cr/Sc, Cr/B4C/Sc, CrN/Sc et CrN/B4C/Sc. Une réflectivité pic de plus de 23% a été mesurée pour un revêtement multicouche CrN/B4C/Sc à un angle d’incidence inférieur à 5°. / The observation of biological samples at a nanometer scale is currently a major topic for biology. In particular, X-ray microscopy in the water-window (between Oxygen and Carbon K-alpha edges, corresponding to a wavelength between 2.4 and 4.4 nm) is off remarkable interest since it enables the visualization of biological samples with a natural high absorption contrast and a high resolution thanks to the short working wavelength. Several such x-ray microscopes have already been developed and showed resolutions down to 12 nm. In this context, we develop at Laboratoire Charles Fabry a full field, near normal incidence mirror based X-ray microscope. The optical design of the microscope was studied and optimized in a first place. It is based on a Schwarzschild objective, with a rather long working distance so that the installation of the sample will be facilitated. The mirrors are to be coated with very short period multilayer coatings containing chromium and scandium. Several multilayer systems with sub-nanometer thick layers ere studied in order to obtain the highest reflectance possible near normal incidence at a wavelength near 3.14 nm. Those systems were Cr/Sc, Cr/B4C/Sc, CrN/Sc and CrN/B4C/Sc. A peak reflectance of 23% has been measured for CrN/B4C/Sc at an incidence angle lower than 5°.

La tomographie par rayons X est une technique d’imagerie non-invasive qui permet de réaliser des images en 3D par l’acquisition de multiples images en 2D. La tomographie X par contraste de phase (XPCT) a été utilisée pour étudier la biodistribution de nanoparticules métalliques (NPs) dans des souris. Ces NPs sont très utilisées comme radiosensibilisants dans la recherche de traitements contre les cancers mais aussi pour marquer des plaques amyloïdes de la maladie d’Alzheimer chez la souris. Grace à la grande brillance du synchrotron ESRF, des images XPCT en haute résolution ont été obtenues et traitées pour produire des modèles en 3D d’organes de souris dopés aux NPs de gadolinium, d’or ou de platine.En parallèle, dans le cadre du projet Européen VOXEL (Volumetric X-ray Extremely Low dose), un microscope compact à rayons X mous a été développé pour l’imagerie cellulaire. Ce microscope fonctionne dans la « fenêtre de l’eau », une région spectrale pour laquelle un bon contraste de la structure cellulaire est réalisable naturellement. Ce microscope est conçu pour réaliser de l’imagerie plénoptique, une technique actuellement testée uniquement dans le visible. Ce système est composé d’une lentille principale et d’une matrice de micro-lentilles couplée à un détecteur, permettant d’enregistrer les composantes angulaires et spatiales des rayons arrivant au niveau du détecteur. Il est ainsi possible de produire des images en 3D à partir d’une seule exposition. Adapter cette technique disruptive aux rayons X aura, un très grand impact pour les applications biomédicales car cela permettra de réduire fortement la dose absorbée par les échantillons par rapport à la méthode conventionnelle de tomographie X. / X-ray tomography is a non-invasive imaging technique that allows producing 3D images following the acquisition of multiple 2D images at many angles. In particular, X-ray Phase-Contrast Tomography (XPCT) has been exploited for resolving the biodistribution of metal-based theranostic nanoparticles (NPs) in mice. These NPs are widely used as radiosensitizers for researches on cancer therapies and, recently to mark amyloid plaques in Alzheimer’s disease in mice. Thanks to the high brightness of ESRF synchrotron, high resolution XPCT images were obtained and thus processed for producing 3D models of mice organs doped with gadolinium, gold or platinum NPs.In parallel, in the framework of a European project, named VOXEL (Volumetric X-ray Extremely Low dose), a compact desktop-size soft X-ray microscope was developed aiming at biological cell imaging. The microscope was designed to be suitable in the so-called “water window” spectral range, where a natural good contrast of the cellular structures is achievable. The microscope was conceived to perform plenoptic imaging, a technology currently tested only in the visible domain. This device is composed of a main lens and a microlens array coupled to a detector, allowing recording the spatial and the angular components of the light rays travelling up to the detector and thus enabling producing 3D images in a single exposure. By adapting this disrupting technology to X-rays, a huge impact for bio-medical applications is foreseen, since it would lead to a drastic decrease of the dose absorbed by samples, compared to traditional X-ray tomography methods.

Mit der Erfindung des Lasers wurden kohärente Lichtquellen allgemein verfügbar. Technische Fortschritte bei Pulsleistung und Pulsdauer ermöglichen linearer und nichtlinearer Wechselwirkungen von Licht und Materie auf ultrakurzen Zeitskalen zu untersuchen. Die Erzeugung von hohen Harmonischen is heutzutage viel verwended um den lichtblitze im extremen Ultraviolett mit bis zu attosekunden pulsedauern zu erzeugen. Diese Methode wurde kürzlich für Spektroskopie mit weicher Röntgenstrahlung erweitert. In dieser wird ein ein Anregungs-Abfrage Aufbau vorgestellt, in dem Höhere Harmonische im weichen Röntgenspektralbereich erzeugt und als ultrakurze Abfrage-Pulse genutzt werden. Ein neu entworfenes Röntgenabsorptionsspektrometer ermöglicht die bisher beste Auflösung und den besten detektierten Fluss an der K-Kante von Stickstoff. Der Aufbau wird genutzt, um die Ionisationsdynamik von diatomarem Stickstoff auf Femtosekunden-Zeitskalen und die anschließende Pikosekunden-Plasmadynamik zu untersuchen. Im Bereich des "Air Lasing", in dem das Lasern von Stickstoff-Ionen, die durch Starkfeld-Ionisation entstehen, untersucht wird, werden neue Erkenntnisse gewonnen. Der geringe Absorptionsquerschnitt von Wasser zwischen den K-Kanten von Kohlenstoff und Sauerstoff, bekannt als Wasserfenster, ermöglicht die Untersuchung von Molekülen und Ionen in wässriger Lösung. Es werden die ersten in eine laser labor gemessenen stationären weichen Röntgenspektren für Ionen und molekulare Systeme in wässriger Lösung vorgestellt. Darüber hinaus wird der Ansatz auch für transiente Absorptionsspektren angewendet. Zusätzliche Daten von Strahlzeiten an Großgeräten ermöglichen einen Vergleich der Methoden. Schließlich werden Ergebnisse von BESSY II zur Untersuchung der Struktur und lokale Umgebung von Protonen in Wasser vorgestellt. Die K-Kanten-Spektroskopie von Protonen-Wasser-Komplexen in Acetonitril vorgestellt erlaubt es die elektronische Struktur der beteiligten Moleküle besser zu verstehen. / The invention of the laser made coherent light sources widely available. Technical advances in pulse power und pulse duration allow the study of linear and nonlinear interactions of light and matter and ultrashort time scales. The highest nonlinear frequency up-converting process, High-order harmonics generation, is today the standard for up to attosecond short table-top sources. This method has been recently applied for ultrafast spectroscopy in the soft x-ray water window. In this thesis, a table-top high-order harmonics setup is presented and used for pump-probe spectroscopy in the water window. A home-built soft x-ray absorption spectrometer enables the so far best resolution and detected flux at nitrogen K-edge. The setup is utilized to study ionization dynamics of diatomic nitrogen on femtosecond time scales and the subsequent picosecond plasma dynamics. In the realm of air lasing, where lasing in nitrogen ions formed by strong field ionization is studied new insides are provided, narrowing down possible theoretical interpretations. The low absorption cross section of water between the carbon and oxygen K-edges known as the water window, enables to investigate molecules and ions in aqueous solution. The first steady-state soft x-ray spectra are presented for ions and molecular systems in aqueous solution recorded with a table-top laser based setup. Furthermore, the approach is also applied for transient absorption spectra. Additional data from beamtimes at large scale facilities allow for a comparison of the approaches. Finally, spectroscopic results taken at BESSY II are presented. The structure and local environment of excess protons in water is studied for more than two centuries and are still controversially discussed. Investigating proton-water complexes in acetonitrile with oxygen K-edge spectroscopy allows for a local probing of electronic orbital interactions and electric field effects on the electronic structure of the participating water molecules.

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