This PDF file contains the front matter associated with SPIE Proceedings Volume 11886, including the Title Page, Copyright information, and Table of Contents.

The 17th International Conference on X-ray Lasers (ICXRL 2020) was a milestone in several ways. Firstly, was a milestone in this scientific community because for the first time the conference came to the participants' home, due to the outbreak of the pandemics, rather than the opposite. The organization of an online event was a challenge because was a brand new platform for both the organizers and the participants, and because it was put together in less than six months. The planned physical event in Rome, already tested with one year in advance, had to be withdrawn as it posed major risks to potential participants. ICXRL 2020 was milestone also because the increased proportion of papers on technological deployment of X-ray lasers. Of course, research on fundamentals and innovation still carried an important part of this thirtyfour year event. Finally, ICXRL 2020 was a milestone also because there were participants from all five continents, no one excluded, and some were forced to incredible efforts to stay up and present their research. A great sign of inclusion. Last but not least, ICXRL 2020 saw four best presentation "Pierre Jaeglé" awards, equally split between female and male students: Adeline Kabacinski (LOA, France), Lydia Rush (CSU, USA, see ref. [33]), Felix Wiesner (FSU, BRD), Julius Reinhard (HIJ, BRD). Another great sign of inclusion.

The series of the International Conference on X-ray Lasers was initiated by Pierre Jaeglé in 1986. Pierre passed away in November 2019 at the age of 88. He is recognized as one of the passionate pioneers of the field of X-ray lasers. In this paper I will remind some of his major scientific achievements, which contributed to the emergence of ultrashort coherent XUV sources generated from intense lasers.

In this paper we tell the story of the X-ray laser, which began as an attempt to extend optical lasers to shorter wavelengths in the 1970’s. Research took off in the 1980’s driven by the rivalry between the United States and Soviet Union in their quest to create a “Star Wars” laser shield against ICBM’s. At the same time large inertial fusion confinement (ICF) lasers, such as Novette and Nova at LLNL, were able to create the first laboratory X-ray lasers in Ne-like Se at 20.6 and 20.9 nm using 2 kJ of energy in a 0.5 ns pulse. These large ICF lasers could only be fired every few hours and used very thin expensive exploding foils as the targets. With the demonstration of the pre-pulse technique at Nova, where a small pulse of a few joules heated a solid target and create a pre-plasma that was then be heated by a second large pulse to create the lasing conditions, X-ray lasers started working robustly at many laser facilities around the world. The advent of high repetition rate psec lasers combined with the pre-pulse technique and grazing incident geometry opened the door to the many table-top X-ray lasers today which can be driven by less than 1 J of energy and operate at 100 Hz repetition rates. This has opened many new research opportunities for scientific research using X-ray lasers.

Almost contemporaneously with the building of the first optical laser at wavelength 694 nm in 1960, theoretical speculation and experiments were underway to produce lasing at shorter wavelengths in the x-ray range. This paper presents a brief review of plasma-based x-ray lasers. Plasma-based x-ray laser research has increased understanding of the atomic physics of plasmas and developed a suite of short wavelength lasers suitable for applications. The history of the development of soft x-ray lasers created by the irradiation of solid targets with pumping optical pulses is examined after setting the work in context with a summary of work covering a broad range of short wavelength coherent sources. The results of methods developed to characterise plasmas-based soft x-ray lasers are discussed.

Compact, repetitively fired, gain-saturated x-ray lasers have been limited to wavelengths above λ=8.85 nm. Here we discuss their extension to λ = 6.85 nm by transient traveling wave excitation of Ni-like Gd ions in a plasma created with an optimized pre-pulse followed by rapid heating with an intense sub-ps pump pulse. Isoelectronic scaling also produced strong lasing at 6.67 nm and 6.11 nm in Ni-like Tb, and amplification at 6.41 nm and 5.85 nm in Ni-like Dy.

Design and development of a compact chirped pulse amplification (CPA) laser is presented. This system will be used to generate coherent tabletop X-rays based on laser-produced plasmas (LPP) for round the clock advanced spectroscopy. The building blocks of the laser are shown and the results from the front-end are laid out. The progress on the amplification stages is presented with a scheme to extract compressed 15 J laser pulses at the output which are to be characterized and hit on rotating target for generating a plasma with enough population inversion (Ne-like or Ni-Like) as such to enable the emission of Soft X-rays. Soft X-rays laser lines from different targets will be characterized and used for different spectroscopy experiments.

Three main paths have been selected within the ELI Beamlines research program for transforming driving laser pulses into brilliant beams of short wavelength radiation: High-order harmonic generation in gases, Plasma X-ray sources, and sources based on relativistic electron beams accelerated in laser-plasma. For each of these research areas, dedicated beamlines are built to provide a unique combination of X-ray sources to the user community. The employment of these beamlines has a well-defined balance between fundamental science and applications in different fields of science and technology. Besides those beamlines, a plasma betatron radiation source driven by the PW-class HAPLS laser system is being commissioned in the plasma physics platform to serve as a unique diagnostic tool for dense plasma and warm dense matter probing.

There is a large performance gap between conventional, electron-impact X-ray sources and synchrotron radiation sources. An Inverse Compton Scattering (ICS) source can bridge this gap by providing a narrow-band, high-flux and tunable Xray source that fits into a laboratory. It works by colliding a high-power laser beam with a relativistic electron beam, in which case the energy of the backscattered photons is in the X-ray (or gamma-ray) regime. Here we present a new conceptual design for an ICS source that is more than two orders of magnitude brighter than the Lyncean Compact Light Source (CLS) currently in user operation. Depending on configuration, this next generation CLS covers an X-ray energy range of about 30-90 keV, or 60-180 keV. It will provide X-ray flux of up to 4 x 1012 photons/s within a beam divergence of 4 mrad and a bandwidth of around 10%. This is well-suited for micro-CT imaging of millimeter-sized samples at micron resolution, with a flux density similar to some high-energy synchrotron beamlines. The beam properties of the new design are also compatible with narrower bandwidth, focused beam applications such as high-energy diffraction. We discuss the novel concepts applied to the design of this X-ray source as well as the resulting beam properties. We present application examples in the areas of imaging, diffraction, and radiotherapy where this system can approach or match the performance of synchrotron beamlines. This will allow transferring many research, industrial and medical applications from the synchrotron, where capacity and access are limited, to a local lab or clinic.

We present a new interferometric technique for gas jets density characterization employing a Wollaston shearing interferometer. The distinctive feature of this setup is the double pass of the probe beam through the gas target facilitated by a relay-imaging object arm that images the object on itself and preserves the spatial information. The double pass results in two-fold increase of sensitivity at the same time as the relay-imaging enables the characterization of gas jets with arbitrary gas density distribution by tomographic reconstruction. The capabilities of the double-pass Wollaston interferometer are demonstrated by tomographic density reconstruction of rotationally non-symmetric gas jets that are used as gas targets for the betatron X-ray source at ELI-Beamlines.

We report temporal coherence measurement of solid-target plasma-based soft X-ray laser (XRL) in amplified spontaneous emission (ASE) mode. By changing the XRL pumping angle, we generate lasing at two-times higher electron density than the routine condition. A relatively shorter coherence time at a higher pumping angle indicates a clear spectral signature of higher electron density in the gain region. We probe the amplification dynamics of XRL in routine, and high electron density conditions to confirm gain-duration reduction resulting from ionization gating in the latter case. We also present recent results on the seeding of a vortex beam carrying orbital angular momentum (OAM) in XRL plasma. A small part of the high topological charge extreme ultraviolet (EUV) vortex is injected in XRL. These preliminary results suggest that the vortex seed indeed can be efficiently amplified. In the end, we propose a pathway towards the seeding of the complete vortex beam and wavefront characterization of the amplified beam.

Optical field ionized (OFI) plasma amplifiers have recently demonstrated sub-picosecond pulses when seeded with high order harmonics. In addition to this, the intensity and phase profile of the amplified harmonic beams carry information about possible plasma inhomogeneities (electron density, lasing ion abundance) that may appear in the amplifier. 1D and 3D modelling has played a fundamental role in these results and it will be required to support present and future experiments. This modelling involves different physical processes and time-scales, from the nanoseconds (hydrodynamics) to the picoseconds (atomic physics) and femtoseconds (dynamics of the amplified beam). Here we briefly present the different codes that have been coupled to fully model this process, from the creation of the plasma to the amplification of XUV and soft X-rays and show how this framework can be applied to study the impact of plasma inhomogeneities in the intensity and phase profile of the amplified beam.

This paper presents a brief review of the x-ray laser development at the Institute of Laser Engineering, Osaka University, implemented with worldwide collaboration. The scaling of the x-ray lasing toward shorter wavelengths has been investigated in the recombination-pumped (RP) and electron-collisional-excitation (CE) pumped x-ray lasers. Extension of the RP x-ray laser close to the water window is described. With the CE x-ray laser, intense lasing of the J = 0-1 line at 19.6 nm in the neon-like Ge ion and lasing over 14.3 – 4.5 nm with the nickel-like ions are reported. Spectroscopic studies of the x-ray lasers are described, including the first observation of polarization of the x-ray laser beam generated by amplified spontaneous emission. The perspective of the plasma-based x-ray lasers is also presented.

The advent of extreme ultraviolet (EUV) and soft x-ray free electron lasers (FELs) has enabled nonlinear optical experiments at wavelengths shorter than the visible-UV range. An important class of experiments is those based on the four-wave-mixing (FWM) approach, which are often based on interactions between pulses at different wavelengths. The exploitation of multiple EUV/soft x-ray wavelengths is not straightforward, but it can significantly expand the range of applications. In this manuscript we report on an experimental approach, based on the concomitant use of a non-collinear split-delay-and-recombination unit (“mini-Timer”) and on a two-color seeded FEL emission scheme (“twin-seed mode”). We used a diamond sample for demonstrating the capability of this setup of generating and detecting a FWM signal stimulated by two-color EUV FEL pulses. This approach can be further exploited for developing experimental methods based on non-linear EUV/x-ray optics.

Studies of the generation and propagation of light fields in the extreme ultraviolet (XUV) can provide insights into the fundamental interaction of atoms in highly excited levels and ionized atoms. In this paper, we present experimental results of nonlinear four-wave mixing (FWM) processes using a combination of XUV radiation and optical pulses in argon gas. The XUV pulses are produced by phase-matched high-order harmonic generation (HHG). Optimized phase-matching of collinear multiple-cycle laser pulses with incommensurate frequencies (800 nm, 1400 nm, and 560 nm) is used to indicate the different pathways of the third-order and fifth-order nonlinear responses in the mixing process in a single gas cell configuration. A perturbative nonlinear optics approach can be used to explain our cascaded wave-mixing patterns. Our results reveal that the time-dependent spectral features of the mixing fields are associated with auto-ionization processes. Overall, the intensity and frequency modulation of the wave-mixing fields provides a new technique to investigate the dynamical evolution of electron wave-packets in atomic and molecular gases.

Solid-state high harmonic generation (SSHHG) is a relatively recent non-destructive technique that offers new insight into the dynamics of strong-field light-matter interaction. At the same time, SSHHG holds promise for being a viable route to engineering innovative, flexible, compact sources with emission in the extreme- ultraviolet (XUV) spectral range. The technique has already been shown to yield XUV light, albeit with low conversion efficiencies, as compared to the more traditional gas-based high harmonic generation (HHG) sources. In this work we demonstrate that a non-collinear, multicolor SSHHG arrangement leads to spectra in the XUV with a high degree of tunability, and a considerable enhancement of the output flux. The observed behaviour can be understood in terms of perturbative optical wave mixing over more than one order of magnitude of the drive intensity. In addition, a model based on the recently-introduced injection current allows accurate predictions over the entire experimental range.

The reflection of a laser pulse by a relativistic-moving mirror is one of the fundamental problems encountered in highpower laser and plasma interactions. It is well known that a laser pulse reflected by a relativistic-flying mirror experiences the intensification, frequency up-shift, and shortening of pulse duration. Thus, it is of fundamental interest to have a mathematical solution expressing the intensity distribution of a laser pulse reflected by a relativistic-flying parabolic mirror. In this paper, we present analytical and mathematical formulae describing the electromagnetic field of a laser pulse reflected and focused by the relativistic-flying parabolic mirror.

We discuss a method for controlling the spectral and temporal characteristics of x-ray radiation produced by a radioactive or synchrotron Mӧssbauer source via its propagation through an optically thick sample of resonant nuclei with a modulated transition frequency. Such modulation is achieved via a Doppler frequency shift due to vibration of the recoilless absorber. We show that this technique can be used both for effective elimination of the resonant absorption (acoustically induced transparency) and temporal shaping of an individual photon, including the production of short pulses. A similar technique can be used for formation and amplification of attosecond pulses in the active medium of a plasma-based x-ray laser, where the resonant transition frequency of ions is modulated by a sufficiently strong infrared field.

The Hartmann wavefront sensor is able to measure, separately and in absolute, the real δ and imaginary parts β of the X-ray refractive index. While combined with tomographic setup, Hartmann sensor opens many interesting opportunities behind the direct measurement of the material density. In order to handle the different ways of using an X-ray wavefront sensor in imaging, we developed 3D wave propagation model based on Fresnel propagator. The model is made in a way to manage any degree of spatial coherence of the source, thus enabling to model accurately experiments using tabletop source, high harmonic generation, plasma-based soft X-ray laser, synchrotron or X-ray free-electron laser. Beam divergence is described in a physical manner consistent with the spatial coherence. The capabilities of the Hartmann wavefront sensor will be compared with experimental results from in-line X-ray Phase Contrast Tomography.

In recent years, integral imaging has received increasing attention as a promising 3D imaging technique with one single exposure. In medical diagnostics, the X-ray integral imaging system potentially has a much shorter exposure time than the conventional computed tomography, reducing the radiation damage to the patient. By replacing the micro-lens array with a micro-Fresnel Zone Plate (FZP) array, the classical visible integral imaging system can be transposed to an X-ray system. However, limited by the micro-scale dimensions of FZP in the array and current manufacturing techniques, the number of zones of FZP is required to be small. This may have an important impact on the FZP imaging performance. Based on the scalar diffraction theory, this paper introduces a simulation method and numerically investigated the effect of the number of zones on the FZP imaging performance under different coherence conditions.

We present an experimental intensity and wavefront characterization of the infrared vortex driver as well as the extreme ultraviolet vortex obtained through high harmonic generation in an extended generation medium. In a loose focusing geometry, an intense vortex beam obtained through phase-matched absorption-limited high harmonic generation in a 15 mm long Argon filled gas-cell permits single-shot characterization of the vortex structure. Moreover, our study validates the multiplicative law of momentum conservation even for such an extended generation medium.

We report on the use of multilayer Laue lenses to focus the intense X-ray Free Electron Laser (XFEL) beam at the European XFEL to a spot size of a few tens of nanometers. We present the procedure to align and characterize these lenses and discuss challenges working with the pulse trains from this unique x-ray source.

We report on the development and implementation of a diagnostic for the temporal characterization of seeded XUV laser pulses, based on laser-dressed photoionization in the sideband regime, using a home-made velocity map-imaging spectrometer as the central element. The diagnostic was recently tested at the LASERIX facility with the seeded Ne-like titanium laser at 38 eV as the XUV source, overlapped with an infrared pulse of variable duration and intensity.

We demonstrate single-shot Fourier transform holography with a 7 μm diameter field of view and picosecond time resolution using a highly coherent ~5 ps pulse duration tabletop Ni-like molybdenum soft X-ray laser at 18.9 nm wavelength. The essentially full spatial coherence soft X-ray source with close to diffraction-limited divergence was implemented utilizing a dual-plasma amplifier scheme. The high flux illumination of ~ 2×1011 photons per pulse was split using a Fresnel zone plate to generate the object and reference beams creating high contrast Fourier transform holograms. The final image was numerically reconstructed by 2D Fourier transform. A minimum half-pitch spatial resolution of 62 nm was obtained.

Lensless imaging requires coherent illumination, which is typically available at beamlines. A study of lensless imaging with a table-top X-ray laser is presented, comparing two alternative data-processing techniques, i.e. using the near and the far field data. In order to have a consistent comparison, a Fresnel zone plate was studied as object, because its modulated structure permits to obtain both Fresnel (near field) and Fraunhofer (far field) pattern simultaneously. Results show factor of 3 difference in imaging resolution, and a major limitation given by the degree of the illumination homogeneity.

Laser-plasma accelerators (LPAs) are known to intrinsically produce broad-bandwidth X-rays through the transverse motion of the accelerated electrons in the plasma wakefield. Due to the compact dimensions of the wakefield structure, this motion results in betatron radiation emission from a small point-like source (of order 1 µm in transverse size). Such a small source size enables high spatial resolution single-shot phase-contrast imaging, even for broad photon-energy spreads, simply by propagating the X-rays through a sample and onto a two-dimensional detector. In this manuscript we study, through simulations, the possibility to extend the resolution to the sub- micron regime. We find that the optimum geometry for <15 keV photons demands short (few-mm) drifts from source-to-sample, a photon flux of order 10⁹ photons/shot, and the necessity to take the longitudinal source dimension into consideration. The presented framework behind the simulations will guide future betatron source development. The same expressions are also valid for other point-like LPA radiation sources such as Thomson- and Compton-scattered radiation.

The short pulse laser ablation have been extensively studied for confirmation and discussion of damage formation including estimations of damage thresholds and probabilities of surface machining. Irradiation examines by the femtosecond soft xray laser reveals formations of smooth craters on silica glass surfaces, and the appropriate selection of the laser wavelength can make the nanometer size modification on silicon surface in the vicinity of the damage threshold. On the other hand, we also revealed that damage thresholds and modification structures obtained by the picosecond soft x-ray laser irradiation provide the same results as the femtosecond soft x-ray laser. This means that not only femtosecond but also picosecond soft x-ray laser irradiation experiments can be contribute to deep understandings of the ablation phenomena.

Recent developments on high-power compact extreme ultraviolet (EUV or XUV) sources have enabled us to study the materials ablation induced by the irradiation of intense EUV light. The interactions of EUV light with matters along the ablation have potential advantage for the use in advanced materials processing. We have studied the charge states and their energy distributions in the EUV ablation plasma using an E´B mass-charge analyzer. The measurement was also conducted for conventional laser ablation plasma induced by a 1064 nm Nd:YAG laser. The results showed noticeable difference between EUV and laser ablations, where EUV ablation only showed singly charged Si ions, and laser ablation showed multiply charged ions up to Si³⁺. The energy spectra of multiply charged ions were distributed in higher energy range. It has been predicted that EUV ablation plasma have higher electron density close to the solid density and lower electron temperature at 1 to few eV, while laser ablation plasma generally has lower electron density around the critical density and higher electron temperature exceeding 10 eV mainly by inverse bremsstrahlung absorption at an irradiation intensity around 10⁹ W/cm² range. Thus, ionization did not proceed much and only singly charged ions were detected for EUV ablation and the electron impact ionization proceeded to have multiply charged ions for laser ablation. This study showed that the experimental results reflected the general characteristics of the ablation plasma, and showed possibilities of modeling of entire EUV ablation dynamics from expanding ions.

In the extreme ultraviolet (EUV) regime, the photon energies are above the threshold for photo-ionization in all solid materials. We examine the absorption coefficients for inverse bremsstrahlung and photo-ionization and the contributions of these processes to EUV absorption under different ionization models. The Saha- Boltzmann ionization model is considered with and without continuum lowering, as well as a novel rate equation model including the photo-ionization transitions in population calculations. We show that photo-ionization plays a significant role early in EUV ablation of solids, but inverse bremsstrahlung absorption dominates once temperatures in the ablated plasma exceed more than a few electron volts.

The paper deals with an analytical study of the problem of pore detection and certification in bulk materials by means of X-ray radiography. The optimum thickness of a sample under X-ray absorption investigation of the pores is found, that can be used for an improvement of the signal-to-noise ratio by the proper X-ray photon energy. In the case of low absorption an X-ray coherent beam can be used for production of phase contrast in the radiographic experiments. We present a simple model to calculate the complex value of the wave field formed by the sample. The model includes two dimensionless parameters: the Fresnel number F= a²/(λz), where a is the pore radius, λ is the wavelength, z is the sample-to-detector distance and the phase number Φ = akδ, where k = 2π/λ and δ is the decrement of the real part of material's relative permittivity. The detailed analysis of the field structure is given with an estimation of the optimal position of the detector. The numerical simulation results are presented as well, which were obtained for the Gaussian type of the pore shape function. The stationary phase method of higher orders has been proven to simplify the Fresnel integral. The developed qualitative visualization of the pores with the help of phase contrast X-ray imaging complements other modern methods of monitoring porous-sensitive materials.

Boron carbide coatings were prepared by reactive sputtering with nitrogen and investigated for their optical properties. Different ratios of N₂/Ar (4%, 8%, and 15% nitrogen ratio) mixture gas was chosen as the sputtering gas. The atomic concentration distribution and elemental chemical states of coatings were characterized by X-ray photoelectron spectroscopy measurements. The B/C ratio was 3.7:1 and the nitrogen content was 18 at.% in the coating, which was sputtered with 4% N₂ mixture gas. And the nitrogen content was increased as the ratio of N₂ increases in mixture gas. In the nitridated B₄C coatings, the boron mainly existed as the formation of BN and B4C compounds. The theoretical reflectivity was performed, and the increase of nitrogen content would reduce the reflectivity in the soft X-ray, especially in the vicinity of 410 eV.

The standard approach to surface analysis is X-ray photoelectron spectroscopy (XPS), which is used to follow electronic structure changes of the catalyst material TiO₂ upon hydrogenation, however, without conclusion whether the effect can be traced back to the hydrogen treatment. Resonant photoemission experiments using a tunable synchrotron X-ray source yields further insights. The integration of the electron yield over all kinetic energies results in X-ray absorption spectra (XAS). Furthermore, in resonant conditions, electrons are excited from a core level to the conduction band and can subsequently be trapped by specific defect states. From this, the observed shallow trap states can be identified as Ti³⁺ states. We quantify the Ti³⁺/Ti⁴⁺ ratio both from XPS and XAS and the oxygen to titanium elemental ratio. The correlation of the results from resonant and non-resonant photoemission reveals that hydrogen defects serve as trap centers, while defects associated with oxygen vacancies serve as recombination centers suppressing trap state emission. The main effect of hydrogen in TiO₂ is the increased disorder in the material.

Laser-induced breakdown spectroscopy (LIBS) is an elemental analysis method thanks to minor sample preparation, rapid analysis, and a spatially resolved sensitivity down to trace level in any kind of sample matrix. State-of-the-art LIBS is operated in the optical spectral range (UV-Vis). Unfortunately, the application of LIBS in material detection is limited by the low precision and repeatability. This is particularly critical for inhomogeneous materials and alternative methods are desirable. Light elements such as Li, as well as F, are difficult to be characterized. The dual LIBS performance was initially studied in a simpler matrix such as LiF, radially collecting simultaneously the XUV and OES spectra from the same laser shot. For the case of LiF, XUV signals proved significantly more stable than in the case of LIBS-OES. The signal of F can be also seen clearly in the spectrum. Observation of the plasma emission at even shorter wavelengths in the extreme ultraviolet (wavelength range 5-20 nm) is supposed to improve the state-of-art limitations of LIBS.

Short-wavelength (λ < 160 nm) Raman spectroscopy offers an advantage of a generally higher sensitivity than Raman spectroscopy in the visible range. An application with high potential is its use for environmental water analysis targeting archetypal compounds that are present in industrial and urban sewage water. However, this application is feasible only if specific performance benchmarks are met. We validate the applicability of a simple and cost-effective deep-UV Raman spectrometer (λexc = 236.5 nm). The analysis brings to the fore that the experimentally derived detection limits the studied archetypal compounds are to high by several orders of magnitude. We outline potential further development and associated limitations. These are the deterioration of the analysed species by photolysis as a consequence of the high photon energy and intensity, and the self absorption of the UV radiation. These effects are explained and partially corrected along a simple mathematical model from which a general limit of detection is estimated.

Extreme ultraviolet (EUV) lasers possess unique properties for ablation and ionization at the nanoscale (≤100 nm) due to their short wavelength, high absorptivity in most materials (i.e., 10’s of nanometers), and efficient photoionization in the laser-created plasmas. When coupled with a mass spectrometer, an EUV laser can be used to analyze and map chemical information in three dimensions with nanoscale spatial resolution. We have previously built an EUV time-of-flight mass spectrometer (EUV TOF) that achieved ~80 nm lateral and ~20 nm depth resolution when mapping the chemical content in organic and inorganic solids. Here, we present results from a recent study that extends EUV TOF’s high resolution capabilities to the analysis of an isotopically heterogenous uranium fuel pellet that was made by blending two isotopically distinct starting materials. We show that EUV TOF can map ²³⁵U/²³⁸U heterogeneity at the 100 nm scale, revealing micron to submicron heterogeneity. For comparison, nanoscale secondary ionization mass spectrometry (NanoSIMS) maps a similar distribution of U heterogeneity on a similar subsample at the same spatial scale. We also show that EUV TOF can measure the isotope ratio in a silver sample using single shot spectra. These results position EUV TOF as a promising technique for performing isotopic analyses at the nanoscale, finding applications in nuclear forensics, geology, and biology as well as in the semiconductor industry.

Extreme ultraviolet laser ablation mass spectrometry (EUV LA-MS), developed at Colorado State University, uses EUV laser wavelengths instead of traditional visible lasers, allowing sub-micron ablation spot sizes while maintaining a good sensitivity for trace element analysis. In this paper, we have explored the capabilities of this device as a non-perturbative technique to measure the temperature of the laser-produced plasma after the laser interaction. Mass spectra obtained from silver, aluminium, gold and silicon samples were used to identify and quantify the ion population created. Additionally, the ionization ratios were calculated and input in a coronal ionization equilibrium model to calculate the effective temperature of the plasma after the ablation process. Temperatures ranging 1.35 to 1.84 eV were measured for the different materials, with heavier elements having lower temperatures than the lighter ones.

We present advanced instrumentation for the investigation of thin organic films offered by a laboratory X-ray absorption fine structure (XAFS) spectrometer for the soft X-ray range. The transmission spectrometer is based on a laser-produced plasma source in combination with a twin-arm reflection zone plate spectrometer. The efficiency and stability of the spectrometer allow for single shot measurements within 500 ps with a resolving power of E/ΔE ~ 900 in a range between 200 eV and 1300 eV. Through the implementation of an optical pump beam, also transient absorption measurements can be performed. The merits of the spectrometer are demonstrated through the investigation of poly[(9,9-dioctylfluorenyl- 2,7-diyl)-alt-co-(1,4-benzo-{2,1‘,3}-thiadiazole)] (F8BT), a polyfluorene copolymer. Transient optical pump soft X-ray probe spectroscopy with 500 ps time resolution detects changes in the C K edge spectrum which can be attributed to the lowest unoccupied molecular orbitals of the molecules in the benzothiadiazole unit.

Laboratory based laser driven short pulse X-ray sources like laser produced plasmas (LPP) and high harmonic generation (HHG) exhibit a great potential for spectroscopy in the soft X-ray range. These sources are complementary to large scale facilities like synchrotrons or free electron lasers. For applications of LPP or HHG sources for time-resolved X-ray absorption spectroscopy in the water window or beyond a high photon flux is crucial. The available photon flux strongly depends on energy, pulse duration and repetition rate of the pump laser. Depending on the experimental needs in timeresolved experiments pulse durations of the X-ray pulse ranging from nanoseconds to sub-femtoseconds are required. In our contribution we will present a highly brilliant LPP source emitting soft X-rays in the photon energy range between 50 and 1500 eV based on CPA and thin disk laser technology as well as the high average power thin disk laser based OPCPA system for high photon flux HHG. In addition we present a new generation of reflection zone plates on spherical substrates, that promises a remarkable high resolution over a wide spectral range making it an ideal and highly efficient diffractive optic for time-resolved NEXAFS experiments in the lab.

X rays have been used for medical imaging since RÖNTGEN's fascinating discovery 125 years ago. The first radiographs of human hands were made public less than a month after his famous paper. The conventional X-ray sources integrated into the CT-machines of today’s hospitals still rely on the same physical principles. X-ray imaging has traditionally offered high spatial resolution and low contrast for soft tissues such as the brain. Magnetic resonance imaging is therefore the method of choice for brain imaging in a clinical setting, although for cellular resolution studies it suffers from limited spatial resolution. The gold standard in post mortem brain imaging is histology, which involves fixation, embedding, physical sectioning, staining, and optical microscopy. Currently, section thickness limits isotropic voxel sizes to 20 μm. Advanced X-ray sources including synchrotron radiation facilities offer complementary modalities such as phase-contrast imaging and spatially resolved small-angle X-ray scattering. We showed that X-ray phase contrast of the human cerebellum with micrometer resolution yields complementary three-dimensional images to magnetic resonance microscopy with even better contrast and spatial resolution. Grating interferometry enabled us to visualize individual Purkinje cells in the nonstained cerebellum. Taking advantage of well-established paraffin embedding, Purkinje cells were visualized within the human cerebellum even with conventional instrumentation. Hard X-ray nano-holotomography allowed for label-free, three-dimensional neuroimaging beyond the optical limit with a spatial resolution below 100 nm. Spatially resolved smallangle X-ray scattering permitted the localization of periodic nanostructures such as myelin sheaths on square-inch brain slices and included the orientational information on the axons. These developments have contributed to the establishment of virtual histology and extended the conventional histology to the third dimension. Further advances are required to image the entire human brain with an isotropic micrometer resolution and to suitably handle the petabyte datasets.

Hard X-ray micro computed tomography can be used for three-dimensional histological phenotyping of zebrafish embryos down to 1 µm or below without the need for staining or physical slicing. Current advances in ze- brafish embryo imaging, however, mostly rely on synchrotron radiation sources or highly advanced laboratory sources, which despite their evident strengths with regard to their beam properties and the implementation of phase contrast imaging techniques, lack accessibility. Therefore, we evaluated the performance of a conventional SkyScan 1275 laboratory µCT scanner in absorption contrast mode for the visualization of anatomical features in ethanol- and paraffin-embedded zebrafish embryos. We compare our results to readily available synchrotron data where 35 anatomical structures were identified. Despite having a more than ten times larger voxel length, approximately two thirds of the features could also be determined with laboratory microtomography. This could allow to monitor morphological changes during development or disease progression on large sample numbers, enabling the performance of preclinical studies in a local laboratory.

To date there have been only indirect indications of the presence of bound sodium accumulation in muscle and skin tissues. Despite their osmotic inactivity, such sodium deposits can effect on mechanical properties of the heart muscle impairing its elasticity and leading to serious heart dysfunctions. In this work an accurate study of the chemical composition of the heart muscle tissue at the cellular level was carried out using the methods of X-ray absorption and fluorescence microscopy. The experiments were carried out on a TwinMic X-ray scanning microscope [3] at ELETTRA synchrotron (Italy) with a resolution of about 1 μm. Comparison of the obtained maps of intra- and extracellular sodium distribution in heart tissues of different laboratory animals has resulted in the first experimental confirmation of the hypotheses about the existence of deposited sodium states in the intercellular space. The paper demonstrates an example of the state-of-the-art medical applications of high spectral brilliance X-ray sources.