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The temporal, spectral, and angular characteristics of the x-ray emissions (photons with energies within 5–1000 keV) are exhaustively investigated during the discharge formation at voltages up to 1 MV in approximately 55 cm air gaps. The temporal correlations between the x-ray emissions and discharge voltage and current waveforms are established. The evolution of the discharge plasma structures developing in the time periods of the x-ray generation is traced with a nanosecond resolution. Based on statistical data, theoretical analysis, and estimates the regularities in the x-ray emission characteristics are revealed together with their relationship with the ionization processes occurring in the gas-discharge medium. On the basis of the obtained experimental data, the probable x-ray generation mechanisms are discussed. The findings can provide a deeper understanding of the physics behind the sources of hard x rays arising during the development of laboratory and atmospheric discharges. [ABSTRACT FROM AUTHOR]

The ability to visualize x-ray and neutron emission from fusion plasmas in 3D is critical to understand the origin of the complex shapes of the plasmas in experiments. Unfortunately, this remains challenging in experiments that study a fusion concept known as Magnetized Liner Inertial Fusion (MagLIF) due to a small number of available diagnostic views. Here, we present a basis function-expansion approach to reconstruct MagLIF stagnation plasmas from a sparse set of x-ray emission images. A set of natural basis functions is "learned" from training volumes containing quasi-helical structures whose projections are qualitatively similar to those observed in experimental images. Tests on several known volumes demonstrate that the learned basis outperforms both a cylindrical harmonic basis and a simple voxel basis with additional regularization, according to several metrics. Two-view reconstructions with the learned basis can estimate emission volumes to within 11% and those with three views recover morphology to a high degree of accuracy. The technique is applied to experimental data, producing the first 3D reconstruction of a MagLIF stagnation column from multiple views, providing additional indications of liner instabilities imprinting onto the emitting plasma. [ABSTRACT FROM AUTHOR]

Oblique shock wave–interface interactions of gases and liquids have been extensively studied in shock tubes using optical methods to measure equation-of-state (EOS) parameters. However, this is difficult with solids due to their opaqueness to visible light. X ray phase contrast imaging (XPCI) has the penetrative strength to probe solids while still being sensitive to mass density and enhancing the visibility of material boundaries. We investigate the accuracy and repeatability of measuring the mean value of the average mass density (areal density divided by thickness) over region S (B S) and flow deflection angle (θ) from XPCI images of a sample. To that end, a Hough transform-based method for measuring θ is developed. To measure B S , the XPCI image intensity probability density function (PDF) is modeled accounting for the spatial distribution of x ray energy, scintillator response, and pulse-to-pulse variation in the x ray intensity. In addition, a Monte Carlo-based algorithm for computing the B S PDF is developed. Both methods are validated on an impact-generated oblique shock wave interacting at a solid polymer-to-polymer interface. This is accomplished through a comparison to hydrodynamic simulations using well-established EOS. Under the modeling framework for the XPCI image intensity, B S is computed with an accuracy of < 0.1 % and precision of 3%–5%, while θ has an uncertainty of 0.2 ° , respectively. This shows that the XPCI-based model that is developed here could be an invaluable tool for high-fidelity testing of hydrodynamic models in shock polar configurations. [ABSTRACT FROM AUTHOR]

Millimeter-thick methylammonium lead tribromide (MAPbBr3) single crystal x-ray detectors have recently raised attention due to their high x-ray attenuation efficiency and good charge transport properties. However, an intriguing feature of the photocurrent response of MAPbBr3 detectors has been largely overlooked in the literature. After biasing, transient sensitivity is measured under x rays at short-circuit (bias = 0 V), thus revealing a large remnant electric field that builds up under bias. Here, we exploit the x-ray sensitivity of MAPbBr3 detectors at zero-bias in order to probe the internal built-in field, as well as to investigate the charge transport properties of the perovskite material. Our model derived from the Hecht equation is able to fully rationalize the response of the detectors both at short-circuit and under moderate applied bias. Moreover, we provide a method for the estimation of the internal electric field, and for the sum of the electrons and holes mobility–lifetime products μ e τ e + μ h τ h. This general method could extend to any perovskite-based x-ray detector exhibiting transient sensitivity at zero-bias. [ABSTRACT FROM AUTHOR]

We investigate the temporal correlation between very-high-frequency (VHF, at frequencies of the order of 10–100 MHz), ultrahigh-frequency (UHF, at frequencies within 1–6 GHz), and x-ray (with photon energies more than 10 keV) emissions, which accompany the development of a high-voltage discharge initiated in a long gap at voltages up to 1 MV. The x-ray and UHF emissions are found to emerge starting approximately from the prepulse current onset observed before the discharge gap breakdown and both gradually decay coming to this instant. The UHF emission spectrum is represented with frequencies up to 6 GHz, with the highest spectral power being achieved within 1–2 GHz. The radio emission power drops sharply at frequencies below 1 GHz and increases closer to 150 MHz with the highest spectral power of VHF radiation being reached within 60–90 MHz. The VHF emission can appear before the discharge current and UHF emission onsets in the form of 100-ns-long prepulses, and its intensity significantly increases as the UHF emission starts. The analysis of the temporal correlation between x rays, VHF, and UHF radiations, discharge current, and voltage waveforms indicates that the generation mechanisms of the discharge electromagnetic radiations are difficult to be interpreted in terms of the developing or colliding streamer concepts. [ABSTRACT FROM AUTHOR]

Three sets of heteroepitaxial diamond crystals grown under nominally identical process conditions on Ir/YSZ/Si(001) substrates have been studied with respect to structural defects, chemical purity, and x-ray induced photoconductivity (PC). The dislocation density that varied systematically between 10 7 and 10 9 cm − 2 had a minor influence on dark conductivity and photoconductive gain G. In contrast, the substitutional nitrogen (N N ) and substitutional boron (N B ) defects, which are both present at very low concentrations (≤ 1 ppb), turned out to be the crucial factors controlling the electrical behavior. Small differences between both resulted in variations of the photocurrents by up to 5 orders of magnitude. The maximum in G of 0.75 × 10 4 was measured in the sample with highest dark conductivity. It could be explained conclusively within our model calculations on gain formation by N N ≤ N B . For low gain samples, we found N N > --> N B . However, the measured G values were far from theoretical predictions. This indicates a dominating role of additional traps. After x-ray switch-off, persistent photoconductivity (PPC) was observed in high gain samples. It was attributed to an energetic barrier hampering the recharging of nitrogen atoms by hole capture. As a possible source, strain fields generated by dislocations are suggested. [ABSTRACT FROM AUTHOR]

X-ray radiography offers the ability to noninvasively inspect the internal structure and material composition of objects. Dual-energy radiography allows material discrimination but is limited in quantitative material measurements due to the broad nature of the interrogating x-ray spectrum. Spectral radiography detectors provide an observation of not just the number of x rays that are transmitted through a sample but also the spectrum. Here, experimental validations of a method to use spectral x-ray radiography to accurately quantify the uranium mass in a powder are presented. An accurate system response model was developed, which includes a model of the incident x-ray source spectrum and a pixel-wise detector response that describes how the transmitted x rays were observed. Further, a calibration to account for the effect of partial x-ray attenuation was developed. The method is demonstrated to be capable of estimating the uranium mass in a variety of uranium oxide powders to a bias of − 0.01 ± 0.62 %. [ABSTRACT FROM AUTHOR]

High-flux capable semiconductor x-ray detectors are essential in various applications, but the detrimental effects of detector polarization limit their use in many cases. Here, we studied the polarization of perovskite CsPbBr3 semiconductor detectors using ultrahigh flux synchrotron x rays (106–1012 photons s−1 mm−2 at 58.61 keV). The CsPbBr3 detectors did not show immediate polarization prominently until a flux higher than 1010 photons s−1 mm−2. Using the pump-and-probe technique, we visualized the spatial and temporal effects of polarization. The polarized region, represented by reduced photocurrent, extended beyond the area under direct irradiation, and the reduced photocurrent persisted after potential de-polarization treatments. We found that stronger applied electric fields and fewer carrier traps can mitigate polarization, represented by less photocurrent deficit. By examining the detectors' current response under controlled ambient light, low, and high-flux x rays, we studied the trap filling and release behavior of CsPbBr3. We discovered that the polarization is caused by partial detector damage due to deep defects generated by ultrahigh flux x-ray irradiation. Our work provides insight into CsPbBr3 polarization under extremely intense x-ray radiation and shows that reducing crystal defects and increasing detector bias voltage are effective solutions. [ABSTRACT FROM AUTHOR]

We investigate the interaction between two magnetic layers separated with a normal metal insertion layer (Ti, Pt, and Ru) using x-ray ferromagnetic resonance (XFMR). We measure the amplitude and phase of the ferromagnetic resonance of both layers. Our results indicate that a ferromagnetic exchange coupling between two layers is a dominant coupling mechanism for a thick insertion metal layer. Based on the exchange coupling model, we extract the smallest value of the indirect exchange coefficient of 1.2 μJ/m2, which corresponds to an exchange field of about 0.36 mT. While this value is difficult to measure with other experimental tools, we were able to measure the small value because XFMR detects a resonance phenomenon of a thin layer generated by an oscillating indirect exchange and the Oersted fields with a phase and layer resolved observation. [ABSTRACT FROM AUTHOR]

In the resolution of the large divergence between pressure calculated by way of axial stress components from elastic constants and pressure determined by an equation of state, a 2nd order pressure dependency of elastic constants is introduced. Incorporating results from the equation of state and ultrasonic measurements in the literature, we determined the pressure dependency of x-ray elastic constants of gold and established functions for the calculation of macro-stress components from its macro-strain counterparts. The precision of stress components through these functions is estimated to be at 1% level. The determination of stress components, including crucial shear components, through analysis of an x-ray diffraction image, is demonstrated. [ABSTRACT FROM AUTHOR]

Direct energy conversion has been investigated using Ni/SiC Schottky junctions with the irradiation of monochromatized synchrotron x rays mimicking the gamma rays of 237Np (30 keV) and 241Am (60 keV). Through current–voltage measurements, electrical energies were obtained for both types of gamma rays. The energy conversion efficiencies based on absorbed energy were found to be ∼1.6%, which is comparable to other previously described semiconducting systems. This result raises the prospect of energy recovery from nuclear wastes utilizing the present system, judging from the radiation tolerant nature of SiC. Additionally, we found different conversion efficiencies between the two samples during the same process. This could be explained using hard x-ray photoelectron spectroscopy and secondary ion mass spectroscopy measurements, suggesting the creation of Ni–Si compounds at the interface in the sample with poor performance. Hence, such combined measurements are useful to provide data that electrical measurements cannot provide us. [ABSTRACT FROM AUTHOR]

The surface erosion of polyethylene is interrogated using pulsed x rays at the Z Machine (Sandia National Laboratories) and with proton beams at the Gamble II generator (Naval Research Laboratory) to validate a coupled model for volumetric thermal ablation, photoionization, finite-rate decomposition, and molecular recombination of radicals. The intense radiation pulses (up to ∼ 10 14 W / m 2 over tens of nanoseconds) are used to generate one-dimensional vapor flows with low ionization fractions and a simplified geometry compared to typical laser ablation, allowing for evaluation of the model under local thermal equilibrium conditions. Areal momentum carried by the ensuing uniaxial hydrodynamic shock is used to indicate the extent of ablation. The threshold fluence for ablation is found to be in close correspondence with the bulk melt transition, and reasonable agreement with the model is obtained for peak temperatures in polyethylene up to 5500 K and heating rates up to 10 11 K / s where thermal decomposition reactions are also active. [ABSTRACT FROM AUTHOR]

Solution grown metal halide perovskites (MHPs) are a class of low-cost, direct conversion semiconducting materials with the potential to meet the need for large areas, high stopping power, and high sensitivity x-ray detectors. While polycrystalline MHP thin films have shown significant potential for meeting this need, their efficiencies for detecting x rays are limited by their thickness. This article presents an MHP variant, methylammonium lead tribromide (MAPB) in the form of 3D polycrystalline mosaic wafers with relatively high hole transport properties that demonstrated stable sensitivity during irradiation. An expedited and efficient detector fabrication method that did not include polishing or sintering was evaluated, and a radiograph of a brass key was produced using electron collection from the resulting wafer. However, a high dose rate was required due to very low sensitivity values. The effects of surface inhomogeneity and radiation damage were investigated as explanatory factors, and these phenomena were further characterized through IV measurements, current response as a function of electric field and x-ray dose rate, and alpha particle irradiation. The results indicated that although compromising surface quality for fabrication efficiency was the primary hindrance to the x-ray detection performance of 3D polycrystalline MAPB, stable performance could still be achieved under reasonable dose rates. [ABSTRACT FROM AUTHOR]

Megavolt x-ray computed tomography (CT) is a powerful tool for three-dimensional characterization. However, its utility is limited for large objects composed of high-atomic number (Z) materials, where x rays fail to penetrate. Information from fast neutron CT (FNCT) can complement x-ray CT reconstructions since fast neutrons can more readily penetrate high-Z objects. Here, we demonstrate a method for combining FNCT and x-ray CT data to create a single reconstruction, more accurate than could be achieved with either x rays or fast neutrons alone. The algorithm was tested on an exemplar comprising multiple concentric, nested cylinders of different materials. Simulated and empirical x-ray CT data were acquired for the exemplar using a 9 MV bremsstrahlung spectrum. Additional simulated and empirical FNCT data were acquired using an accelerator based fast neutron source. The FNCT data were used to synthesize x-ray CT data and augment the x-ray CT data missing due to lack of penetration. This approach mitigates artifacts that would otherwise negatively affect the accuracy and resolution of a single-modality reconstructed volume. [ABSTRACT FROM AUTHOR]

Energy-dispersive x-ray diffraction of thermographic phosphors has been explored as a complementary temperature diagnostic to visible phosphor thermometry in environments where the temperature-dependent optical luminescence of the phosphors is occluded. Powder phosphor samples were heated from ambient to 300 ° C in incremental steps and probed with polychromatic synchrotron x rays; scattered photons were collected at a fixed diffraction angle of 3.9 °. Crystal structure, lattice parameters, and coefficients of thermal expansion were calculated from the diffraction data. Of the several phosphors surveyed, YAG:Dy, ZnO:Ga, and GOS:Tb were found to be excellent candidates for diffraction thermometry due to their strong, distinct diffraction peaks that shift in a repeatable and linear manner with temperature. [ABSTRACT FROM AUTHOR]

Dental caries is a bacterial infectious disease that destroys the structure of teeth. It is one of the main diseases that endanger human health [R. H. Selwitz, A. I. Ismail, and N. B. Pitts, Lancet 369(9555), 51–59 (2007)]. At present, dentists use both visual exams and radiographs for the detection of caries. Affected by the patient's dental health and the degree of caries demineralization, it is sometimes difficult to accurately identify some dental caries in x-ray images with the naked eye. Therefore, dentists need an intelligent and accurate dental caries recognition system to assist diagnosis, reduce the influence of doctors' subjective factors, and improve the efficiency of dental caries diagnosis. Therefore, this paper combines the U-Net model verified in the field of biomedical image segmentation with the convolution block attention module, designs an Attention U-Net model for caries image segmentation, and discusses the feasibility of deep learning technology in caries image recognition so as to prepare for the next clinical verification. After testing, the Dice similarity coefficient, mean pixel accuracy, mean intersection over union, and frequency-weighted intersection over the union of teeth segmentation with Attention U-Net are 95.30%, 94.46%, 93.10%, and 93.54%, respectively. The Dice similarity coefficient, mean pixel accuracy, mean intersection over union, and frequency-weighted intersection over the union of dental caries segmentation with Attention U-Net are 85.36%, 91.84%, 82.22%, and 97.08%, respectively. As a proof of concept study, this study was an initial evaluation of technology to assist dentists in the detection of caries. There is still more work needed before this can be used clinically. [ABSTRACT FROM AUTHOR]

Combining an x-ray free electron laser with a high-power laser driver enables the study of equations-of-state, high strain-rate deformation processes, structural phase transitions, and transformation pathways as a function of pressure to hundreds of GPa along different thermodynamic compression paths. Future high repetition-rate laser operation will enable data to be accumulated at >1 Hz, which poses a number of experimental challenges, including the need to rapidly replenish the target. Here, we present a combined shock compression and an x-ray diffraction study on epoxy (50% vol.)-crystalline grains (50% vol.) slurry targets, which can be fashioned into extruded ribbons for high repetition-rate operation. For shock-loaded NaCl-slurry samples, we observe pressure, density, and temperature states within the embedded NaCl grains consistent with observations from shock-compressed single-crystal NaCl. [ABSTRACT FROM AUTHOR]

A promising approach for direct detection of quantum entanglement in solid state materials is probing with entangled particles. X-rays are ideal for characterization of many materials but have not been generated as entangled pairs in useful numbers, even at the most powerful synchrotron sources. This proposal describes how x-rays in fully entangled N00N states (with N = 2) can be produced by applying Hong-Ou-Mandel interferometry at an x-ray synchrotron source. The technical requirements for indistinguishable photons, x-ray beamsplitters, and interferometer design are met with existing resources. The entangled x-ray biphotons can be filtered from the unavoidable single photon background by simple diffraction from an analyzer crystal, resulting in intense beams suitable for characterizing quantum materials. [ABSTRACT FROM AUTHOR]

The method of generating x-rays using the pyroelectric effect has garnered interest for applications that desire portability and low power consumption, particularly for real-time in-field and on-line analyses. However, the x-ray intensity produced by this type of x-ray generator is low and inconsistent compared to conventional x-ray tubes. The properties of several pyroelectric materials, including LiTaO3, LiNbO3, and PMN-xPT, were studied and subsequently tested on an in-house developed x-ray generator to explore their suitability for the application. The production of electrons to subsequently generate x-ray relies on the process of ferroelectric electron emission and field ionization to be dominant over charge compensation via the DC conductivity of the pyroelectric material. Given that the time of temperature change occurs faster than the material's charge relaxation time, it was found that the ratio of the pyroelectric coefficient to relative permittivity determined the performance of the x-ray generator. Thus, the x-ray count rates and end-point energies produced by LiTaO3 showed that it continues to be a strong candidate for such x-ray generation applications. [ABSTRACT FROM AUTHOR]

In situ x-ray diffraction (XRD) during ion implantation or thin film deposition is a powerful method to follow the time evolution of diffusion and phase transition processes in thin films, even as the depth resolution is still dominated by the information depth of the x rays. However, in the case of sputter etching with energetic ions at moderate temperatures, where no diffusion or phase transformation processes are active, this limitation is no longer of concern. Here, thin surface layers which are removed by sputtering can be identified with a depth resolution of 25 nm or better—while information from the substrate—despite overlayers of several micrometers—is accessible. However, considerable mathematical operations are necessary to convert the time series of diffractograms measured by XRD into a depth series. In this paper, a method is highlighted describing which depth-resolved properties of thin films can be accessed using such in situ measurements during ion beam sputtering in the model system austenitic stainless steel + nitrogen: (i) the influence of concentration gradients on the peak shape and peak width for conventional XRD scans in Bragg–Brentano geometry is determined; (ii) correlations between the local nitrogen concentration and the local lattice expansion can be established; and (iii) the evolution of the scattering intensity with depth becomes accessible, thus depth-resolved information on defect densities or grain size (normal to the surface) can be extracted without resorting to transmission or scanning electron microscopy. [ABSTRACT FROM AUTHOR]

Dual-energy computed tomography (CT) provides a better material classification capability than traditional CT. A scintillator is an essential component that determines the optical resolution, detective quantum efficiency, and energy separation of the dual-layer dual-energy CT system. In this paper, we propose a new dual-layer scintillator combination composed of CsI:Tl and LYSO:Ce for dual-energy CT imaging. The x-ray attenuation physical process of CsI:Tl and LYSO:Ce combination is simulated on Geant4. The energy distribution and luminescence of different thicknesses of the scintillator combination are investigated by simulation experiments. Then, the optimal thicknesses of the combination are designed based on simulation results. Furthermore, a dual-layer dual-energy CT system using the scintillator combination is built, and practical dual-energy imaging experiments are implemented in the system. Simulation results indicate that the CsI:Tl and LYSO:Ce combination can effectively realize dual-energy detection. The optimal thickness is 100 μm for CsI:Tl and 500 μm for LYSO:Ce. Practical experiments show that the dual-energy CT system using the CsI:Tl and LYSO:Ce combination has low noise. Materials of the metal mixture sample and the igneous rock sample are correctly separated using the dual-energy data obtained by the CsI:Tl and LYSO:Ce combination. Therefore, the CsI:Tl and LYSO:Ce combination is expected to be used in dual-energy CT imaging studies of complex materials, such as metals, bones, and rocks. [ABSTRACT FROM AUTHOR]

We apply charged-particle simulation to determine the constraints imposed additionally on the photoemission electron microscope (PEEM) when x rays are applied to image buried objects. PEEM initiates its image acquisition by reading the electron-emission profile on the specimen surface, but the profile is not invariant if the electrons originate from a buried object. In this work, we show that, other than the anticipated intensity reduction, the electron-emission profile projected from a buried object displays a blurrier edge for a deeper burial, whereas the distribution of an emission angle becomes narrower for electrons carrying greater kinetic energy. The burial not only redefines the objects seen by PEEM but also introduces additional depth and energy dependence to the resulted images. We demonstrate that inserting a contrast aperture in the PEEM lens can improve the image quality and ease the burial dependence. [ABSTRACT FROM AUTHOR]

When a photon pulse illuminates a cavity, photoelectrons are emitted from the surface of the cavity, thereby producing the system-generated electromagnetic pulse (SGEMP). Previously, simulations on the SGEMP in a low-pressure environment using a swarm model showed poor applicability to describe the dynamics of photoelectrons and plasmas. In this work, a 3D electromagnetic particle-in-cell with the Monte Carlo collisions model was constructed to investigate the effect of low-pressure air (0–500 mTorr) on the cavity SGEMP response. To model air plasma created by high-energy (keV) photoelectron flows, six kinds of particles (electrons, N2, O2, N2+, O2+, and O2−), as well as the elastic, ionization, attachment, and excitation collisions, were included in the model. The results showed that the peak electric field was in the order of 106 V/m. The peak electric field decreased with increasing air pressure because of dissipation of the space charge barrier (SCB) owing to the generation of secondary electron-ions. The dissipation of the SCB allowed more axially moving photoelectrons, so the fraction of transmitted current and the peak magnetic field increased. The energy conversion between the charged particles and the electromagnetic fields is discussed. Approximately 9% of the photoelectron energy was converted to electromagnetic energy for the SGEMP in vacuum. When the gas pressure increased, the electromagnetic energy conversion rate decreased. The energy relaxation of secondary electrons played an important role in the evolution of the plasma density. To validate the established simulation model, the calculated current was compared with those in the benchmark experiments. [ABSTRACT FROM AUTHOR]

In the present work, a kilojoule plasma focus device, PF-2 kJ, is adopted as a pulsed x-ray source to study the effects of pulsed radiation in cancer cells. Low dose hyper-radiosensitivity (LDHRS) effects have been explored in various cancer cell lines using conventional x-ray irradiation. To the best of our knowledge, the LDHRS effects have not yet been explored using pulsed x-rays. Cell death was evaluated in human colorectal (DLD-1 and HCT-116) and breast (MCF-7) cancer cell lines (monolayer cell cultures) irradiated with 10 (∼0.24 Gy), 20 (0.61 Gy), and 40 (∼1.1 Gy) pulses (FWHM ∼ 90 ns, dose rate ∼107 Gy/min with a dose of 0.025 Gy per pulse). The LDHRS cell death effect in the DLD-1 cell line irradiated with pulsed x-ray is three times higher than the reported for a conventional continuous x-ray source at two times higher doses. LDHRS was also observed in HCT-116 and MCF-7 cells exposed to 10 and 20 x-ray pulses, respectively, which are reported not to exhibit LDHRS when conventional continuous x-ray sources are used. Besides, a normal colorectal cell line, CCD-841-CoN, does not show a significant cell death at 10 pulses. These preliminary results suggest a selective effect of low-dose pulsed x-rays on cancer cells. The present work demonstrates the applicability of plasma focus devices for cancer research. Further possibilities in the exploration of pulsed x ray of high-dose rate and low total dose in radiotherapy research are opened. [ABSTRACT FROM AUTHOR]

We report a bulk-sensitive x-ray magnetic microscope that exploits a new magneto-optical effect in x-ray emission, referred to as x-ray magnetic circularly polarized emission (XMCPE). An advantage of XMCPE is a large magnetic dichroic effect for 3 d transition-metal elements in the hard x-ray region, which enables the realization of a bulk-sensitive microscope suited to iron- and cobalt-rich ferromagnetic materials. We constructed a scanning microscope with 10 μ m lateral resolution. A key element is a Montel-type collimating mirror that widely collects the divergent x rays emitted from a sample and converts them into a well-collimated x-ray beam, which is required for circular polarization analysis. Owing to this mirror, the obtained XMCPE spectra of metallic iron exhibited strong intensity and a large magnetic dichroic effect. The performance of the microscope is also demonstrated by the acquisition of magnetization images of an electrical steel sheet with an insulating coating. [ABSTRACT FROM AUTHOR]

Table-top neutron/x-ray sources are of great interest for uses in neutron activation analyses, in neutron/x-ray radiography, and also in medical applications. Inertial electrostatic confinement fusion (IECF) is a multiple neutron source that can emit neutrons, protons, x rays, etc., as basic products when operated in both continuous and pulsed modes. In this work, D-D neutrons are produced in the steady-state mode using a cylindrical IECF device. The neutron production rate has been optimized by using cathodes having different dimensions and geometrical transparencies. The maximum neutron production rate is found to be approaching 10 7 n / s , using a cathode having eight grid wires and a diameter of 3 cm. The neutrons are successfully used for neutron activation analysis of materials containing explosive elements. X-ray spectrum having a wide range of photon energies (30–70 keV) has been detected from this device while operated in the continuous mode. X-ray radiography of high density objects has also been performed and reported for the first time using the cylindrical IECF source with negative polarity of the central grid in this paper. [ABSTRACT FROM AUTHOR]

Distribution and density of dislocations as a function of CdTe epilayer thickness as well as their effect on device dark current were studied using a p-CdTe/n-CdTe/n+-Si heterojunction diode type x-ray detector. A high dislocation density was found in thin devices, which decreased by more than an order of magnitude when the device thickness was increased to 35 μm. First, the dislocation density decreased rapidly with the CdTe thickness but the decrement was slowed down for the CdTe thicknesses above 20 μm. The device dark current showed a strong dependence on dislocation density, which increased with an increase in the dislocation density. A nearly temperature independent dark current was observed in thin devices suggesting that trap-assisted tunneling (TAT) through the dislocation-related current paths was dominant. Dark currents of thicker devices, on the other hand, could be explained due to contributions from both TAT and generation-recombination currents. Furthermore, one possible detector design that helps us to reduce the dark current is also proposed. [ABSTRACT FROM AUTHOR]

Gas puff Z-pinch experiments with annular Ar and Ne gas shells have been conducted on the Compact Experimental System for Z-pinch and Ablation Research (CESZAR) linear transformer driver (LTD) with 500 kA current and 160 ns rise time. Here, we present results from the first systematic gas puff Z-pinch experiments using a fast (≤ 200 ns) LTD as a driver, in which we show that 7% of the stored energy in the capacitors is coupled to plasma kinetic energy as estimated via self-emission and laser schlieren images. 0D and 1D simulations—which do not allow instability growth and thus reach greater maximum average velocities—using initial conditions inferred from experimental implosion trajectories predict coupling in excess of 10% of the stored energy. The Ar and Ne implosions were comparably massed and thus achieved similar maximum kinetic energies, though the Ne pinches were more stable and the x-ray pulses were longer and produced higher yield: 2–5 ns and 0.21–0.52 J (0.15–0.37 J/cm) of Ar K-shell and 12–25 ns and 2.2–3.9 J (1.6–2.6 J/cm) of Ne K-shell, respectively. The difference in stability is most likely attributed to variations in initial conditions such as density distribution and gas breakdown initiation. [ABSTRACT FROM AUTHOR]

The development of new x-ray and γ-ray spectrometers based on AlInP photodiodes with increased quantum detection efficiency and improved energy resolution is reported. The spectroscopic responses of two AlInP p+–i–n+ mesa photodiodes (10 μm i layer, the thickest so far reported) were investigated at photon energies from 4.95 to 88.03 keV; the detectors and preamplifier were operated at 30 °C. Energy resolutions (full width at half maximum) of 750 ± 40 eV and 850 ± 30 eV at 4.95 keV were achieved with the two detectors. The energy resolution deteriorated with increasing photon energy; this was in accordance with the increasing Fano noise with energy and suggested negligible incomplete charge collection noise across the photon energy range investigated. The measured voltage output of each spectrometer was found to be linear as a function of incident x-ray photon energy. The count rate (measured at 8.63 keV) was also found to linearly increase with incoming x-ray photon flux for the investigated spectrometers. These results, which were obtained using the thickest AlInP photodiodes produced so far, suggest that AlInP detectors are highly promising candidates for future uncooled x-ray and γ-ray spectrometers. [ABSTRACT FROM AUTHOR]

The dense plasma focus (DPF) can be an intense source of x rays, wherein the insulator sleeve strongly dictates the electrical breakdown, which subsequently affects the formation of a plasma sheath and a collapse phase. Experiments on a 25 kJ DPF (operated at 4.4 kJ) are carried out to demonstrate the influence of insulator surface morphology on the pinch structure, dynamics, and x-ray yield using a Ne fill. Two borosilicate insulators are directly compared, one with a smooth finish and the other machined with four circumferential grooves traversing the perimeter of the exterior insulator surface. Comparisons are made through same-shot imaging diagnostics of the evolving plasma sheath during breakdown, rundown, and at the pinch in addition to the time-resolved measurements of emitted x rays via filtered photodiodes. The presence of structures on the insulator sleeve reduces x-ray production across all fill pressures by a factor of 2.8 ± 2.4 on average and reduces the highest x ray producing shots by a factor of 5.5 ± 1.8. Observations of sheath asymmetry and inhomogeneity at lift-off are observed and correlated with subsequent observations of off-axis radial collapse. Taken together, this suggests that local variations in the insulator surface decrease the spatial uniformity of the sheath, leading to an azimuthally asymmetric focus, reduced electron densities, and, ultimately, degraded x-ray production. [ABSTRACT FROM AUTHOR]

As the grating-based phase contrast imaging has drawn much attention in various scientific fields, there is an increasing demand for a compact imaging system with high efficiency in practical applications. In this paper, a compact imaging configuration by replacing the source grating in a conventional imaging system with a robust, easily-fabricated, and cost-effective x-ray polycapillary lens is proposed and its feasibility is examined using a full-scale Monte Carlo simulation. A typical x-ray spectrum for diagnostic mammography is adopted in the simulation. Under this spectrum, a new polycapillary lens is designed and optimized to meet the requirement of the imaging system. The phantom consists of polyethylene, cortical bone, and adipose tissue spheres of different sizes. An accurate phase image of the phantom is successfully reconstructed using an eight-step phase-stepping method. Excellent agreement of the phase shift and attenuation of the phantom is obtained between the simulation and the theoretical prediction. Compared with a conventional imaging system using a source grating at the same parameters, the imaging efficiency of our proposed system is improved 1.7 times, while its background visibility is reduced from 44.4 % to 12.4 %. Our results suggest the possibility of developing such a bench-top system for flexible phase contrast imaging applications. [ABSTRACT FROM AUTHOR]

Phosphorescent octahedral metal cluster complexes are highly attractive in terms of biomedical applications, particularly in the area of luminescent diagnostics and photodynamic therapy (PDT). The ability of clusters to be excited by x-radiation followed by red/near infrared emission makes them a new promising class of photosensitizers for deep-PDT. This work demonstrates a direct observation of x-ray-excited optical luminescence of hexanuclear clusters, by example of rhenium cluster complex Na4[{Re6Se8}(CN)6], in a true aqueous solution. The article also describes point-by-point the details and pitfalls of studying cluster radioluminescence in aqueous solution. [ABSTRACT FROM AUTHOR]

The availability of pulsed x rays on short timescales has opened up new avenues of research in the physics and chemistry of shocked materials. The continued installation of shock platforms such as gas guns and high power lasers placed at beamline x-ray facilities has advanced our knowledge of materials shocked to extreme conditions of pressure and temperature. In addition, theoretical advancements have made direct correspondence with high-pressure x-ray experiments more viable, increasing the predictive capability of these models. In this paper, we discuss both recent experimental results and the theory and modeling that has been developed to treat these complex situations. Finally, we discuss the impact that new platforms and increased beam time may have on the future direction of this field. [ABSTRACT FROM AUTHOR]

We report deflagration-to-detonation transition phenomena in cylindrical columns of porous explosives based on octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX). The HMX powder and LX-14 (95.5 wt. % HMX and 4.5 wt. % estane polyurethane) prills were observed with high-speed cameras and flash x rays under conditions that allow for precise scaling and registration of the recorded images. These experimental results test the conventional assumption of axisymmetric, effective one-dimensional burning. Polycarbonate confinement tubes allowed this direct imaging with steel spheres employed as radio-opaque fiducials. Spheres embedded in the explosive column revealed the displacement of the explosive prior to deflagration. X-ray and fast camera images show that a dense plug of compact explosive develops ahead of the deflagration front. The internal fiducials register both internal changes in the plug and changes in the position between successive x-ray images. Tantalum witness strips placed on the inner wall of the explosive channel revealed radial expansion of the tube bore at successive x-ray exposures, indicating the internal pressure of about 100 MPa just before detonation. Images indicate that the deflagration is not only asymmetric but also involves newly observed transient phenomena just before detonation. We typically see a brief but continuous increase in deflagration speed and the formation of a deflagration channel that bypasses the plug just prior to detonation. We hypothesize that these phenomena play an important role in the deflagration-to-detonation transition itself. [ABSTRACT FROM AUTHOR]

A Thomson scattering light source can produce polarization-controllable x rays with quasi-monochromaticity and high brightness, making it an excellent probe for x-ray imaging and nuclear physics research. In this paper, a clear physical picture of the polarization transfer process from a laser to x rays is given based on a dipole radiation model. For arbitrary interaction geometries between a laser and relativistic electrons, the electric field relation between the scattered x rays and the laser is derived analytically. The result shows that the polarization characteristics of the laser can be completely transferred into x rays, regardless of the interaction geometry. Meanwhile, the polarization of scattered x rays is dependent on the collecting angle. As the collecting angle increases, both the degree of polarization (DOP) and the bandwidth of scattered x rays will be degraded. A collecting angle confining scattered x rays of 5 % rms bandwidth can guarantee a DOP higher than 97 % for both linear and circular polarizations. A method for any polarization control of scattered x rays is demonstrated by using wave plates for the laser. Both the rotation of linear polarization and the switch of polarization state from linear polarization to circular polarization and from left-handed polarization to right-handed polarization can be easily realized. [ABSTRACT FROM AUTHOR]

We are developing large Transition Edge Sensor (TES) arrays in combination with a frequency domain multiplexing readout for the next generation of X-ray space observatories. For operation under an AC-bias, the TESs have to be carefully designed and optimized. In particular, the use of high aspect ratio devices will help us to mitigate non-ideal behavior due to the weak-link effect. In this paper, we present a full characterization of a TES array containing five different device geometries, with aspect ratios (width:length) ranging from 1:2 up to 1:6. The complex impedance of all geometries is measured in different bias configurations to study the evolution of the small-signal limit superconducting transition parameters α and β , as well as the excess noise. We show that high aspect ratio devices with properly tuned critical temperatures (around 90 mK) can achieve excellent energy resolution, with an array average of 2.03 ± 0.17 eV at 5.9 keV and a best achieved resolution of 1.63 ± 0.17 eV. This demonstrates that AC-biased TESs can achieve a very competitive performance compared to DC-biased TESs. The results have motivated a push to even more extreme device geometries currently in development. [ABSTRACT FROM AUTHOR]

Exploding bridgewire detonators are an industry standard technology used for over 75 years and valued for their precise timing and safety characteristics. Despite widespread use, their functional mechanism remains controversial with both shock and non-shock mechanisms attributed. In this work, we reexamine the bridgewire detonator function with a suite of modern diagnostics and compare these observations with the existing literature. Traditional detonator observations consisted of voltage applied to the bridgewire and time dependent current, integral response measurements such as case motion, and more recently Schlieren imaging of the detonator surface. In this work, we add visible light emission, x-ray transmission, proton radiography, and temperature measurements during detonator function in addition to voltage, current, and function times. The addition of in situ observations of light emission, temperature, and density gives us new insight into the mechanisms of explosive bridgewire detonator function. We see a distinct separation in time, location, symmetry, and velocity of bridgewire output and detonation onset. During the time between bridgewire burst and the initiation of detonation, we observe a temperature ramp in the input pellet. In this paper, we present the suite of measurements and comparisons with the literature on integral response measurements. [ABSTRACT FROM AUTHOR]

Model refinements for the edge illumination x-ray phase contrast imaging method have been developed to improve simulation accuracy for high energy, polychromatic beams. High-energy x rays are desirable in imaging due to their penetrative power and, for biological samples, their lower dose deposition rate. Accurate models of such scenarios are required for designing appropriate imaging systems and to predict signal strength in complex settings such as clinical imaging or industrial quality assurance. When using optical components appropriate for high-energy x rays in a non-synchrotron setting, system performance was observed to deviate from that predicted by existing models. In this work, experimental data utilizing increasing thicknesses of a known filter material are used to illustrate the limitations of existing models and as validation for the new modeling features. Angular filtration of the cone beam was observed to be the most significant effect; however, specific features of the source and detector are also shown to affect system performance. We conclude by showing that a significantly improved agreement between experimental and simulated data is obtained with the refined model compared to previously existing ones. [ABSTRACT FROM AUTHOR]

The ferroelectric, ferroelastic, and dielectric properties as well as the crystal structure were investigated for polycrystalline donor doped lead zirconate titanate (PZT) with grain sizes ranging from 0.25 to 5 μm, which were prepared using a novel zirconium titanium hydrate precursor (ZTH) with a specific surface area of 310 m2/g. Piezoforce microscopy was used to investigate the change in the domain structure, revealing a change in the domain configuration from a complex 3D structure to a simple lamellar domain formation at a 1 μm grain size that corresponded to a rapidly increasing internal mechanical stress observed with in situ synchrotron x-ray experiments. The correlation between the change in domain configuration, increasing internal stresses, effects of poling on the crystal structure, and the macroscopic ferroelectric and ferroelastic properties are discussed in detail, allowing a deeper understanding of size effects in polycrystalline donor doped PZT ceramics. [ABSTRACT FROM AUTHOR]

A GaAs/Al0.8Ga0.2As separate absorption and multiplication (SAM) x-ray avalanche photodiode (APD) structure was grown by metalorganic vapor phase epitaxy. Mesa photodiodes of different diameters (200 μm and 400 μm) were fabricated from the structure. Two of the photodiodes (one of each diameter) were characterized at 20 °C for their electrical properties and response to x rays using an 55Fe radioisotope x-ray (Mn Kα = 5.9 keV; Mn Kβ = 6.49 keV) source. An energy resolution of 508 eV ± 5 eV full width at half maximum (FWHM) at 5.9 keV was achieved at an apparent avalanche gain, M, of 1.1. This is the best energy resolution so far reported for GaAs/AlxGa1−xAs x-ray SAM APDs. The noise components associated with the achievable spectroscopic energy resolutions are reported. Comparisons between the 200 μm and 400 μm diameter GaAs/AlxGa1−xAs SAM x-ray APDs and recently studied GaAs p+-i-n+ detectors were made, showing that the inclusion of the avalanche layer improves the achievable energy resolution; energy resolutions of 508 eV FWHM at 5.9 keV at M = 1.1 and 603 eV FWHM at 5.9 keV at M = 1.2 were achieved with the 200 μm and 400 μm diameter GaAs/AlxGa1−xAs SAM x-ray APDs, respectively; this is better than was previously reported for similar devices without avalanche layers: 690 eV FWHM at 5.9 keV and 730 eV FWHM at 5.9 keV for 200 μm and 400 μm diameter GaAs p+-i-n+ detectors, respectively [Lioliou et al., J. Appl. Phys. 122, 244506 (2017)]. [ABSTRACT FROM AUTHOR]

We characterize the nanoscale periodic Sc/Mg two-layer, Sc/Mg/Co trilayers, and the Sc/Co/Mg/Co quadrilayer designed as dispersive elements for x-ray spectroscopy in the nitrogen K range (390 eV). The samples are prepared by magnetron sputtering with Mg and Sc layers being a few nanometers thick and Co layers being of subnanometric thickness. We apply nondestructive (x-ray reflectivity and x-ray fluorescence in a standing wave mode) and destructive (transmission electron microscopy) techniques to obtain a relevant description of the deposited stacks. It turns out that a strong interdiffusion takes place in the two-layer leading to poor reflective properties. Interdiffusion also occurs in the trilayers and quadrilayer but between the Sc and Co layers. These systems can be considered as periodic ScCo/Mg two-layers with well-defined layers. As a consequence, the Sc/Co/Mg/Co multilayer is found interesting to use for spectroscopy as a reflectance of 32% is expected in the N K range in the water-window range. [ABSTRACT FROM AUTHOR]

Luminescence measurements of CsCdF3:Mn reveal material properties suitable for UV and X-ray sensing. Mn2+ substitutes for Cd2+ with octahedral crystal field parameters 10Dq = 7020 ± 120 cm−1 and B = 773 ± 13 cm−1. UV stimulation at 250 nm results in intense Mn2+ emission and also in the production of F-centers and additional defects. Continuous 250 nm stimulation charges the material, enhancing the Mn2+ emission intensity over time due to the filling of shallow traps that contribute to persistent luminescence. When the stimulation is ceased, Mn2+ emission is observed as an afterglow. F-centers give rise to optically stimulated luminescence (OSL) that is temporally stable and can be stimulated at wavelengths near 300 nm. We propose a model that describes these effects, where UV stimulation results in electron transfer from Mn2+ to the conduction band and subsequent electron trapping in various defect states. X-ray stimulation produces Mn2+ radioluminescence that varies in intensity by 0.004%/Gy after a 300 Gy priming dose. The X-ray irradiation also produces OSL-active F-centers and the defects that cause the afterglow. Thermoluminescence measurements reveal low-temperature peaks that are correlated with the afterglow and high-temperature peaks that are correlated with the OSL, after both X-ray and UV irradiations. The luminescence of Mn2+ in CsCdF3:Mn may be useful for radiation sensing, where the real-time changes in Mn2+ emission under X-ray and UV stimulation allow for real-time dose measurements, and the OSL induced by each irradiation allows for retrospective dose monitoring. [ABSTRACT FROM AUTHOR]

Strain engineering is a promising technology with potential application in memory devices, electronic elements, photoactive materials, etc. Nanoscale imaging of the strain is therefore important to better understand the operating condition of the device, growth processes, and influences of other factors. X-rays offer the advantage over electron-based techniques in that they offer high spatial resolution and access to volumetric information within nanostructured materials. This paper describes the basic physics behind strain at the nanoscale and provides a concise summary of the efforts in coherent diffractive imaging for the imaging of the displacement fields in nanocrystals. Although the approach is still under development, with instruments being continuously improved, a number of important results have already been demonstrated. [ABSTRACT FROM AUTHOR]

The recent advances in the inelastic background analysis of XPS spectra recorded with hard X-rays (HAXPES) make this method a powerful, non-destructive solution to retrieve the depth distribution of deeply buried elements. In this work, we apply this technique to study diffusion phenomena, upon annealing, in power transistor devices. We present a complete analysis of a sample under different stages of the fabrication process. We investigate the accuracy of the determination of the elemental depth distributions and concentrations with the inelastic background analysis. This is done by cross-checking with destructive techniques such as TEM/EDX and XPS depth profiling, and we shed light on the complementarities with HAXPES core-level analysis. We obtain consistent results which show the formation of an inhomogeneous structure, consisting of a blend of Al, Ga, and Ta, created during annealing. The inelastic background analysis permits us to successfully retrieve the depth distributions of Al, Ga, and Ta as well as the concentration of these elements in each layer, over 70 nm below the surface. This is a reliable solution to investigate diffusion phenomena and improve the fabrication processes of devices with critical and deeply buried interfaces. [ABSTRACT FROM AUTHOR]

Absorption of hard x-rays in GaAs creates excitations that can dramatically alter the propagation of optical laser pulses with photon energies near the bandgap. Measurements of optical transmission through a thin crystalline wafer of GaAs after absorption of an intense x-ray synchrotron pulse demonstrate how x-ray induced optical transparency depends on the recombination of excited conduction band electrons and valence band holes via Auger, spontaneous emission, and especially stimulated emission processes. The x-ray induced band fluorescence spectrum also reveals amplified spontaneous emission at the high x-ray fluences used, confirming the importance of stimulated emission. For laser pulses with sufficiently high fluence, the interaction of optically excited electrons with x-ray excited electrons can quench the enhanced laser transmission. [ABSTRACT FROM AUTHOR]

The equation of state and the unit cell parameters of triamino-trinitrobenzene (TATB) have been measured up to 66 GPa by x-ray diffraction on multi-grain samples. A custom indexing of the diffraction pattern was implemented to enable an unambiguous assignment of the diffraction peaks. The structural data reveal a more isotropic response to compression above 10 GPa, indicating that the van der Waals forces are no more the dominant interplanar interactions. The unit cell parameters are compared with density functional theory calculations, including the empirical D2 correction for the van der Waals interactions. An excellent agreement is obtained up to 20 GPa and an increasing deviation above. The present determination of the TATB isothermal equation of state is reliable for detonation physics applications. [ABSTRACT FROM AUTHOR]

The generation of powerful nanometer x-ray radiation in cascaded high-gain free-electron lasers (FELs) with two-frequency undulator is studied. An advanced phenomenological model of single pass FEL is developed, which describes both linear and nonlinear harmonic generation from seed and initial shot noise; it includes calibrated corrections for all loss factors, specific for each FEL harmonic in each cascade. In this way, it differs from other phenomenological models, which account for the energy spread or divergence equally for all FEL harmonics. The new model, calibrated with a FEL experiment and numerical 3D simulations, is employed for the analysis of the FEL power dynamics to obtain maximum high-harmonic power in the X-ray band at the shortest possible FEL length with a low seed frequency and electron energy. The advantages of the two-frequency undulators in FEL prebunchers are demonstrated; their use in the cascaded FELs is proposed. Several such FELs with two-frequency undulators are simulated. The nanometer X-ray radiation production is studied in high-gain cascaded FELs with the seed wavelengths, matching peak reflectivities of MoRu/Be and Mo/Si. Dozens of megawatts of X-ray radiation are modeled at ≈40m in a multi-cascade FEL, seeded from commercially available F2 excimer laser [ABSTRACT FROM AUTHOR]

Femtosecond resolution pump-probe experiments are now routinely carried out at X-ray Free Electron Lasers, enabled by the development of cross-correlation "time-tools" which correct the picosecond-level jitter between the optical and X-ray pulses. These tools provide very accurate, <10 fs, measurement of the relative arrival time, but do not provide a measure of the absolute coincidence time in the interaction. Cross-correlation experiments using transient reflectivity in a crystal are commonly used for this purpose, and to date no quantitative analysis of the accuracy or stability of absolute coincidence time determination has been performed. We have performed a quantitative analysis of coincidence timing at the SACLA facility through a cross-correlation of 100 ± 10 fs, 400 nm optical pulses with 7 fs, 10.5 keV X-ray pulses via transient reflectivity in a cerium-doped yttrium aluminum garnet crystal. We have modelled and fit the transient reflectivity, which required a convolution with a 226 ± 12 fs uncertainty that was believed to be dominated by X-ray and laser intensity fluctuations, or assuming an extinction depth of 13.3 μm greater than the literature value of 66.7 μm. Despite this, we are able to determine the absolute coincidence time to an accuracy of 30 fs. We discuss the physical contributions to the uncertainty of coincidence time determination, which may include an uncharacterised offset delay in the development of transient reflectivity, including cascading Auger decays, secondary ionisation and cooling processes. Additionally, we present measurements of the intrinsic short-term and long-term drifts between the X-rays and the optical laser timing from time-tool analysis, which is dominated by a thermal expansion of the 25m optical path between tool and the interaction region, seen to be ~60 fs over a period of 5 h. [ABSTRACT FROM AUTHOR]

Extremely short X-ray pulses in the attosecond (as) range are important tools for ultrafast dynamics, high resolution microscopy, and nuclear dynamics study. In this paper, we numerically examine the generation of gigawatt (GW) mode-locked (ML) multichromatic X-rays using the parameters of the Pohang Accelerator Laboratory (PAL)-X-ray free electron laser (XFEL), the Korean XFEL. In this vein, we analyze the ML-FEL [Thompson and McNeil, Phys. Rev. Lett. 100, 203901 (2008)] and mode-locked afterburner (MLAB) FEL [Dunning et al., Phys. Rev. Lett. 110, 104801 (2013)] schemes on the hard X-ray beamline of the PAL-XFEL. Using the ML scheme, we numerically demonstrate a train of radiation pulses in the hard X-ray (photon energy ~12.4 keV) with 3.5GW power and 16 as full-width half maximum (FWHM) pulse duration. On the other hand, using the MLAB scheme, a train of radiation pulses with 3GW power and 1 as FWHM (900 zs in RMS) pulse duration has been obtained at 12.4 keV photon energy. Both schemes generate broadband, discrete, and coherent spectrum compared to the XFEL's narrowband spectrum. Furthermore, the effect of slotted foil is also studied first time on the MLAB-FEL output. Numerical comparisons show that the temporal structure of the MLAB-FEL output can be improved significantly by the use of the slotted foil. Such short X-ray pulses at XFEL facilities will allow the studies of electron-nuclear and nuclear dynamics in atoms or molecules, and the broadband radiation will substantially improve the efficiency of the experimental techniques such as Xray crystallography and spectroscopy, paving the way for outstanding progress in biology and material science. [ABSTRACT FROM AUTHOR]

A method for generating high quality multilayer blazed gratings using ion beam assisted deposition is proposed and analyzed with numerical simulations. Conventional fabrication methods for multilayer blazed gratings are limited by unwanted smoothing of the surface profile during multilayer deposition. By contrast, we demonstrate that our proposed method is capable of producing gratings that retain a nearly ideal blazed grating profile after the deposition of an arbitrary number of layers. Through numerical analysis, we establish the conditions in which this procedure produces a high quality multilayer blazed grating. These gratings would be suitable for use in the extreme ultraviolet or soft X-ray regime. We also discuss how the control parameters may be selected to optimize the gratings formed in an experiment. [ABSTRACT FROM AUTHOR]