Annular wire array implosions on the Sandia Z-machine can produce >200 TW and 1-2 MJ of soft x rays in the 0.1-10 keV range. The x-ray flux and debris in this environment present significant challenges for radiographic diagnostics. X-ray backlighting diagnostics at 1865 and 6181 eV using spherically-bent crystals have been fielded on the Z-machine, each with a ~ 0.6 eV spectral bandpass, 10 μm spatial resolution, and a 4 mm by 20 mm field of view. The Z-Beamlet laser, a 2-TW, 2-kJ Nd:glass laser (λ=527 nm), is used to produce 0.1-1 J x-ray sources for radiography. The design, calibration, and performance of these diagnostics is presented.

The results of theoretical and experimental studies of anisotropic plasma sources are reported. They are based on x-ray line spectropolarimetry, a powerful new tool for investigating anisotropy of high-temperature plasmas. It is based on theoretical modeling of polarization-sensitive x-ray line spectra recorded simultaneously by two spectrometers with different sensitivities to polarization. The difference in these polarization-sensitive spectra is used to diagnose the parameters of anisotropic electron beams in plasmas. Theoretical predictions of polarization which cover a broad spectral range from K- to M-shell line radiation are presented. The results of Ti and Mo x-pinch polarization-sensitive experiments at UNR are overviewed. This diagnostic can be applied not only to x-pinches as demonstrated here but to laser-generated and other laboratory x-ray sources.

The X pinch plasma emits subnanosecond bursts of x-rays in the 3 - 10 keV energy range from a very small source. As such, it has been used for high-resolution point-projection imaging of small, dense, rapidly changing plasmas, as well as submillimeter thick biological samples. The very small x-ray source size of the X pinch provides high spatial coherence of the x-rays, enabling the X pinch to be used for imaging low absorption, low contrast objects with excellent spatial resolution by incorporating wave-optics effects. The reverse procedure has been used to determine the X pinch x-ray source size: well-defined micro-fabricated slits were imaged by point-projection radiography, and the detailed patterns were compared with wave-optics calculations of the expected image patterns on film as a function of x-ray source size and energy band. In addition, an x-ray streak camera was used to study the X pinch source size as a function of time. Dynamic shadow images of a boron fiber with a tungsten core and glass fiber sheathed in plastic were compared with a time-integrated radiographic image. Source sizes as small as 1.2 μm (full width at half maximum, assuming a Gaussian spatial intensity profile for the source) have been inferred.

X pinch radiation produced by electron beams accelerated in the X pinch minidiode ranging in energy from 10 to 100 keV has been studied and used to image a variety of different objects. The experiments have been carried out using the XP pulser (470 kA, 100 ns) at Cornell University and the BIN pulser (280 kA, 120 ns) at the P.N. Lebedev Physical Institute. This electron-beam-generated x-ray source's geometric, temporal and spectral properties have been studied over different energy ranges between 10 and 100 keV. The imaging was carried out in a low magnification scheme, and spatial resolution of a few tens of μm was demonstrated.

Experimental results of complex studies of x-ray/EUV radiation from hot dense x-pinch Ti, Fe, Mo, and W plasmas generated by a pulse-powered z-pinch machine with I_max~0.9 ÷ 1.0 MA and a current rise time of 100 ns are overviewed. Structures and spatial dimensions of 0.9-1.0 MA x-pinch sources in a wide energy range of 0.15 - 0.6 keV, 1-10 keV and 10-100 keV are analyzed. Generation of different types of hot spots in high-current multiburst x-pinches are described and a possible explanation of observed effects based on generation of shockwaves in plasmas are discussed. Hard x-ray x-pinch spectra are analyzed. The analysis of time and energy scaling of 0.9 - 1.0 MA x-pinch x-ray/EUV pulses indicate the possible existence of competing mechanisms of the dissipation of the initial discharge x-pinch energy. The future applications of the high current x-pinch as the sub-keV-10 keV radiation driver and the 50 - 100 keV backlighter are discussed.

According to the ISMT roadmap, Extreme Ultraviolet lithography (EUVL) is the most promising technology to reach the 45-nm node for industrial production and to satisfy the famous law of Moore beyond 2007. Already in 1998 the first European EUVL project (EUCLIDES) has been launched under the leadership of ASM Lithography. Shortly after that in 1999, the national R&D program PREUVE started in France to improve EUVL related technologies and to build the first experimental lithography bench (BEL) in Europe. Finally, in 2001, the main European industrial companies as well as academic and national laboratories have federated within the important MEDEA+ effort to overcome the main technological challenges and to industrialize EUVL in time. Indeed, one of the most important challenges of EUVL concerns the achievement of very powerful, clean and reliable sources. The present paper will give the current state of European EUVL source technology and an overview of the different approaches. Main results are reviewed and the remaining challenges are discussed.

At Laser-Laboratorium Goettingen different types of laser-plasma EUV sources based on gas and cluster targets were tested to optimize the spatially resolved EUV radiation with respect to maximum EUV intensities, small source diameters, and pointing stability. The EUV radiation is generated by focusing a Q-switched Nd:YAG laser at 1064nm into a pulsed gas puff target. By the use of different target gases, broad-band as well as narrow-band EUV radiation is obtained, respectively. The influence of the laser and target gas parameters on the plasma shape and EUV intensity was investigated by the help of specially designed EUV pinhole cameras, utilizing evaluation algorithms developed for standardized laser beam characterization. In addition, a rotatable pinhole camera was developed which allows spatially and angular resolved monitoring of the soft X-ray emission characteristics. With the help of this camera a strong angular dependence of the EUV intensity was found. The results were compared with fluorescence and Rayleigh measurements for visualization of the target gas jet. To explain these results a theoretical model was developed, including the reabsorption of the EUV radiation in the surrounding target gas. In addition, an EUV-sensitive Hartmann sensor was utilized to characterize the wavefront of 13nm radiation before and after reflection from Mo/Si multilayer mirrors.

Characteristics of extreme ultraviolet (EUV) light at the wavelength between 5 to 20 nm from rare gas cryogenic targets irradiated with a nano-second laser pulse are studied. Spatial distribution of the EUV light and the ion current was measured and found to vary as cos²θ and cos⁶θ, respectively, where θ is an angle to the target normal. Energetic ions were detected, which had a velocity of the order of 10⁶ cm/s. According to the observed cos²θ spatial distribution, the spatially-integrated total EUV output energy for the xenon cryogenic target was evaluated to be 1.5 mJ/pulse, leading to the conversion efficiency of 0.2%/pulse.

JMAR develops Laser-Produced Plasma (LPP) sources for lithography applications, and has specifically developed Collimated laser-Plasma Lithography (CPL) as a 1 nm collimated point source and stepper system to address sub-100nm lithography needs. We describe the CPL source development, show demonstrated sub-100nm printing capability, and describe status of a beta lithography tool. The system will be power-scaled to address silicon device contacts and vias at 90nm and below. This development has much in common with LPP Extreme UltraViolet Lithography (EUVL) sources; an EUV source concept is presented to address the high power requirements of that Next Generation Lithography (NGL).

Inertial electrostatic confinement (IEC) devices offer a unique method to generate energetic ions for excitation of rare gas and rare gas halide excimers. A unique feature for this approach is that it allows small sized units with the ion source and excimer medium contained in vessels of order 30-cm radius. The IEC operates by applying a high negative voltage (up to -100 kV) on a spherical mesh grid (cathode) located in the center of a grounded grid (anode), all within a spherical vacuum vessel. A plasma discharge is created between the grids. The cathode extracts ions from the discharge and accelerates them towards the center of the device. Large ion background gas collision densities are created in the center region and along the ion beam paths, creating intense light emission. An alternate approach discussed here allow lower operating pressures and reduced ion thermalization, giving improved emission efficiencies, uses an external RF ion generator to separate the injected species from the mixture. The injector increases the device size, but a compact RF source has been developed which involves injector diameters of only ~ 6 cm by 30- cm length. Designs for such devices and their operation will be described.

We have previously proposed the use of mass-limited, tin-containing laser plasma sources for EUV lithography applications. Here we report advances in measurements of the spectral output, conversion efficiency, and debris emission from these sources. We also report progress in the use of repeller field debris inhibition techniques for this source.

The advantages of droplet and claster Li-contained targets for debris free EUV generation are estimated on base of analytical modeling and simulation. Conversion efficiency of laser energy into EUV energy from such targets is found to reach a few percents. The laser prepulse is proposed to enhance the laser energy conversion into emission at wavelength of 13.5 nm.

Future progress of x-ray lasers call for specific facilities intended to x-ray laser studies and development of a large variety of x-ray laser applications. This paper presents LASERIX, a future x-ray laser facility under construction for optimization of transient collisional excitation x-ray lasers, study of new x-ray laser schemes, and development of applications.

High-order harmonics generated by weakly relativistic femtosecond laser pulses interacting with solid and thin foil targets were studied. It was found that the conversion efficiency is one or two orders of magnitude larger than that of gas-harmonics and thus due to the high laser intensity also the harmonics are very intense. In addition, anomalies and complex interference structures have been observed in the harmonic spectra of the solid targets. They are explained by simulations. Furthermore, for the first time intense harmonics were observed from thin foil targets and, in particular, from the target rear side. This type of studies provides a promising tool for obtaining information about the laser plasma interaction itself, e.g., on the presence of large fields and oscillations inside the foil up to a penetration depth comparable to the laser wavelength.

FESTA has been developing short pulse X-ray generation technologies using Laser-Compton scattering. Two years ago, X-ray generation with a 90-degree collision configuration was achieved using a photocathode as the electron source and a 100fs Ti:sapphire laser as the photon source. Electron and laser light pulses were synchronized so that the fluctuation of X-ray intensity was 25% (rms). In the next stage, the x-ray generation system is being modified for use in practical applications. The electron energy has been raised to 40 MeV to increase to X-ray photon energy. Laser power will be increased to 0.5 J/pulse with a 100Hz repetition rate. The laser gain medium has been changed to Yb:S-FAP which is pumped by laser diodes. The synchronization system will be further modified to increase its stability. These technologies will be used to generate 15 -to 30 keV X-ray pulses with a stable peak-to-peak intensity for use in several applications.

A summary of recent developments of x-ray spectroscopy for the application in laser produced plasma experiments is given. They are based on an advanced theoretical analysis of the radiation emission originating from autoionizing states and the realization of high resolution x-ray spectromicroscopy methods. Particular emphasize is given on non-Maxwellian particle analysis, strongly coupled plasmas and interpenetrating plasma sheaths of laser produced and compressing (pinching) plasmas.

A transmission crystal spectrometer was utilized to record the hard x-ray spectra from laser-produced plasmas in the 12 keV to 60 keV energy range and with a resolving power of E/ΔE≈100. This emission is of interest for the development of hard x-ray backlighters and hot electron diagnostics. Planar foils of U and Pb were irradiated at the OMEGA laser facility by 24 beams (12 on each side of the foil) with no beam smoothing. The spectra typically exhibited a few intense and relatively narrow features in the 12 keV to 22 keV energy range. Initial analysis suggested that these hard x-ray features are inner-shell transitions resulting from L-shell vacancies created by energetic electrons. The observed transition energies were slightly higher than the neutral-atom characteristic x-ray energies, and calculations suggested that the transitions are in the Ni-like or lower ionization stages.

Laser to X-ray conversion efficiencies in the 1.5 - 4.5 keV photon energy range from solid targets irradiated by 2 ps duration KrF laser pulses of wavelength 248 nm and irradiance up to 2 x 10¹⁶ Wcm^-2 have been measured. Unusually, a CCD camera working in single photon counting mode has been used to record the emitted spectra with moderate (λ/Δλ ≈ 50) spectral resolution. Efficiencies in converting laser energy to X-ray emission into 2π steradian are in the range 10^-3 to 10^-6 respectively for photon energies from 1.5 to 4.5 keV.

We have measured the production of hν equal to or greater than 4.5 keV x-rays from low-density Ti-doped aerogel targets at the OMEGA laser facility (University of Rochester). The targets were 2.2 mm long by 2 mm diameter beryllium cylinders filled with Ti-doped (3 atomic percent) SiO₂ foam. The doped-foam density was ≈ 3 mg/cc. Forty beams of the OMEGA laser (λ = 351 nm) illuminated the two cylindrical faces of the target with a total power that ranged from 7 to 14 TW. The laser interaction fully ionizes the target (formula available in paper), and allows the laser-bleaching wave to excite, supersonically, the high-Z emitter ions in the sample. The heating of the target was imaged with a gated (200 ps time resolution) x-ray framing camera filtered to observe > 4 keV. 2-D radiative-hydrodynamic calculations predict rapid and uniform heating over the whole target volume with minimal energy losses into hydrodynamic motion. An x-ray streak camera, also filtered to observe > 4 keV, was used to measure the rate of heat propagation in the target. Ti K-shell x-ray emission was spectrally resolved with a two-channel crystal spectrometer and also with a set of filtered aluminum x-ray diodes, both instruments provide absolute measurement of the multi-keV x-ray emission. Back-scattered laser energy is observed to be minimal. We find between 100 to 400 J of output with 4.67 equal to or less than hv equal to or less than 5.0 keV, predicted target performance is a factor of 2 - 3 too low in this range.

X-ray spectra of a few picosecond duration were emitted by aluminum, selenium and samarium thin foils irradiated with a 100 TW, 300 fs laser at 0.53 μm wavelength. They were measured in the 1600 eV range with high temporal and spectral resolution, using a high-speed streak camera coupled to a conical Bragg crystal. Gradients were limited by using thin foils (300 to 800 Å) deposited on a 50 μm gold pinhole. Frequency Domain Interferometry was set to measure the velocity of the critical density at the rear of the target and deduce the electron temperature. A few picosecond duration X-ray spectra have been measured. Sm spectra showed no spectral features in the measured wavelength range, providing a spectrally homogeneous backlighter for absorption spectroscopy. The duration of the emission was shorter when observed through a pinhole. 1-D hydrodynamic simulations coupled to an atomic collisional-radiative code have been used to simulate the X-ray emission of aluminum. The main features of the experimental time resolved spectra, obtained for the pinhole target have been well reproduced, for an initial temperature of 700 ± 100 eV.

We are studying the feasibility of utilizing Kα x-ray sources in the range of 20 to 100 keV as a backlighters for imaging various stages of implosions and high aerial density planar samples driven by the NIF laser facility. The hard x-ray Kα sources are created by relativistic electron plasma interactions in the target material after a radiation by short pulse high intensity lasers. In order to understand Kα source characteristics such as production efficiency and brightness as a function of laser parameters, we have performed experiments using the 10 J, 100 fs JanUSP laser. We utilized single-photon counting spectroscopy and x-ray imaging diagnostics to characterize the Kα source. We find that the Kα conversion efficiency from the laser energy at 22 keV is ~3 x 10^-4.

Starting from FCI2 simulations showing good multi-keV conversion efficiencies of a preformed plasm from thin foils heated by two laser pulses, experiments have been performed with titanium and copper on the Omega laser facility at University of Rochester. The advantages of using this method are efficiencies close to gas targets due to the under-dense plasma created by the pre-pulse and X-ray emissions available at high photon energies that cannot be reached with gas targets. Optimum parameters (laser intensities, delay between the two pulses and thickness of the foil) for titanium and copper foils were estimated from simulations. An increase in the multi-keV conversion efficiency (above 4 keV) by a factor of 2, compared to the case without pre-pulse, is clearly shown on titanium targets. X-ray emission was measured by different diagnostics in good agreement and close to simulations results.

High resolution x-ray emission spectra of plasma created by laser irradiation of rare-gas (Ar, Kr, Xe) clusters have been measured at laser intensities over 10¹⁹ W/cm² and 30-fs pulse duration. To make these measurements possible, in addition to the effort to decrease a prepulse intensity using Pockels cell switches, micron-size clusters were produced using a specially designed conical nozzle. The Boltzmann equation and a detailed collisional radiative model are solved simultaneously as a function of time to model the time integrated x-ray spectra of the transient plasma. The results are quantitatively in good agreement with the experimentally observed x-ray emission spectra of Ar clusters.

A review of our progress in the realization of an ultrashort-pulse laser-driven hard-x-ray source based on the combination of a femtosecond laser system with an x-ray diode is given. New results on the development of electron-based compact EUV sources for "at-wavelength" metrology are presented. Detailed investigations of spectral, spatial, and temporal characteristics of both sources are performed and possible applications are discussed.

Important design factors are evaluated for a high average power, clean EUV light source by laser produced plasma. The basic requirements are high average power, high stability, and long lifetime, and these are closely relating with absorption loss by xenon, repetition rate, and fast ion generation. These subjects are evaluated based on experimental data and analytical model of a laser produced xenon plasma.

A Nuclear Pumped Flashlamp (NPF) is closely related to a Nuclear-Pumped Laser NPL in that both use nuclear radiation to excite the medium. The NPF does not require as high peak power as is needed for NPL inversion. Still, with a reactor source, a large volume NPF can be designed to deliver extremely large fluorescence in the UV up to the infrared range, depending on the media employed. The NPF can then be used for industrial applications or for pumping a laser requiring a high intensity light pump. The first experimental example of this approach was a ³He-XeBr₂ NPF employed in 1993 to pump a small iodine laser. The present paper discusses issues involved in scaling such a NPF up to an ultra high energy output.

The emission spectra of laser produced plasmas of pure tin targets are dominated by recombination continuum emission throughout the entire EUV spectral region with intense structure due to line emission dominating the spectra in the 13 - 14 nm region. This feature arises from resonant 4p⁶4dⁿ - 4p⁵4dⁿ⁺¹ + 4p⁶4d^n-14f emission lines that are generally concentrated in a narrow band, 5 - 10 eV wide, which overlaps considerably in adjacent ion stages to form an intense unresolved transition array (UTA). Such plasmas are optically thick; the strongest lines are attenuated and frequently appear in absorption. However, if tin comprises a few percent of a predominantly low-Z matrix, the recombination is suppressed and the plasmas can become optically thin to resonance radiation. Under these conditions, resonance line emission can dominate the spectra. The application of a collisional radiative (CR) model, combined with ab initio atomic structure calculations, allows one to estimate the laser plasma parameters that will optimize the UTA as efficient narrow bandwidth emitters of EUV radiation. The dependence on laser power density of both in-band emission and debris generation from pure tin targets is presented. The influence of a pre-pulse on the plasma output is also investigated.

A set of spectral analytic instruments has been developed for absolute intensity measurements in a spectral range of 1 - 600 Å: (1) several modifications of grazing incidence spectrographs; (2) EUV monochromator- spectrometer with a constant angle of deviation; (3) focusing crystal von Hamos spectrometer using cylindrical mica and pyrolytic graphite crystals and a CCD linear array as a detector. These instruments are useful for plasma diagnostics, x-ray and EUV spectroscopy of laser-generated plasmas and capillary discharge plasmas, x-ray and EUV reflectometry, radiometry and x-ray fluorescence application.

A new research project on extreme ultraviolet (EUV) source development has just been started at the Institute of Laser Engineering, Osaka University. The main task of this project is to find a scientific basis for generating efficient, high-quality, high power EUV plasma source for semiconductor industry. A set of experimental data is to be provided to develop a detailed atomic model included in computer code through experiments using GEKKO-XII high power laser and smaller but high-repetitive lasers. Optimum conditions for efficient EUV generation will be investigated by changing properties of lasers and targets. As the first step of the experiments, spherical solid tin and tin-oxide targets were illuminated uniformly with twelve beams from the GEKKO XII. It has been confirmed that maximum conversion efficiency into 13.5 nm EUV light is achieved at illumination intensity less than 2 x 10¹¹ W/cm². No significant difference is found between laser wavelengths of one μm and a half μm. Density structure of the laser-irradiated surface of a planar tin target has beem measured experimentally at 10¹² W/cm² to show formation of double ablation structure with density plateau by thermal radiation transport. An opacity experiment has just been initiated.

A new imaging detector for EUV or soft-X-ray radiation based on optically stimulated luminescence (OSL) of lithium fluoride (LiF) films or crystals is presented. The first micro-radiography images of biological samples and of meshes obtained on LiF using a laser-plasma source or an X-ray laser are shown, and (up to now) a resolution better than one micron is demonstrated. The dependence of the coloration density vs the deposited X-ray dose is considered and the advantages of this new diagnostic technique for both coherent and non-coherent EUV sources, compared with CCDs detectors, photographic films and photoresists are discussed. This new detector is extremely suitable for laser plasmas and for X-ray lasers sources.

A novel laser-pumped X-ray source is used to investigate generation of shock waves in a semiconductor and conformational changes in a molecular crystal. Ultrashort Cu-Kα pulses are generated by focusing 130 fs laser pulses from the ATLAS titanium-sapphire laser of our institute on a slowly moving copper tape. Irradiating Si(111) surfaces with a few 100 mJ/cm² pulses at 800 nm we observe an increase in the integrated reflection on a relatively slow time scale of several 100 ps. This observation is explained by the increased geometrical structure factor generated by the shock wave propagating into a mosaic crystal. The work on conformational changes was performed with DMABN (dimethylaminobenzonitrile, sum formula C₉H₁₀N₂). A pump-probe experiment using the third harmonic of the titanium-sapphire laser (λ = 265 nm) as the pump yields indications of an increase of the 004 reflection in a time shorter than 10 ps. Such an increase is expected owing to photo-induced rotation of the two methyl groups around the major axis of the molecule.

Multi-keV X-ray source from intense laser-cluster interaction was experimentally studied. A special effort was first made in order to characterize the cluster target. K-shell emission of Argon clusters (around 3 keV) was then studied when irradiated by kHz, 30 fs, 10¹⁷ W.cm^-2 laser pulses. High-resolution spectra are presented, in this spectral range, as a function of laser duration and average cluster size. Signature of very highly charged ions (Ar¹⁶⁺) was observed with relatively low intensity laser pulses (few 10¹⁵ W.cm^-2). This feature is not yet clearly understood nor reproduced by simulations. Optimal laser pulse duration was observed for X-ray production, depending on the cluster size. For the first time to our knowledge, the duration of K-shell X-ray bursts was measured with a home-made streak camera to be on the picosecond scale.

The invention of high-power ultra short pulse lasers has opened way to investigations aimed at creation of a new type of bright x-ray source for different applications including material science and time resolved x-ray diffraction for biology. The conversion efficiency of the laser energy incident onto a solid target into the x-ray emission depends on many factors, including the temporal profile of laser pulse. We report here the results of our theoretical and experimental investigations of the line x-ray emission from layer solid targets irradiated by ultra short laser pulses. The parameters of laser pre-pulse and target thickness are optimized in order to get the maximum laser energy conversion into the emission in the selected x-ray line. Multi-layer foils are proposed in order to increase the energy of K-α line emission from laser plasma simultaneously with shortening of x-ray pulse up to hundred femtoseconds. The emission is studied, both experimentally, and by means of analytical model and numerical simulations.

Hard x-ray (8-100 keV) spectrum emission from plasma produced by femtosecond laser solid target interactions and Kα x-ray conversion efficiency have been studied as a function of laser intensity (10¹⁷ W/cm² ~ 10¹⁹ W/cm²), pulse duration (70 fs ~ 400 fs), laser pulse fluence and laser wavelength (800 nm and 400 nm). The Ag Kα x-ray conversion efficiency produced by a laser pulse at 800 nm with an intensity I = 4x10¹⁸ W/cm² can reach 2x10^-5. We discuss the behavior of Kα conversion efficiency scaling laws as a function of the laser parameters. We found that the Kα x-ray conversion efficiency is more dependent on laser fluence than on pulse duration or laser pulse intensity. The conversion efficiency exhibits a similar value at I ~ 1x10¹⁸ W/cm² when we work with a high contrast laser pulse at 400 nm or with a low contrast laser pulse at 800 nm, but in the first case it presents a higher scaling law. Consequently, the use of 400 nm laser pulses could be an effective method to optimize the Kα x-ray emission via vacuum heating mechanisms.

Ultrabright and ultrashort x-ray pulses may be used for time resolved studies of phase transitions in materials and potentially for x-ray microscopy applications. Through the interaction of high intensity ultrashort laser pulses (~100fs, 10¹⁵ -10¹⁷ W/cm²) with solid targets, high temperature and high density plasma is formed on the material surface. Electrons are accelerated in the plasma and multi keV x-rays are generated when they interact with the target material. Such hot electrons are produced from resonance absorption and other nonlinear interactions both at the solid density surface and in the underdense plasma. Initial experimental measurements of keV x-ray emission from microplasmas generated by 130fs, 800nm, 0.5mJ Ti:Sapphire laser pulses focused to intensities of ~10¹⁶ -10¹⁷ W/cm² onto a solid target have been carried out. The keV x-ray emission has been characterized both in air and in vacuum. In particular, the scaling of x-ray conversion efficiency and the dependence on pulse energy, angle of incidence and pressure have been studied. The x-ray conversion efficiency improves through the use of a prepulse, indicating that the interactions in the underdense plasma also contribute to hot electron and keV x-ray generation.

We report on the first measurements of a XANES spectrum of solvated Fe(CO)₅ using an ultrafast laser driven plasma x-ray source operating at 2 kilohertz repetition rate. The measured spectrum is compared to theoretical XANES spectra based on DFT structure calculations of the solvated complex. The used x-radiation is generated by irradiating a solid metal target with ultrafast high-intensity laser pulses. The subsequently generated high-density plasma emits x-ray pulses with sub-picosecond temporal resolution and an x-ray spectrum extends to energies far higher than the desired spectral range. Since these spectral components potentially falsify the XANES measurements, they were suppressed by the x-ray optical setup.

New approaches of a spectrally tunable backlighting schemes based on a spherically bent crystal are considered. In a contrary to the traditional backlighting scheme, in which the investigated objects should be placed between the backlighter and the crystal, for the considered schemes an object is placed downstream of the crystal, before the tangential or after the sagittal focus and an image of the object is recorded at the distance from the object corresponded to the needed magnification. The magnification is defined by the ratio of the distances form the sagittal focus to the detector and from the object to the sagittal focus. A ray tracing modeling and experimental images of test meshes, obtained at an incidence angles of the backlighter radiation of 10° and 22°, are presented. It is demonstrated that, at incident angles up to 22°, a linear transformation of the obtained astigmatic images allows to reconstruct them with an accuracy (5 - 15%). A spatial resolution around 10 μm in a field of view of some mm² is achieved, for the spectral range around 9 Å. It is also demonstrated that spherically bent crystals could be used for X-ray imaging of a self emitting plasma structures with a spatial resolution at least 50 μm in a field of view of some square millimeters for angles of incidence up to 22°.

An experiment on Soft X-ray Contact Microscopy (SXCM) performed on Caenorhabditis elegans nematodes is discussed. This sample has been selected since it is a well studied case used as model in many biological contexts. The experiment has been performed using the iodine PALS laser source to generate pulsed soft X-rays from laser-plasma interaction, using molybdenum and gold as targets. Typical intensities on the targets exceeded 10¹⁴ W/cm². The SXCM imprints have been recorded on Polymethilmetacrylate (PMMA) photo resists which have been chemically developed and analyzed with an Atomic Force Microscope (AFM) operating in constant force mode. The use of error signal AFM images together with topography AFM images, did allow an easier recognition of biological patterns, and the identification of observed structures with internal organs. Several organs were identified in the SXCM images, including cuticle annuli, alae, pharynx, and three different types of cell nuclei. These are the first SXCM images of multi-cellular complex organisms.

In the plasma flash x-ray generator, a high-voltage main condenser of approximately 200 nF is charged up to 50 kV by a power supply, and electric charges in the condenser are discharged to an x-ray tube after triggering the cathode electrode. The flash x-rays are then produced. The x-ray tube is a demountable triode that is connected to a turbo molecular pump with a pressure of approximately 1 mPa. As electron flows from the cathode electrode are roughly converged to a rod copper target of 3.0 mm in diameter by the electric field in the x-ray tube, weakly ionized linear plasma, which consists of copper ions and electrons, forms by target evaporation. At a charging voltage of 50 kV, the maximum tube voltage was almost equal to the charging voltage of the main condenser, and the peak current was about 15 kA. When the charging voltage was increased, the linear plasma formed, and the K-series characteristic x-ray intensities increased. The K-series lines were quite sharp and intense, and hardly any bremsstrahlung rays were detected. The x-ray pulse widths were approximately 700 ns, and the time-integrated x-ray intensity had a value of approximately 30 μC/kg at 1.0 m from the x-ray source with a charging voltage of 50 kV.

Polycapillary optics can be employed as efficient low pass devices in conjunction with simple absorption filters to produce narrow band radiation from conventional broadband x-ray tube sources. Narrow band filtration has been shown to be adequate for low-resolution protein crystallography without a monochromator and for investigating energy-dependent phenomena such as Compton scatter production. For applications that would benefit from more monochromatic or more parallel input beams, polycapillary collimating optics can be used to collect divergent radiation and redirect it towards a monochromatizing crystal to produce orders of magnitude higher diffracted intensity than from pinhole collimation. The implementation of high contrast monochromatic and refractive index imaging with a very low power source has been demonstrated. Polycapillary optics can also be used to provide spatial resolution for inherently monochromatic applications such as microfluorescence and radioscintigraphy.

A fundamental study on quasi-monochromatic parallel radiography using a polycapillary plate and a copper-target x-ray tube is described. The x-ray generator consists of a negative high-voltage power supply, a filament (hot cathode) power supply, and an x-ray tube. The negative high-voltage is applied to the cathode electrode, and the anode electrode is connected to the ground. In this experiment, the tube voltage was regulated from 12 to 22 kV, and the tube current was regulated within 3.0 mA by the filament temperature. The exposure time was controlled in order to obtain optimum x-ray intensity, and the maximum focal spot dimensions were approximately 2.0 x 1.5 mm. The polycapillary plate was J5022-16 (Hamamatsu Photonics Inc.), and the plate thickness was 1.0 mm. The outer, effective, and hole diameters were 33 mm, 27 mm, and 10 μm, respectively. Quasi-monochromatic x-rays were produced using a 10 μm-thick copper filter with a tube voltage of 17 kV, and these rays were formed into parallel beams by the polycapillary. The radiogram was taken using a computed radiography system utilizing imaging plates. In the measurement of image resolution, the resolution hadly varied according to increases in the distance between the chart and imaging plate using a polycapillary. We could observe a 50 μm tungsten wire clearly, and fine blood vessels of approximately 100 μm were visible in angiography.

We introduce a novel electron-impact x-ray source based on a high-speed liquid-metal-jet anode. Basic thermal power load calculations indicate that this new anode concept potentially could increase the achievable brightness in compact electron-impact x-ray sources by more than a factor 100 compared to current state-of-the-art rotating-anode or micro-focus sources. A first, successful, low-power proof-of-principle experiment is described and the feasibility of scaling to high-brightness and high-power operation is discussed. Some possible applications that would benefit from such an increase in brightness are also briefly described.

A novel type of electron-impact x-ray source based on the interaction of energetic electrons with a turbulently flowing liquid metal target is presented. The electrons enter the liquid through a thin (several microns thick) window, separating the liquid from the vacuum region in which the cathode is situated. Several electron window materials including diamond, tungsten and molybdenum were tested in combination with the liquid metal GaInSn. Satisfactory agreement has been obtained between the predictions of thermal transport models and the measured dependence of the loadability on fluid velocity. The liquid metal technology appears to represent a significant improvement in continuous loadability relative to stationary anode x-ray tubes.

Cherenkov radiation in the soft x-ray region is generated in narrowband regions at inner-shell absorption edges. Mainly low-Z elements are suitable Cherenkov sources, which emit in a photon energy range from 30 eV to 1 keV and require moderate electron energies up to 25 MeV. Generally, in the soft x-ray region materials are highly absorbing and therefore the Cherenkov radiation theory is discussed for absorbing media. A detailed description includes transition radiation that is generated at the interface when the relativistic electron exits the material. We show that the transition radiation yield equation, when it is adopted for an absorbing medium, includes Cherenkov radiation. Based on this approach it is shown that the spectral intensity of Cherenkov radiation in the soft x-ray region is large compared to transition radiation for moderate electron energies. First measurements of soft x-ray Cherenkov radiation in the water-window spectral region, generated in titanium and vanadium foils, are discussed in detail. The measured spectral and angular distribution of the radiation, and the measured total yield (≈ 10^-4 photon per electron) are in agreement with theoretical predictions based on the refractive index data. We show that the brightness that can be achieved using a small electron accelerator is sufficient for practical x-ray microscopy in the water window.