A laser driven electron x-ray source (LEXS) using a high repetition rate, terawatt laser system is described. The laser system has adopted design features that make it more suitable for the generation of hard x-ray pulses. These features include a simplified pumping scheme to reduce cost and complexity, a l/4 broadband regenerative amplifier to support high-energy, short optical pulse generation, and a 50-Hz repetition rate to achieve both desired pulse energy and simple compressor design. Preliminary results on x-ray generation using this system are reported. A new method, ultrafast selected energy x-ray absorption spectroscopy (USEXAS), based on this LEXS is discussed.

Non-thermal melting of semiconductor crystals, phase transitions on a sub-picosecond time scale can be studied by optical pump x-ray probe experiments. Powerful femtosecond lasers deliver brilliant ultrashort K_(alpha ) pulses on a time scale from 100 fs to 1 ps that can be optimized for these pump-probe experiments. These experiments consist of two diffracting elements: (i) a bent crystal imaging the flash x-ray source in a narrow spectral window; and (ii) the sample crystal diffracting the ultrashort x-ray pulse. As penetration depths of optical pump beam are usually much shorter than x-ray extinction depths, best sensitivity to ultrafast structural changes is obtained for minimum x-ray extinction depths. This can be achieved by selecting samples containing heavy elements, thin crystalline film samples and by using asymmetric Bragg reflections, respectively. Several theoretical codes have been developed to optimize design of the instruments. X-ray topographic cameras and diffractometers were modified for fabrication and characterization of 2D bent crystals. Best practical results were obtained when structurally perfect wafers of Si, Ge, and quartz crystals were prepared while monitored by x-ray topography and diffractometry. After a final check of x-ray imaging and reflection properties of the toroidal crystals, monochromatic x-ray beam and laser pump beam are adjusted spatially to coincide on the sample crystal. Because converging x-rays impinge on the sample crystal, its rocking curve can be registered as a spatial distribution on the detector. In comparison to synchrotron experiments where about 10⁴ pulses must be integrated, in these experiments rocking curves can be recorded in a single or in a few laser shots. Ultrafast processes are studied in Langmuir Blodgett films containing Cd, in bulk semiconductors, such as InSb, and in CdTe semiconductor films. Focused, pulsed monochromatic x-rays have been transmitted through biological samples to register many reflections, which opens the way to ultrafast studies in structural biology.

Results of fs laser-produced plasma diagnostics, which were provided using Focusing Spectrometer with Spatial Resolution having as an x-ray detector Princeton x-ray CD or Hamamatsu x-ray MCP, are presented. A portable, high-luminosity spherically bent crystal spectrometers were designed for the purposes of measuring very low emissivity x-ray spectra of different targets, heated by fs laser radiation, with simultaneously high spectral and space resolution. Large open aperture mica spherically bent crystals are used as dispersive elements of spectrometers. High tunability allowed to receive high-resolved spectra of clusters, heated by 35 fs Ti:Sa laser pulses with energy only 15 mJ in spectral ranges: 15-17 angstrom - for H- and He-like ions of Oxygen, 5-5.7 angstrom for Ne-like ions spectra of Kr, 3.0- 3.4 and 3.7-4.4 angstrom for H- and He-like spectra of Ar without any realignment of x-ray CCD spectrometer using one set up. Using another alignment ste up of spectrometer with x-ray MCP has been received spectra of solid targets, heated by 60 fs Ti:Sa laser pulses in spectral ranges: 15.2-17.5 angstrom near resonance lines of He-like ion of fluorine, 7.6-8.75 angstrom for spectra between He_(alpha ) and K_(alpha ) lines of Al and near Rydberg lines of Ne-like Cu, 3.04 - 3.5 angstrom for spectra around K_(alpha ) lines of Ca, 1.38-1.59 angstrom for spectra around K_(alpha ) lines of Cu. Some results of plasma diagnostics for both cases of clusters and solid targets, heated by fs laser radiation are presented and discussed.

We have characterized the ultrafast solid-liquid transition of InSb and CdTe semiconductors by time resolved x-ray diffraction in the femtosecond timescale. Visible spectroscopic data were obtained together with x-ray measurements to characterize the dense electron-ho9le plasma at the origin of the phase transition following the IR excitation.

We propose a cross-correlation technique for measuring the shape of an ultrashort soft x-ray-pulse using the rapid change in the Kr⁺ population that occurs during optical field-induced ionization. By calculating the time evolution of the Kr charge states during ionization, we showed that the increase in the Kr⁺ population operates as 'switch', and the transient state of Kr⁺ during the sequential ionization operates as 'sampling gate' for measuring a soft x-ray-pulse shape. The temporal resolution of this technique is expected to overcome the limitation imposed by the ionizing laser pulse duration as a result of the ultrafast nature of optical field-induced ionization. Using the 'switch' operation, we measured a soft x-ray-shape pulse are 15.6 nm emitted from W plasma produced by a 100-fs laser pulse. Assuming a Gaussian temporal profile, we found the soft x-ray-pulse duration to be about 4 ps. This result is in good agreement with the duration measured with an x-ray streak camera thus configuring the feasibility of this 'switch' operation. The 'sampling gate' operation will be useful for directly measuring the original pulse shape of a femtosecond soft x-ray.

Ultrafast high-intensity laser pulses incident upon condensed matter targets can generate solid-density plasmas that emit x-ray pulses with sub-picosecond temporal structure and significant spatial coherence. Such ultrafast laser-driven plasma x-ray sources based on solid and liquid targets are currently under construction in our laboratory. Performance details at several kilohertz laser pulse repetition rates are discussed. As an application of the temporal structure of laser-generated x-ray pulses, ultrafast x-ray absorption fine structure (UXAFS), currently under development, is discussed. It allows, in principle, to measure the structural dynamics of atoms during a chemical process in solution. An overview over UXAFS is presented and properties of our ultrafast x-ray absorption spectrometer are discussed. First calculations of time dependent UXAFS-spectra for ironpentacarbonyl are presented. Ultrafast molecular dynamics depend on the structure of the solvated molecule at the moment of photo-excitation. This structure depends on the solute's interaction with the solvent. Furthermore, the solute's vibrational modes and structure are correlated, solvent dependent, and can be measured by mid-infrared and x-ray absorption spectroscopy. Such measured spectra are presented and correlated with semi-empirical quantum calculations in order to elucidate the solvation environment of transition metal coordination complexes in various solvents.

Recent advances in femtosecond laser plasma x-rays sources have resulted in several experiments to explore the dynamics of physical and chemical processes on the femtosecond time scale. We present our most recent progresses on the development of an intense broadband x-ray source in the multi-keV range, for application to time-resolved EXAFFS experiments. Experiments have been realized with two different CPA laser systems having different pulse durations and characteristics. X-ray emissions in the 5KeV range generated form solid targets with the INRS Nd:Glass laser and the UCSD Ti:Sapphire laser have been characterized through high resolution and time resolved x-ray spectroscopy. The application of this source to time resolved EXAFS measurements with a sub-picosecond time resolution will also be discussed.

The droplet laser plasma source has previously been shown to have many attractive features as a continuous, almost debris-free source for EUV and x-ray applications. In a combined experimental and theoretical study, we analyze the interaction physics between the laser light and the target over a range of conditions.

Cryogenic liquid jets of either nitrogen or argon of up to 30 micrometer in diameter were exposed to intense laser fields with pulse durations between 70 fs and 3 ns leading to intensities of 10¹⁶ W cm^-2 and 10¹³ W cm^-2, respectively. The emission of extreme UV light and soft X-rays investigated by means of an absolutely calibrated soft X-ray spectrograph shows the characteristic lines of highly ionized nitrogen and argon atoms. For nitrogen the emitted photon flux at the longer pulse length was several orders of magnitude higher than for 70 fs pulses whereas for argon pulse durations around one ps lead to the highest conversion efficiency (CE) from laser to soft X-ray radiation.

Characterization measurements of a laser-produced x-ray source based on a double-stream ga puff target are presented. The target was irradiated with a Nd:glass laser producing 1 ns pulses with energy up to 10 J. Production in the wavelength range up to 200 nm have been measured form xenon, krypton, argon, and nitrogen targets using the transmission grating spectrometer with the back-illuminated CCD and the absolutely calibrated silicon photodiodes. Spectral characteristics of x-ray and EUV emissions are presented.

The life time of the first multilayer mirror (the condenser) in optical systems for projection Extreme Ultra-Violet (EUV) lithography based on Laser Produced Plasmas (LPP) is limited both by the debris bombardment and by the EUV radiation photoablation. These problems can be dramatically reduced by using krypton as debris stopper, exploiting its high atomic weight (21 times the helium value) and its high transparency in the EUV region only between 60 and 90 eV. We demonstrate both theoretically and experimentally that by filling the laser-target interaction chamber with krypton at low pressure (a few mbar) it is possible to stop efficiently the small debris (having a size smaller than 1 micron, including ions, neutrals and clusters) while keeping a reasonable transmission of the EUV radiation in the 60-90 eV range. In particular, this is experimentally demonstrated for a solid target LPP based on a tantalum or copper tape target and pumped by a large energy (4 J - 120 ns) XeCl excimer laser. The poor transmission of krypton, out of the above mentioned spectral window, significantly reduces the exposition of the condenser mirror to useless radiation. This new technique for stopping the debris has recently been patented by our group. As far as the larger size debris is regarded, a dramatic reduction of their flux has been obtained by decreasing the laser intensity on the target, still keeping a laser to EUV energy conversion as high as 0.7 percent/eV/sr at 70 eV, from a Ta target, together with a shot to shot EUV pulse energy stability better than 1 percent.

X-ray emissions form Xe cryogenic target, Kr cryogenic target and Xe gas target were studied and compared. A high average high peak brightness pulsed Nd:YAG laser was successfully developed as a driver for high average power laser plasmas x-ray sources. A target system that can supply cryogenic targets without interrupting the operation was also developed. Any discrete images of fast debris of several 10 micrometers or more in diameter were not observed in backlighting experiments. A new approach to extinguish the fast debris from the cryogenic target by using 'laser shower' was proposed and proved to be practical.

We have performed studies of keV x-ray production from (formula available in paper) rare gas clusters submitted to intense IR laser pulses. Up to (formula available in paper) per pulse at a moderate atomic density have been observed. High resolution spectroscopy studies in the case of (formula available in paper) clusters have also been performed, gibing unambiguous evidence of highly charge ions with K vacancies production. We have determined the photon energies and the absolute photon emission yields as a function of several physical parameters governing the interaction: size and atomic number of the clusters, peak intensity of the laser. Unexpectedly low laser intensity thresholds have been measured. The result obtained indicate nevertheless that x-rays may be emitted before cluster explosion on a subpicosecond time scale, and that several mechanisms must be involved in the first stage of the production of the hot nanoplasma induced from each cluster.

Large Xe-clusters have been excited with 50 fs and 2 ps pulses from a Ti:Sa multi - TW laser at 800 nm wavelength. Additionally a 10 ns Nd:YAG laser at 1064 nm wavelength was used to heat Xe-cluster/gas and a liquid Xe-spray target. Absolute yield measurements of EUV-emission in a wavelength range between 10 nm and 15 nm in combination with target variations were carried out. The ps-laser pulse has resulted in about 30 percent enhanced and spatially more uniform EUV-emission compared to fs-laser excitation. Similar emission has been obtained with ns-pulse exposure of different target modifications which also act back to the EUV-source size. Absolute emission efficiencies at 13.4 nm of up to 0.8 percent in 2pi sr and 2.2 percent bandwidth were measured.

A laser-based EUV plasma source is described, which is going to be utilized for characterization of EUV optical components and sensoric devices in the wavelength region from 11 to 13nm. EUV radiation is generated by focusing a Nd:YAG laser into a double stream gas puff target. By the use of different target gases, broadband as well as narrow-band EUV radiation can be obtained. The emission characteristics of the radiation is monitored by the help of different diagnostic tools including a pinhole camera, an EUV spectrometer, and various EUV photodiodes, either directly or after reflection from multilayer mirrors. Moreover, first wavefront measurements of EUV radiation are performed with the help of a specially designed wavefront analyzer based on the Hartmann-Shack principle, which was sensibilized for 13nm radiation. This device can be used as an alternative to interferometric measurements for an assessment of the optical quality of EUV optics, e.g. for at wavelength monitoring of aberrations (including Zernike analysis), as well as for on-line monitoring of heating effects.

Review of systematic investigations of x-ray radiation properties of different clusters heated by short-pulse high- intensive TI:Sa laser radiation is presented. The cluster targets were formed by the adiabatic expansion in vacuum of an Ar or CO₂ gas puff produced by a pulsed valve with a Laval or conical nozzles. The gas jet pressure is varied form 15 up to 100 bar. Detailed theoretical modeling of cluster parameters have been done and compared with experimental measurements. High spectrally and spatially resolved x-ray spectra near resonance lines of H- and He- like ions of oxygen and Ar have been obtained and detailed spectroscopic analysis was consistent with a theoretical two-temperature collisional-radiative model of irradiated atomic clusters incorporating with an effects of highly energetic electronics. The role of laser prepulse for x-ray intensity emission and its spatial distribution were investigated in details. X-ray spectra radiation from plasma with electron density more than 10²² cm^-3 was at first time observed. Big effect of fast electrons influence on the x-ray emission of He-like Ar spectra was demonstrated. Comparison with data under various experimental conditions clearly demonstrated that for increasing x-ray output form plasma the most essential to increase size of clusters and has reasonable value of ps prepulse.

X-ray sources in the 3-7 keV energy regime can be produced by laser-irradiating mid- and high-Z gas-filled targets with high-powered lasers. A series of experiments have been performed using underdense targets that are supersonically heated with approximately 35 kJ of 0.35 micrometers laser light. These targets were cylindrical Be enclosures that were filled with 1-2 atms of Xe or Ar gas. L-shell x-ray emission is emitted from the plasma and detected by Bragg crystal spectrometers and x-ray diodes. Absolute flux measurements show conversion efficiencies of approximately 10 percent in the multi-kilovolt x-ray emission. These sources can be used as bright x-ray backlighters or for material testing.

A compact device, based on fast capillary discharge plasmas, is an intense EUV and soft x-ray source of radiation. Th plasma is created by a discharge of low-inductance capacitors through a gas-filled ceramic capillary. Parameters of the discharge are: maximum current of 25 kA at applied voltage 40 kV, a pulse duration of 20-30 ns at FWHM, and a rise time of 1.5 ns. The soft x-ray and EUV emission of multiply charged ions is investigated using a compact 1 meter grazing incidence spectrometer-monochromator with a constant angle of deviation. The use of various gases allows the observation of XUV spectra in a wide spectral range (4- 45 nm). A Xe-filled capillary discharge shows intense radiation near 13.5 nm - the region of interest for EUV lithography applications. A reflectometer is used for testing grazing incidence gratings.

We report on a fast soft x-ray source consisting in a high temperature small diameter plasma column produced by electric discharge in a ceramic capillary. This source was developed to produce pulses of few hundred nanosecond duration for EUV lithography, x-ray microscopy applications and also with the aim of developing a soft x-ray amplifier. We obtained experimental results concerning the intensity and spectral analysis of the emitted x radiation pumped by a 30-40 kA, 100-200 ns, electric discharge at 1 Torr pressure in Ar gas. We refer also on the spectra obtained using CO₂, as plasma medium, after the optimization of the discharge setup and electrical parameters.

A novel x-ray tube has been produced by using a line filament as a cathode. It is found that the electrons emitted form the filament arrive on the anode in a line perpendicular to the direction of the filament. The image of the x-ray emitting area on the anode obtained with a x-ray pinhole camera and a CCD detector shows a slightly curved line. The formation of this curved line is explained by Monte Carlo calculations, which include electric and magnetic fields in the x-ray tube as well as Joule heating, surface cooling, and thermal conduction in the cathode. The experimental result sand the result form the Monte Carlo calculations are presented.

The application of x-ray sources to imaging of dense objects is standard technique. The quality of the x-ray image depends both on the x-ray source wavelength and on the flux. To improve the flux of the x-ray source it is important to understand how the conversion efficiency scales with laser irradiance and target material. We present measurements of x-ray conversion efficiency in sold Cr, Fe, Ni Zn and Ge targets as s function of the laser irradiance using the OMEGA laser facility. The results show a steep decease in the conversion efficiency with increasing Z while the scaling of conversion efficiency with laser irradiance can show a peak. Values for x-ray yield are determined using time-integrated crystal spectrometer data.

Several methods of using the X pinch as a source of x-ray radiation for the radiography of dense plasmas and other objects are presented. These methods do not use pinholes, instead taking advantage of the small source size and short x-ray emission duration of the X pinch radiation. Detailed measurements of the emission characteristics of X pinches made using different wire materials and in different energy ranges using a set of x-ray diagnostics with high temporal and spatial resolution are presented. Several applications of the X pinch are discussed.

Hot dense lanthanum plasmas have been produced by irradiating a solid Lanthanum target with a high contrast 400fs laser pulses at 3 X 10¹⁸ W/cm². The M-shell emission has been recorded in the wavelength range 10A-14A using a high-resolution crystal spectrometer. The emission has been time resolved using our PX1 x-ray streak camera with a temporal resolution of 350fs. A superconfiguration model for non-LTE plasmas coupled to hydrodynamics calculations is used to discuss the measurements. Our work indicates that a correct understanding of intermediate and high Z dense plasmas, created with femtosecond clean laser pluses, requires time resolved spectroscopy with femtosecond resolution and NLTE atomic physics coupled to plasma hydrodynamics.

X-ray spectra in the energy range 12-60 keV were recorded by a transmission crystal spectrometer form targets irradiated by the 60 beam, approximately kJ, OMEGA laser. The targets consisted of planar silver and gold foils, spherical gold targets, and krypton-filled CH shells. The time-integrated spectral images were recorded by a CCD sensor with a phosphor conversion screen. Emission features identified in the spectra include the silver K(alpha) line at 22.1 keV and the helium-like krypton resonance line series at 13-17 keV.

We have developed the stress-strain in-situ measurement system of rotating object with a low timing-jitter pulsed x- ray source triggered by a laser plasma and the triggering jitter of the pulsed x-ray was less than 2nsec. This technique was applied to measure the lattice constant variation of a rotating sample under the influence of stress caused by a centrifugal force.

Absolute x-ray calibration of laser-produced plasmas was performed using a CCD linear array and a focusing crystal spectrometer. The plasmas were created by a Nd glass laser and a high repetition rate Nd-YAG laser. A commercial CCD was used for x-ray detection. The CCD linear array has 3724 pixels giving a total length of approximately 30 mm. First the CCD detector was absolutely calibrated using laser- produced plasmas and an FE⁵⁵ isotope source. The sensitivity of the detector was about two orders of magnitude higher than x-ray photographic film. The CCD detector was used for monitoring the absolute x-ray yield, for finding the optical focal position, for estimating the flux density on the target and for measuring the electron temperature of the plasma. In combination with a focusing von Hamos spectrometer the detector was used for absolute spectral measurements and determination of the plasma parameters. This spectrometer is promising for absolute spectral measurements of x-ray radiation of low-intensity sources and for numerous practical applications.

Two types of x-ray sources for dual energy subtraction angiography (DESA), laser-based and conventional, were investigated. A Tabletop Terawatt laser was used to create x-ray source with Ba, La, Nd, Gd, and Ce targets. A theoretical model of image quality was developed. A Figure of Merit, FOM equals SNR./(integral dose)1/2, was obtained. Images of an angiographic contrast detail phantom were obtained using laser-driven x-ray source in DESA regime and a standard angiography unit in DSA regime. The log-signals due to Iodine contrast agent in the images were measured and compared with the theoretical model predictions. The integral dose was estimated. We found that the La and Ba lines extracted by a monochromator are optimal for imaging Iodine contrast with laser-based DESA. In this case, SNR exhibits three- to five-fold improvement, as compared to SNR expected for a tube-based DESA system. Consequently, dose utilization, as defined by FOM, improves by factor of two to three, depending on patient thickness and scatter conditions. When only filters are used, SNR and FOM due to laser-based system are comparable to those due to tube-based DESA. In this case, preferable target/filter combination for the laser system is Ba/I and Ce/Nd for the low- and high-beam, respectively.

The application of the X pinch x-ray source for phase-contrast x-ray radiography of low absorption materials is demonstrated. The X pinch is a source of radiation in the 1-10 keV x-ray band with extremely small size and short pulse duration. The small source size provides high spatial coherence of the imaging x-ray beam, enabling it to be used to image low absorption, low contrast objects with excellent spatial resolution. Images with spatial resolution better than 3 micrometers of exploded, insulated 25 micrometers W wire and biological objects are presented. The advantages of the X-pinch over other x-ray sources are discussed.

A novel experimental setup for transmission x-ray microscopy is presented. It is based on the use of a point isotropic x- ray source and a single spherical crystal. The x-ray beam intensity is modulated by the object attenuation, then monochromatized and enlarged using a spherical crystal and, lastly, imaged using a detector downstream of the crystal. We demonstrate by ray tracing technique and experimental testing that this system allows microscopy studies with image resolution better than the dimensions of the source, high magnification ratios, and great field of view. Microscopes using this model ca be easily built using different micro x-ray sources, like conventional x-ray tube generators, x-rays emitted by laser generated plasmas or synchrotron radiation. Utilization of spherically bent crystals to obtain high-resolution, large field, monochromatic images in a wide range of Bragg angles is demonstrated for the first time. High quality monochromatic images with high magnification about 15-35 times and spatial resolution over a large field of view were obtained. Some possible applications and preliminary experimental verification of the feasibility of the setup are also presented.

Ultra-short x-ray sources are generated by focusing sub- picosecond lasers on massive targets. The emission duration of a samarium x-ray source produced with a 100 TW sub- picosecond laser was measured using an ultra-fast X-ray streak camera. The spectral range was limited around 7.5-8.5 angstrom, the range in which samarium can be used as a backlighter for K(alpha) aluminum absorption experiments. The spectral time-evolution and the duration of samarium emission were measured. Preliminary calculations performed with non-local-thermodynamic equilibrium atomic physics show the plasma cooling which occurs with a characteristic time longer than predicted by radiative hydrocode simulations.