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We report on the J-KAREN-P laser facility at QST, which can provide PW peak power at 0.1 Hz on target. The system can deliver short pulses with an energy of 30 J and pulse duration of 30 fs after compression with a contrast level of better than 1012. Such performance in high field science will give rise to the birth of new applications and breakthroughs, which include relativistic particle acceleration, bright x-ray source generation, and nuclear activation. The current achieved laser intensity on target is up to > 9x1021 Wcm-2 with an energy of ~9 J on target. The interaction with a 3 to 5- μm stainless steel tape target provides us electrons with a typical temperature of more than 10 MeV and energetic proton beams with typical maximum energies of > 40 MeV with good reproducibility. The protons are accelerated in the Target Normal Sheath Acceleration regime, which is suitable for many applications including as an injector into a beamline for medical use, which is one of our objectives.

We present an overview of our systematic studies of the surface modifications resulting from the interactions of both single and multiple picosecond soft x-ray laser (SXRL) pulses with materials, such as gold (Au), copper (Cu), aluminum (Al), and lithium fluoride (LiF). We show experimentally the possibility of the precise nanometer size structures (~10–40 nm) formation on their surfaces by ultra-low (~10–30 mJ/cm2 ) fluencies of single picosecond SXRL pulse. Comparison experimental results with the atomistic model of ablation, which was developed for the single SXRL shot interaction with dielectrics and metals, is provided. Theoretical description of surface nanostructures is considered and is shown that such structures are formed after laser illumination in a process of mechanical spallation of ultrathin surface layer of molten metal. Spallation is accompanied by a strong foaming of melt, breaking of foam, and freezing of foam remnants. Those remnants form chaotic nanostructures, which are observed in experiments. Our measurements show that electron temperature of matter under irradiation of SXRL was lower than 1 eV. The model calculation also predicts that the ablation induced by the SXRL can create the significant low electron temperature. Our results demonstrate that tensile stress created in LiF and metals by short SXRL pulse can produce spallative ablation of target even for drastically small fluencies, which open new opportunities for material nano processing.

To study the ablation process induced by the soft x-ray laser pulse, we investigated the electron temperature of the ablating material. Focused soft x-ray laser pulses having a wavelength of 13.9 nm and duration of 7 ps were irradiated onto the LiF, Al, and Cu surfaces, and we observed the optical emission from the surfaces by use of an optical camera. On sample surfaces, we could confirm damage structures, but no emission signal in the visible spectral range during ablation could be observed. Then, we estimated the electron temperature in the ablating matter. To consider the radiation from a heated layer, we supposed a black-body radiator as an object. The calculation result was that the electron temperature was estimated to be lower than 1 eV and the process duration was shorter than 1000 ps. The theoretical model calculation suggests the spallative ablation for the interaction between the soft x-ray laser and materials. The driving force for the spallation is an increasing pressure appearing in the heated layer, and the change of the surface is considered to be due to a splash of a molten layer. The model calculation predicts that the soft x-ray laser with the fluence around the ablation threshold can create an electron temperature around 1 eV in a material. The experimental result is in good accordance with the theoretical prediction. Our investigation implies that the spallative ablation occurs in the low electron temperature region of a non-equilibrium state of warm dense matter.

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Experimental demonstration of multi-charged heavy ion acceleration from the interaction between the ultra-intense short pulse laser system and the metal target is presented. The laser pulse of

We present an overview of our systematic studies of the surface modifications resulting from the interactions of both single and multiple picosecond soft x-ray laser (SXRL) pulses with materials. We show experimentally the possibility of the precise nanometer size structures formation on their surfaces by ultra-low fluencies of single picosecond SXRL pulse. Theoretical description of surface nanostructures is considered and is shown that such structures are formed after laser illumination in a process of mechanical spallation of ultrathin surface layer of molten metal. Spallation is accompanied by a strong foaming of melt, breaking of foam, and freezing of foam remnants. Those remnants form chaotic nanostructures, which are observed in experiments. Our results demonstrate that tensile stress created in materials by short SXRL pulse can produce spallative ablation of target even for drastically small fluencies, which open new opportunities for material nano processing.

To study the interactions between a soft x-ray laser (SXRL) and various materials, we irradiated Al, Au, Cu, and Si with the SXRL beam pulses having a wavelength of 13.9 nm and duration of 7 ps. Following the irradiation, the induced structures were observed using a scanning electron microscope and an atomic force microscope. With single pulse irradiation, conical structures were observed on the Al surface, and ripple-like structures were formed on the Au and Cu surfaces. The conical structures were destroyed under multiple SXRL pulse irradiation. On the other hand, the developments of modified structures were observed after multiple pulse irradiations on the Au and Cu surfaces. On the Si surface, deep holes, that seemed to be molten structures induced by the accumulation of multiple pulse irradiations, were found. Therefore, it is concluded that the SXRL pulse irradiations of various material surfaces cause different types of surface modifications, and the changes in the surface behaviors are attributed to the differences in the elemental properties of each materials, such as the melting point and the attenuation length of x-rays.

We demonstrate a new ion diagnosis method for high energy ions by utilizing a combination of a single CR-39 detector and plastic plates, which enables to detect high energy ions beyond the detection threshold limit of the CR-39. This detection method coupled with a magnetic spectrometer is applied to identify high energy ions of 50 MeV per nucleon in laser-driven ion acceleration experiments using cluster-gas targets.

Review of results, obtained by using recently proposed new imaging detector, based on formation of color centers in LiF crystal and LiF film, for in situ high performance measurements of near-field and far-field properties of soft X-ray lasers (SXRL) beams is presented. Experiments have been carried out with laser-driven transient-collision plasma SXRL and free electron SXRL beams. It was demonstrated that due to favorable combination of high spatial resolution, high dynamic range and wide field of view this technique allows measuring not only intensity distribution across the full beam and in local areas, but also permits to evaluate coherence and spectral distribution of radiation across the beam. Experimental diffraction patterns in the images of periodical structures are analyzed by comparison with the modeled ones in the last case. The estimated accuracy of measurements is between 10-20%.

We present experimental results, theory, and simulations demonstrating two novel sources of coherent X-ray radiation generated in the relativistic laser (>10 18 W/cm 2 ) interaction with easily accessible, repetitive, and debris-free gas jet targets. The first source is based on a relativistic mirror reflecting a counter-propagating laser pulse. A strongly nonlinear breaking wake wave driven by an intense laser pulse can act as a semi-transparent relativistic flying mirror. Such a mirror directly converts counter-propagating laser light into a high-frequency (XUV or X-ray) ultrashort pulse due to the double Doppler effect. In the experimental demonstration with the 9 TW J-KAREN laser, the flying mirror generated in a He gas jet partially reflected a 1 TW pulse, providing up to ~10 10 photons, 60 nJ (~10 12 photons/sr) in the XUV range (12.8-22 nm). The second source is demonstrated with the laser power ranging from 9 to 170 TW in experiments with the J-KAREN and Astra Gemini lasers. The odd and even order harmonics generated by linearly as well as circularly polarized pulses are emitted forward out of the gas jet. The 120 TW laser pulses produce harmonics with ~3×10 13 photons/sr (~600 μJ/sr) in the 120±5 eV spectral range. The observed harmonics cannot be explained by previously known mechanisms (atomic harmonics, betatron radiation, nonlinear Thomson scattering, etc.). We introduce a novel mechanism of harmonic generation based on the relativistic laser-plasma phenomena (self-focusing, cavity evacuation, bow wave generation), mathematical catastrophe theory which explains the formation of structurally stable electron density singularities, spikes, and collective radiation of a compact charge driven by a relativistic laser.

Compact sources of high energy protons (50-500MeV) are expected to be key technology in a wide range of scientific applications 1-8. Particularly promising is the target normal sheah acceleration (TNSA) scheme 9,10, holding record level of 67MeV protons generated by a peta-Watt laser 11. In general, laser intensity exceeding 1018 W/cm2 is required to produce MeV level protons. Enhancing the energy of generated protons using compact laser sources is very attractive task nowadays. Recently, nano-scale targets were used to accelerate ions 12,13. Here we report on the first generation of 5.5-7.5MeV protons by modest laser intensities (4.5 × 1017 W/cm2) interacting with H2O nano-wires (snow) deposited on a Sapphire substrate. In this setup, the plasma near the tip of the nano-wire is subject to locally enhanced laser intensity with high spatial gradients, and confined charge separation is obtained. Electrostatic fields of extremely high intensities are produced, and protons are accelerated to MeV-level energies. Nano-wire engineered targets will relax the demand of peak energy from laser based sources.

The paper is devoted to experimental and theoretical studies of ablation of condensed matter by optical (OL),extreme ultraviolet (EUV) and X-ray lasers (XRL). Re sults obtained at two dierent XRL are compared. The“rst XRL is collision Ag-plasma laser with pulse duration L = 7 ps and energy of quanta h =89.3 eV, whilethe second one is EUV free electron l aser (EUV-FEL) and has parameters L =0.3 ps and energy of quanta 20.2eV. It is shown that ablation thresholds for these XRL at LiF dielectric are approximately the same. A theory ispresented which explains slow growth of ablated mass w ith ”uence in case of XRL as a result of transition fromspallative ablation near threshold to evaporative ablation at high ”uencies. It is found that the metal irradiatedby short pulse of OL remains in elastic state even in hig h shear stresses. Material strength of aluminum at veryhigh deformation rates V/V 10 9 s 1 is de“ned.Keywords: Short pulse laser ablation, EUV and X-ray laser ablation of LiF, material strength de“ned in laserexperiment

This paper gives an overview of recent progress of laser-driven plasma x-ray lasers in Japan Atomic Energy Agency (JAEA). Fully spatial coherent plasma x-ray laser (XRL) at 13.9 nm with 0.1 Hz repetition rate has been developed using new driver laser system TOPAZ, and the succeeding optimization of the pumping condition has realized more efficient generation of the coherent x-ray pulse. The 0.1 Hz XRL is now routinely used in the wide variety of the application experiments: The highlights of these applications are the study of fluctuation in the atomic structure of ferroelectric substances under the phase transition using the double XRL probe beam technique and the construction of new x-ray laser interferometer to observe nano-scale dynamics of materials.

Electromagnetic wave generation in the extreme ultraviolet (XUV) and infrared (IR) wavelength range occurs during the interaction of intense short laser pulses with underdense plasmas. XUV pulses are generated through laser light reflection from relativistically moving electron dense shells (flying mirrors). A proof-of-principle and an advanced experiment on flying mirrors are presented. Both of the experiments demonstrated light reflection and frequency upshift to the XUV wavelength range (14-20 nm). The advanced experiment with a head-on collision of two laser pulses exhibited the high reflected photon number. IR radiation, which is observed in the forward direction, has the wavelength of 5 μm and dominantly the same polarization as the driving laser. The source of the IR radiation is attributed to emission from relativistic solitons formed in the underdense plasma.

A model that solves simultaneously both the electron and atomic kinetics was used to generate synthetic X-ray spectra to characterize high intensity ultrashort-laser-driven target experiments. A particle-in-cell simulation was used to model the laser interaction for both cluster and foil targets and provided the initial electron energy distribution function (EEDF) for a Boltzmann solver. Previously reported success in the spectroscopic characterization of an irradiated Ar cluster target has motivated the authors to apply this technique in a feasibility study to assess the possibility of recording time resolved spectra of a 10 micron Ti foil target irradiated by a 500 fs, I= 1.0 × 10 18 W/cm 2 short-pulse laser. Though this model suggests that both Ar cluster and Ti foil plasmas are held in a highly non-equilibrium state for both the EEDF and the ion level populations for several picoseconds, the spectral line features of the foil experiment was shown to evolve too quickly to be seen by current ultrafast time resolved spectrometers.

Among insulating materials containing point defects, Lithium Fluoride, LiF, is a radiation sensitive material well known in dosimetry and as active medium in optically pumped optolectronic devices. Primary and aggregate electronic defects, known as colour centres (CCs), can be efficiently produced in LiF by low-penetrating radiation. A novel imaging detector for soft X-ray microscopy, based on photoluminescence from laser active CCs, is currently under development. The continuous shrinking dimensions of photonic devices has prompted us to use thin LiF films, directly grown by thermal evaporation on different substrates, as recording media in Extreme Ultra-Violet contact-lithography experiments for the fabrication of permanent, regular, light-emitting microstructures, produced with high spatial resolution on large areas in short exposure times. The experiments were performed by using geometrical masks in an excimer-pumped laser-plasma source and the samples analyzed by confocal laser scanning microscopy. Strong visible photoluminescence at room temperature was measured from very thin surface layers. A preliminary comparison between the optical response of CCs in thin LiF films grown on glass and silicon substrates with respect to LiF crystals was performed. The polycrystalline LiF films show a higher sensitivity, which is discussed taking into account light confinement effect in the investigated planar structures.

High-resolution X-Ray spectromicroscopy methods were used for investigations of fs laser interaction with N2O cluster media. Elongated (up to 8.5 mm) femtosecond laser self-channeling in N2O cluster media under sufficiently low laser intensity (0.5-4x1017 W/cm2) was observed. Results are revealing a strong macroscopic effect on laser beams owing to their interaction with a gas of clusters. This has occurred at moderate pulse intensities, so the effect is unrelated to either relativistic self-focusing or ponderomotive filamentation. Enough homogeneous multicharged ions plasma with bulk electron temperature around 100 eV was observed along the plasma channel. The spectral lines shapes of the H- and He-like Oxygen ions demonstrated the presence of strong "blue wings", which are caused by Doppler-shifted lines radiation from the essential fraction of ions (~10-2 - 10-3) with energies 0.1 - 1.5 MeV. The slope of Doppler-shifted lines radiation is good approximated by ~300 KeV ion temperatures.© (2006) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Periodic luminescent patterns based on active color centers have been efficiently created in Lithium Fluoride (LiF) crystals and films by Extreme Ultra-Violet (EUV) light and soft x-rays from a laser-plasma source by masking the incoming radiation. Strong visible photoluminescence at room temperature has been measured from colored geometric microstructures, produced with high spatial resolution on large areas in short exposure times. Accurate spectrophotometric measurements allow estimating a significant increase in the real part of the refractive index, locally induced by the formation of high concentrations of stable primary and aggregate electronic defects at the surface of the LiF irradiated crystal, in a very thin layer, whose depth has been evaluated around 50 nm. On the basis of a semi-classical dipole-electromagnetic field interaction model, the contribution of different kinds of point defects to the overall refractive index change has been quantified. Promising opportunities in the fabrication of passive and active devices for integrated optics, such as gratings and distributed lasers, are offered by the use of this kind of radiation.

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 a. 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°.

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 10 19 W/cm 2 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 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.

The recent progress in the development of the tabletop soft x-ray lasers pumped by capillary discharges has opened the possibility of the widespread use of these coherent sources for applications. In this paper, we present the latest results achieved in our laboratory concerning the optimization of a 46.9nm capillary discharge pumped soft x-ray laser and the imaging of the laser beam on Lithium Fluoride (LiF, films), which appears to be a new promising x-ray detector. The use of LiF allows a high spatial resolution (smaller than 1μm) on large areas, high-contrast imaging and simple manipulation. The laser, which is pumped by 18-20kA, 150-180ns long current pulses at a repetition rate of 0.1Hz, is produced in 3.2mm diameter up to 45cm length alumina capillary tubes filled with Ar at the initial gas pressure of 300-600mTorr. At the capillary lengths examined, the laser is operating in the saturation regime giving an output energy of about 300μJ per pulse and high coherence degree.

The miniaturization of optical devices is a key objective in the field of photonics, and a large set of materials and techniques are under investigation. Among the former, lithium fluoride (LiF) is of particular interest because it is almost not hygroscopic and it can host stable color centers (CCs) produced by ionizing radiation and emitting in the visible spectral range even at room temperature (RT) under optical excitation. The increasing demand for low-dimensionality photonic devices imposes the utilization of advanced lithographic techniques for producing luminescent structures with submicrometric spatial resolution. We present an innovative irradiation method producing CCs in LiF crystals and films by using an EUV and soft X-ray laser-plasma source. This technique is able to produce colored patterns with high spatial resolution on large (more than 10 cm2) areas in a short exposure time compared with other irradiation methods. The colored LiF samples have been characterized by optical absorption and photoluminescence measurements for different irradiation fluences.

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.© (2001) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

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.© (2001) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

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.© (2001) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

At the Z6 experimental area of the Gsesellshaft fur Schwerionenforschung in Darmstadt experiments with the nhelix laser facility were carried out to determine the plasma parameter sch as temperature, degree of ionization and expansion dynamics for laser heated targets, which are used for the ion beam-plasma-interaction experimental series. Spatially resolved x-ray spectroscopy with spherically bent mica crystals showed well collimated jets of He- and H-like ions emerging out of the front and rear surface of the target with energies in the MeV range.

The combination of a table-top laser produced plasma X-ray source and spherically bent crystals for the soft X-ray region is used in traditional X-ray microscopy schemes. The X-ray source is well localized both spatially (approximately 20 micrometer) and temporally (1 ps - 10 ns, it depends on the used laser) and it is spectrally tunable in a relatively wide range (6 - 19 angstrom). High quality monochromatic ((delta) (lambda) /(lambda) approximately 10-5 - 10-3) images with high spatial resolution (up to approximately 4 micrometer) and in a large field of view (few mm) are presented. For many applications, these low-cost compact systems can offer a simple alternative to the larger installations which are usually used. It was demonstrated that the spherically bent crystals can be efficiently used in a wide ((Theta) equals 40 - 90 degrees) range of reflection angles, thus allowing wide wavelength selection. A very efficient concentration of monochromatic X-Ray radiation into different spot shapes (line, circle spot, etc) is demonstrated.© (1999) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

The authors present experimental results of a high efficiency Ne-like Fe transient collisional excitation x-ray laser using the COMET 15 TW table-top laser system at LLNL. The plasma formation, ionization and collision excitation of the x-ray laser have been optimized using two sequential laser pulses: a plasma formation beam with 5 J energy of 600 ps duration and a pump beam with 5 J energy of 1.2 ps duration. Since the observation of strong lasing on the 255 {angstrom} 3p-3s J = 0-1 transition of Ne-like Fe, they have achieved high gains of 35 cm{sup {minus}1} and saturation of the x-ray laser. A five-stage traveling wave excitation enhances the strongest Fe 3p-3s 255 {angstrom} lasing line as well as additional x-ray lines. A careful characterization of the plasma column conditions using L-shell spectroscopy indicates the degree of ionization along the line focus.

Recent transient collisional excitation x-ray laser experiments are reported using the COMET tabletop laser driver at the Lawrence Livermore National Laboratory (LLNL). Ne-like and Ni-like ion x-ray laser schemes have been investigated with a combination of long 600 ps and short {approximately}1 ps high power laser pulses with 5-10 J total energy. We show small signal gain saturation for x-ray lasers when a reflection echelon traveling wave geometry is utilized. A gain length product of 18 has been achieved for the Ni-like Pd 4d{r_arrow}4p J=0-1 line at 147 {angstrom}, with an estimated output of {approximately}10{micro}J. Strong lasing on the 119 {angstrom} Ni-like Sn line has also been observed. To our knowledge this is the first time gain saturation has been achieved on a tabletop laser driven scheme and is the shortest wavelength tabletop x-ray laser demonstrated to date. In addition, we present preliminary results of the characterization of the line focus uniformity for a Ne-like ion scheme using L-shell spectroscopy.

A large volume excimer laser, HERCULES, has been successfully applied as pump for a soft x-ray plasma source. The laser pulse duration has been varied from the natural value of 120 ns down to 10 ns, reaching different emission spectra from the plasma which have resulted to be optimum for different applications of the plasm source itself. Some experimental results on the applications of the source to different fields are presented; the choice of the best laser parameters in relation to the applications of the plasma source are also discussed.© (1998) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

A high brightness x-ray source has been obtained by focusing the large aperture excimer laser HERCULES on a solid target with a laser intensity of more than 10 13 W/cm 2 . The characteristics of the x-ray source for different laser time evolution in the range 6-120 ns are investigated. Experimental result on specific applications of the source, like the soft x-ray contact microscopy and the low photon energy radiobiology will be presented.

A large volume non-conventional XeCl excimer laser (HERCULES) emitting long pulses (from 10 ns up to 120 ns at a wavelength of 308 nm) has been used to drive a soft x-ray plasma source. The x-rays pulse duration and the energy conversion efficiency in different spectral regions have been measured; x-rays emission lasting up to 100 ns has been obtained in the 70 eV region. The dependence of x-ray pulse duration on the size of the laser spot is discussed. The x- ray source can be operated both in vacuum and in helium at atmospheric pressure. This allows irradiating over a large area both for contact microscopy of living specimens (up to 1 mm2 windows) and for radiobiology (up to some cm2 windows). The experimental results obtained for these two applications as well as for radiographic images of living insects are discussed.

In the present paper we are demonstrated achievement of high spatial resolution for x-ray spectrum of plasma produced by 20 mJ, high-repetition 120 fs laser using a Bragg-Fresnel linear zone plate structure on the mica crystal surface. We had also measured x-ray spectra near resonance line of He (alpha ) of Mg XI with simultaneously high spectral (up to (lambda) /(Delta) (lambda) equals 10000) and spatial ((Delta) x equals 10 micrometers ) resolution from plasma, heated by such laser, using spectrograph with spherical bent crystal. We demonstrated the important role of inner-shell excitation mechanism for low confinement parameters and propose new excitation channels from highly populated excited states (Li-like and Be-like satellite levels). The collision excitation cross sections for these processes do not decrease with principal quantum number. These channels can be also subject to electron beam excitation. It was shown also the big role of transient effects for Rydberg- Satellites due to a strong three-body recombination into high n-states in the cooling phase. Total spectra simulations are in rather close agreement with experimental results. New 3d 10 4 - 3d 9 4l6f spectral features of Cu-like barium, previously observed as unresolved transition arrays, are resolved at first time in present paper and enabling plasma diagnostics which were not possible before. The plasma electron density and temperature are found to be in the ranges: N e equals 5 X 10 21 - 10 22 cm -3 and kT e equals 100 - 50 eV, respectively. The generation of intense, collimated monochromatic x-ray beams ((lambda) approximately 9.5 angstroms) results are presented too.

The investigations of ultrashort (0.4-0.6 ps) laser pulse radiation interaction with solid targets have been carried out. The Trident subpicosecond laser system was used for plasma creation. The X-ray plasma emission was investigated with the help of high-resolution spectrographs with spherically bent mica crystals. It is shown that when high contrast ultrashort laser pulses were used for plasma heating its emission spectra could not be explained in terms of commonly used theoretical models, and transitions in so called {open_quotes}hollow atoms{close_quotes} must be taken into account for adequate description of plasma radiation.

The results are presented of investigations of extremely dense plasmas generated from exploding wires using a new method, monochromatic x-ray backlighting. In this method, shadow images of a bright, dense plasma can be obtained with high spatial resolution using monochromatic radiation from a separate plasma, permitting a major reduction in the required backlighting source power. The object plasma is imaged utilizing x-ray optical elements with spherically bent mica crystals. In particular, shadow images of exploding Al wire plasmas in the 1s 2 -1s3p line radiation of He-like Al XII were obtained. The images confirm the existence of a low density 'corona' around the wire at an early stage of the wire explosion process, with a dense core at the original wire position. Test experiments were also done with laser produced backlighter plasmas. Spatial resolution of 10 microns was demonstrated. The scheme described here is useful for backlighting extended high density plasmas, and could be a less costly alternative to using x-ray lasers for such purposes.

Spectroscopic investigations of the x-ray emission of plasmas heated by 120 ps, frequency doubled pulses from the JANUS Nd:glass laser are presented. High Z K-shell spectra emitted from slab targets heated to near 10 17 W cm -2 intensity are investigated. High resolution ((lambda) /$DELTA(lambda) > 5000) x-ray spectra of multicharged ions of He-like Ti, Co, Ni, Cu, and also H-like Sc in the spectral range 1.5-3.0 angstrom are obtained in single laser shots using a spherically bent Mica crystal spectrograph with a 186 mm radius of curvature. The spectra have 1D spatial resolution of about 25 micrometers and indicate that the size of the emission zone of the resonance transitions is keV and density approximately 10 22 cm -3 . These experiments demonstrate that with modest laser energy, plasmas heated by high-intensity 120 ps lasers provide a very bright source of hard approximately 8 keV x-ray emission.

Crystallographic and dispersion characteristics of muscovite at different reflection orders (2 divided by 24) for (001) lattice planes were investigated theoretically. Measurements of integral reflectivity were done for (10 divided by 38) reflection orders by using Cu and Mo X- tube radiation. Experimental results were compared with calculations for perfect and mosaic crystals. The integrated reflectivity for spherically bent mica crystals with R equals 100 and 186 mm have been calculated for various reflection orders. The results of these calculations show that muscovite crystals can be used in high reflection orders for high-resolution spectroscopy only if the crystal perfection is high enough, which provides the narrow reflection curve widths. These theoretical considerations are supported by results obtained in various plasma spectroscopic experiments. Nearly perfect muscovite crystals have been shown by using Lang and section topographic techniques for both flat and spherically bent muscovite crystals respectively. The high-quality of such crystals was also demonstrated using the scheme of obtaining a `parallel' x-ray beam and x-ray microscope schemes. Possible applications of high-quality muscovite spherical crystals are discussed.

Creation of Bragg X-ray optics based on transmitted and reflection crystals, bent on cylindrical or spherical surfaces, is discussed. Application of such optics for obtaining one and two dimensional monochromatic images of different plasma sources in the wide spectral range 1 - 20 angstroms are described. Samples of spectra obtained with spectral resolution up to (lambda) /(Delta) (lambda) approximately 1000 and spatial resolution up to 18 micrometers are presented.© (1994) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.