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One of the unique features of the PHELIX laser installation is the combination of the ultra-high intensity laser with the heavy-ion accelerator facility at GSI and its planned extension FAIR. Due to this combination, PHELIX will allow novel investigations in the fields of plasma physics, atomic physics, nuclear physics, and accelerator studies. An important issue within the scientific program is the generation of high quality x-ray laser beams for x-ray laser spectroscopy of highly-charged ions. The long range perspective is the study of nuclear properties of radioactive isotopes within the FAIR [1] project. A novel single mirror focusing scheme for the TCE XRL has been successfully implemented by the LIXAM/MBI/GSI collaboration under different pump geometries. Intense and stable laser operation with Ni-like Zr and Ni-like Ag was demonstrated at pump energies between 2 J and 5 J from the PHELIX pre-amplifier section. [ABSTRACT FROM AUTHOR]

Optical-field-ionization collisional-excitation soft x-ray lasers in clustered gas jets were experimentally investigated in detail. A tomographic measurement based on laser machining technique was used to resolve the growth of x-ray lasing intensity as a function of position in a cluster jet, exploring the origins of the dependences of x-ray lasing intensity on atom density and laser polarization. The presence of optimal atom density was found to be a result of ionizationinduced refraction. An unexpected observation is that circular polarization appears to be not the optimal polarization ellipticity, which may be a manifestation of effects of pre-ionization at the laser-cluster ionization front. [ABSTRACT FROM AUTHOR]

Experiments carried out on SIGNAL facility have shown that X-ray lasing in Ne-like Ar plasma of fast capillary discharge occurs when directions of preionization current pulse and main current pulse are the opposite. When the currents directions are the same we don't observe the X-ray lasing. In this report we give the interpretation of this effect. The role of the preionization current pulse is not just formation of partially ionized gas to quickly tear the plasma away from the capillary walls when the main pulse comes (Z-pinch effect) but also formation of stabilizing magnetic field (in the case of oppositely directed current pulses). [ABSTRACT FROM AUTHOR]

In recent years z-pinch configuration is considered for implementing a nitrogen recombination X-Ray Laser at λ≈13.4nm. The required plasma conditions at the pinch time are Te~ 140eV and Ne~ 1020cm-3. Lasing can occur after the plasma cools to Te<60eV, in a time scale of a few nanoseconds (<5nsec). A capillary discharge z-pinch apparatus was built (Imax≈60kA, τ¼=70nsec), and examined by means of radiation measurements with filtered X-Ray diode (XRD). By using different filters it is possible to identify the emission from He-like and H-like nitrogen. We show that at the pinch time the electron temperature is well above 80eV, and the total cooling period, to Te<60eV, is shorter than 5nsec. Future complementary XRD and spectroscopic measurements are being planned. [ABSTRACT FROM AUTHOR]

CAPEX-U device is a pulse-power apparatus capable to deliver a "short-circuit" discharge current ~ 120 kA in a quarter-period ~ 80 ns. Its characteristic features are direct optical access to both discharge electrodes, and laser triggering of the main spark gap (for exact synchronization of detectors and applications). It is described, how CAPEX-U joint with SHOW device will be used for soft X-ray amplification on nickel-like silver ions (generated by exploding wire in water), and how the pressure at the SHOW axis was measured. [ABSTRACT FROM AUTHOR]

A comparative study of the capillary pinching discharges in argon and nitrogen is presented. Requirements on plasma parameters needed for laser collision and recombination pumping are stated. The results of the computer modelling are compared with previously published experimental results for argon laser and with recent experiments done with the same capillary filled by nitrogen. [ABSTRACT FROM AUTHOR]

Experiments with CAPEX-U apparatus were done to more understand the differences between Ar and N active media created during the pinch compression, respectively. Capillary discharge current, X-ray narrow band radiation and EUV spectrum temporal behavior were measured. Results of laboratory experiments for both gas fillings under various currents and initial pressures are shown. Computer simulations show that current quasi-period shortening and higher amplitude is needed. [ABSTRACT FROM AUTHOR]

In the given paper results of elaboration, numerical and experimental modeling, and also research of radiation sources on the base of low-inductive capillary discharges are presented. Author's approach is to use a running wave of sliding avalanche discharges for gas pre-ionization and main z-discharges for collisional excitation pumping. Full-scale testing showed, that this approach allows to create compact radiation sources. Numerical predictions in further increasing of input power efficiency are informed. [ABSTRACT FROM AUTHOR]

We report on different experimental investigations regarding the use of the 0.3 mJ, 0.3 Hz, 1.7 ns, 46.9 nm Ar laser developed at the University of L'Aquila. Firstly, we have investigated the potentiality of the EUV laser in the ablation of hard dielectrics such as CaF2 and LiF crystals, which are largely transparent to the visible and to the ltraviolet laser light. We determined the ablation thresholds and the ablation rates for these two crystals and compared the results with the values obtained with other kinds of visible-ultraviolet laser systems. Secondly, we investigated a method to manipulate the intense soft X-ray laser beam based on the use of hollow waveguides. We used monocapillary tubes in a multireflection regime to achieve a substantial modification of the intensity distribution of the beam. These results can be of great interest for several applications of these soft X-ray laser sources. [ABSTRACT FROM AUTHOR]

The beta-decay of atomic tritium produces the ion 3He+ at the first exited state 2s with the probability of 25%. This state can irradiate two photons (two-photon lifetime is about 0.01 ms) or one photon (the lifetime is 173 s). The ztimulated emission of one-photon may depress the two-photon decay. This is a soft X-ray laser with the wavelength 310 angstroms (40.8 eV). The first problem of two-photon decay depression is solved by largereflectivity mirrors for 310 A. The periodic array of non-dispersive, periodically positioned, quasi-dielectric cylinders in vacuum oriented along the axis of X-ray emission has narrow-band reflection of about 100{%} for wavelength closed to the distance between dielectric cylinders. Such array with quasi-dielectric cylinders periodically located at about 300 angstroms chess table can be realized by forthcoming lithography methods. Two such mirrors shape the proper resonator for generated emission and form good divergency of (coherent) X-ray beam. The second problem of 310 A radiation absorption by tritium atoms in bounded-free electron transitions may be solved by application of (strong) permanent magnetic field to the tritium sample. The magnetic field produces the spectrum of permitted free electron energy in one direction (of X-ray propagation). While the energy of possible free electron 27.2 eV is out of this spectrum, the bounded-free transition is forbidden, and the absorption of stimulated emission is depressed by several orders and becomes negligible small. The theoretical limit of X-ray continuous laser power is 0.15 mW per cubic cm of liquid atomic tritium. The required magnetic field is about 300 kGs. [ABSTRACT FROM AUTHOR]

A planned experiment to realize an innershell x-ray laser in atomic sodium by pumping with the Zn x-ray laser at 21.2 nm, presently operated at the PALS laser facility, is presented. According to model calculations, a gain of more than 60 cm-1 is expected for a sodium density of 1016 cm-3 and the given pump laser data. [ABSTRACT FROM AUTHOR]

We report new time-resolved measurements for 50 nm thick Al and Ge buried layer targets. The top-coat thickness of carbon is varied between 0 and 100 nm. A single beam of the Compact Multipulse Terawatt (COMET) laser is frequency doubled, at 527 nm wavelength, up to 1 J energy in a 500 fs (FWHM) pulse and focused to a maximum of 7 x 1017 W cm-2 with an off-axis parabola. An RbAP (001) von Hamos curved crystal spectrometer with an 500 fs x-ray streak camera is fielded to measure the time history of the Al n = 2 - 1 K-shell emission and the Ge n = 3 - 2 L-shell emission in the 7 - 10 Å waveband. The main objective is to generate and study hot, Te ~ 100 - 200 eV, dense, ne ~ 1023 cm-3, thermal plasmas in tamped optically thin targets under a range of laser irradiance conditions. We observe short-lived emission lasting a few picoseconds and indications of cooler, denser plasmas with increasing thickness of the tamping carbon layers. [ABSTRACT FROM AUTHOR]

The possibility of the creation and the application prospects of the laser-electron X-ray generator based on the Thompson scattering of the laser radiation on a bunch of relativistic electrons are considered. Such a generator fills the existing gap between X-ray tubes and synchrotron sources, which is several orders of magnitude in terms of the brightness, average intensity, size and also in the construction and exploitation costs. The layout of beam-lines and experimental stations intended for the applications of the X-ray laser-electron generator to the investigation of the elemental composition and material structure and biological objects is discussed. [ABSTRACT FROM AUTHOR]

A prototype of laser unit for Laser Electron X-Ray Generator is constructed on the basis of the optoelectronic control. The laser system in which an optoelectronic negative feedback is realized by means of a signal reflected from an intracavity Pockels cell polarizer is proposed and tested. The design provides flexible control over pulse train time structure. [ABSTRACT FROM AUTHOR]

A laser-produced tin (Sn) plasma is an attractive extreme-ultraviolet(EUV) light source for the next generation lithography in terms of its brightness and compactness. Radiative properties and hydrodynamics of the laser-produced Sn plasmas are quite important for investigating the optimum conditions for EUV generation. Several experiments have been performed to clarify the above issues;(i) EUV spectra emitted from isolated Snq+ (5 < q < 15) ions and opacity spectrumof a 30-eV Sn plasma have been measured as fundamental data for accurate modelingradiation energy transport in plasmas, (ii) electron density profile in 13.5 nmemission dominant region of a laser-produced Sn plasma was measured with a laserinterferometer for understanding hydrodynamics of an EUV source plasma. (iii) benchmarking one-dimensional (1D) radiation-hydrodynamic simulation codewith multiple laser beam irradiated spherical 1D Sn plasma. Based on the experimentalresults and calculations, it was found that optically thinner plasma emits 13.5 nm light more efficiently. Optical depth of Sn plasma is actively controlledwith changing laser pulse duration and the use of low-density porous target. [ABSTRACT FROM AUTHOR]

An ultra-high laser pulse creates the relativistic collective phenomenasuch as high energy proton generation induced by high energy electrons, high orderharmonic generation with a relativistic collective electron motion, intenseMeV x-ray generation via Bremstrahlung as well as ultra-short mono-energeticelectron bunch generation, an intense THE radiation with the thin foil or gas targettechniques. These beams interact with matter with quantum effects. We call themquantum beams. Here we describe the high intensity laser driven multiple quantumbeams for applications such as various pump-probe techniques. [ABSTRACT FROM AUTHOR]

Copyright of X-Ray Lasers 2006 is the property of Springer eBooks and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Results of our preliminary studies for a demonstration of soft X-ray laser Thomson scattering in laser-produced dense plasma are presented. The investigated plasmas are produced by single-side heated foil targets using a 300-ps pulse of 438-nm wavelength at irradiances between 1013 and 1014 Wcm-2. The Nelike zinc X-ray laser, delivering ~ 1 mJ of focused energy at 21.2 nm, is injected to the plasma as the Thomson probe. The X-ray laser pulse is timed to arrive to the plasma 0.5 or 1 ns after the peak of the optical pulse, encountering electron densities in the range of 1020-1022 cm-3. The spectrum near 21 nm, emitted at ~ 30°with respect to the incident X-ray laser, is analyzed by a flat-field spectrometer viewing through the back of the target. The results show that the choice of appropriate target material and thickness are essential to the success of this experiment. From the spectroscopic measurements using Al and polypropylene (C3H6) foils, the latter appears as a suitable candidate for Thomson scattering experiments near 21 nm. A weak spectral feature near 21.2 nm potentially indicating Thomson scattering was observed using a 1.2 μm polypropylene foil. Further data analysis is required to support this conclusion. [ABSTRACT FROM AUTHOR]

We show results obtained using XUV interference microscopy to observe in situ nanometer-scale modifications of optical surfaces exposed to intense sub-ns laser pulses. The surface was irradiated by a blue "damaging" laser (438 nm) and diagnosed by a soft X-ray laser based on neon-like zinc, emitting at 21.2 nm. Investigated objects were thin plane beam-splitters made of fused silica (SiO2). This technique could be used to reveal effects involved in formation of laser-induced damages in optical surfaces exposed to intense laser pulses. [ABSTRACT FROM AUTHOR]

Specific structural changes in Sc/Si multilayers (MLs) irradiated by nanosecond 46.9-nm single laser pulses with fluences of 0.04-5.00 J/cm2 were studied by methods of SEM and cross-sectional TEM. The threshold damage was found to be 0.08 J/cm2. The ML melts down under the fluence F >0.08 J/cm2, and the exothermic reaction of silicide formation starts. Main degradation mechanisms of MLs are discussed. The results of this study can be used for development of advanced multilayer mirrors capable handling the intense radiation conditions of new generation coherent X-ray sources. [ABSTRACT FROM AUTHOR]

A grazing Kirkpatrick-Baez (K-B) microscope was designed for hard x-ray (8keV; Cu Ka radiation) imaging in Inertial Confinement Fusion (ICF) diagnostic experiments. Ray tracing software was used to simulate optical system performance. The optimized theoretical resolution of K-B microscope was about 2 micron and better than 10 micron in 200 micron field of view. Tungsten and boron carbide were chosen as multilayer materials and the multilayer was deposited onto the silicon wafer substrate and the reflectivity was measured by x-ray diffraction (XRD). The reflectivity of supermirror was about 20 % in 0.3 % of bandwidth. 8keV Cu target x-ray tube source was used in x-ray imaging experiments and the magnification of 1x and 2x x-ray images were obtained. [ABSTRACT FROM AUTHOR]

Near normal incident high reflective and polarized multilayer mirrors were designed and fabricated for Ni-like Ta X-ray laser working at the wavelength of 4.48 nm. The influence of the imperfect interface on the reflectivity of the multilayer was simulated. Using the direct current magnetron sputtering technique, the Cr/C and Cr/Sc multilayers were deposited. Then, the layer thickness and structure of the multilayer were measured and fitted by an X-ray diffractometer. The reflectivities of these multilayers were measured on the beam line UE56/1-PGM at BESSY-II. At grazing incident angle of 85°, the measured peak reflectivities were 7.50% and 6.12% for Cr/C and Cr/Sc multilayer mirrors, respectively. At the grazing angle of 44°, the s-reflectivity is 13.61% for Cr/C multilayer polarizer. The measurement and simulation results suggest that the interface roughness strongly reduces the reflectivity of the multilayers. Thus, there is still a potential for improvement by introducing diffusion barriers and using more perfect substrate. [ABSTRACT FROM AUTHOR]

The extreme ultraviolet (EUV) molybdenum/silicon (Mo/Si) multilayers were fabricated using the direct current magnetron sputtering method on different preparation substrate: (a) wiped method, (b) untreated and (c) ultrasonic cleaning method. To meet the requirement of comprehensive characterization of morphology of substrates for EUV multilayer, a suitable combination of different measuring techniques, such as atomic force microscopy (AFM), x-ray diffractometer (XRD) rocking curve and synchrotron radiation (SR) reflectance, were chosen. It is shown that the reflectance of x-ray multilayers is sensitive to the roughness and cleanness of the substrate from the SR measurement results, and the maximum reflectance of 68.6% at 13.5nm was obtained using the ultrasonic cleaning method. It is demonstrated on the analysis according to the experimental results that the combination of surface characterization techniques using the AFM, x-ray scattering technique and SR characterization can be used for investigating the detail topography information of the substrate. [ABSTRACT FROM AUTHOR]

A plasma generated by a tightly focused ~ 14 μm (FWHM), 600 ps duration laser beam at an irradiance of 1013 W cm-2 on a flat aluminum target is investigated. We report new findings that give a better understanding of the energy transport mechanisms in the measured plasma. The formation of a small, on-axis dip or concave electron density profile is observed. Detailed modeling of the spatial and temporal profile of a laser-produced plasma with the 2-D LASNEX hydrodynamics code gives good agreement with the observed features. The observed cold plasma formation along the target surface hundreds of microns away from the small focal spot is generated by heated material outside of the laser focus. Plasma generated by low intensity wings in the laser spatial profile is augmented by soft x-ray radiation from the hot coronal plasma heated by the laser. The simulations show that the x-ray heating will produce a plasma outside the focal spot without the low intensity wings. Strong thermal electron conductive heating due to large thermal gradients continues to generate ablation outside the laser spot and formation of lobes on each side of the focal spot. [ABSTRACT FROM AUTHOR]

We have developed a fully coherent x-ray laser at 13.9 nm and the application research has been started. The generation of submicron x-ray beam is important for the application of high intensity x-ray beam, such as the non-linear optics, the material science, and the biology. The submicron x-ray bee am is generated by the soft x-ray laser with using a Fresnel zone plate. The spot diameter is estimated about 680 nm (290 nm at FWHM) by the theoretical calculation. In this experiment, the diameter of the x-ray beam is measured by the knife-edge scan. The diameter and the intensity are estimated 730 nm (310 nm at FWHM) and 3x1011 W/cm2, respectively. [ABSTRACT FROM AUTHOR]

Copyright of X-Ray Lasers 2006 is the property of Springer eBooks and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Optical spectroscopy is a key tool to monitor and therefore analyse properties of laser emission light sources such as X-Ray lasers. A spectrograph instrument that produces flat field detection over relative wide spectral range enables quick and reliable analysis of X-Ray laser emitted spectra thanks to the easy coupling with CCD camera or MCP detector. We present a compact spectrograph design based on aberration corrected toroidal diffraction gratings dedicated to optical spectroscopy in the VUV and Soft X-Ray wavelength range. The toroidal aberration corrected grating acts as a diffractive and focusing element allowing compact design with only one optical element. Such compact design provides high throughput, good wavelength purity as well as great stability and reproducibility. After a review of the flat field toroidal grating parameters design, we present the performances of several toroidal gratings optimised for operation in the 2.5 to 170 nm wavelength range. Measured spectra of pinch discharge sources are presented to illustrate the performance of toroidal spectrograph instruments [ABSTRACT FROM AUTHOR]

The interaction of large xenon clusters with an x-ray laser pulse having a wavelength of 13.9 nm and intensity of up to 2x1010 W/cm2 was investigated using a time-of-flight ion mass spectrometer. The photon energy is high enough to photoionize the inner-shell electron of the Xe atom. In contrast to the experiment at synchrotron radiation, the enhancement of double Auger decay probability with increasing cluster size and x-ray laser intensity was observed for the first time. [ABSTRACT FROM AUTHOR]

The first soft X-ray free-electron laser has recently been put into operation at DESY in Hamburg. Tunable soft X-ray coherent radiation can be generated at the FLASH (Free-electron LASer in Hamburg; formerly known as VUV FEL or TTF2 FEL). In the interaction experiments reported here, the laser system provided ~ 25-fs, ~ 10-μ J pulses of 32-nm radiation. We irradiated thin (500 nm) layers of poly (methyl methacrylate) - PMMA deposited on a silicon substrate by single, focused FLASH pulses. The pulse energy was adjusted using a gas attenuator. [ABSTRACT FROM AUTHOR]