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In this work, the first proof of the principal of an in situ diagnostics of the heavy-ion beam intensity distribution in irradiation of solid targets is proposed. In this scheme, x-ray fluorescence that occurs in the interaction of heavy-ions with target atoms is used for imaging purposes. The x-ray conversion to optical radiation and a transport-system was developed, and its first test was performed in experiments at the Universal Linear Accelerator in Darmstadt, Germany. The Au-beam intensity distribution on thin foils and Cu-mesh targets was imaged using multiple x-ray pinholes (polychromatic imaging) and 2D monochromatic imaging of Cu Kα radiation by using a toroidally bent silicon crystal. The presented results are of importance for application in experiments on the investigation of the equation of states of high energy density matter using high intensity GeV/u heavy-ion beams of ≥1010 particles/100 ns. [ABSTRACT FROM AUTHOR]

We report here on the results of comparative experimental measurements of laser energy absorption in a bulk and different morphology nanowire arrays interacting with relativistically intense, ultra-high temporal contrast femtosecond laser pulses. We compare polished, flat bulk samples with vertically and randomly oriented nanowires made of ZnO semiconductor material. The optical absorption of the 45° incident laser pulses of ∼40 fs duration with a central wavelength of 400 nm at intensities above 10 19 W cm 2 was determined using an integrating Ulbricht sphere. We demonstrate an almost twofold enhancement of absorption in both nanowire morphologies with an average of (79.6 ± 1.9)% in comparison to the flat bulk sample of (45.8 ± 1.9)%. The observed substantially enhanced absorption in nanowire arrays is also confirmed by high-resolution x-ray emission spectroscopy. The spectral analysis of the K-shell x-ray emission lines revealed that the He-like resonance line emission from highly ionized Zn (Zn28+) is only present in the case of nanowire arrays, whereas, for the flat bulk samples, only neutral and low charge states were observed. Our numerical simulations, based on radiative-collisional kinetic code FLYCHK, well reproduce the measured He-like emission spectrum and suggest that high charge state observed in nanowire arrays is due to substantially higher plasma temperature. Our results, which were measured for the first time with femtosecond laser pulses, can be used to benchmark theoretical models and numerical codes for the relativistic interaction of ultrashort laser pulses with nanowires. [ABSTRACT FROM AUTHOR]

We present experimental evidence of ultra-high energy density plasma states with the keV bulk electron temperatures and near-solid electron densities generated during the interaction of high contrast, relativistically intense laser pulses with planar metallic foils. Experiments were carried out with the Ti:Sapphire laser system where a picosecond pre-pulse was strongly reduced by the conversion of the fundamental laser frequency into 2ω. A complex diagnostics setup was used for evaluation of the electron energy distribution in a wide energy range. The bulk electron temperature and density have been measured using x-ray spectroscopy tools; the temperature of supra-thermal electrons traversing the target was determined from measured bremsstrahlung spectra; run-away electrons were detected using magnet spectrometers. Analysis of the bremsstrahlung spectra and results on measurements of the run-away electrons showed a suppression of the hot electron production in the case of the high laser contrast. Characteristic x-ray radiation has been used for evaluation of the bulk electron temperature and density. The measured Ti line radiation was simulated both in steady-state and transient approaches using the code FLYCHK that accounts for the atomic multi-level population kinetics. The best agreement between the measured and the synthetic spectrum of Ti was achieved at 1.8 keV electron temperature and 2 × 1023 cm−3 electron density. By application of Ti-foils covered with nm-thin Fe-layers, we have demonstrated that the thickness of the created keV hot dense plasma does not exceed 150 nm. Results of the pilot hydro-dynamic simulations that are based on a wide-range two-temperature Equation of States, wide-range description of all transport and optical properties, ionization, electron, and radiative heating, plasma expansion, and Maxwell equations (with a wide-range permittivity) for description of the laser absorption are in excellent agreement with experimental results. According to these simulations, the generation of keV-hot bulk electrons is caused by the collisional mechanism of the laser pulse absorption in plasmas with a near solid step-like electron density profile. The laser energy, first deposited into the nm-thin skin-layer, is then transported into 150 nm depth by the electron heat conductivity. This scenario is opposite to the volumetric character of the energy deposition produced by supra-thermal electrons. [ABSTRACT FROM AUTHOR]

We explore the InSb-semiconductor lattice dynamics after excitation of high density electron-hole plasma with an ultrashort and intense laser pulse. By using time resolved x-ray diffraction, a sub-mA and sub-ps resolution was achieved. Thus, a strain of 4% was measured in a 3 nm thin surface layer 2ps after excitation. The lattice strain was observed for the first 5 ps as exponentially decaying, changing rapidly by time and by depth. The observed phenomena can only be understood assuming nonlinear time dependent laser absorption where the absorption depth decreases by a factor of twenty compared to linear absorption. [ABSTRACT FROM AUTHOR]

We have measured the polarization purity of undulator radiation at 12.9 keV, with hitherto unachievable precision. We could measure a polarization purity of 1.8×10-4 by using a silicon channel-cut crystal with six Bragg reflections at 45¯ as analyzer. [ABSTRACT FROM AUTHOR]

Besides intensity and direction, the polarization of an electromagnetic wave provides characteristic information on the crossed medium. Here, we present two methods for the determination of the polarization state of x rays by polarizers based on anomalous transmission (Borrmann effect). Using a polarizer-analyzer setup, we have measured a polarization purity of less than 1.5×10-5, three orders of magnitude better than obtained in earlier work. Using the analyzer crystal in multiple-beam case with slightly detuned azimuth, we show how the first three Stokes parameters can be determined with a single angular scan. Thus, polarization analyzers based on anomalous transmission make it possible to detect changes of the polarization in a range from degrees down to arcseconds. [ABSTRACT FROM AUTHOR]

Hot electron generation plays an important role in the fast ignition approach to inertial confinement fusion (ICF) and other applications with ultra-intense lasers. Hot electrons of temperature up to 10-20MeV have been produced by high contrast picosecond duration laser pulses focussed to intensities of ~1020W cm-2 with a deliberate pre-pulse on solid targets using the Vulcan Petawatt Laser facility. We present measurements of the number and temperature of hot electrons obtained using an electron spectrometer. The results are correlated to the density scale length of the plasma produced by a controlled pre-pulse measured using an optical probe diagnostic. 1D simulations predict electron temperature variations with plasma density scale length in agreement with the experiment at shorter plasma scale lengths (<7.5 μm), but with the experimental temperatures (13-17 MeV) dropping below the simulation values (20-25MeV) at longer scale lengths. The experimental results show that longer interaction plasmas produced by pre-pulses enable significantly greater number of hot electrons to be produced. [ABSTRACT FROM AUTHOR]

Suggested is a tomography-like method for studying properties of solid-density plasmas with cylindrical symmetry, such as formed in the interaction of high-power lasers with planar targets. The method is based on simultaneous observation of the target x-ray fluorescence at different angles. It can be applied for validation of existing hypotheses and lately for reconstruction of the plasma properties with three-dimensional resolution. The latter becomes straightforward if the resonance x-ray self-absorption is negligible. The utility of the method is demonstrated by examples. [ABSTRACT FROM AUTHOR]

X-ray emission from hollow ions offers new diagnostic opportunities for dense, strongly coupled plasma. We present extended modeling of the x-ray emission spectrum reported by Colgan et al. [Phys. Rev. Lett. 110, 125001 (2013)] based on two collisional-radiative codes: the hybridstructure Spectroscopic Collisional-Radiative Atomic Model (SCRAM) and the mixed-unresolved transition arrays (MUTA) ATOMIC model. We show that both accuracy and completeness in the modeled energy level structure are critical for reliable diagnostics, investigate how emission changes with different treatments of ionization potential depression, and discuss two approaches to handling the extensive structure required for hollow-ion models with many multiply excited configurations. [ABSTRACT FROM AUTHOR]

We developed a detection scheme, capable of measuring X-ray line shape of tracer ions in μm thick layers at the rear side of a target foil irradiated by ultra intense laser pulses. We performed simulations of the effect of strong electric fields on the K-shell emission of silicon and developed a spectrometer dedicated to record this emission. The combination of a cylindrically bent crystal in von Hámos geometry and a CCD camera with its single photon counting capability allows for a high dynamic range of the instrument and background free spectra. This approach will be used in future experiments to study electric fields of the order of TV/m at high density plasmas close to solid density. [ABSTRACT FROM AUTHOR]

Laser-driven ion acceleration has been experimentally investigated by irradiating, with tightly focused femtosecond laser pulses at 5×1019 W/cm2, thin metal foils, which have been back-coated with a μm thick dielectric layer. The observation we report shows the production of MeV proton bunches with an unexpected highly uniform spatial cross section. [ABSTRACT FROM AUTHOR]

Spectrally resolved two-dimensional imaging of ultrashort laser-produced plasmas is described, obtained by means of an advanced technique. The technique has been tested with microplasmas produced by ultrashort relativistic laser pulses. The technique is based on the use of a pinhole camera equipped with a charge coupled device detector operating in the single-photon regime. The spectral resolution is about 150 eV in the 4–10 keV range, and images in any selected photon energy range have a spatial resolution of 5 μm. The potential of the technique to study fast electron propagation in ultraintense laser interaction with multilayer targets is discussed and some preliminary results are shown. [ABSTRACT FROM AUTHOR]

Particle pulses generated by laser-plasma interaction are characterized by ultrashort duration, high particle density, and sometimes a very strong accompanying electromagnetic pulse (EMP). Therefore, beam diagnostics different from those known from classical particle accelerators such as synchrotrons or linacs are required. Easy to use single-shot techniques are favored, which must be insensitive towards the EMP and associated stray light of all frequencies, taking into account the comparably low repetition rates and which, at the same time, allow for usage in very space-limited environments. Various measurement techniques are discussed here, and a space-saving method to determine several important properties of laser-generated electron bunches simultaneously is presented. The method is based on experimental results of electron-sensitive imaging plate stacks and combines these with Monte Carlo-type ray-tracing calculations, yielding a comprehensive picture of the properties of particle beams. The total charge, the energy spectrum, and the divergence can be derived simultaneously for a single bunch. [ABSTRACT FROM AUTHOR]

We present comparative x-ray spectroscopic measurements using an x-ray film, a charged-coupled device (CCD), and imaging plates as the detectors. An aluminum K-shell x-ray emission in the energy range of 1.8–2.15 keV is produced from a laser-produced plasma, and dispersed using a flat crystal spectrometer. Our interest is in the response of these detectors to weak x-ray emission, their suitability for quantitative and absolute measurements, as well of ease of use. We find that scientific-grade CCD detectors offer superior signal-to-noise performance, while imaging plates are a viable alternative particularly if large detection areas or curved surfaces are required. Despite the excellent spatial resolution of an x-ray film, imaging plates are preferred to film for quantitative measurement as signal to noise ratio is greater by an order of magnitude. [ABSTRACT FROM AUTHOR]

Detailed measurements of the angular distribution of 3 ω0/2 radiation are presented in short scale length plasmas (0.8–7 μm) generated by laser radiation at intensities reaching the relativistic level (1016–6×1018 W/cm2). The experimental results are in very good agreement with theoretical predictions based on two-plasmon decay and stimulated Raman scattering instabilities. New three-halves harmonic generation mechanisms are an identified characteristic of femtosecond laser induced parametric instabilities. These are the joint interaction of incident and reflected laser beams as well as stimulated Raman scattering. It is shown both experimentally and theoretically that the three-halves harmonic radiation is a useful preplasma diagnostic tool. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]

We present a new x-ray spectrometer setup based on a conically curved mica crystal in the von Hamos configuration. An x-ray sensitive charge coupled device or streak camera can be easily coupled in a perpendicular orientation to the spectrally resolved x-ray line focus. Shifting the crystal along its axis of symmetry allows one to change the dispersion and the signal flux density on the detector. A large spectral range at high resolution and adjustable signal intensity is accessible with this setup. [ABSTRACT FROM AUTHOR]

Temporal evolutions of the electron temperature and density profiles in the inertial confinement fusion core plasma were obtained through a combination of experimental technology to create a uniform core, diagnostics developments, and a data analysis technique to obtain an optimal solution. In the experiment, time- and space-resolved x-ray spectroscopic measurements were carried out; an x-ray streak spectrograph and a monochromatic x-ray framing camera provided temporal evolution of x-ray spectrum and monochromatic emissivities, respectively. The spectrum and emissivity profile were iteratively fitted as a function of electron temperature, density, and space. Then, optimal solutions were successfully extracted with the help of Niched-Pareto genetic algorithm. Temporal behavior between those data is well corrected by comparing spatially and spectrally integrated intensities. The resultant profiles were compared with hydrocode simulations, showing that spatially averaged electron temperature and density evolutions are well replicated by the simulations, but their detail spatial profiles do not agree with them. [ABSTRACT FROM AUTHOR]

Monochromatic x-ray imaging with toroidally bent crystals has been applied to investigate critical issues in laser fusion research in collaboration with Jena University [for example, I. Uschmann et al., Rev. Sci. Instrum. 66, 734 (1995)]. Described in this article is the study on x-ray diagnostics to provide simultaneously time, space, and spectral resolutions for the laser fusion experiments by the use of toroidally bent crystals. A monochromatic x-ray imager was developed, which consists of two sets of identical five bent crystals and a fast x-ray framing camera. The attained spatial resolution of 6 μm, time resolution of 34 ps, and spectral resolution of 10 eV are high enough to observe temporal evaluation and temperature distribution of the laser fusion hot core. In addition, a new x-ray imager with bent crystal was developed to investigate hydrodynamic instabilities occurring in laser-driven planer targets as one of the most critical issues in laser fusion research. The imager was so designed as to match the experiments using rather thick, massive targets irradiated under the same condition as in the high-gain experiments. Configuration and specifications of the imager are presented. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Presents an effective x-ray optical method to focus x-ray pulses shorter than on picosecond by using spherically or toroidally bent crystals. Calculation of the spectral, spatial and time-dependent properties of focusing by two-dimensional bent crystals; Achievement of monochromatic imaging.

A double-crystal x-ray spectrometer (DCS) has been used to obtain high-resolution x-ray spectra of laser-produced plasmas. The DCS has a high dispersion, and thus can obtain highly resolved spectra in circumstances where the resolution of a conventional single-crystal Bragg spectrometer at comparable source-to-detector distances would be limited by the source size. In addition the DCS also yields unit-magnification one-dimensional spatial resolution in the direction perpendicular to the spectral direction. The instrument produces two spectra symmetrically disposed about a central wavelength, which makes it especially useful for measuring spectral line shifts. Analysis of the spectra from hydrogenic aluminium and helium-like chlorine indicates a resolving power (λ/Δλ) greater than 2500 and a spatial resolution better than 30 μm. [ABSTRACT FROM AUTHOR]

A special crystal monolith was fabricated for absolute measurements of x-ray wavelength. It consists of two fiat quartz plates, accurately cut relative to reflecting net planes, with a fixed distance between them. Absolute wavelengths (i.e., without use of reference lines) of L-shell laser produced spectra of Cu, Ge, As, etc. have been measured in the 7.5-8.5 Å with an accuracy of Δλ/λ=10[sup -5]. Our Johann type x-ray spectrometer with a cylindrically bent quartz has been used to reveal line coincidences necessary for photopumping processes. In this scheme source-size influences are smaller, therefore, line profiles have been measured at a spectrometer resolution better than 5000. Because of its focusing in the sagittal plane, a von Hámos type x-ray spectrometer has been used to detect the small x-ray emission of subpicosecond laser-produced plasmas (E=2 mJ, t=100 fs). X-ray spectra of A1 both K[sub α], K[sub β] lines and He[sub α]-resonance line with its satellites. Finally, a multichannel x-ray microscope has been designed and fabricated. It consists of several two-dimensionally bent crystals where each of them images one x-ray line emitted by a laser-produced plasma. The spatial resolution of x-ray line images is about 5 µm, and the width of the spectral ranges is Δλ/λ=10[sup -4] to 10[sup -2]. Thus, the spatial distribution of ions radiating in selected x-ray lines have been found being of interest in the study of population inversions. [ABSTRACT FROM AUTHOR]

Presents an experimental and numerical analysis of the collision of two plasmas produced from laser-exploded aluminum (Al)/Al and Al/magnesium pairs of foils. Use of imaging and spectroscopic x-ray techniques; Ion temperatures measured; Development of Eulerian multifluid simulations with coupling to atomic physics postprocessing.

We demonstrate that an ultrashort-pulse laser-driven x-ray diode can be used for time-resolved experiments on a picosecond timescale. Hence, acoustical phonons in germanium are observed after ultrashort laser-excitation and the results are compared with calculations according to a microphysical model. We also show the advantages of this kind of picosecond x-ray source compared to other sources on the basis of its properties. [ABSTRACT FROM AUTHOR]

A calibrated x-ray spectrometer was used to characterize an intense 4.5 keV Kα source. Generated from the interaction of 30 J-320 fs laser pulses focused on 25 μm thick Ti foils, the conversion efficiency into Ti Kα line is estimated to (9±6)×10-5. Highly efficient collection, monochromatization and focusing were achieved using an ellipsoidally bent highly oriented pyrolytic graphite crystal. The measured 700 μm full width half maximum (FWHM) focal spot leads to a fluence of (3.0±2.1) mJ/cm2 hence paving the way to the study of intense x-ray pulse interaction with matter as demonstrated by a first simple experiment. [ABSTRACT FROM AUTHOR]

The displacive phase transition in SrTiO3 was investigated by means of x-ray diffraction. We used 4.5 keV photons thus probing only a very thin region near the surface. In the low temperature phase the lattice parameters evolve substantially different than in bulk material. We also investigated the phase transition under the influence of an epitaxial coating with YBaCu2O7 and found the nature of the phase transition changed. The near-surface region behaves like an epitaxial thin SrTiO3 film. [ABSTRACT FROM AUTHOR]

We have performed an analyzer crystal based phase contrast imaging (ABI) experiment using a rotating anode x-ray source. The use of such an incoherent source demonstrates the potential of ABI as a quantitative characterization tool for the laboratory environment. A phase contrast image of a plastic phantom was recorded on high resolution x-ray film and the projected thickness was retrieved from a single image. The projected thickness recovered from the phase contrast image was shown to quantitatively agree with a reference optical microscope measurement. [ABSTRACT FROM AUTHOR]

We have studied the duration of Si-Kα x-ray pulses generated by two subsequent femtosecond-laser pulses (λ=395 nm, pulse duration=180 fs) separated by 20 ps, which were focused on a glass target to intensities of a few 1017 W/cm2. A toroidally bent crystal was used to image the Si-Kα pulses emitted by the target on the cathode of an ultrafast streak camera. While the duration of the first Kα pulse is 1.1 ps, the duration of the second Kα pulse is considerably longer by ≈0.7 ps. This effect is attributed to the preplasma created by the first laser pulse and seen by the second one. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]

A comparative study of temporally and spectrally resolved K-shell emission from aluminum targets heated with 150 fs Ti:sapphire laser pulses at 790 and 395 nm is presented at an intensity of 5×10[sup 17] W/cm[sup 2]. Whereas at 395 nm spectrally broad intense plasma lines and a weak Kα line with durations (full width at half maximum) of 1–2 ps are observed, the spectrum at 790 nm shows weak narrow plasma lines and an intense Kα line with durations of 3–5 ps. © 2002 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Reports on the first use of toroidally bent crystals to record two-dimensional, spatially resolved, monochromatic images of laser-produced fusion plasma. Determination of electron temperature by seeding the deuterium fuel wit argon; Evaluation of the intensity ratio of the two monochromatic images.

Obtained experimental results demonstrate that x rays can be focused to a point by using one flat InSb crystal with elliptically shaped modulated structures based on the Bragg and Fresnel diffraction principles. Ti Kα radiation and InSb (111) reflections are used to focus a 20-μm source size to a point of 9 μm, which is in good agreement with predictions from the wave-optics approach. The quality of the modulated structure fabrication is judged by the shape of the focal spot, which indicates no visible aberration effects. © 1996 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Spatially resolved x-ray spectra of the Al Lyman α group emitted from the surface of the laser- irradiated targets display plasma regions where the resonance line is suppressed and the dielectronic satellites dominate. Calculations based on multilevel collisional-radiative code and two-dimensional hydrodynamic simulations relate this spectral distribution to a presence of the cold overcritical density plasma inside the crater at the target surface. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

X-ray spectroscopy of laser-driven imploded inertial confinement fusion (ICF) cores has proven to be a powerful diagnostic of spatially averaged temperature and density plasma conditions at the collapse of ICF implosion experiments. Temperature and density time histories can be extracted from the analysis of time-resolved x-ray line spectra using the temperature and density sensitivity of line intensities and Stark-broadened line shapes. The next step in the spectroscopy of imploded cores is the bracketing of core plasma gradients as a function of time. To this end, we discuss a spectroscopy diagnostic which is based on the self-consistent and simultaneous simulation and analysis of time-resolved x-ray line spectra and x-ray monochromatic images. Abel inversion of x-ray monochromatic images provide line emissivity spatial profiles; this information is critical for the determination of gradients in the core. We apply this technique to the analysis of data recorded in Ar-doped ICF implosion experiments driven with the GECCO XII laser system at Osaka University. In these experiments, time-resolved x-ray line spectra and x-ray monochromatic images were simultaneously recorded for the Ar He β and Ly β spectral features. From the analysis of the data we can extract the time history of temperature and density gradients in the core through the collapse of the implosion. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

For the generation of a well defined prepulse in high intensity laser plasma interactions, we implemented a newly developed prepulse device into a multiterawatt titanium:sapphire amplifier system. The temporal delay between the prepulse and main pulse is variable between -350 ps and + 100 ps. If the laser pulse is focused on a target, the spatial overlap of the two pulses in the focal point is corrected automatically over the entire range. It is possible to attenuate the main pulse as well as the prepulse independently of each other by more than one order of magnitude. We investigated the dependence of the Kα emission of the laser produced plasma of a silicon target on the delay between the prepulse and main pulse. An increase of the yield of the Kα emission by a factor of 2 for a temporal delay of several tens of picoseconds between the prepulse and main pulse was measured. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]

We introduce a setup to measure high-resolution inelastic x-ray scattering at the High Energy Density scientific instrument at the European X-Ray Free-Electron Laser (XFEL). The setup uses the Si (533) reflection in a channel-cut monochromator and three spherical diced analyzer crystals in near-backscattering geometry to reach a high spectral resolution. An energy resolution of 44 meV is demonstrated for the experimental setup, close to the theoretically achievable minimum resolution. The analyzer crystals and detector are mounted on a curved-rail system, allowing quick and reliable changes in scattering angle without breaking vacuum. The entire setup is designed for operation at 10 Hz, the same repetition rate as the high-power lasers available at the instrument and the fundamental repetition rate of the European XFEL. Among other measurements, it is envisioned that this setup will allow studies of the dynamics of highly transient laser generated states of matter.

We present a Michelson interferometer for 13.5 nm soft x-ray radiation. It is characterized in a proof-of-principle experiment using synchrotron radiation, where the temporal coherence is measured to be 13 fs. The curvature of the thin-film beam splitter membrane is derived from the observed fringe pattern. The applicability of this Michelson interferometer at intense free-electron lasers is investigated, particularly with respect to radiation damage. This study highlights the potential role of such Michelson interferometers in solid density plasma investigations using, for instance, extreme soft x-ray free-electron lasers. A setup using the Michelson interferometer for pseudo-Nomarski-interferometry is proposed.