bluuebunny/crossref_metadata_2025 huggingface dataset:
Review of the soft-X-ray laser research at CEL-V
Authors: Naccache D. , Bourgade J-L. , Combis P. , Keane C. J. , Le Breton J-P. , Louis-Jacquet M. , Macgowan B. J. , Matthews D. L. , Perrine J-P. , Thiell G.
Published: March 2009

We present some significant results of collisional excitation X-ray laser experiments in plasmas produced by a laser. We studied the amplification in Ne- and Ni-like ions by varying both the nature and the thickness of targets, the irradiation, and the wavelength of the driving laser. Some potentially interesting scalings as a function of the atomic number of the lasing element are demonstrated in the Ne-like system. An order-of-magnitude increase in gain in the Ni-like experiments was determined.
Z scaling of collisional Ne-like X-ray lasers using exploding foils: Refraction effects
Authors: Jacquemot S. , Decoster A.
Published: March 2009

Neonlike ions have long been recognized as candidates for producing soft-X-ray lasers along 1s22s22p53p → 1s22s22p53s transitions. A series of experiments using exploding-foil targets driven by high-power lasers was performed at CEL-V and LLNL, and demonstrated amplified spontaneous emission in germanium, selenium, strontium, and molybdenum. We present here simulations of these experiments and discuss the importance of refraction effects on the propagation of the lasing X-rays and on the scaling of this scheme to shorter wavelengths.
X-ray emission by the rear side of laser-irradiated gold targets
Authors: Babonneau D. , Bocher J. L. , Bayer C. , Decoster A. , Juraszek D. , Perrine J. P. , Thiell G.
Published: March 2009

We present results of X-ray emission by the rear side of gold thin targets irradiated by the Phebus laser at λ = 0.35 μm, τ = 0.7 and 1.3 ns, and EL = 1.5 kJ. A streak camera coupled with a transmission grating gave the time-resolved X-ray emission of the rear side. Also, a streak camera coupled with a slit allowed us to obtain information about the space and time evolution of the plasma. Some other diagnostics gave information about the energy balance and the X-ray conversion efficiency. The results are in good agreement with previous ones obtained with the Octal laser, particularly on optimum thicknesses for X-ray conversion efficiencies. Values of the thermal flux limiter are deduced. Simulations with FCI 1 code with multigroup radiative transfer and non-LTE ionization reproduce the experimental results only about some points. A number of reasons, such as 2-D effects and problems of opacity, are invoked.
Time-resolved LIBS experiment for quantitative determination of pollutant concentrations in air
Authors: Casini M. , Harith M. A. , Palleschi V. , Salvetti A. , Singh D. P. , Vaselli M.
Published: March 2009

We propose a new time-resolved laser-induced breakdown spectroscopy (TRELIBS) system for quantitative determination of small amounts of pollutants in gas. Some experimental results showing the high resolution of the method are reported, and possible improvements of the system are discussed.
Gas lens applications
Authors: Michaelis M. M. , Cunningham P. F. , Cazalet R. S. , Waltham J. A. , Notcutt M.
Published: March 2009

Various gas lenses are briefly reviewed, together with their imperfections. We discuss the applicability of these lenses as objectives for telescopes and as the final focusing element of high-power laser systems: cw lasers in industry and pulsed lasers for plasma research. A novel phase conjugate experiment employing a gas lens is described. Pulsed gas lenses are proposed as a solution to the problems of high laser fluence and radiation damage in post-break-even fusion experiments.
A simple kinetic model for electron-beam-pumped KrF lasers
Authors: Harvey E. C. , Shaw M. J.
Published: March 2009

A kinetic model for KrF is presented that, by neglecting all but the most important kinetic processes, adequately describes the performance of electron-beam-pumped KrF lasers by a few, simple analytical expressions. The expression for the saturation intensity as a function of pump rate and gas composition is checked by measurements of gain saturation in both argon-rich and krypton-rich laser mixtures. The effects of fluorine burn-up are considered and are shown to impose a fundamental relationship between output fluence and efficiency of KrF laser amplifiers.
Numerical study of an X-ray-driven carbon foil
Authors: Kaiser N. W. , Meyer-Ter-Vehn J. , Ramis R.
Published: March 2009

The radiation hydrodynamics of a 125-μm thin carbon layer illuminated by thermal radiation of Trad = 200 eV temperature is studied within a multigroup radiation model. Whereas a major part of the incident photons deposit their energy by K-shell absorption close to the surface, soft photons below the K edge and hard photons (hv > 800 eV) penetrate deeper into the material and drive a heat wave with a sharp front. A nonablated mass fraction of 20% is accelerated with a hydrodynamic efficiency of 11%. About half of the incident radiation flux is reemitted by the heated carbon plasma. The heat front trajectory can be reproduced by the analytical heating wave model when effective opacity parameters corresponding to the most penetrating components are used.
Nuclear driven flashlamps
Authors: Prelas M. A. , Boody F. P. , Miley G. H. , Kunze J. F.
Published: March 2009

Due to the low power density of pumping schemes for nuclear-pumped lasers prior to 1978, a method of utilizing the efficient production of narrow band fluorescence from excimers was developed. This method has since been referred to as a nuclear driven flashlamp. It is possible to achieve sufficient power densities, when combining the flashlamp with novel techniques of reactor/laser interfaces, to drive efficient, high power lasers directly with products from nuclear reactions.
Simulation of laser–plasma interactions with atomic and radiation effects
Authors: Marchand R. , Fedosejevs R. , Capjack C. E. , Lee Y. T.
Published: March 2009

A one-dimensional Lagrangian code is used to model the interaction of laser light with plasma. The equation of state used is a realistic, piecewise analytic fit, which allows simulations starting from normal density and temperature conditions. The atomic physics required in the code (ionization, radiation rate, and opacities) is interpolated from tables generated using a non-LTE hydrogenic atom model. Radiation transport is treated approximately using a new, numerically efficient recursive algorithm. Results from numerical simulations are compared with recent X-ray measurements from Al, Ti, and Fe plasmas. The code is also used to investigate the X-ray conversion efficiency and the effect of radiation transport on the mass ablation rate and ablation pressure.
Modulational instability in the beat-wave generation
Authors: Pesme D. , Karttunen S. J. , Salomaa R. R. E. , Laval G. , Silvestre N.
Published: March 2009

The coupling of a large amplitude plasmon, generated by the beat-wave process, to ion acoustic waves may lead to modulational or decay instabilities, which are investigated here. A general dispersion relation obtainable from Zakharov equations predicts large growth rates (∼ωpi) for short wavelength modulations. To avoid these, extremely short pulse lengths are required in the beat-wave experiments. Due to the very long wavelength of the beat-plasmon, the decay instability is not likely below the ke V-temperatures.
Nd: YAG laser with plasma mirror
Authors: Kubeček V. , Vrbová M.
Published: March 2009

Nd: YAG laser action controlled by a solid target-plasma reflectivity is reported. A quasi-continuous mode-locking pulse train consisting of 26 ± 4 ps pulses was observed using a two-stage laser amplifier and a carbon target. A single pulse energy of 0.2 mJ and a peak power density at the target of about 1011 W/cm2 were measured.
Characterization and optimization of a laser generated plasma source of soft X rays
Authors: Rogoyski A. M. , Charalambous P. , Hills C. P. , Michette A. G.
Published: March 2009

An investigation into the feasibility of using a laser-generated plasma source of soft X rays as a laboratory based instrument for biological imaging and microlithography is presented. A preliminary characterization of the source has been carried out with carbon, copper and aluminum targets with specific interest in generating a monochromatic source of soft X rays in the ‘water window’. Measurements of X-ray production with respect to angular distribution, effects of cratering and different focusing conditions are reported. Initial conclusions on the optimization of the source for use in biological imaging are drawn.
Laser–plasma-interaction experiments using multikilojoule lasers
Authors: Drake R. Paul
Published: March 2009

This paper summarizes the results of several laser–plasma-interaction experiments using multikilojoule lasers, and considers their implications for laser fusion. The experiments used 1·06-, 0·53-, 0·35-, and 0·26-μm light to produce relatively large, warm, planar plasmas and to study the effect of laser wavelength and density-gradient scale length on the Stimulated Raman Scattering and on the scattering of light at frequencies near the incident laser frequencey by Stimulated Brillouin Scattering or other processes. The results of these experiments suggest that some laser wavelength between 0·2 and 0·6 μm will be required for high-gain laser fusion.
Non-uniform irradiation with inverse bremsstrahlung absorption in spherical laser targets
Authors: Sanz J. , Ibáñez F. , Nicolás J. A. , Tagare S. G.
Published: March 2009

Inverse bremsstrahlung absorption in the spherical, quasi-steady corona of a weakly nonuniform laser-irradiated target is considered. Here we have assumed that laser irradiation is almost spherical, justifying a linear analysis in terms of spherical harmonics. Our analysis is applicable for low intensities and short wavelength pulses. Complete results for ablation pressure, mass flow rate, and critical surface location are given in terms of Legendre index.
Studies of thin foils acceleration by pulsed laser beam
Authors: Burdonsky I. N. , Velikovich A. L. , Gavrilov V. V. , Gol'tsov A. Yu. , Zhuzhukalo E. V. , Kovalsky N. G. , Liberman M. A. , Pergament M. I.
Published: March 2009

Experimental studies of the ablative acceleration of thin foils as carried out on the “Mishen” device (Nd laser, λ = 1·06μm, 3 nsec pulses) are reported. The plasma corona in the range of power densities 1013–1014 W/cm2 is shown to absorb 80–90% of the laser beam energy, the classical collisional absorption mechanism being the main one. Jet-like and filamentary structures are observed in the laser-plasma interaction; however, the main plasma parameters are found to be independent of the presence (or absence) of such structures. The measured hydrodynamic efficiency of stable ablative acceleration in plane geometry is ≲5%. The production of high-speed cumulative jets with irradiated thin-wall hollow conical targets is reported as an example of a non-traditional ablative acceleration geometry.
UV excimer laser produced plasma and it's application to laser plasma switching
Authors: Lou Qihong
Published: March 2009

The characteristics of a laser plasma created by a high intensity UV excimer laser were investigated. The UV laser plasma was used as a switch for control of the laser pulse duration for the first time. An X-ray preionized XeCl laser pulse duration can be changed from 10 to 85 ns. This technique is useful for many applications of excimer lasers requiring various pulse durations.
Numerical simulation of the X-ray energetics in spherical plasmas
Authors: Dinguirard J. P. , Mostacci D. , Briand J. , Gomes A. , Kieffer J. C. , Quemener Y. , Arnas C. , Berge L. , Armengaud M.
Published: March 2009

1-D computer simulations have been performed to study the influence of X-rays preheating on the compression of spherical laser-produced plasmas. The targets are glass microballoons filled with Neon at the initial pressure 10 bars. It is assumed that the only significant absorption process in the Neon is by inverse bremsstrahlung absorption. The results indicate that the radiative preheating energy has a nonnegligible effect on the compression, and a study of the Lawson criterion shows that this effect is more important for high-Z target shell materials and for thicker shells.
Diagnosis of laser produced plasmas using fusion reaction products
Authors: Evans P. M. , Fews A. P. , Toner W. T.
Published: March 2009

Experiments have been performed at the Central Laser Facility, Rutherford Appleton Lab., UK. using novel techniques in which laser produced plasmas have been diagnosed by measurements of the charged thermonuclear reaction products. Two types of experiment are being reported here. Firstly, thermonuclear alpha particles from an exploding pusher target have been used to determine the growth of the Rayleigh–Taylor instability in a separate laser driven planar foil. The resulting alpha particle range loss distributions provide a direct measurement of the foil thickness distribution and hence the instability. The R–T instability has been observed in a number of foils with range losses varying between almost zero to over lOμm. Secondly, a thermonuclear particle backlighting technique has been used in the measurement of the stopping power of hot plasma for different materials. The ratio of plasma stopping power to that of the cold material is measured and compared to a value obtained from theoretical modelling. The solid state nuclear track detector CR–39 has been used as a diagnostic for these experiments. A sophisticated image analysis system has been developed to enhance and improve data recovery.
Some peculiarities in stark broadening of spectral lines of hydrogen-like ions in a dense plasma
Authors: Ljublin B. V. , Yasevich V. Yu. , Yakovlev D. G.
Published: March 2009

Stark broadening of Lyman lines in high density plasmas is treated theoretically to study the effects of the fields inside the plasmas, the microfield, and the oscillating fields from Langmuir waves. Resonance features are expected to be observed from the line profiles, especially about the microfield.
Parametric instabilities due to multiwavelength excitation
Authors: Tan Weihan , Liu C. S. , Guzdar P. N. , Lee Y. C.
Published: March 2009

The effects of finite bandwidth and random-phase pumping on parametric instabilities have been studied extensively (Thomson & Karush 1974; Thomson 1975; Laval et al. 1977). The possibilities arising from the use of this method and a time delay to obtain a spatial incoherence uniform illumination have been proven in experiments (Lehmberg & Obenschain 1983; Mima & Kato 1982; Kato & Mima 1982; Richardson 1981). In this paper we investigate this subject in an alternative way and obtain some results on the influence of the gain profile on parametric instabilities.
Improvements to ion-correlation experiments in dense plasmas
Authors: Shiwai B. A. , Djaoui A. , Hall T. A. , Tallents G. J. , Rose S. J.
Published: March 2009

Improved measurements of ion-correlation effects in a dense shock-compressed plasma are presented. The extended X-ray-absorption fine-structure (EXAFS) technique on the aluminum K edge is used to observe the short-range order within a dense plasma. Densities of about three times solid density were measured with good accuracy. The experimental measurements of density give results that are in good agreement with the MEDUSA onedimensional fluid code predictions. The improved quality of the data enabled us to calculate the ion coupling parameter during the compression and the subsequent heating of the plasma. An estimation of the temperature is given on the basis of published models, and an approximate agreement is obtained with the MEDUSA code predictions.
X-ray emission from thin-foil laser-produced plasmas
Authors: Gizzi L. , Batani D. , Biancalana V. , Giulietti A. , Giulietti D.
Published: March 2009

We studied X-ray emission from laser plasmas produced by irradiation of thin plastic foils with 1.064-μm Nd laser light at intensity up to 2 x 1013 W/cm2 with 3-ns pulses. The level of X-ray emission at different spectral windows was measured versus laser intensity and foil thickness. The electron temperature of the X-ray source was also measured. At intensity above 6 x 1012 W/cm2 our data showed the formation of nonthermal tails in the X-ray spectrum, which has been related to two plasmon decay instability.
Laser-induced breakdown of argon gas near a metal surface
Authors: Kumar V. , Thareja R. K.
Published: March 2009

Laser-induced breakdown of argon gas near a metal surface is studied. It is observed that the threshold laser energy required to break down argon gas is reduced in the presence of a metal surface. Photoelectric emission from the metal surface dominates the thermionic emission to reduce the threshold laser energy for breakdown.
Intrinsic angular momentum of the electromagnetic field
Authors: Ximing Deng
Published: March 2009

The main point of the hydrodynamic model of the electromagnetic field (Deng Ximing & Fang Honglie 1979, 1980) is that the motion of the electromagnetic field can be divided into two parts: orbital motion and intrinsic motion. This paper defines an intrinsic angular momentum deduced from the intrinsic motion and a related Î (imaginary number) operator, whose basic properties are discussed. In addition, the conservation property of the intrinsic angular momentum and the relation between it and the spin angular momentum of the electromagnetic field are described.
Study of laser-driven shock wave propagation in Plexiglas targets
Authors: Dhareshwar L. J. , Naik P. A. , Kaushik T. C. , Pant H. C.
Published: March 2009

An experimental study of laser-driven shock wave propagation in a transparent material such as Plexiglas using a high-speed optical shadowgraphy technique is presented in this paper. A Nd:glass laser was used to produce laser intensity in the range 1012-1014 W/cm2 on the target. Optical shadowgrams of the propagating shock front were recorded with a second-harmonic (0.53-μm) optical probe beam. Shock pressures were measured at various laser intensities, and the scaling was found to agree with the theoretically predicted value. Shock pressure values have also been obtained from a one-dimensional Lagrangian hydrodynamic simulation, and they match well with experimental results. Shadowgrams of shock fronts produced by nonuniform spatial laser beam irradiation profiles have shown complete smoothing when targets with a thin coating of a material of high atomic number such as gold were used. Shock pressures in such coated targets are also found to be considerably higher compared with those in uncoated targets.
Ion cluster interaction with cold targets for ICF: Fragmentation and stopping
Authors: Deutsch C.
Published: March 2009

Heavy ion clusters are considered for driving an inertial confinement fusion (ICF) pellet. They are shown to be effective at much lower energy than required for atomic ions. Multifragmentation is discussed with a maximum entropy hypothesis. Direct pressure imparted to a DT pellet is estimated. The stopping of strongly correlated ion cluster debris flowing in a degenerate electron jellium target is calculated for polarized and unpolarized (with respect to velocity) projectiles. A reduced stopping occur for elongated configurations at low velocities (υ ⋍ 1 a.u.) and very dense targets. Transverse geometries experience a very large and enhanced stopping. Systematic trends are stressed out. Largest stopping is achieved when debris correlation lengths are smaller than the target jellium screening length.
Equation of state and the phase diagram of dense fluid helium in the region of partial ionization
Authors: Förster Andreas , Kahlbaum Torsten , Ebeling Werner
Published: March 2009

The plasma composition, equation of state, and phase diagram of dense helium plasma were calculated for temperatures of 104...105K, total atom densities of 1015... 1025cm−3, and pressures up to 102TPa, including the region of partial ionization and strong Coulomb coupling. The basic thermodynamic potential was chosen to be the free energy density with contributions due to Coulomb interaction, hard-core repulsion, and van der Waals-like attraction for a mixture of differently charged atoms and free electrons. For the first time, we show the potential occurrence of a sequence of plasma phase transitions. In helium, they correspond to the ionization steps He0→He+and He+→He++respectively. The properties of the coexisting phases were determined by a Maxwell construction based on the combined chemical potential.
Average atom model and EOS calculations: DFT approach
Authors: Drska L. , Sinor M.
Published: March 2009

The knowledge of the properties of atoms in high-temperature/density plasmas is of deep interest in many fields of physics. Theoretical studies and interpretation of the inertial confinement fusion experiments is one of the examples. On the basis of the density functional formalism, a model of matter at extreme conditions is presented. Application of the model is illustrated by examples of average ionization state and equation of state calculations.
Linear response of partially ionized, dense plasmas
Authors: Błeński T. , Cichocki B.
Published: March 2009

We propose a new formalism to electronic polarizability of dense, partially ionized plasmas. This formalism is based upon the density functional theory for the electronic equilibrium, the random phase approximation for the density response of electrons, and the cluster expansion in the averaging over ionic configurations. The first term in the final cluster expansion for the imaginary part of electron polarizability corresponds to the Lindhard dielectric function formula. The second term contains the electronic states of the average atom. The additional effects that result from this theory are: channel mixing (screening), “inverse Bremstrahlung” corrections, and free-bound electronic transitions. Our approach allows the plasma (collective) and atomic physics phenomena to be treated in the frame of one formalism. The theory can be applied for stopping power and opacity calculations.
High-intensity laser interactions with tenuous plasma and ionization processes in noble gases
Authors: Boreham B. W.
Published: March 2009

The results of experimental studies of the interactions between high-intensity 25-ps pulses from a neodymium laser and tenuous plasmas are reviewed. Electrons expelled laterally from the laser focus regions were observed to have energies of up to 1.5 keV and both the maximum electron energy and the measured electron energy spectra were found to be characteristic of acceleration by ponderomotive forces, which usually are the main part of the general nonlinear forces. These results confirmed the naive force theory and emphasized the major importance of nonlinear effects at high laser intensities.
Transient effects in strongly correlated nonequilibrium plasmas
Authors: Armbrüster G. , Majer B. , Reimann U. , Toepffer C.
Published: March 2009

We study strongly correlated plasmas far from equilibrium with the ultimate aim of describing the cooling of heavy ion beams by electrons. With the help of molecular dynamics (MD) computer simulations, we conclude that the relaxation of a two-component plasma depends strongly upon the preparation of the initial configuration. If the initial data have no intercomponent correlations, such will build up during the evolution so that the intercomponent potential energy decreases while the kinetic energy increases. These effects become more pronounced for strongly coupled plasmas and limit the efficiency of electron cooling. We cannot confirm certain mean-field predictions on the influence of an external magnetic field on the cooling process. A study of the relaxation of anisotropic velocity distributions for a one-component plasma shows deviations from meanfield results for strongly coupled plasmas.
Recent results on implosions directly driven at λ = 0·26-μm laser wavelength
Authors: Koenig M. , Malka V. , Fabre E. , Hammerling P. , Michard A. , Boudenne J. M. , Batani D. , Garçonnet J. P. , Fews P.
Published: March 2009

New diagnostics were implemented on the implosion experiments performed at LULI to improve our measurements of hydroefficiencies: Neutron chronometry gives the time of emission of the fusion reaction products as measured from the peak of the laser pulse; thereby making it possible to correlate the neutron emission with X-ray emission. Core imaging, based upon a maximum entropy reconstruction technique, leads to core size determination and also is a promising diagnostic for wall nonuniformities induced by irradiation conditions. A simple model is developed to retrieve experimental spectra of α-particles.
Three-wave parametric instabilities in long-scale-length, somewhat planar, laser-produced plasmas
Authors: Drake R. P.
Published: March 2009

Three-wave parametric instabilities, in which an incident, laser-light wave resonantly decays into two decay waves, have long been recognized to potentially play a large role in the physics of laser-produced plasmas. Many effects have been predicted, but only gradually and with difficulty have experiments developed the ability to observe some of them. One obstacle has been that the behavior of the instabilities often depends upon the scale length and planarity of the plasma. My collaborators and I have worked for several years to overcome this specific obstacle and when necessary now work routinely with plasmas that are thousands of laser wavelengths in the axial and transverse scale lengths of the plasma parameters. This has allowed us to report the first observations of some instabilities and study the scaling behavior of several instabilities as well.
KrF laser-plasma interaction experiments with ns and ps pulses
Authors: Offenberger A. A. , Fedosejevs R. , Fujita M. , Tsui Y.-Y. , Broughton J. N.
Published: March 2009

We report on KrF laser-plasma interaction studies at focused intensities up to 4 × 1014 W/cm2 for pulse durations of 1–2 ns and up to 1015 W/cm2 for pulse duration of 100 ps. The longer-pulse experiments are concerned with quantifying two important features of the ablating plasma. Stimulated Brillouin scattering at moderately large L/λ has been measured in detail as a function of intensity, target Z, and angle of incidence θ to compare with modeling calculations of backscatter in inhomogeneous plasma. In addition, electrodynamic charge analyzer measurements have been made for varying intensity and target Z to compare with hydrodynamic calculations of ion expansion and recombination. In the short-pulse experiments, we report on X-ray conversion measurements for 100-ps laser-irradiated targets of varying Z at laser intensities of 1·5 × 1014 and 1015 W/cm2. In particular, it is shown that higher laser intensity leads to a substantial increase in X-ray conversion efficiency.
Self-backlighting study of a mix in a laser-accelerated planar target
Authors: Mucchielli F. , Holstein P. A. , Meyer B. , Périgaud N. , Vanderpotte O.
Published: March 2009

Experimental treating of hydrodynamic instabilities in laser-accelerated planar targets have pointed out the creation of a mix between a heavy material and a light one. The experiment described here is intended to answer the question: “Is this mix homogeneous or is it an interpenetration of both materials in the form of bubbles and spikes?” The method chosen to study the mix is self-backlighting, that is, backlighting of the target by its own X-ray emission. Comparison of the front and rear X-ray pinhole images of the target allows us to obtain information about the local areal density. Indeed, if 20-μm diameter Au dots are deposited on the target rear face some structures corresponding to these dots are observed on the rear image. The resolution imposed by the pinholes is about 10 μm. By using stable targets Au/CH, we obtained a good coincidence between front and rear pinhole images of the target. By doing the same comparison for unstable targets Au/CH/Au, the coincidence of the images is not significantly different from that obtained with stable targets. Therefore, in this experiment hydrodynamic instabilities do not create structures with dimension larger than 10μm.
X-ray shadowgraphy applications in ablatively accelerated planar foil studies
Authors: Bolotin V. A. , Burdonsky I. N. , Gavrilov V. V. , Gol'tsov A. Yu. , Zhuzhukalo E. V. , Zavyalets S. V. , Kondrashov V. N. , Kovalsky N. G. , Pergament M. I.
Published: March 2009

The article reviews experiments on flash X radiography of laser-accelerated foils. The spatial resolution, sensitivity, spectral range, and signal-to-noise ratio of measurements were carefully optimized and characterized. The method was used at the Mishen facility to measure a distribution of mass ablative rate across the focal spot and for observation of the transverse plasma flows during the drive laser pulse.
Investigations of laser interaction with high-Z targets
Authors: Mróz W. , Nowak-Goroszczenko A. , Wołowski J. , Woryna E.
Published: March 2009

This article presents the tendency of the changes of Nd-laser plasma parameters in dependence upon increasing target atomic numbers. In the experiment, the following targets — (C8H8)n, SiO2, Al, Cu, Ta, and Au — were investigated. For targets with Z higher than 13, the two-temperature plasma is observed with temperatures Te =500–600 eV and Te≅ 100 eV. Energy carried by ions from the low-temperature plasma can be higher than half the total energy carried by ions. The number of ions from low-temperature, X-ray-heated plasma can be by an order of magnitude higher than the number of ions from thermal plasma (Te = 500–600 eV).
Simulation and experimental studies on the evolution of a laser spark in air
Authors: Zeng X. C. , Singh D. P. , Palleschi V. , Salvetti A. , De Rosa M. , Vaselli M.
Published: March 2009

Experimental and theoretical studies on the evolution of shock waves in air plasma induced by laser spark have been carried out. The systematic study of the shock wave has been performed experimentally and 1-D numerical code of radiation hydrodynamics (1-DRHC) has been used to simulate the later stage of laser spark in air. The numerical results on the propagation of shock waves and the expansion of hot plasma are presented and subsequent results on the first divergent and convergent shock waves are found to be in good agreement with the experimental data.
Spectroscopic study of plasma produced with a heavy ion maxilac beam
Authors: Belyaev G. E. , Bryunetkin B. A. , Golubev A. A. , Mahrt-Olt K. , Skobelev I. Y. , Faenov A. Y. , Hoffmann D. H. H. , Sharkov B. Y.
Published: March 2009

Spectroscopic study of plasma produced through bombardment of the 1 × 3 mm2 area on the surface of a solid Mg target with Kr+ ions is carried out. Spectral lines of Mg I and Mg II ions were observed in the visible range (200–600 nm). The plasma parameters Ne = 1.4.1017 cm−3 and Te = 0.8 eV are calculated from electron impact broadening of the 4f–3d line of Mg II and from the ratio of intensities for the 4f–3d and 4s–3p lines of Mg II. The ionic composition of the plasma is determined. The detected X-ray emission is shown to be the characteristic emission of the target.
An effect of the target position relative to the laser focus on X-ray emission from the laser plasma
Authors: Chvojka M. , Králiková B. , Krouský E. , Láska L. , Maŝek K. , Renner O. , Rohlena K. , Skála J. , Ŝtirand O. , Trenda P.
Published: March 2009

The first harmonics beam generated by an iodine laser system was focused by an f/2 optics on an Al foil target. The X-ray output from the laser plasma both in the line and broad-band spectra was registered over an interval around the “ideal” focus. It was found that the maximum X-ray power is not obtained in the focus itself but for a somewhat larger focal spot outside the focus. To explain this phenomena, temperature and density measurements were in addition made. The plasma temperature evaluated from both the line (He-like Al XII resonant line and j, k, l satellites) and broad-band spectra (two foil method) was also measured and found to be largely constant in the vicinity of the focus. The line and broad-band temperatures differ, the broad-band temperature being about 25% higher. The electron density was equally determined using an intercombination line.
Experimental study of X-ray emission from laser-irradiated planar targets on “Mishen” Facility
Authors: Bolotin V. A. , Burdonskii I. N. , Gavrilov V. V. , Gol'tsov A. Yu. , Zavyalets S. V. , Zhuzhukalo E. V. , Kondrashov V. N. , Koshevoi M. O. , Pergament M. I. , Rupasov A. A. , Shikanov A. S.
Published: March 2009

X-ray emission from planar targets irradiated by 1.054-μm laser pulses was observed with temporal, spatial, and spectral resolution. The main purpose of these measurements was the investigation of energy transfer in multilayer targets and X-ray conversion efficiency. A mass ablation rate was determined from temporal analysis of multicharged ion line emission and a key role of corona X-ray emission in accelerated material preheating was established.
Formation of an elongated plasma column by a magnetic confinement of a laser-produced plasma
Authors: Pisarczyk T. , Faryński A. , Fiedorowicz H. , Gogolewski P. , Kuśnierz M. , Makowski J. , Miklaszewski R. , Mroczkowski M. , Parys P. , Szczurek M.
Published: March 2009

In this article, we present the formation of an elongated plasma column by combining a laser plasma with an external magnetic field. The laser plasma is produced by irradiating solid targets with a focused Nd-glass laser. The targets were placed on the axis of the two, single-turn magnetic coils, which provided a magnetic field up to 500 kg in the target region. The expanding laser plasma is confined by the magnetic field and an elongated and uniform plasma column is formed on the axis of the coils. The plasma column emits strong, soft X-ray radiation. The pinhole photographs show that the plasma column is at least 5 mm long. To study the interaction of the expanding laser plasma with a magnetic field, the laser probing diagnostic was used.
A possible effect of ASE high intensities on gain values in plasmas
Authors: Sureau A.
Published: March 2009

It is shown that large gainlengths of amplified spontaneous emission (ASE) together with collisional effects in plasmas are liable to generate modifications in population inversions and then in observed gain values. In the case of the Ne-like Se24+ ion, one can expect a significant reduction of the J = 0–1 transition gain value at the wavelength of 18.24 nm.
Inverse population of the H-like F ion levels in a recombining laser-produced plasma confined in a strong magnetic field
Authors: Faryński A. , Gogolewski P. , Karpiński L. , Kuśnierz M. , Makowski J. , Mroczkowski M. , Szczurek M. , Bryunetkin B. A. , Faenov A. J. , Skobelev I. J.
Published: March 2009

Experimental investigations of laser-produced plasma expansion in a strong (−20T) magnetic field have been carried out. The image and spectra of the plasma flame in the soft X-ray spectral region have been obtained. It has been shown that the strong magnetic field limits the transverse plasma expansion and strongly effects the ion-level populations.
Study of X-ray laser interaction plasmas
Authors: Kodama R.
Published: March 2009

Atomic processes in X-ray laser interaction plasmas are investigated by using a collisional-radiative model. Population inversions on free-bound transitions can be produced by photoionization above a threshold of incident X-ray laser intensity and lead to stimulated free-bound emission (SFBE). Free-bound lasers pumped by intense X-ray lasers are proposed and their feasibility is investigated simply considering X-ray laser interaction plasmas.
Progress in UV soft X-ray imaging
Authors: Schirmann D. , Bocher J. L. , Le Breton J. P. , Mens A. , Sauneuf R.
Published: March 2009

Soft X-ray imaging detection is usually made by using 101–01, 101–07, or SA1 Kodak films. Recent progress in thinned CCD fabrication allows us now to replace films by thinned CCDs to detect UV soft X-ray light with an enhanced sensitivity. We developed a thinned CCD system, and to demonstrate its applicability to replace photographic films we tested it behind a broad spectral range soft X-ray transmission grating spectrometer and a soft X-ray Mo/Si multilayer mirror telescope. Soft X-ray spectra and soft X-ray pictures of laser-created plasma are presented using these instruments implemented with a thinned CCD readout.
Theoretical analysis of double-crystal spectrograph for high-resolution spectroscopy of laser-generated X-rays
Authors: Renner O. , Kopecký M.
Published: March 2009

Vertical dispersion variant of the double-crystal spectrograph is analyzed and its basic quantitative characteristics (luminosity, resolving power) are computed using ray tracing code. It is shown that geometric apparatus smearing is minimized due to high dispersion and spectral resolution may considerably exceed the single-crystal diffraction limit. Performing high-resolution spectral work, the efficiency of the double-crystal apparatus exceeds that of the flat single-crystal spectrograph. The usefulness of this method in laser plasma spectroscopy is demonstrated analyzing the detection of phosphorus He-like resonance line and its satellites.
Strengths and weaknesses of KrF lasers for inertial confinement fusion applications learned from the AURORA laser
Authors: Harris D.B. , Allen G.R. , Berggren R.R. , Cartwright D.C. , Czuchlewski S.J. , Figueira J.F. , Hanson D.E. , Hauer A. , Jones J.E. , Kurnit N.A. , Leland W.T. , Mack J.M. , McDonald T.E. , McLeod J. , Rose E.A. , Sorem M. , Sullivan J.A. , Watt R.G.
Published: March 2009

The AURORA KrF laser at Los Alamos became operational in August 1989. AURORA is the first integrated system for demonstrating the capability of a KrF laser to perform target physics experiments for inertial confinement fusion (ICF) and is currently configured as a 5-kJ, 5-ns, 96-beam device. Both laser physics and ICF target physics experiments have been performed over the last year. Of the four major amplifiers in the AURORA laser system, one performed better than expected, one performed about as expected, and two performed below expectations. The causes of the variability in the amplifier performance are now well enough understood that this information can be used to improve the detailed design of the NIKE laser currently under construction at the Naval Research Laboratory. design of the NIKE laser currently under construction at the Naval Research Laboratory. High-dynamic-range pulse shapes have been propagated with minimal distortion through the AURORA amplifier chain, verifying theoretical predictions. Target physics experiments have been performed with intensities greater than 100 TW/cm2, pulse lengths ranging from 2–7 ns, and spot-size diameters from 500–1100 µm. The analysis of this first-generation kJ-class KrF laser target physics facility identified the strengths and weaknesses of KrF lasers for ICF applications. Detailed measurements of amplifier performance led to a better understanding of issues for KrF laser-fusion systems, and design studies for future KrF lasers for ICF applications incorporate improvements based in part on AURORA experience.
Development of high-performance KrF and Raman laser facilities for inertial confinement fusion and other applications
Authors: Shaw M.J. , Edwards B. , Hirst G.J. , Hooker C.J. , Key M.H. , Kidd A.K. , Lister J.M.D. , Ross I.N. , Bailly-Salins R. , Harvey E.C.
Published: March 2009

This article describes the current status of the KrF development programme based on the Sprite laser system at the Rutherford Appleton Laboratory. High reliability and high shot rate have been demonstrated. Using a unique KrF-pumped Raman laser architecture, beam brightness exceeding 2×1019 Wcm-2 sterad-1 giving a focussed intensity >5 ×1017 Wcm-2 has been achieved. The development of transform-limited short-pulse oscillators is shown to be of importance in avoiding spectral broadening in air propagation of high-intensity beams. Beam smoothing of KrF beams in a multiplexed configuration has been demonstrated for the first time. The technique of echelon-free induced spatial incoherence has been shown to produce smooth intensity distributions in the far field, which remain essentially unchanged on amplification. The development of pulsed-power systems capable of exciting multikilojoule laser amplifiers for the next phase of development, the Supersprite system, is briefly discussed.
Performance of the Asterix IV iodine laser
Authors: Baumhacker H. , Brederlow G. , Fill E. , Volk R. , Witkowski S. , Witte K.J. , Schrödter Ch.
Published: March 2009

The single-beam Asterix IV high-power iodine laser, presently operated at a pulse length of 0.3 ns, has achieved its projected output power of 4 TW. It is designed to deliver output pulses with lengths ranging from 0.1–3 ns with a maximum power of 5 TW and an energy of up to 2 kJ. This laser has been developed on the basis of 10 years of experience with the 1 TW Asterix III laser and with the support of a 1-D and 3-D pulse propagation code. Special emphasis has been put on increasing the overall efficiency of the laser system and obtaining a laser beam intensity profile as homogeneous as possible. In this article, the measures for improving the laser performance and the results obtained hitherto are presented.
Neutron damage and activation of the first wall of inertial confinement fusion reactors: Recycling and waste disposal
Authors: Perlado J.M. , Sanz J.
Published: March 2009

Even though general conclusions cannot be derived for all the protection schemes in inertial confinement fusion (ICF) reactors, the feasibility of the ferritic alloy HT-9 as the main component of the first structural wall (FSW) in ICF facilities using thin-film Li17Pb83 liquid protection, flowing through porous tubes (INPORT), can be demonstrated as a solution in terms of radiation damage. Swelling and shift in the ductile-brittle transition temperature (DBTT) can be analyzed using the results of experimental fast-fission reactors, which are demonstrated to be good experimental tools in that ICF range. The good performance of HT-9 is remarkable. The generation of new solid transmutants and the depletion of initial constituents need also be considered. Further, a reduced-activation HT-9 (niobium-free) has been studied using recycling and shallow land burial (SLB) criteria. The recycling using that HT-9 is shown to be not feasible, as is SLB waste disposal. The unexpected critical role of some short-lived isotopes is remarkable, and more research on their nuclear data must be performed.
Magnetic suspension of a pellet for inertial confinement fusion
Authors: Yoshida H. , Katakami K. , Sakagami Y. , Azechi H. , Nakarai H. , Nakai S.
Published: March 2009

In inertial confinement fusion experiments, the symmetrical implosion calls for a new scheme: a nonsupported pellet. In this article, the first experiment is conducted using a plastic pellet covered with thin ferromagnetic material. In the system, the digital-phase-lead-compensator takes the position-related signal and processes it to provide a driving signal for the magnetic suspender. The suspended pellet is irradiated by the Gekko XII laser, having its total energy 2700 J with pulse width 800 ps at the wavelength 0.53 μm. The X-ray pinhole photograph confirms the spherically symmetrical implosion at the pellet core. At irradiation, the neutron yield is also observed.
Ejected electron energy dependence of ionization cross section of He and Ar atoms by fission fragments bombardment
Authors: Rykov V.A. , Dyachenko P.P. , Mahrov F.V. , Sokolov Yu.V.
Published: March 2009

We present the cross section for the ejection of electrons from helium and argon by 252Cf fission fragments, differential in the ejected electron energy. The electron energy ranges from 10 to 1,500 eV. The experimentally obtained cross sections are compared with calculations in the framework of Gryzinski&s theory and Gerjuoy&s theory. The results of the energy loss partitioning are presented. It is demonstrated that there is reasonable agreement between Gerjuoy&s theory and experiment.
Nuclear reactor-pumped laser atomic xenon operated at 2.48 µm
Authors: Bochkov A. , Kryzhanovsky V. , Lyubimov O. , Magda E. , Mukhin S.
Published: March 2009

A fission fragment-pumped Ar-Xe laser at 2.48 ¼m is reported. A threshold level of 3 × 107 thermal neutrons/cm2s was found with a 0.01% laser efficiency. The mechanism associated with temperature effects on laser performance is identified.
Nuclear pumping of I2 vapor in dense gases
Authors: Mavlyutov A.A. , Mis'kevich A.I. , Salamakha B.S.
Published: March 2009

The luminescence spectra of dense inert gas mixtures with iodine vapors excited by α-particles of 238Pu and 239Pu sources were investigated from 200 to 1,000 nm. In luminescence spectra of He-I2, Ar-I2, and Kr-I2 mixtures besides atomic lines corresponding to (np-ns) transitions of inert gas atom (n = 4 and 5 for Ar and Kr, respectively) there exist 288-, 320-, 342-, and 500-nm iodine molecular bands. The 342-nm (D&3II2g - A&3II2u) band has the highest intensity in these spectra and the highest intensity in the Kr-I2mixture. The measured bandwidth of the 342-nm band is equal to 24 A (full width at half maximum). In the Xe-I2 spectrum, the 342-nm band does not exist but the 253-nm Xel* excimer band has the highest intensity in it. The measured bandwidth of the 253-nm band equals 27 Å.
Third excimer continua in neon and argon
Authors: Krötz W. , Ulrich A. , Busch B. , Ribitzki G. , Wieser J.
Published: March 2009

The emission of the third continuum of argon in the wavelength range between 175 and 250 nm and the vacuum ultraviolet emission of neon (λ < 100 nm) has been studied by timeresolved optical spectroscopy. The target gases at pressures between 2 and 100 kPa were excited with a pulsed beam of 100 MeV 32S9+ ions from the Munich Tandem van de Graaf accelerator. Wavelength spectra recorded in different time windows after the 2-ns beam pulses show that two different components contribute to the third continuum of argon. A radiative lifetime of 5.71 ± 0.08 ns for the Ar22+ molecule and a rate coefficient k3 = (1.46 ± 0.12) x 10-30 cm6/s for the reaction Ar2+ + 2Ar → Ar22+ + Ar were obtained from the pressure dependence of time spectra at a wavelength of 190 nm. From time- and pressure-dependent studies of the third continuum emission of neon at a wavelength of 99 nm, rate coefficients k2 = (3.6 ± 0.3) x 10-13 cm3/s for the bimolecular reaction Ne2+ + Ne→ 2Ne+ and k3 = (2.84 ± 0.09) X 10-31 cm6/s for the termolecular reaction Ne2+ + 2Ne → Ne22+ + Ne were determined.
Overview of nuclear-pumped lasers
Authors: Miley George H.
Published: March 2009

The first demonstration of a nuclear-pumped laser (NPL) dates back to the mid-1970s while theoretical studies started earlier. This history will be briefly reviewed, followed by a discussion of the present status of various NPL concepts. Both physics and engineering issues are noted. Most attention has been given to gaseous media due to problems associated with radiation damage in liquid- and solid-state media. Various pumping methods, ranging from direct pumping of the laser medium to the use of nuclear-pumped flashlamps, will be discussed. Recent experimental results on pumping of O2(1Δ), the first demonstration of a nuclear-pumped flashlamp-driven laser XeBr*-I, and the new 3He-Ne-H2 NPL will be presented. Potential applications and corresponding NPL requirements, e.g., the long delay time requirements for an inertial fusion driver based upon NPLs, will be reviewed.
Hugoniot measurements on copper to 0.8 TPa by laser-driven shock waves
Authors: Yuan Gu , Yonggang Wang , Sizu Fu , Jiang Wu , Songyu Yu , Binggen Wan , Guanlin Zhou , Xin Wang , Guojiang Han , Yixin Zeng , Minxun Ma
Published: March 2009

An experiment on Al-Cu impedance-match targets, carried out at the Shenguang highpower laser facility, is described. The shock adiabat of Cu in the pressure region 0.4- 0.8 TPa, measured experimentally, is close to the extrapolated results of the data at lower pressure obtained with a high-explosive loading facility and also is in agreement with the data at high pressure measured in the underground nuclear test environment.