bluuebunny/crossref_metadata_2025 huggingface dataset:
Intense light-ion beams provide a robust, common-driver path toward ignition, gain, and commercial fusion energy
Authors: Ramirez J.J. , Cook D.L. , Rice J.K. , Matzen M.K. , Johnson D.L. , Boyes J.D. , Olson C.L. , Prestwich K.R. , Clauser M.J. , Mehlhorn T.A. , Stinnett R.W. , Allshouse G.O. , Kulcinski G.L. , Moses G.A. , Peterson R.R. , Engelstad R.L.
Published: March 2009

Intense light-ion beams are being developed for investigations of inertial confinement fusion (ICF). This effort has concentrated on developing the Particle Beam Fusion Accelerator II (PBFA II) at Sandia as a driver for ICF target experiments, on design concepts for a high-yield, high-gain Laboratory Microfusion Facility (LMF), and on a comprehensive system study of a light-ion beam-driven commercial fusion reactor (LIBRA). This article reports on the status of design concepts and research in these areas.
Subthreshold diagnostics of He–Cd active medium for direct nuclear-pumped lasers
Authors: Dyachenko P.P. , Dorofeev Yu.B. , Poletaev E.D. , Tarasko M.Z.
Published: March 2009

The time and wavelength dependencies of luminescence resulted from 11 low-lying Cd II levels in He-Cd medium excited by 252Cf fission fragments have been measured in the temperature range from 553 to 669 K and various buffer gas pressures (1.5–5 atm). The method used is based upon applying multichannel coincidence technique and single-photon spectrometry. The lifetime, pumping rate, and luminescence spectral line width data obtained for 325- and 441.6-nm transitions have been used to estimate lasing characteristics of He-Cd medium under optimal conditions.
Heavy-ion beam pumping as a model for nuclear-pumped lasers
Authors: Ulrich A. , Busch B. , Krötz W. , Ribitzki G. , Wieser J. , Murnick D.E.
Published: March 2009

Heavy-ion accelerators can provide various beams from protons to uranium ions with energies ranging from a few keV/u to more than 1 GeV/u. The Munich Tandem van de Graaff accelerator has been used for most of the experiments described in this article. It can provide continuous or pulsed beams of almost all elements with particle energies of about 3.5 MeV/u. The pulse width is typically 2 ns. Maximum DC-beam currents of the order of 10 μA can be obtained, for example, for 32S ions. When the beam is focused to a beam spot of about 3 mm diameter, the flux of the ions is comparable to the flux of fission fragments used for nuclear-pumped lasers. Ion beam pumping is therefore well suited for model experiments of nuclear-pumped lasers. Technical aspects of ion beam-pumped lasers are discussed and the results of the lasers that have thus far been pumped by this method aresummarized. As ion beams are available either continuous or at high-pulse repetition rates ranging from tens of kHz to MHz, detailed spectroscopic and time-resolved studies of the emission of light induced by heavy-ion excitation of the target material can easily be performed. Experiments in which the emission by rare gas excimers and line radiation from atoms and ions has been studied are described. Lifetime measurements of excited levels at different target densities were used to measure collisional rate constants.
Parametric design study of a nuclear-pumped laser-driven inertial confinement fusion power plant
Authors: Beller Denis E. , Jacobson John M. , Miley George H. , Petra Maria , Shaban Yasser
Published: March 2009

In an earlier preliminary design study, we proposed a novel nuclear-pumped laser-driven (NPL) inertial confinement fusion (ICF) power reactor that represents an important variation on the “neutron feedback” concept for ICF. This NPL-driven ICF concept also included an advanced, DT-seeded, D3He-fueled pellet and magnetic protection of the first wall of the reactor chamber. Advantages that were demonstrated for this approach included increased efficiency for laser-to-target energy coupling, increased efficiency for thermalto-electric energy conversion, and reduced neutron activation and waste. The coupling efficiency is enhanced because a nuclear-pumped flashlamp is directly pumped by fission fragments from uranium micropellets within the lamp medium. The thermal conversion efficiency is greater because a large fraction of the ICF pellet&s fusion yield is in charged Finally, the fraction of the fusion yield carried by neutrons is significantly reduced in comparison with pure D-T-fueled pellets; thus, neutron-induced activity in the first wall is decreased and safety is increased. The initial study indicated these factors could result in a required driver energy of 5 MJ (vice 10 MJ currently projected) and a pellet gain of only 50 (vice 100 currently projected) for a feasible l,000-MWe power reactor operating with approximately six pellets per second. The current study includes a refined analysis of an NPL-driven ICF power reactor of this type. A cylindrical design for the fission/NPL blanket is selected as a “natural” geometry for pumping the NPL. Required enrichments and criticalities are then predicted for the multiplication of the fusion neutron yield needed to pump the NPL. Based upon these results, we report a more detailed parametric study of the efficiencies for converting neutron, X-ray, and plasma yields from advanced ICF pellets into electrical and optical energy flows required in this concept. We also examined breeding tritium in a lithium blanket layer. Results from these studies help define topics and parameter spaces for further research on this unique reactor concept.
Nuclear-induced XeBr* fluorescence pumping of the atomic iodine laser
Authors: Williams W.H. , Miley G.H.
Published: March 2009

Lasing in atomic iodine pumped with incoherent, nuclear-stimulated XeBr* fluorescence is reported. These experiments represent the first demonstration of a nuclear flashlamppumped laser of any type. The fluorescence of XeBr* under nuclear pumping is also discussed.
Powerful Nd:glass laser with composite active elements incorporating WFR cells and output pulse compressors
Authors: Belousov V.N. , Nizienko Yu.K.
Published: March 2009

A new scheme for a large-scale solid-state laser system for inertial confinement fusion application is proposed. Double-pass amplifiers composed of a large number of Nd:glass rods and flash lamps between them are used together with phase-conjugation cells and output stimulated Brillouin scattering pulse compressors. The results of the preliminary experimental tests are presented, and the advantages of the proposed scheme are discussed.
Satellite observations of currents and waves in space plasmas
Authors: Potemra T. A. , Engebretson M. J. , Zanetti L. J. , Erlandson R. E. , Bythrow P. F.
Published: March 2009

When viewed from outer space, the earth's magnetic field does not resemble a simple dipole, but is severely distorted into a comet-shaped configuration by the continuous flow of solar wind plasma. A complicated system of currents flows within this distorted magnetic field configuration called the ‘magnetosphere’ (See figure 1). For example, the compression of the geomagnetic field by the solar wind on the dayside of the earth is associated with a large-scale current flowing across the geomagnetic field lines, called the ‘Chapman-Ferraro’ or magnetopause current. The magnetospheric system includes large-scale currents that flow in the ‘tail’, the ring current that flows at high altitudes around the equator of the earth, field-aligned ‘Birkeland’ currents that flow along geomagnetic field lines into and away from the two auroral regions, and a complex system of currents that flows completely within the layers of the ionosphere, the earth's ionized atmosphere. The intensities of these various currents reach millions of amperes and are closely related to solar activity. The geomagnetic field lines can also oscillate, like giant vibrating strings, at specified resonant frequencies. The effects of these vibrations, sometimes described as ‘standing Alfvén waves’, have been observed on the ground in magnetic field recordings dating back to the beginning of the century. Observations of currents and waves with satellite-borne magnetic field experiments have provided a new perspective on the complicated plasma processes that occur in the magnetosphere. Some of the new observations are described here.
A grain plasma model of galaxies
Authors: Wollmanm E. R.
Published: March 2009

Electrical quasi-neutrality is not a general property of a thermalized self-gravitating plasma. If the massive component of a two-component plasma consists of charged macroscopic solid grains for which the charge-to-mass ratio is of order then self-gravitation and thermalization lead to substantial large-scale charge separation. An alternative statement of the condition for substantial equilibrium charge separation is that the Jeans length and Debye length of the plasma are similar.

We consider a system of condensations in such a plasma and show that properties of the system are similar to observed properties of the system of galaxies.
Hydrodynamic Hamilton theory for discussing the space charge (Langmuir–Child Law) at high density particle currents between poles
Authors: Passow Cord
Published: March 2009

In order to calculate more generally the space-charge limited current between two points of different voltage, modern differential geometrical methods are applied. This problem was first treated by Child (1911) and later by Langmuir (1913). It is possible, for example, to account for effects due to more than one charge component as well as the influence of a neutral background gas (which causes ionization and scattering of charge carriers). A systematic derivation of the self-consistent representation based on a Hamilton theory for density functions is given, and solution methods are discussed. The concept is designed to investigate ion and electron diodes with very intense currents, but it may also be useful for treating space charge problems in a stationary plasma.
Density ratios in compressions driven by radiation pressure
Authors: Lee S.
Published: March 2009

It has been recently suggested (Hora & Miley 1984) that in the cannonball scheme of laser compression the pellet may be considered to be compressed by the ‘brute force’ of the radiation pressure. For such a radiation-driven compression, this paper applies an energy balance method to give an equation fixing the radius compression ratio κ which is a key parameter for such intense compressions. A shock model is used to yield specific results. For a square-pulse driving power compressing a spherical pellet with a specific heat ratio of 5/3, a density compression ratio Γ of 27 is computed. Double (stepped) pulsing with linearly rising power enhances Γ to 1750. The value of Γ is not dependent on the absolute magnitude of the piston power, as long as this is large enough. Further enhancement of compression by multiple (stepped) pulsing becomes obvious. The enhanced compression increases the energy gain factor G for a 100 μm DT pellet driven by radiation power of 1016 W from 6 for a square pulse power with 0·5 MJ absorbed energy to 90 for a double (stepped) linearly rising pulse with absorbed energy of 0·4 MJ assuming perfect coupling efficiency.
Current generation in laser plasma using the preaction of low-energy radiation pulse on the target
Authors: Barkhudarov E. M. , Gelashvili G. V. , Gumberidze G. G. , Taktakishvili M. I.
Published: March 2009

The paper demonstrates the possibility of the current increase in laser plasma by more than one order at the preaction of low-energy pulse on the target. The conversion effectivity of 0·32% is obtained at the intensity of the principal pulse of a CO2 laser equal to 4 × 109 W/cm2 and at the residual gas pressure of 10−5 torr.
Energy transport through thin aluminum foils in laser-target experiment
Authors: Mróz W. , Arendzikowski R. , Denus S. , Farny J. , Fiedorowicz H. , Jeziak K. , Mamczur M. , Nagraba S. , Pawłowicz W. , Wilczyński A. , Wołowski J. , Bitzan P. , Drska L. , Limpouch J. , Loncar G. , Pina L. , Vondrasek J.
Published: March 2009

The paper presents results of an investigation of energy transport in 6-μm aluminum foils covered with a silver or gold layer irradiated with 1·06-μm, 1-ns laser-pulse at intensities 1013to 1014 W/cm2. The increase in mass ablation rate and volume heating of accelerated fragment of the foil as well as the increased range of lateral energy transport were registered. The measured plasma parameters from aluminum foils were used for testing the one-dimesional numerical code.
Obtaining microspherical cryotargets by the method of contact point
Authors: Denus S. , Muniak W. , Woryna E.
Published: March 2009

In this paper we present main parameters of the thermonuclear fuel and relations connecting the thickness of an isothermal homogeneous cryolayer with gaseous microballoon parameters. A model of the temperature field calculation (the azimuthal temperature gradient and the temperature distribution) and the way of shaping it under practical experimental conditions by the contact-point method is presented. The temperature distribution calculation explains the “sag” effect observed in many experiments.
Ion emission characteristics from laser-produced plasmas with steep density gradients
Authors: Rohr K. , Dinger R. , Weber H.
Published: March 2009

Ion emission from laser-produced plasma with small focal spots (20 μm) has been investigated for s- and p-polarization of the Nd–YAG laser at IL = 6 * 1013 W/cm2. The target has been Plexiglas (Hg, C5, O2) n, and the ion analysis has been charge, mass and velocity resolved for emission angles between 15° and 65°. It is found that additional resonance absorption mainly leads to an enhancement of the number of totally emitted ions which is essentially uniform for a large region of the velocity spectrum. The total increase in plasma expansion energy is by a factor of more than 3·5. The relatively low enhancement of the average initial temperature produces an unexpected asymptotic charge distribution with higher charges if resonance absorption is not present.
Recent results of experiments associated with cryogenic pulsed ion diodes
Authors: Kasuya K. , Horioka K. , Yoneda H. , Sumitani H. , Tomita H. , Kato S. , Goino Y. , Teii S. , Tazima T.
Published: March 2009

Beam productions from ammonia ice were tried for the first time to obtain proton beams with reasonable purity under the liquid nitrogen cooling. Beam focusings and neutron productions under the target irradiations were tried with water ice. Resonant and optical interferometries were applied to observe the behavior of neutral particles within the anode-cathode gaps.
Production and applications of cluster beams
Authors: Becker E. W.
Published: March 2009

Cluster beams may be produced by screening out the core portion of a partially condensed supersonic jet and introducing it into a high vacuum chamber. Potential applications of such beams are reported here and include accelerator targets, plasma generation, nuclear fuel injection into fusion devices, and production of thin layers for microelectronics and optics.
Effect of target atomic number on laser induced ablation pressure scaling
Authors: Shirsat T. S. , Parab H. D. , Pant H. C.
Published: March 2009

Laser induced ablation pressure as a function of absorbed laser intensity for low and moderate atomic number targets has been experimentally determined using a 1·06-μm laser at an irradiance of 5 × 1011to 1 × 1013W cm−2. Ablation pressure variations with the absorbed laser intensity indicate a transition from a self-regulating ablation to a deflagration scaling for low atomic targets. The experimental results have also been corroborated with theoretical models and a two dimensional hydrodynamic code.
Effects of helium buffer gas on the atomic carbon nuclear-pumped laser at low power densities
Authors: Chung A. K. , Peck M. S. , Prelas M. A.
Published: March 2009

A computer model has been developed and benchmarked for the nuclear-pumped atomic carbon laser. Experiments have been performed with the atomic carbon laser and with the radiolysis of CO2 as a benchmark for the model. The results of the CO2 radiolysis are described.
Calculation of atomic excitation processes of X-ray laser plasmas irradiated by short-pulse intense KrF laser pulses
Authors: Sasaki A. , Yoneda H. , Ueda K. , Takuma H.
Published: March 2009

An atomic model of the laser-produced Al plasma has been developed and used to analyze excitation processes of recombination pumping soft X-ray lasers. A soft X-ray gain for H-like Balmer-α line and He-like 3d-2p transition in short-pulse intense KrF laser (IL = 1014–1015 W/cm2, T = 10–100 ps)-produced Al plasmas are calculated for various laser temporal pulse shapes to find the condition for efficient production of population inversion. Results from different models are compared and requirements for the atomic model for X-ray laser design are discussed.
Direct- and indirect-driven reactor targets
Authors: Kiu K.
Published: March 2009

Theoretical and numerical analyses are given for direct- and indirect-driven reactor targets, from which 3-GJ fusion output energy is released. For a reactor target, which has a large radius and long implosion time, supersonic flow of imploding D–T fuel in the converging nozzle (in sphere) is important for adiabatic compression of fuel. For a direct-driven target, pellet gain depends much upon the region where the beam deposits its energy. Phase mixing is also important to increase the absorption rate of irradiating laser light. When a strong light with a phase is concentrated on a small region of target surface, collective electron motion on the target surface radiates electromagnetic waves, which reduce the electron motion. When beam irradiation on the target is not uniform, an indirect-driven target must be used because a direct-driven target is weak for nonuniform irradiation. For an indirect-driven reactor target, which requires a long implosion time, expansion of radiator and absorber layers causes the decrease in radiation temperature. There is the optimum target structure with respect to the aspect ratio (radiation gap distance).
Calculations and diagnostic applications of Stark-broadened absorption line profiles for theL-shell ions of argon
Authors: Haynes D. A. , Mancini R. C. , Hooper C. F.
Published: March 2009

We calculated Stark-broadened absorption line profiles forn= 1 ton= 2 inner-shell transitions in theL-shell ions of Ar for electron number densities between 5 × 1023cm-3and 5 × 1024cm-3and for temperatures in the range 100–600 eV. These line profiles are used to calculate the frequency-dependent optical depth of hot, dense Ar plasmas. We also investigated the possibility of using Stark-broadened absorption line profiles for diagnostic applications.
Nonstationarity of stimulated Raman scattering in a homogeneous plasma slab
Authors: Jovanović M. S. , Škorić M. M.
Published: March 2009

Nonstationarity of stimulated Raman backscattering in a finite homogeneous plasma slab is examined. Slowly varying envelope equations are analyzed taking into account a damping and a convection of an electron plasma wave, with a nonzero source boundary condition assumed. The linear analysis method is used for examination of stability of saturated stationary amplitude solutions. When linear wave damping is sufficiently small or absent, these solutions are spatially periodic and appear linearly unstable to small perturbations. However, a direct numerical simulation of the backscattering process in a lossless case shows that the system tends to quasistationary state with maximum reflectivity (R → 1). If the electron plasma wave damping exceeds a certain critical value, a spatially aperiodic solution raises and the Raman backscattering process becomes stable.
Experiments on generation of a high-power ion beam in a plasma-filled diode
Authors: Bystritskii V. M. , Kharlov A. V. , Mesyats G. A. , Mytnikov A. V. , Sinebrjukhov A. A.
Published: March 2009

The experimental results on high-power ion beams (HPIB) generation in a plasma-filled, spherical-focusing diode with self-magnetic insulation that was placed for a load at nanosecond accelerator PARUS of 0.2-TW power and 60-ns pulse duration (in a matched load case) are given. The regimes of plasma-filled diode operation and generation of the ion beam were investigated. For optimal time delay between the plasma gun's pulse and accelerator firing, the stable operation in the plasma opening switch mode with a power enhancement factor of 2.3 and efficiency of ion beam generation of 20–25% was obtained. The maximal value of the ion current density reached in the focal plane was 15 kA/cm2.
Physics of fusion pumped lasers
Authors: Pappas D. S.
Published: March 2009

A novel concept is described which utilizes a liquified rare gas as both an energy converter and high-density lasing media. The concept allows the advantage of the large mean-free path of high energy fusion neutrons together with a highly-efficient mechanism for volumetric production of 1 MeV electrons which causes ionization and excitation throughout the medium. This scheme coupled together with the high efficiency for light production of liquid excimers may provide the possibilities for a new dimension in high power lasers.
Ion heating as a limiting process in CO2 laser induced Brillouin scattering
Authors: Giles R. , Offenberger A. A.
Published: March 2009

Two complementary models invoking ion heating are presented which, together with pump depletion, quantitatively account for the principal observations (reflectivity, spectral shape, saturation) of stimulated Brillouin scattering (SBS) in a CO2 laser/plasma interaction experiment. A simple energy balance model, which incorporates ion heating and includes a consistent calculation of ion wave damping, is applicable for steady state convective growth of the ion waves (long interaction times). A more refined model, which includes a calculation of the trapped ion fraction (along with heating), is applicable for SBS in a transient regime. Strong ion wave damping has been consistently observed in both cases in our high intensity CO2 laser/plasma scattering experiments. A variety of measurements have been made to investigate the basic features of SBS and associated density fluctuations for both long pulse (40 ns) and short pulse (2 ns) CO2 laser irradiation. Measured parameters reported here include plasma density, temperature, density scalelength, SBS reflectivity, and spectral characteristics. Together with previous measurements of density fluctuations (amplitude, wavenumber spectra, spatial and temporal information), the observed behavior confirms that Brillouin scattering is dominated by strong ion trapping, heating and ion wave damping for the laser/plasma parameters prevailing in these experiments.
ELBA (electron beams in accelerators) particle simulation code
Authors: Joyce Glenn , Krall Jonathan , Slinker Steven
Published: March 2009

ELBA is a three-dimensional, particle-in-cell, simulation code that has been developed to study the propagation and transport of relativistic charged particle beams. The code is particularly suited to the simulation of relativistic electron beams propagating through collisionless or slightly collisional plasmas or through external electric or magnetic fields. Particle motion is followed via a coordinate “window” in the laboratory frame that moves at the speed of light. This scheme allows us to model only the immediate vicinity of the beam. Because no information can move in the forward direction in these coordinates, particle and field data can be handled in a simple way that allows for very large scale simulations. A mapping scheme has been implemented that, with corrections to Maxwell's equations, allows the inclusion of bends in the simulation system.
Study of the emissivity of the rear face of a shocked foil with temporal and X-UV spectral resolution in single and colliding foil experiments
Authors: Fabbro R. , Faral B. , Gauthier J. C. , Chenais-Popovics C. , Geindre J. P. , Pepin H.
Published: March 2009

The emissivity of the rear of a shocked foil is spectrally and temporally resolved by coupling a transmission grating (1000 I/mm) and an X-UV streak camera (with a low density Csl photocathode), providing a high temporal resolution over a large spectral range. The shock is generated with two techniques: direct illumination of a single Al foil with a 0.26 μm wavelength laser (ablation pressure ≈ 50 Mbars) or by colliding an Al foil with a laser accelerated CH foil (generated pressures greater than 100–200 Mbars). Different thicknesses of Al are used in single foil experiments, and different initial spacing and impacted foil thicknesses are used in double foil experiments. Double foil experiments indicate that targets can be optimized for high pressure generation, and single foil experiments show that there is a radiative heat wave, around 200 eV, due to the heating of the foil by X rays emitted in the ablated region during the laser pulse. Double foil experiments have been compared with 2-D hydrodynamic Lagrangian simulations and single foil experiments have been compared with 1-D hydrodynamic Lagrangian simulations taking into account radiative heat transfer.
Interaction of integrated beams with thin foils and microballoons
Authors: Strangio C. , Caruso A.
Published: March 2009

The results of the interaction of laser beams integrated by an optical system composed of two arrays of 256 elements each are presented. Optical dark-field shadowgraphy as well as interferograms show significant smoothing effects when compared with experiments performed in the same conditions but without beam integrators.
Hydrodynamic evolution of laser driven diverging shock waves
Authors: Harith M. A. , Palleschi V. , Salvetti A. , Singh D. P. , Tropiano G. , Vaselli M.
Published: March 2009

Spherically symmetric shock waves have been produced via Nd3+laser induced break-down in helium, nitrogen and air at pressures ranging from 760 Torr to 2300 Torr. The measurements are performed at different absorbed laser energies (E0= 0.05 J to 2 J) at the center of the experimental spherical glass cell where the breakdown of the gas takes place. The temporal evolution of the shock wave followed by a double-pulse, doublewavelength holographic technique is described hydrodynamically well by the point strong explosion theory. The ambient gas counterpressure plays a negligible role in determining the shock wave motion even at low laser energy absorption (E0≤, 0.5 J), whereas it has an appreciable effect on the gas density jump at the shock wave itself. The experimental data on temporal evolution of the density jump of the gas and the corresponding theoretical profiles obtained adopting a non-self-similar solution at the same laser absorbed energy are found to be in good mutual agreement.
Calculations of radiation opacity for high Z elements
Authors: Błeński Tomasz , Ligou Jacques
Published: March 2009

We present some results of our opacity calculations for lead and gold at temperatures and densities relevant to ICF conditions. We use an average atom model based on the temperature dependent Thomas-Fermi shell approach. The absorption bands (broadening of lines) are accounted for with a simple T.F. fluctuation formula. The independent particle bound-bound, bound-free, and free-free photon cross-sections are taken without further approximations.
Enhanced vacuum laser-impulse coupling by volume absorption at infrared wavelengths
Authors: Phipps C. R. , Harrison R. F. , Shimada T. , York G. W. , Turner T. P. , Corlis X. F. , Steele H. S. , Haynes L. C. , King T. R.
Published: March 2009

We report measurements of vacuum laser impulse coupling coefficients as large as 90 dyne/W, obtained with single μs-duration CO2 laser pulses incident on a volume-absorbing, cellulose-nitrate-based plastic. This result is the largest coupling coefficient yet reported at any wavelength for a simple, planar target in vacuum, and partly results from expenditure of internal chemical energy in this material. Enhanced coupling was also observed in several other target materials that are chemically passive, but absorb light in depth at 10-μm and 3-μm wavelengths. We discuss the physical distinctions between this important case and that of simple, planar surface absorbers [such as metals] which were studied in the same experimental series, in light of the predictions of a simple theoretical model. Ablation parameters for use with the model were determined in separate experiments near threshold in air and in vacuum. The transition from volume- to surface-absorption behavior in the infrared is described as being controlled by fluence-limiting and wavelength conversion in the uppermost target layer.
Evaluation of gas lens laser-produced plasmas
Authors: Waltham J. A. , Notcutt M. , Cunningham P. F. , Michaelis M. M.
Published: March 2009

A Q-switched ruby laser, focussed by means of both gas and glass lenses, was used to irradiate massive planar carbon targets. Two different laser configurations were used, giving differing spatial beam qualities. Faraday cups positioned at various angles about the target were used to monitor ion flow properties of the resulting laser-produced plasmas. These flow properties were used to compare the laser-plasma producing characteristics of the lenses.
Hydrodynamical evolution and radiation confinement of rough surfaces exposed to thermal radiation in indirectly driven ICF targets
Authors: Caruso A. , Pais V.A.
Published: March 2009

2–D hydrodynamical simulations have been used to study the effects of surface finish on the evolution of planar analogs for the components of indirect-driven inertial confinement fusion (ICF) targets (cavity surfaces and capsules) when exposed to the same uniform, assigned, temporally profiled thermal radiation bath. For the time-dependence of the radiation temperature was assumed to be the one resulting from 1-D simulations of a highgain indirectly driven target. The perturbation wavelength has been taken in the interval 2.5–40 μm, as suggested by the typical lengths appearing in the 1-D hydrodynamic evolution. The results for the evolution of 300 Å initial perturbation amplitude will be presented, because the results obtained for other amplitudes (somewhat smaller or larger) are qualitatively the same. The results do not seem very encouraging for the indirect-drive approach, at least in the form presented in the current literature, as the simulations show the onset of fast-growing hydrodynamical unstable modes, both on the capsule surface and on the cavity surface, producing dramatic effects on symmetry and radiation confinement.With regard to the (gold) cavity surface, for the shortest wavelengths the evolution enters the nonlinear phase in the early stages of the interaction, producing (due to surface area increase and thermal field rippling) a decrease by a factor of 3–4 of a conventionally defined radiation confinement parameter. For these same wavelengths stabilization mechanisms due to ablative polishing, finite gradient, or overpressure tend to be ineffectual. Similar results are obtained for the capsule surface at short wavelengths. In this case, in addition to an enhancement (up to factor of 10) of the ablation rate (and energy absorption) due to surface area increase and ripple effects, the flow behind the first shock wave turns out to be turbulent, with “eddies” having typical products of angular velocity x time of the order of unity or greater. The situation is not encouraging even for longer wavelengths; in this case, in addition to the generation of eddies in the fuel, the flow exhibits a transverse matter pile-up with consequent generation of holes in the thermal shield and premature fuel preheating.
Rayleigh-Taylor instability in the incompressible shell with allowance for ablative stabilization
Authors: Lebo I.G. , Rozanov V.B.
Published: March 2009

A physical-mathematical model for the development of the boundary instability of a spherical incompressible-liquid shell, with due regard for the ablation effect, is considered.
Temporal evolution of the inversion condition for the X-ray Balmer-α transition in ions of short-laser-pulse produced recombining plasmas
Authors: John R.W. , Brunner W.
Published: March 2009

When generating population density inversion and X-ray gain in the ions of a recombining plasma produced by short laser pulses it is essential to consider the energy level occupation as explicitly time-dependent. In the framework of a four-level model with time-dependent pumping terms, the inversion condition for the Balmer-α transition in H-like ions is derived in closed form, dependent, apart from specified initial conditions, on the atomic number Z, with the free-electron density Ne, the electron temperature Te, the Lyman-α escape probability E21, and the time t. In particular, at a short time after the initial time chosen near the time of the onset of recombination the Balmer-α inversion requires that Ne must be larger than some critical value depending on Te and Z.
One-dimensional computation of discharge-pumped excimer lasers under repetitive operations
Authors: Kasuya K. , Horioka K. , Hikida N. , Watanabe M. , Kawakita Y. , Kato S. , Okuda H.
Published: March 2009

Zero-dimensional numerical computation of electrical discharge-pumped excimer lasers is extended to a one-dimensional model that is used to study the effects of the density perturbations of the background neutral gas and the nonuniform predischarge (which means preionization in this paper) electron density on the transition of the uniform discharge to the nonuniform prestage state leading to the onset of arc formation (which is not included in this particular model). It was found that a local density depression of 1% or an enhancement of the local electric field of 1% can increase the local energy input by several hundred percent. The initial electron density perturbations, on the other hand, are found to modify the energy input by the same order of magnitude as the initial perturbations.
Volume ignition targets for heavy-ion inertial fusion
Authors: Martínez-Val J.M. , Eliezer S. , Piera M.
Published: March 2009

Inertial confinement fusion (ICF) targets can be imploded by heavy-ion beams (HIBs) in order to obtain a highly compressed fuel microsphere. The hydrodynamic efficiency of the compression can be optimized by tuning the ablation process in order to produce the total evaporation of the pusher material by the end of the implosion. Such pusherless compressions produce very highly compressed targets for relatively short confinement times. However, these times are long enough for a fusion burst to take place, and burnup fractions of 30% and higher can be obtained if the volume ignition requirements are met. Numerical simulations demonstrate that targets of 1-mg DT driven by a few MJ can yield energy gains of over 70. Although direct drive is used in these simulations, the main conclusions about volume ignition are also applicable to indirect drive.
Self-similar solutions of screw-pinch plasma implosion
Authors: Choe W. H. , Venkatesan R. C.
Published: March 2009

A self-similar analysis of supersonic compression of a “screw-pinch” plasma is carried out that generalizes earlier analyses of pure θ-pinch and Z-pinch implosions. Solutions are found for various implosion modes. It is shown that the screw-pinch plasma implosion differs qualitatively from θ-pinch and Z-pinch implosions.
Near-threshold ablation of target material irradiated with pulsed ion beams
Authors: Kitamura A. , Asahina T. , Furuyama Y. , Nakajima T.
Published: March 2009

The process of target ablation induced by pulsed ion beams is investigated. The beam power density of 0.01–0.1 GW/cm2 is around the sublimation energy of the target material. The thickness of the layer to be removed from the target is estimated from the temperature distribution calculated numerically with a diffusion equation. The emitted particles are collected with C collectors, which are later subjected to RBS and SEM/EPMA analyses. It is found that ablated particles forming a film on the collector amount to only 10% of the target atoms within the maximum range of the ions, while a significant amount of the ablated material is observed as macroscopic particles with equivalent diameters up to several tens of micrometers. TOF measurements of the ablation plume together with RBS measurements of thin-film targets after irradiation suggest that the formation of the film is predominated by vaporization from the surface of the ablated mass, which is recondensed on the collector before completing the vaporization.
Beam–plasma interaction experiments with heavy-ion beams
Authors: Dietrich K.-G. , Mahrt-Olt K. , Jacoby J. , Boggasch E. , Winkler M. , Heimrich B. , Hoffmann D. H. H.
Published: March 2009

The progress of the experimental research program at GSI for studying beam-plasma interaction phenomena is reported. Heavy-ion beams from the new accelerator facility SIS/ESR at GSI-Darmstadt are now available for experiments, and will soon deliver ≥ 109 particles per pulse in 100 ns. Focused on a small sample of matter, the beams will be able to produce a high-density plasma and to permit investigation of interaction processes of heavy ions with hot ionized matter.

For the intense beam from the new heavy-ion synchrotron (SIS), a fine-focus system has been designed to produce a high specific deposition power beam for target experiments with a beam-spot radius of 100 μm. We further discuss improvements of this lens system by nonconventional focusing devices such as plasma lenses.

Intense-beam experiments at the RFQ Maxilac accelerator at GSI have already produced the first heavy-ion-induced plasma with a temperature of 0.75 eV. New diagnostic techniques for investigating ion-beam-induced plasmas are presented. The low-intensity beam from the GSI UNILAC has been used to measure energy deposition profiles of heavy ions in hot ionized matter. In this experiment an enhancement of the stopping power for heavy ions was observed. The current experimental research program tests basic plasma theory and addresses key issues of inertial confinement fusion driven by intense heavy-ion beams.
Pulsed-power-generated plasma of high reproducibility
Authors: Kunze H. , Noll R. , Haas C. R. , Elfers M. , Hertzberg J. , Herziger G.
Published: March 2009

Plasmas of high reproducibility that are suitable for beam-plasma experiments are generated by a pulsed-power z-pinch discharge. The z-pinch device is designed as a plasma target for the investigation of ion beam-plasma interactions. The dynamic plasma state is characterized by the electron density, the electron temperature, and the magnetic field distribution, which are observed using time-resolved diagnostics. For z-pinch discharges in hydrogen, average electron densities of up to (2.6 ± 0.1) × 1018 electrons/cm3 were measured interferometrically. Electron temperatures in the range 2–7 eV are determined by time-resolved spectroscopy. The reproducibility of the electron density of the z-pinch discharge in terms of shot-to-shot fluctuations is estimated to be better than 3%. This is a favorable condition for performing beam-plasma experiments.
Non-LTE radiation transport in moderate-density plasmas
Authors: MacFarlane J. J. , Wang P. , Moses G. A.
Published: March 2009

We present results from non-LTE line radiation transport calculations for high-temperature, optically thick plasmas with densities ∼1016-1020 ions/cm3. The calculations are based on an escape probability radiative transport model in which the atomic rate equations are solved self-consistently with the radiation field. Steady-state ionization and excitation populations are determined by detailed balancing of atomic processes, with photoexcitation effects included. Atomic data are computed using a combination of Hartree-Fock, semiclassical impact-parameter, and distorted-wave calculations. Our results indicate that the reabsorption of line radiation significantly alters the level populations and reduces the radiation flux from several types of fusion-related plasmas. We also compare our results with those obtained from multigroup radiation diffusion calculations, and discuss the ramifications of our results for ICF target chamber plasmas.
Atomic physics for inertial fusion using average correlated hydrogenic atom model
Authors: Maynard G. , Deutsch C. , Fromy P. , Katsonis K.
Published: March 2009

The influence of discrepancies between analytical expressions for charge changing cross section on the ionization state of swift heavy ions interacting with hot and dense plasmas is analyzed within the framework of our new average correlated hydrogenic atom model. Making use of our Classical Trajectory Monte-Carlo results, we show that the partial charge transfer cross section into the projectile atomic levels has the same importance as the total charge transfer cross section.
Charge-exchange and energy-loss statistics of swift penetrating ions
Authors: Sigmund P. , Närmann A.
Published: March 2009

A general and powerful formalism has been developed for computation of energy-loss spectra of penetrating charged particles in the presence of charge exchange. Options on the input side are the cross sections for electron capture and loss, transition rates for radiative and nonradiative spontaneous processes and their associated energy losses or gains, and finally, cross sections for all processes that contribute to particle stopping but are not associated with charge exchange. The formalism generates an n × n transfer matrix, where n is the number of states needed for an adequate description of the projectile under consideration. This matrix delivers the joint distribution of energy loss and exit charge state for a given incident charge state and energy.

The formalism can be used in principle as an alternative for Monte Carlo simulation, but until now we have concentrated on direct evaluation of key experimental parameters related to the energy-loss spectrum integrated over all exit charge states, in particular, mean energy loss, straggling, and skewness. Generally, valid analytic expressions have been found for these quantities, each of which can be separated into a stationary term representing chargestate equilibrium and a transient depending on the incident charge state. A brief survey is given of current analytic and numerical efforts addressing other experimental parameters.
Cryogenic targets for modern ICF experiment
Authors: Aleksandrova I.V. , Koresheva E.R. , Osipov I.E. , Panina L.V.
Published: March 2009

The physics of the formation of cryogenic fuel layers with various internal structures has been studied in regard to the development of promising layering techniques for modern inertial confinement fusion (ICF) experiments. The investigations have been made with inertial confinement fusion target (ICF targets) and in a target modeling system (TMS) with the nonisochoric process of cryogenic layer formation. The results indicate that the solidlayer structure in TMS differs essentially from that obtained in ICF targets. The thermal history of a fuel layer at separation into the condensed and vapor phases is found to depend upon whether the initial gas density is more, less, or equal to the critical value for a given fuel material. The issue on the fuel-layer fabrication in the form of a long-living quasiamorphous
layer is considered. A new low-temperature method to homogenize a polycrystalline cryogenic layer has been proposed and examined. The operational temperature was 4.2 K. The time to achieve the complete homogeneity of solid hydrogen was 150 s. No limitation, with respect to the thickness of a cryogenic layer, was found. The critical target is suggested as a new type of an ICF target.
Successive uptapering and stationary self-trapped propagation of a laser beam in a saturating nonlinear medium
Authors: Medhekar Sarang , Rajkamal  , Konar S.
Published: March 2009

A steady-state analysis of Gaussian laser beam in a nonlinear medium has been presented. It is shown that an oscillatory self-guided beam (whose width is oscillating with the propagation distance) in a saturable nonlinear medium can be uptapered by material gain. Moreover, the present investigation suggests that under certain conditions it is possible to obtain a stationary self-guided beam (planar wavefront) in a nonabsorbing medium from an initially oscillatory (nonplanar wavefront) beam in a nonabsorbing medium by uptapering it in a gain medium.
X-ray backlighting imaging of mixed imploded targets
Authors: Yaakobi B. , Shvarts D. , Epstein R. , Su Q.
Published: March 2009

The X-ray image of a compressed shell (enhanced by high-Z doping) was used in recent experiments to diagnose the effect of shell-fuel mixing. The emission ring (due to the limb effect) moves toward smaller radii due to mixing. We show here that using backlighting imaging can greatly enhance future imaging experiments. In addition to the emission ring, a backlighting absorption ring can appear around it. The absorption ring is virtually unaffected by mixing. Thus, the relative position of the two rings constitutes a mixing signature. In other words, the absorption ring delineates the colder part of the shell and is a true signature of the compression, whereas the emission ring reflects the shell material motion due to mixing.
Shock pressure and free surface velocity measurements in confined interaction — Response of new VF2/VF3 piezoelectric gauges
Authors: Boustie M. , Couturier S. , Romain J.P. , Zagouri D. , Simonnet H.
Published: March 2009

To determine the peak pressure induced versus the incident intensity of a neodymium (Nd) glass pulsed laser, with a duration of 25 ns in glass confined geometry, two methods have been comparatively used. Free surface velocity measurements have been performed using an electromagnetic gauge. The results are compared with pressure measurements realized at the back of irradiated aluminum targets with the use of polyvinylidene fluoride (PVDF) gauges. Both diagnostics provide consistent results. The measurements of peak pressure as a function of laser irradiance are used to determine the calibration curve (current density versus loading pressure) for new VF2/VF3 copolymer shock gauges used in this lasermatter interaction configuration. These experimental set-up deliver time resolved measurements that are interpreted by the shock-propagation phenomena.
Some applications of laser-induced shocks on the dynamic behavior of materials
Authors: Boustie M. , Rességuier T. De , Hallouin M. , Migault A. , Romain J.P. , Zagouri D.
Published: March 2009

High-power pulsed lasers are used widely nowadays as shock generators. They settle as a complementary technique to the conventional shock generators by the high peak pressure and short duration shocks they deliver. They are used to investigate the feasibility of new industrial processes and to get information on the behavior of matter in specific conditions of extremely high strain rate. In this paper, some studies about typical applications of laser shocks are presented: surface densification of porous materials, spallation in ductile and brittle materials, α-ε phase change in iron, and an estimate of the relaxation time for this transition. Laser shock experiments provide additional data on the dynamic behavior of materials at the nanosecond time scale.
Laser ion source of Synchrophasotron and Nuclotron in Dubna
Authors: Monchinsky V.A. , Kalagin I.V. , Govorov A.I.
Published: March 2009

Since 1976, the laser ion source (LIS) has been operated at the Laboratory of High Energies. At present, the LIS is used to perform experiments on relativistic beams of Li, B, C, N, O, F, Mg, and Si nuclei
Progress with gas lenses
Authors: Michaelis M.M. , Kuppen M. , Prause A. , Forbes A. , Viranna N. , Lisi N.
Published: March 2009

Three gas lenses appear promising for fusion and other applications. We review progress of the understanding and scaling of two of these lenses and discuss their potential for industry, advanced research, and fusion.