bluuebunny/crossref_metadata_2025 huggingface dataset:
Plasma diagnostics using Kα satellite emission spectroscopy in light ion beam fusion experiments
Authors: MacFarlane J.J. , Wang P. , Bailey J.E. , Mehlhorn T.A. , Dukart R.J.
Published: March 2009

Kα satellite spectroscopy can be a valuable technique for diagnosing conditions in high energy density plasmas. Kα emission lines are produced in intense light ion beam plasma interaction experiments as 2p electrons fill partially open Is shells created by the ion beam. In this paper, we present results from collisional-radiative equilibrium (CRE) calculations which show how Kα emission spectroscopy can be used to determine target plasma conditions in intense lithium beam experiments on Particle Beam Fusion Accelerator-II (PBFAII) at Sandia National Laboratories. In these experiments, 8–10 MeV lithium beams with intensities of 1–2 TW/cm2 irradiate planar multilayer targets containing a thin Al tracer. Kα emission spectra are measured using an X-ray crystal spectrometer with a resolution of λ/∆λ = 1200. The spectra are analyzed using a CRE model in which multilevel (NL ∼ 103) statistical equilibrium equations are solved self-consistently with the radiation field and beam properties to determine atomic level populations. Atomic level-dependent fluorescence yields and ion-impact ionization cross sections are used in computing the emission spectra. We present results showing the sensitivity of the Kα emission spectrum to temperature and density of the Al tracer. We also discuss the dependence of measured spectra on the X-ray crystal spectral resolution, and how additional diagnostic information could be obtained using multiple tracers of similar atomic number.
Analytic optimization of ion-driven hohlraums
Authors: Slutz S.A.
Published: March 2009

An analytic model of ion beam driven hohlraums is presented which is used to determine the optimal hohlraum design parameters. It is shown that the radiation intensity within the hohlraum can exceed the average ion intensity driving the hohlraum. This “greenhouse effect” significantly lowers ion beam intensity requirements for driving a fusion microexplosion.
The interaction of large fast carbon clusters with plasma
Authors: Nardi E. , Zinamon Z.
Published: March 2009

The energy loss and disintegration dynamics of large carbon clusters (C60 molecules) in hot plasmas is calculated. The calculation self-consistently includes the cluster disintegration, the evolution of the charge of the fragment ions, the screened Coulomb forces among them, and the effects of interference between neighboring ions on the energy loss. A range of projectile energies and plasma parameters is considered. A large enhancement factor in the energy deposition due to the interference is found at the early stage of the interaction.
Lasers with combined nuclear pumping
Authors: Prelas Mark A.
Published: March 2009

The use of nuclear radiation to excite lasers is examined from the perspective of nuclear flashlamps. Nuclear driven flashlamps can also be used as photon sources for photochemical and photovoltaic events. This can lead to the large scale production of chemicals and electricity.
Electron shock waves moving into an ionized medium
Authors: Hemmati Mostafa
Published: March 2009

The propagation of electron driven shock waves has been investigated by employing a one-dimensional, three-component fluid model. In the fluid model, the basic set of equations consists of equations of conservation of mass, momentum, and energy, plus Poisson's equation. The wave is assumed to be a shock front followed by a dynamical transition region. Following Fowler's (1976) categorization of breakdown waves, the waves propagating into a preionized medium will be referred to as Class II Waves. To describe the breakdown waves, Shelton and Fowler (1968) used the terms proforce and antiforce waves, depending on whether the applied electric field force on electrons was with or against the direction of wave propagation. Breakdown waves, i.e., return strokes of lightning flashes, therefore, will be referred to as Antiforce Class II waves. The shock boundary conditions and Poisson's equation for Antiforce Class II waves are different from those for Antiforce Waves. The use of a newly derived set of boundary conditions and Poisson's equation for Antiforce Class II waves allows for a successful integration of the set of fluid equations through the dynamical transition region. The wave structure, i.e., electric field, electron concentration, electron temperature, and electron velocity, are very sensitive to the ion concentration ahead of the wave.
Time dependence of the inversion condition and optimized X-ray emission in recombining laser-produced plasmas
Authors: Brunner W. , John R.W.
Published: March 2009

The recombination X-ray laser scheme is considered in the case of recombining plasmas produced by laser pulses which are short to such a degree that the condition for inversion in X-ray transitions of the ions is essentially time-dependent. Using an analytic four-level model, applicable for H-like and Li-like ions, we calculate the inversion conditions for the 4→3, 3→2, and 2→l transitions in H-like ions as functions of time. As we have already shown, a drastic change occurs, especially for the 3→2 transition. To achieve inversion, for short times the free-electron density as a function of the temperature Te, Neinv(Te), must be greater than a critical density Nesh (Te), Neinv(Te) > Nesh(Te), whereas for longer times in the quasi-steady state, Neinv(Te) must be smaller than a critical density Neqv(Te), Neinv(Te) < Nequ(Te). We also consider the evolution of the inversion condition in the intermediate time domain. The time duration of the existence of the short-time 3→2 inversion condition–in the time interval from the initial state with unoccupied lower levels to the quasi-steady state—is in the main determined by t α 1/A21; for example, one has t ≈ 730 fs for Na.

In a plasma produced in particular by optical-field ionization, during the initial cascade populating the excited levels, an inversion may be possible in the 2→1 resonance line transition in the transient regime. The inversion in this transition is of interest especially because of the arising possibility to achieve X-ray gain at shorter wavelengths. In the transient case, an inversion occurs for a small time depending on the temperature Te and the density N.

In addition, we discuss generally the time behavior of the population densities (especially of N3) and show that an optimal population density occurs, on the one hand, for very short times (fs region, depending on Z). On the other hand, however, the optimal (ion-)density-temperature relation is determined via a time of the optimal population density required with regard to the experimental conditions.
Three-dimensional simulations and analysis of the nonlinear stage of the Rayleigh-Taylor instability
Authors: Hecht J. , Ofer D. , Alon U. , Shvarts D. , Orszag S.A. , Shvarts D. , McCrory R.L.
Published: March 2009

The nonlinear stage in the growth of the Rayleigh-Taylor instability in three dimensions (3D) is studied using a 3D multimaterial hydrodynamic code. The growth of a single classical 3D square and rectangular modes is compared to the growth in planar and cylindrical geometries and found to be close to the corresponding cylindrical mode, which is in agreement with a new Layzer-type model for 3D bubble growth. The Atwood number effect on the final shape of the instability is demonstrated. Calculations in spherical geometry of the late deceleration stage of a typical ICF pellet have been performed. The different late time shapes obtained are shown to be a result of the initial conditions and the high Atwood number. Finally, preliminary results of calculations of two-mode coupling and random perturbations growth in 3D are presented.
How double layers accelerate charged particles
Authors: Eliezer S. , Kolka E. , Szichman H. , Hora H. , Green F.
Published: March 2009

After the theory of dynamic double layers in laser-produced plasmas arrived at several significant results in agreement with measurement, including particle acceleration, a clarification was given to the paper by Bryant et al. (1992) negating such acceleration. The discrepancy seems to be in the definition of static double layers in contradiction with dynamic double layers that are created in laser-induced plasma. We present here new results on the acceleration of electrons in a laser-irradiated plasma by double layer mechanisms. A simple analytical example is given.
Time-resolved X-ray spectroscopy of optical-field-ionized plasmas
Authors: Borgström S. , Starczewski T. , Svanberg S. , Wahlström C.-G. , Fill E. , Steingruber J.
Published: March 2009

The time-dependent soft X-ray emission of helium and nitrogen plasmas generated by optical-field ionization is reported. The experiments were carried out by focusing pulses of the high-power Ti:sapphire laser of the Lund Institute of Technology (λ = 796 nm, pulse duration 150 fs, pulse energy 150 mJ) to a 50-μm diameter spot close to a nozzle, using He and N2 as target gases. The emission on He+, N4+, and N3+ resonance lines was recorded by means of a flat-field grating spectrometer coupled to an X-ray streak camera. A pronounced difference in the temporal shape of the emission of the Lyman-α line of hydrogen-like helium and of the 2p−3d resonance lines of lithium-like and beryllium-like nitrogen was observed. The helium line exhibited an initial spike followed by a slow revival of the emission, whereas the nitrogen lines showed a slow decay after a fast initial rise. These observations are explained with the help of simulations.
A study of random phased laser spots
Authors: Ceccotti T. , Bastiani S. , Bastiani S. , Giulietti A. , Biancalana V. , Chessa P. , Giulietti D. , Danson C.
Published: March 2009

Far-field images produced using different random phase plates on a pulsed laser beam focused with variousf/numbers were recorded by a charge-coupled device (CCD) camera and then analyzed. Envelope spot sizes agree with diffraction theory while mean sizes of the pattern structures have been found to be larger than the diffraction limit. The probability density distribution of intensity in the focal plane is not the expected exponential. A central symmetry of the pattern has also been seen after suitably aperturing the beam. Some consequences for the use of powerful RPP-treated laser beams in laser-plasma interactions are discussed.
ORION: Clearing near-Earth space debris using a 20-kW, 530-nm, Earth-based, repetitively pulsed laser
Authors: Phipps C.R. , Albrecht G. , Friedman H. , Gavel D. , George E.V. , Murray J. , Ho C. , Priedhorsky W. , Michaelis M.M. , Reilly J.P.
Published: March 2009

When a large piece of space debris forced a change of flight plan for arecent U.S. Space Shuttle mission, the concept that we are trashing space as well as Earth finally attained broad public awareness. Almost a million pieces of debris have been generated by 35 years of spaceflight, and now threaten long-term space missions. The most economical solution to this problem is to cause space debris items to reenter and burn up in the atmosphere. For safe handling of large objects, it is desired to do this on a precomputed trajectory. Due to the number, speed, and spacial distribution of the objects, a highly agile source of mechanical impulse, as well as a quantum leap in detection capability are required. For reasons we will discuss, we believe that the best means of accomplishing these goals is the system we propose here, which uses a ground-based laser system and active beam phase error correcting beam director to provide the impulse, together with a new, computer-intensive, very high-resolution optical detection system to locate objects as small as 1 cm at 500-km range. Illumination of the objects by the repetitively pulsed laser produces a laser-ablation jet that gives the impulse to de-orbit the object. A laser of just 20-kW average power and state-of-the-art detection capabilities could clear near-Earth space below 100-km altitude of all space debris larger than 1 cm but less massive than 100 kg in about 4 years, and all debris in the threatening 1–20-cm size range in about 2 years of continuous operation. The ORION laser would be sited near the Equator at a high altitude location (e.g., the Uhuru site on Kilimanjaro), minimizing turbulence correction, conversion by stimulated Raman scattering, and absorption of the 530-nm wavelength laser beam. ORION is a special case of Laser Impulse Space Propulsion (LISP), studied extensively by Los Alamos and others over the past 4 years.
Asymptotic measurements of free surface instabilities in laser-induced shock waves
Authors: Werdiger M. , Arad B. , Henis Z. , Horowitz Y. , Moshe E. , Maman S. , Ludmirsky A. , Eliezer S.
Published: March 2009

An experimental technique based on optical scattering to detect melting in release of strongly shocked materials is presented. This method is used to study the asymptotic behavior of the free surface of shock-loaded materials. After reflection of a shock wave from a metallic sample free surface, occurrence of a solid to liquid transition will induce a dynamic behavior such as mass ejection and development of instabilities. A study of the mass ejection due to laser-induced shock waves in aluminium, copper, and tin targets is presented. Shock waves of order of hundreds of kilobars to more than one megabar are produced by a Nd:YAG laser system with a wavelength of 1.06 μm, pulse width of 7 ns FWHM focused to spot of 200 μm. The velocities, size, and topological structure of the ejected particles are measured. The radii of the ejecta are in the range 0.5–7 μm.
Shock-wave physics experiments with high-power proton beams
Authors: Baumung K. , Bluhm H.J. , Goel B. , Hoppé P. , Karow H.U. , Rusch D. , Fortov V.E. , Kanel G.I. , Razorenov S.V. , Utkin A.V. , Vorobjev O.Yu.
Published: March 2009

At the Karlsruhe Light Ion Facility (KALIF) high-power proton beams with power densities up to ∼ 1 TW/cm2 are generated depositing up to 40 kJ of ion energy in a focal spot of 6∼8-mm diameter. With peak proton energies of ∼ 1.7 MeV, specific power densities of up to 200 TW/g and energy densities of several MJ/g can be realized. This is a regime in which experiments providing information on the equation of state (EOS), dynamics of the beam interaction with condensed targets, and properties of solids and plasma at high-energy densities are of particular interest. In the present paper we report on shock-wave experiments using solid targets and high-resolution laser-Doppler velocimetry. The empirical data provided are used to verify code simulations and the used EOS-data in these calculations, to investigate the beam-target interaction, and to perform series of shock-wave measurements of properties of different materials. The ∼40-ns FWHM proton beam can be used to generate, by material ablation or impact of ablatively accelerated flyers, intense shock waves, permitting the investigation of shock compressibility, dynamic failure of solids under nanosecond load duration, phase transitions, and viscosity at strain rates up to ∼108 s-1. Recently an improved line-imaging velocimeter was set up to measure the spatial velocity variation with a maximum resolution of < 10 μm, opening the possibility to address new issues like growth of instabilities or local dynamics of the spall fracture.
Optical smoothing for shock-wave generation: Application to the measurement of equations of state
Authors: Batani Dimitri , Bossi Simone , Benuzzi Alessandra , Koenig Michel , Faral Bernard , Boudenne Jean Michel , Grandjouan Nicolas , Atzeni Stefano , Temporal Mauro
Published: March 2009

Experimental results are presented on shock-wave generation in solid samples, irradiated directly by optically smoothed laser beams. Random phase plates and phased zone plates have been successfully used. In particular, the last technique allowed the production of uniform shock fronts that have been used for equation of state experiments at pressures above 10 Mbar. Pressures higher than 35 Mbar were achieved in gold, by using laser pulses with energy E ≈ 100 J, and structured, two-step, two-material targets.
XUV emission from an elongated plasma column produced using a high-power laser with a gas puff target
Authors: Fiedorowicz Henryk , Bartnik Andrzej , Szczurek Mirosław , Fill Ernst , Li Yuelin , Pretzler Georg
Published: March 2009

We report the first studies on the formation of an elongated plasma column suitable for X-ray laser experiments, using a gas puff target irradiated with a high-power laser. The gas puff targets, produced by pulsed injection of a small amount of gas from a high-pressure solenoid valve through a nozzle in the form of a slit, have been characterized by optical interferometry and X-ray backlighting. The formation of a hot plasma column up to 30-mm-long is demonstrated. The spatial uniformity of the column was monitored by means of an X-ray pinhole camera. XUV spectra measurements for SF6 gas puff targets show predominant 3–2 line of hydrogenic fluorine (λ = 8.1 nm), however, only linear increasing of its intensity with the target length was observed.
Fiber Z-pinch experiments and calculations in the finite Larmor radius regime
Authors: Haines M.G. , Dangor A.E. , Coppins M. , Choi P. , Mitchell I.H. , Chittenden J.P. , Bayley J.M. , Rossel R.F. Aliaga , Arber T.D. , Beg F. , Bell A.R. , Scheffel J. , Decker G. , Russell P. , Worley J.F.
Published: March 2009

The dense Z-pinch project at Imperial College is aimed at achieving radiative collapse to high density in a hydrogen plasma, and also to study plasmas close to controlled fusion conditions. To this end, the MAGPIE generator (2.4 MV, 1.25, and 200 ns) has been built and tested, and is now giving preliminary experimental data at 60% of full voltage for carbon and CD2 fibers. These discharges are characterized by an initial radial expansion followed by the occurrence of m = 0 structures with transient X-ray emission from bright spots. Late in the discharge a disruption can occur, accompanied by hard X-ray emission from the anode due to an energetic electron beam and, in the case of CD2 fibers, a neutron burst. Concomitant theoretical studies have solved the linear stability problem for a Z-pinch with large ion Larmor radii, showing that a reduction in growth rate of m = 0 and m = 1 modes to about 20% of the magnetohydrodynamic (MHD) value can occur for a parabolic density profile when the Larmor radius is optimally 20% of the pinch radius. Two dimensional MHD simulations of Z-pinches in two extremes of focussed short-pulse laserplasma interactions and of galactic jets reveal a nonlinear stabilizing effect in the presence of sheared flow. One-dimensional simulations show that at low line density the lower hybrid drift instability can lead to coronal radial expansion of a Z-pinch plasma.
Corpuscular diagnostics and processing methods applied in investigations of laser-produced plasma as a source of highly ionized ions
Authors: Woryna E. , Parys P. , Wołowski J. , Mróz† W.
Published: March 2009

This paper presents a set of complementary corpuscular diagnostics applied in experiments for investigation of laser-produced plasma as a source of ions. The measuring possibilities and methods for processing experimental data of a cylindrical electrostatic ion energy analyzer, a Thomson parabola ion analyzer, various types of electrostatic probes, a detector of neutral atom fluxes, as well as methods for visualization of ion emission areas are discussed. Special attention was focused on the ion-induced secondary electron emission problem and its influence on the accuracy of the measurements.
Ion production by lasers using high–power densities in a near infrared region
Authors: Rohlena K. , Králiková B. , Krása J. , Láska L. , Mašek K. , Pfeifer M. , Skála J. , Farny J. , Parys P. , Wołowski J. , Woryna E. , Mróz W. , Roudskoy I. , Shamaev O. , Sharkov B. , Shumshurov A. , Bryunetkin B.A. , Haseroth H. , Collier J. , Kuttenbeger A. , Langbein K. , Kugler H.
Published: March 2009

Results are presented of experiments on ion production from Ta targets using a short pulse (350–600 ps in focus) illumination with focal power densities exceeding 1014 Wcm-2 at the wavelength of an iodine photodissociation laser (1.315 μm) and its harmonics. Strong evidence of the existence of tantalum ions with the charge state +45 near the target surface was obtained by X-ray spectroscopy methods. The particle diagnostics point to the existence of frozen high charge states (<53+) of Ta ions in the far expansion zone at about 2 m from the target. The measured charge state-ion energy distribution indicates the highest energy (>4 MeV) for the highest observed charge states. A tentative theoretical explanation of the observed anomalous charge state freezing phenomenon in the expanding plasma produced by a subnanosecond laser pulse is given.
Acceleration of Ta10+ ions produced by laser ion source in RFQ MAXILAC
Authors: Dubenkov V. , Sharkov B. , Golubev A. , Shumshurov A. , Shamaev O. , Roudskoy I. , Streltsov A. , Satov Y. , Makarov K. , Smakovsky Y. , Hoffmann D. , Laux W. , Müller R. W. , Spädtke P. , Stöckl C. , Wolf B. , Jacoby J.
Published: March 2009

Demonstration of matching a laser ion source to the GSI RFQ-Maxilac linear accelerator and the acceleration of a 1.8-mA current beam of Ta10+ ions up to 45 keV/u energy is presented. A 10J/μs CO2 laser has been used to produce a hot plasma plume, emitting highly charged tantulum ions. The correct geometry and potential distribution of the matching section has been designed in accordance with the results of computer simulations by using the AXCEL code. Measurements of the charge state distribution of the accelerated beam indicate that it contains about 70% Ta10+ and 30% Ta11+ ions.
Physical mechanisms leading to high currents of highly charged ions in laser-driven ion sources
Authors: Haseroth Helmut , Hora Heinrich
Published: March 2009

Heavy ion sources for the big accelerators, for example, the LHC, require considerably more ions per pulse during a short time than the best developed classical ion source, the electron cyclotron resonance (ECR) provides; thus an alternative ion source is needed. This can be expected from laser-produced plasmas, where dramatically new types of ion generation have been observed. Experiments with rather modest lasers have confirmed operation with one million pulses of 1 Hz, and 1011C4+ions per pulse reached 2 GeV/u in the Dubna synchrotron. We review here the complexities of laser-plasma interactions to underline the unique and extraordinary possibilities that the laser ion source offers. The complexities are elaborated with respect to keV and MeV ion generation, nonlinear (ponderomotive) forces, self-focusing, resonances and “hot” electrons, parametric instabilities, double-layer effects, and the few ps stochastic pulsation (stuttering). Recent experiments with the laser ion source have been analyzed to distinguish between the ps and ns interaction, and it was discovered that one mechanism of highly charged ion generation is the electron impact ionization (EII) mechanism, similar to the ECR, but with so much higher plasma densities that the required very large number of ions per pulse are produced.
Laser-driven ion source for reduced-cost implantation of metal ions for strong reduction of dry friction and increased durability
Authors: Boody Frederick P. , Höpfl Reinhard , Hora Heinrich , Kelly Jak C.
Published: March 2009

Extensive studies of ion implantation into near surface areas of materials have demonstrated astonishing changes of such properties as surface tension, friction, and durability. The cost of implanted ions is currently rather high due to the limited ion current density of the usual ion sources, especially if ions from sources other than gaseous plasma must be used. The advent of the laser ion source, which offers many orders of magnitude higher current densities than classical ion sources, may change the scenario for a wide range of applications, making ion implantation as crucial a manufacturing technology in the future for other industries as it is today for microelectronics.
Interaction of heavy ion beams with dense plasmas
Authors: Stöckl C. , Boine-Frankenheim O. , Roth M. , Süb W. , Wetzler H. , Seelig W. , Kulish M. , Dornik M. , Laux W. , Spiller P. , Stetter M. , Stöwe S. , Jacoby J. , Hoffmann D.H.H.
Published: March 2009

The main objective of the experimental plasma physics activities at the Gesellschaft für Schwerionenforschung (GSI) is the interaction processes of heavy ions with dense ionized matter. Gas discharge plasma targets were used for energy loss and charge state measurements in a regime of electron density and temperature up to 1019 cm-3 and 20 eV, respectively. Progress has been achieved in the understanding of charge-exchange processes in fully ionized hydrogen plasma. An improved model taking excitation-autoionization processes into account has removed most of the discrepancies of previous theoretical descriptions. Furthermore, it was found that the energy loss of the ion beam serves as an excellent diagnostic tool for measuring the electron density in partially ionized plasmas such as argon. The experience with these methods will be used in the future to diagnose dense laser produced plasmas. A setup with a 100 J/5 GW Nd:glass laser, currently under construction, will provide access to density range up to 1021 cm-3 and temperatures of more than 100 eV. To reach electron densities near solid-state density (1023 cm-3), heavy ion heated frozen rare gas crystals were used. The first hydrodynamic motion of ion heated solid material was observed. Vacuum-ultraviolet (VUV) spectroscopy was applied to diagnose these strongly coupled nonideal plasmas.
X-ray laser scheme driven by two laser pulses
Authors: Baer A. , Schwob J.L. , Eliezer S. , Henis Z. , Eliezer S.
Published: March 2009

A study is presented to find a compact X-ray laser in the spectral range of the water window. A double laser pulse method that requires a minimum energy with an optimal timing is proposed. The precreated plasma with an optimal ion distribution is heated by a short second pulse creating the required population inversion. In particular, the Ni-like 4d→4p transitions in tantalum, tungsten, and cesium are calculated.
Equation of state information from beam-target interaction experiments at KALIF
Authors: Goel Balbir , Vorobiev Oleg Yu.
Published: March 2009

Intense ion beams can be used to generate ultrahigh pressures in condensed matter. Lightion beams generated at the Karlsruhe Light Ion Facility (KALIF) typically have a focus of less than 1-cm diameter. The maximum power density at KALIF achieved so far is of the order of 1 TW/cm2. In the energy deposition zone of the targets, the 1.5-MeV protons of the KALIF beam deposit energy of the order of 100 TW/g or 5 MJ/g. A strongly coupled, hot, dense plasma is thus created by the action of a light ion beam on matter. The high pressure generated in this region has been used to accelerate thin foils to velocities up to 12.5 km/s. A successful interpretation of these experiments can serve as a check of theoretical models and of the equation of state (EOS) data. The present paper contains an investigation of the hydrodynamics of thin aluminum foil accelerated by light ion beams at KALIF using Bθ0-diode. The peak power density in these experiments was 0.15 ± 0.05 TW/cm2. The results of simulations depend mainly on two factors: power density evolution at the target and the EOS for the strongly coupled dense and hot plasma. The beam power density evolution has been carefully remeasured recently. It turned out that the available EOS data do not reproduce experimental results satisfactorily. We have formulated a simple EOS formula in a modified Mie-Grüneisen form. We assume the Grüneisen parameter to be a function of temperature and density. The parameters of this EOS have been adjusted to reproduce experiments at KALIF. In the present paper analysis of beam-target interaction experiments at KALIF is presented using our analytic EOS. We show that such experiments can give information on EOS data in the region of strongly coupled plasma.
Correlated ion stopping in a classical dense plasma
Authors: Deutsch Claude , Fromy Patrice , Zwicknagel Günter
Published: March 2009

The stopping at low (V < Vth) and high (V ≤ Vth) velocity, of N strongly correlated ion debris is investigated for the case of a dense and classical electron target. The considered topologies of cluster projectile charges are taken cubic like, and circular, respectively. A specific emphasis is given to the N-dependence, and also to the topological features of the corresponding enhanced correlated stopping.
Spectroscopic analysis of hot dense plasmas: A focus on ion dynamics
Authors: Hooper C.F. , Haynes D.A. , Garber D.T. , Mancini R.C. , Lee Y.T. , Bradley D.K. , Delettrez J. , Epstein R. , Jaanimagi P.A.
Published: March 2009

A brief discussion of the standard theory of line broadening is presented together with an analysis of selected laser-driven implosion experiments. The effect of improved theoretical procedures on experimental analysis is discussed. In particular, we consider the combined effects of ion dynamics and opacity on line profiles used in the analysis of these plasmas. The experiments discussed were performed at the University of Rochester Laboratory for Laser Energetics (LLE). The results presented in this paper illustrate the usefulness of plasma line broadening in diagnosing hot dense plasmas and in understanding fundamental plasma processes.
Basic features of correlated ion stopping in plasmas
Authors: Zwicknagel Günter , Deutsch Claude
Published: March 2009

We reconsider correlated ion stopping in plasmas with the aim to emphasize the basic features and their underlying physics. For a better understanding of the effects connected with correlated ion stopping, it is useful to distinguish two types of correlated ion stopping, characterized by a small or large ratio of the correlation length of the ions to the screening length in the plasma. These two types of correlated ion stopping are of rather different character. We describe and explain these differences and give some generic examples of ion structures and ion clusters to demonstrate the basic features of both types of correlated stopping. This shows that only the short-range correlations always yield an enhanced stopping, whereas the long-range correlations, in general, reduce the stopping compared to single, individual ions. We mainly consider classical plasmas; the basic features, however, remain unchanged for a jellium target as well as for a plasma at any degeneracy.
Shock wave excitation by soft X rays
Authors: Fortov V.E. , Dyabilin K.S. , Lebedev M.E. , Smirnov V.P. , Grabovskij E.V.
Published: March 2009

The behavior of matter under intense soft X-radiation is considered. An impulse of X-radiation (about 2–1012 W/cm2) produced a strong shock wave in the sample. The velocity of this shock wave was measured. A shock compression about 300 GPa in the lead target was achieved.
Analytical study of recombination X-ray lasers in an adiabatic expanding plasma
Authors: Li Yuelin
Published: March 2009

The collisional recombination process in highly ionized plasma and relevant reheating of the plasma are analyzed in the parameter regime appropriate for X-ray lasing. A method for describing the rate of collisional recombination is proposed based on a compact threelevel atomic model. Reheating of the plasma due to collisional recombination is described by a time-dependent adiabatic exponent γ. Using a self-similar description of the free expanding plasma, the gain of recombination lasing is investigated. In comparison with an open two-level atomic model, the present model gives lower gains appearing later in time. The inclusion of plasma reheating reduces the peak gain and shifts it to later times. Although the three-level model is shown to give a good qualitative description of the atomic processes, a considerable discrepancy was observed when compared with simulations for hydrogenlike carbon.
New concept on the application of supersonic gas jets for space charge neutralized beam transport in an ICF reactor chamber
Authors: Spiller P. , Varentsov V. L.
Published: March 2009

One of the most crucial problems of a heavy ion fusion (HIF) driver is the transport of the beam from the final focusing system to the fusion target. The conventional focusing scheme is based on ballistic transport, assuming that all space charge effects can be kept sufficiently small. To achieve a space charge neutralized beam transport, other more sophisticated schemes like beam transport in a plasma channel have been suggested. Inspired by the results of the first experiments on the generation of adequate discharge-driven plasmas, we suggest applying a pulsed supersonic gas jet for the high-current discharge channel creation, thereby improving the plasma channel stability. The supersonic jet is produced by a gas expansion into the reactor chamber through a converging-diverging nozzle that has a hollow inner tube on its axis for both heavy ion and UV laser beam injection.
Fast-charging Blumlein pulse forming line
Authors: Masugata K. , Tsuchida S. , Saitou H. , Yatsui K. , Shibata K. , Shigeta M.
Published: March 2009

A fast-charging, discharge-switch-free Blumlein pulse forming line has been developed for high-voltage pulsed power generation. In the BL, a saturable charging inductor (CI) of amorphous metallic core is utilized and, as a result, fast-charging (charging time ≈220 ns) is obtained with a reduced prepulse. In addition, by using CI as a step-up transformer, the impedance of the output pulse can be converted to 4Z, Z, Z/4. By using the BL with a Marx generator of 300 kV and 1.1 kJ, an output of —580 kV at 24 kA and a pulse length of 60 ns are obtained, with a current rise time of less than 16 ns. The energy transfer efficiency of the line (output pulse energy/charging energy of a pulse forming line) is evaluated to be more than 92%.
Effects of neutron heating on ignition and energy gain of laser-imploded D-T pellets
Authors: Johzaki T. , Nakao Y. , Nakashima H. , Takabe H. , Oda A. , Kudo K.
Published: March 2009

On the basis of coupled neutronic/hydrodynamic calculations, we examine the neutron heating effects on the ignition and burn propagation in laser-imploded D-T pellets. The fusionproduced neutrons deposit their energy all over the pellet region since the mean-free-path of the neutron is long. The fraction of neutron energies deposited to the central spark region during the ignition phase is too small to reduce the threshold energy of the laser for ignition. In the burn phase, the neutron heating decreases the maximum compression ratio and accelerates the plasma expansion. The inclusion of neutron heating hence decreases the pellet gain from the value in the case without neutron heating. Calculations neglecting the transport of neutron recoils overestimate the neutron heating rate in the reactor-grade pellets.
Quantitative measurement feasibility for 3D distributions of hydrodynamic quantities in the turbulent mixing zone of two gases
Authors: Bashurin V.P. , Bashurov V.V. , Bogunenko Yu.D. , Bondarenko G.A. , Pletenev F.A. , Starodubtsev V.A.
Published: March 2009

In doing research on the turbulent mixing (TM) of two gases different in density, it is of great interest to study experimentally the 3D density distribution pattern of chemically nonreactive gases in the TM zone. For this purpose, noncontact and, particularly, optical techniques to obtain experimental data may be attractive. This article discusses the possibility of using pulsed laser interferometry in this application. Based on this technique, the experiment should result in the mixture density distribution integrated along the light path. Requirements for high-quality interference patterns have been analyzed in application to typical experimental conditions, to show that they may be produced with specific restrictions set on the mixture constitution. Generally, the TM zone has no symmetry. Therefore, the problem of reconstructing 3D density distributions (TDD) of gases can be solved by sufficiently providing many TM zone integral projections (or aspects). It is technically difficult and expensive to achieve this large number of aspects (N> 10). Therefore, it is essential that a reconstruction method be selected to allow the solution of the problem with the least possible number of aspects. Given that the experiment data are incomplete, the reconstruction methods that are based on the concept of maximum data entropy did well. Information a priori about the solution to be sought for an isobaric gas mixture is that its each constituent has invariable density. Thus, a functional data entropy can be defined that is similar to Fermi gas in statistical physics. An algorithm has been suggested for reconstruction as a modified maximum-bounded entropy procedure (Bashurin et al. 1995). This makes reasonable good reconstruction achievable even with as few aspects as N = 4. Experiments on the study of TM of a propane jet in air using a four-aspects laser interferometer were provided and reconstruction of propane concentration distribution was conducted. The results allow determination of the TM zone spectral characteristics.
Theoretical study of a linear accelerator used as a VUV/X-ray source using the inverse Compton scattering mechanism:Comparisons and applications
Authors: Schill Robert A. , McCrea Edward
Published: March 2009

A classical linear theory is used to compare large synchrotron sources to a rf linear accelerator employed as a VUV/X-ray source. Comparisons are made on a per-pulse basis. It is demonstrated that the linear accelerator as an X-ray source is comparable to large synchrotron accelerators with wiggler insertion devices at the experiment. Applications to lithography, X-ray microscopy, X-ray spectroscopy and detector calibration are examined. Excluding lithography, the linear accelerator with an appropriate laser source is a useful source of X rays for these applications. As verification, classical results are compared with quantum mechanical results and are shown to be in good agreement.
Equation of State in Laser Shock Simulations
Authors: Godwal B.K. , Sikka S.K. , Kaushik T.C.
Published: March 2009

A three-term equation of state is used for the simulation of hydrodynamic shock phenomena. The reliability of it is tested by comparing the isotherms and shock Hugoniots obtained from it with available experimental data. This is illustrated for three typical materials Al, Pt and Au, which are of considerable interest for inertially confined thermonuclear fusion studies. We observe that reliable equation of state (EOS) data can be generated for nonmetallic substances like CH2. The EOS is used in the simulations of laser-driven shocks in double-layered target aluminum on gold (Al-Au) using hydrodynamic code employing a simplified laser-absorption model. The output from it is compared with the recent laser-driven shock experiments of Koeniget al.
A self-consistent Power Relation for an Inverse Compton Scattering Theory
Authors: Schill Robert A.
Published: March 2009

In a self-consistent manner, the total power for linear inverse Compton scattering between a Gaussian electron beam colliding head on with a Gaussian laser beam is obtained. The theory is shown to agree with well-known limiting cases. Coupling among harmonic modes is explicitly shown in the resultant power relation. Even so, for the parameters of interest, harmonic modes are negligible compared to the fundamental mode. Total power calculations are of importance in detector calibration. The theory is applied using practical linear accelerator and laser parameters.
Test of a High-gradient Low-emittance Electron Gun
Authors: Villa F. , Villa F. , Luccio A.
Published: March 2009

A maximum electric field E = 2.65 GV/m with an accelerated electron current of 1 KA has been obtained, for pulse lengths of 130 ps, in an electron gun based on Pulse Power Technology. This is the highest accelerating field ever achieved in the presence of such a large current. Measurements of beam emittance and energy from 0.4 to 2.65 MeV show that the scaling of the invariant emittance with electric field and with beam current is consistent with theoretical predictions. A few applications of high-gradient acceleration are discussed.
Density Diagnostics of an Argon Plasma by Heavy Ion Beams and Spectroscopy
Authors: Wetzler H. , Süss W. , Stöckl C. , Tauschwitz A. , Hoffmann D.H.H.
Published: March 2009

Experiments have been performed to investigate charge state and energy loss of 5.9-MeV/u uranium ions in a partially ionized dense argon plasma with 1017≤ne≤ 1019cm−3and 1 ≤Te≤ 10 eV. The charge state of the ions was found to be equal to the equilibrium charge state in cold gas. The energy loss offered a useful tool for plasma density diagnostics. Spectroscopic measurements using the electron collision broadening of ArII- and ArIII-lines in the visible and UV spectral region confirm this plasma density data.
Determination of the color temperature in laser-produced shocks
Authors: Bossi Simone , Hall Tom A. , Mahdieh Mohammed , Batani Dimitri , Koenig Michel , Krishnan Jothy , Benuzzi Alessandra , Boudenne Jean Michel , Lower Thorsten
Published: March 2009

Experimental results on the determination of the color temperature in shock waves produced with lasers are presented. The method is based on imaging the target rear side in two different spectral windows and on using phased zone plates to produce high-quality shocks. The shock velocity is also measured, allowing, with the use of the equation of state, the real shock temperature to be deduced and compared with the measured color temperature.
Stopping Power in Strongly Coupled Plasmas
Authors: Morawetz K.
Published: March 2009

The stopping power of dense nonideal plasmas is calculated in different approximations. The T-matrix approximation for binary collisions is compared with the random phase approximation (RPA) approximation for dielectric fluctuations. Within a microscopic model, the dynamical evolution of the velocity of the projectile is calculated. It reproduces well experimental values for the stopping of fast heavy ions. Further improvements due to correlations are discussed. Both concepts, cluster decomposition and memory, are compared and it is found that they lead to the same quantum virial corrections of the Beth-Uhlenbeck type in equilibrium. However, memory in the kinetic equation causes an additional renormalization of the effective energy transfer in nonequilibrium.
T-matrix Approximation of the Stopping Power
Authors: Gericke D.O. , Schlanges M. , Kraeft W.D.
Published: March 2009

An expression for the stopping power is derived in the quantum T-matrix approximation. The transport cross sections needed for a numerical evaluation are calculated using a scattering phase-shift analysis. Numerical results are given for the stopping power of an electron beam running into an electron gas. The temperature and density dependencies of the stopping power are discussed. Finally, dynamical screening is included in the weak coupling limit according to a kinetic equation proposed by H.A. Gould and H.E. DeWitt.
Fast ignitor: Fluid dynamics of channel formation and laser beam propagation
Authors: Hain S. , Mulser P.
Published: March 2009

The concept of fast ignitor is intimately connected with the fundamental phenomenon of ultra-intense light beam propagation through dense matter in which kinetic effects combine with radiation pressure dominated hydrodynamics to form a complex scenario of extremely non-linear physics. In this paper, the fluid dynamic aspect of channel formation in a highly over-dense plasma is studied and possible attenuation mechanisms of the propagating pulse are evaluated in one dimension. Under the assumption that mass ablation reaches a quasistationary state, the radiation-assisted ablation pressure, the speed of the bow shock, and the density steepening around the critical point are determined self-consistently from the ID fluid conservation relations and the electromagnetic wave equation. Due to ponderomotive profile steepening, the ablation pressure is reduced by 40% in the subsonic region and is dominated by the radiation pressure in the supersonic domain. Channel lengths are calculated for various intensities and pellet compression ratios. Likewise, the nonlinear propagation of a superintense electromagnetic wave in an underdense plasma channel is investigated for the ID case with the help of a relativistic fluid model.
Ion model of a hot dense plasma
Authors: Orlov N.Y.
Published: March 2009

Results are presented for a theoretical model, known as the ion model (IM), recently elaborated to calculate the radiative opacity of a hot dense plasma. The model is based on the self-consistent field method for subsystems obeying Gibbs statistics. The results are compared with calculations that use the Hartree-Fock-Slater model and with experimental data. A theory is proposed to explain the extraordinary spectral line-shift phenomenon associated with such plasmas.
Some studies on picosecond laser produced plasma expanding across a uniform external magnetic field
Authors: Rai V.N. , Shukla M , Pant H.C.
Published: March 2009

Some characteristics of the picosecond laser produced plasma expanding across an externally applied magnetic field (0.6T) have been reported. Two to three times enhancement in X-ray emission from copper plasma has been observed for the laser intensity range ∼5 X 1011 to 5 X 1012 W/cm2. The X-ray yield has been found to increase with an increase in the magnetic field intensity. Enhancement in X-ray emission is correlated with confinement of expanding plasma either in external magnetic field or in high ambient gas pressure. Generation of some highfrequency instability and fast ions was also observed in the plasma along with bouncing of plasma near the β = 1 surface where kinetic pressure of plasma equals magnetic pressure.
Dense Z-pinch plasma as a dynamical percolating network: From laboratory plasmas to a magnetoplasma universe
Authors: Kukushkin A.B. , Rantsev-Kartinov V.A.
Published: March 2009

The results of a high-resolution processing, based on techniques of fractal dimension analysis, of experimental data from earlier experiments on the linear Z-pinches are presented, which prove the electric current-carrying plasmas to be a random fractal medium. The basic building block of this medium is identified to be an almost-closed helical filamentary magnetoplasma configuration (we call it heteromac). The heteromacs are coupled together through long-range self-sustained filamentation and, thus, form a dynamical percolating network with dissipation. The results (i) extend recently identified phenomenon of the 3D large-scale (up to several centimeter size) helical filamentary plasma structures (Kukushkin et al. 1994, 1995, 1997a) in plasma focus gaseous discharges to the case of Z-pinch gaseous discharges and (ii) provide a novel view into the dynamics of Z-pinch's necks, plasma spikes, and magnetic bubbles as well as into generic features of electric current-carrying plasmas varying from low-electric current laboratory plasmas to cosmic plasmas. This covers about 30 orders of magnitude of length scale and suggests unprecedented opportunities for interpolating between and extrapolating from well-understood phenomena. A magnetoplasma universe model is suggested.
Weibel instability analysis in laser-produced plasmas
Authors: Bendib K. , Bendib A. , Bendib K. , Bendib A. , Sid A. , Bendib K.
Published: March 2009

Analytic analysis of collisionless Weibel modes in laser-created plasmas is presented. The heat flux (HF), the plasma expansion (PE), and the inverse bremsstrahlung absorption (IBA) sources have been investigated. It has been shown that for short laser wavelengths (λL < 1 µm) and high laser fluxes (I > 1014 W/cm2), the inverse bremsstrahlung absorption is the most efficient Weibel mechanism for producing strong magnetic fields in the vicinity of the critical layer. For large laser wavelengths (λL < 10 µm), the production of the magnetic fields in the vicinity of the critical layer, due to the plasma expansion mechanism, is as important as the ones due to the thermal transport and the inverse bremsstrahlung absorption mechanisms. Useful scaling laws of convective e-foldings, with respect to the laser and the plasma parameters, are also derived.