bluuebunny/crossref_metadata_2025 huggingface dataset:
A design study of HIF, HIBLIC-I
Authors: Yamaki T.
Published: March 2009

In 1982 to 83 a preliminary conceptual design of a heavy-ion-driven inertial fusion (HIF) system, called HIBLIC-I (Heavy Ion Beam and LIthium Curtain) was worked out (The Working Group on ‘HIBLIC-I’ 1984). Its principal aims are: (i) to find out the critical issues in this approach to fusion power plant, (ii) to assess its feasibility and (iii) to promote good collaboration between different fields (such as accelerator physics, plasma science and reactor technology) and of different institutions in Japan. (Obayashi 1981; Hirao 1982).
Hydrodynamic derivation of double layers (DL) and electric fields in plasmas
Authors: Hora Heinrich
Published: March 2009

The hitherto successful hydrodynamic plasma theory needed the simplifying assumption of quasi-neutrality. Earlier known ambipolar fields in plasma surfaces were considered as exceptions and Alfvén's model of a complementary description by plasma currents was criticized. Fields in plasmas were derived from the kinetic theory of turbulence. Following a model for the nonlinear force of laser–plasma interaction, we needed a general description of the plasma without space charge neutrality which succeeded numerically and analytically. High electric fields due to inhomogeneities inside plasmas were derived explaining for the first time quantitatively the reduction of thermal conduction in laser-fusion, the measured inverted double layers including a new type of resonance process, the MeV α-upshift by nonlinear-force driven caviton fields and the radial fields in tokamaks which cause plasma rotation.
On self consistent electrostatic fields in inhomogeneous plasmas for the hydrodynamic approximation
Authors: Dragila R.
Published: March 2009

The self consistent electrostatic field due to plasma inhomogeneities and associated with free expansion of a plasma into a vacuum is evaluated in the framework of two-fluid hydrodynamics and the corresponding generalized Rieman's self-similar solution found. The case of an adiabatic expansion is also discussed and the results obtained are applied to a laser produced plasma with a characteristic electron temperature of 1 keV and a characteristic time scale of 1 nsec.
Geometric focusing of intense pulsed ion beams from racetrack type magnetically insulated diodes
Authors: Yatsui K. , Tokuchi A. , Tanaka H. , Ishizuka H. , Kawai A. , Sai E. , Masugata K. , Ito M. , Matsui M.
Published: March 2009

Focusing properties and mechanisms are experimentally investigated of an intense pulsed light-ion beam or a medium-mass ion beam extracted from racetrack type magnetically insulated diodes. Quantitative determinations are made for three factors that affect the focusing ability of the beam, i.e., local divergence angle, deviation angle from ideal trajectory and space-charge effect. Behaviour of electrons in an anodecathode gap as well as neutralizing process of the ion beam by electrons are studied in connection with beam focusing. It is found that there is a close correlation between ion yield and electron irradiation on the anode. By adopting a perforated cathode instead of a vane cathode to ensure good uniformity of electric field in the accelerating gap, we have succeeded in significantly reducing the divergence angle. Several new diagnostic techniques and methods have been developed, yielding information such as the time-resolved trajectory and profile or incident angle of the beam. Electron temperature of the anode plasma is theoretically anticipated from the ions observed experimentally. From an estimate of beam divergence due to a space-charge effect, it is suggested that ‘breakeven’ can be achieved without using conventional z-discharged plasma channels if a bunch of boron beams is utilized.
Spectral analysis of half harmonics emission from laser-plasmas
Authors: Karttunen S. J.
Published: March 2009

Spectral structure of various half harmonic (ω0/2, 3ω0/2 and 5ω0/2) emission from an inhomogeneous plasma is analyzed. Several interaction mechanisms are studied and the effects of plasmon refraction and reflection are included in the analysis. These modify earlier results of the homogeneous plasma model considerably and increase the number of possible coupling configurations. The predictions of results in the different lasertarget experiments are discussed.
Novette facility: activation and experimental results
Authors: Manes K. R. , Barr O. C. , Bliss E. S. , Drake R. P. , Godwin R. O. , Gritton D. G. , Hildum J. S. , Holloway F. W. , Hurley C. A. , Johnson B. C. , Kuizenga D. J. , Merritt B. , Ozarski R. G. , Reinecker F. , Severyn J. R. , Speck D. R. , Summers M. A. , Suski G. J. , Wallerstein E. P.
Published: March 2009

From the neodymium glass laser system Novette with two beams of 74 cm diameter and 18 kJ energy per pulse output in the nanosecond range, the design, the steps of the construction, and results of the system are reported. The two beams are synchronized to 5 psec and conversion to green light up to 78% has been realized. Conversion to four times the laser frequency is measured with more than 25% conversion. Simulation and measurement of laser beam properties at several locations permit an analysis to define the final Nova configuration. About half of Novette's experiments were to study short wave length laser–plasma interactions for the then better coupling by inverse bremsstrahlung mechanisms for inertial confinement fusion with laser intensities up to 1017W/cm2. Experiments were divided between high density implosion research and non-local thermodynamic equilibrium plasma conditions.
Thermal flux limitation and thermal conduction inhibition in laser plasma
Authors: Weihan Tan , Min Gu
Published: March 2009

The physical mechanisms of thermal flux limitation and thermal conduction inhibition in laser plasmas are analyzed. A numerical calculation accounting for the non-negative electron distribution function and pressure gradient has been given.
A model for inhibition of thermal transport in laser produced plasmas
Authors: Lee P. H. Y. , Willi O.
Published: March 2009

We show that the thermal transport in laser produced plasmas can be inhibited due to the outward plasma blow-off which is in the opposite direction to the inward heat transport. A simple model is proposed in which the steady state heat transfer equation, including the convective term for a point heat source, is solved. A simple analytical expression for the ratio of effective to classical conductivity depending on the blow-off velocity is obtained. With this model, present experimental data on thermal transport can be qualitatively, but consistently described.
Non-uniform illumination of laser targets
Authors: Evans R. G.
Published: March 2009

Attempts to accelerate and implode laser targets are hindered by the non-uniformities present in real laser beams. The effects of non-uniform illumination are ‘smoothed’ by thermal transport in the low density ablation plasma but amplified by the fluid instabilities (Rayleigh–Taylor) present in the high density accelerated material. In this paper the effects of different assumptions concerning the plasma thermal conductivity are analysed and the inclusion of the full fluid equations is shown to introduce oscillatory (acoustic) and growing (Rayleigh–Taylor) phenomena into the fluid response.
Los Alamos Krypton Fluoride Laser Program
Authors: Jensen Reed J. ,   Participants in the Los Alamos Advanced Laser Program
Published: March 2009

In this paper we introduce designs that provide short duration megajoule pulses of ¼ micron wavelength light at efficiencies near ten percent.
Observation of long life plasma generated in a cavity by CO2 lasers
Authors: Daido H. , Fujita M. , Terai K. , Miki F. , Nishihara K. , Murakami M. , Mima K. , Nakai S. , Yamanaka C. , Hasegawa A.
Published: March 2009

Plasmas with long life times (∼20 ns) are generated in a cavity target by intense CO2 laser pulses (2 × 1014W/cm2). The plasma life depends on the configuration of irradiation and target, which may infer thermal conduction inhibition by the laser-generated magnetic field. The experimental results agree with those of computer simulations with magnetic inhibition of thermal conduction.
Short-pulse CO2 laser systems for plasma investigation at the IPPLM
Authors: Badziak J. , Borzecki M. , Chojnacka A. , Dźwigalski Z. , Janulewicz K. , Jarocki R. , Kalbarczyk A. , Kubicki J. , Kurzyński Z. , Perliński L. , Sikorski Z. , Teter J.
Published: March 2009

This paper presents the multigigawatt single-beam CO2 laser system and the configuration and the main subsystems of the 0.5 TW four-beam CO2 laser system being built at the IPPLM. Selected construction details and early test results are given.
High energy krypton fluoride amplifiers for laser-induced fusion
Authors: Sullivan J. A. , von Rosenberg C. W.
Published: March 2009

This paper discusses the general requirements for inertial confinement fusion, technology requirements and choices, overall efficiencies, and laser system costs for scaling krypton fluoride amplifiers to high energy, and describes the design of a 100 kilojoule double-pass KrF power amplifier.
Magnetic self-compression in laboratory plasmas, quasars and radio galaxies. Part II
Authors: Lerner Eric J.
Published: March 2009

A model of quasars and radio galaxies and their associated jets is further elaborated here. The model, presented in Part I of this paper, is based on magnetic selfcompression as the process involved in producing extremely high energy densities. In the present paper, the results derived in Part I are used to predict radiation spectra from quasars, and to extend the model to radio galaxies. The role of magnetic self-compression of magnetic vortices in the origin of filamentary superclusters of galaxies is briefly discussed.
Streaming modes in final beam transport for heavy ion beam fusion
Authors: Stroud P.
Published: March 2009

A key issue in the design of an HIF reactor cavity is the transport of the heavy ion beam from final focusing, across the cavity, to the target. Previous estimates have indicated that streaming instabilities will disrupt the beam transport for a background chamber gas pressure of 10−4 to 10−1 torr. The most attractive liquid lithium first wall reactor cavity designs produce a background gas density in just this pressure range. A detailed analysis of the streaming instabilities has now demonstrated that the beam can be transported through this background. The important fact that had been neglected is that a mode with a given wave number will grow for only a small fraction of the transport time, due to the changing beam and electron densities during transport. This analysis opens wide an attractive window for reactor cavity design.
Plasma induced energy deposition and radiation transport effects in ion beam heated plane metal targets and analytic solutions of the non-linear radiation conduction equation
Authors: Long K. A. , Tahir N. A.
Published: March 2009

The effects of microscopic energy deposition in hot, dense plasmas and radiation transport in plasmas, on the interaction of ion beams with plane metal targets are investigated in this paper. In order to do this we analyze the plasma dynamics of ablatively accelerated plane metal foils. The physical analysis of these results is achieved by the derivation of solutions of the non-linear radiation conduction equation with boundary temperatures which increase in time. We illustrate, by means of numerical simulations, how range shortening due to plasma effects such as increased energy loss to excited electrons and an increased effective charge due to a reduction in the recombination rate, may be compensated for by radiation transport. The effect of radiation transport and detailed microscopic energy deposition on ion beam implosions, including hydrodynamic instability, is discussed.
Experimental results for high intensity KrF laser/plasma interaction
Authors: Offenberger A. A. , Fedosejevs R. , Gupta P. D. , Popil R. , Tsui Y. Y.
Published: March 2009

A high power KrF laser system employing beam multiplexing and stimulated Raman or Brillouin scattering to produce pulses as short as 1 ns and focused intensities on target of 1011 to 1014 W/cm2 has been developed for laser/plasma interaction research. A variety of investigations have been pursued on single and multilayer targets with variable atomic numbers. Absorption, transport, X-ray conversion, ion expansion characteristics, mass ablation and ablation pressure scaling, and stimulated scattering instabilities are among features that have been studied as a function of laser intensity. A wide variety of laser and target diagnostics are employed including focal plane imaging cameras for energy distribution and UV and soft X-ray streak cameras for temporally resolving the incident laser pulse and X-ray emission. Experimental results will be presented and our current understanding of the KrF laser/plasma interaction will be discussed.
Model equation-of-state for any material in conditions relevant to ICF and to stellar interiors
Authors: Atzeni S. , Caruso A. , Pais V. A.
Published: March 2009

A simple model Equation-of-State (EOS) for matter in conditions of interest to Inertial Confinement Fusion (ICF) and to Stellar Interiors is developed. It yields pressures and specific energies in good agreement with accurate EOS tabulations, for matter in the density range 10−6 < ρ < 104 g cm−3 and in the temperature range 0 ≤ T < 100 KeV, with the only exception being the liquid and gaseous phases of the undissociated molecular substances.

This EOS can be used for any element or mixture, requiring, as input data, only the chemical composition (A, Z, and abundancy of each element of the mixture) and three macroscopic constants of the material.
Experimental evidence of the generation of multi-hundred megabar pressures in 0.26 μm wavelength laser experiments
Authors: Fabbro R. , Faral B. , Virmont J. , Pepin H. , Cottet F. , Romain J. P.
Published: March 2009

A 9 μm thick aluminium foil is accelerated to a velocity of about 160 km/s by a laser of 0.26 μm wavelength and intensity of 1015 W/cm2 and collides with an aluminium impact foil. The measurement of the velocity of the induced shock wave in the impact foil, using a step method at the rear of the impact foil, gives pressures in the multi-hundred megabar range. The dynamics and constraints of this shock wave are presented and the effect of X-ray preheating, which can be important at this laser wavelength, is discussed.
Laser beam self-focusing in an nc/100 plasma with 20 ns and 3 ns pulses
Authors: Giulietti A. , Giulietti D. , Lucchesi M. , Vaselli M.
Published: March 2009

The interaction of a laser beam (1·06 μm) with an underdense plasma produced by optical breakdown of helium was experimentally studied. Evidence for whole beam self-focusing is reported and discussed.
Laser and plasma conditions at the onset of Raman scattering in an underdense plasma
Authors: Tarvin J. A. , Busch Gar E. , Gabl E. F. , Schroeder R. J. , Shepard C. L.
Published: March 2009

The laser and plasma conditions at the onset of Raman scattering have been measured in plasmas formed from thin-foil targets. The targets were Al disks 50 to 250 nm thick and 200 to 500 μm in diameter mounted on 100 nm polymer films. The incident wavelength was 526 nm. Raman scattering was observed for nominal intensities from 1014 W/cm2 to 5 × 1014 W/cm2. The most important observation of the experiment is that the density-gradient scale-length at onset is independent of intensity. One would expect the scalelength at onset to be inversely related to the intensity, since the convective gain for stimulated Raman scattering (SRS) is proportional to the product of intensity and scalelength.
Space-time structure of the light reflected in an experiment on solid matter irradiation by laser light
Authors: Caruso A. , Strangio C.
Published: March 2009

A study of the space-time structure of the light reflected when a plastic target (CH)n is irradiated at a maximum power of 1012 watt/cm2 by a Nd glass laser pulse of nanosecond duration is described. The reflected light has been used for time integrated spot imaging, whereas the time dependence of the reflected power at different angles has been studied by optical guides of different length coupled with a single fast photodiode. It has been found that: 1) the spot images are formed by a high contrast stationary speckle pattern, indicating the presence of a random phase mixing in the back-scattered light; 2) the interaction is characterized by a high reflection in the initial stages (t ≤ 0·3 ns) followed by almost complete absorption.
Absolute soft x-ray measurements with a transmission grating spectrometer
Authors: Eidmann K. , Kishimoto T. , Herrmann P. , Mizui J. , Pakula R. , Sigel R. , Witkowski S.
Published: March 2009

Absolute measurements of the soft x-ray emission (50 eV < hv< 1000 eV) from laser plasmas were made with transmission gratings, including pinhole-grating combinations for spatially resolved spectroscopy. Kodak 101–01 film was absolutely calibrated as a function of wavelength with the help of a bolometer, the laser plasma being used as a source. An example of a quantitatively analyzed, space-resolved pinhole grating spectrum recorded on film will be shown.
Laser program development at CEL-V: overview of recent experimental results
Authors: Buresi E. , Coutant J. , Dautray R. , Decroisette M. , Duborgel B. , Guillaneux P. , Launspach J. , Nelson P. , Patou C. , Reisse J. M. , Watteau J. P.
Published: March 2009

A significant effort has been made recently at CEL-V to improve laser facilities. OCTAL, the eight beam, 2 kJ laser, has been equipped with phosphate glass and KDP frequency tripling systems. PHEBUS, a two beam 20 kJ neodymium glass laser based on NOVA technology was denned and built and will be tested in early 1986 in close collaboration with Lawrence Livermore National Laboratory.

In the field of diagnostics, the development of soft X-ray emission analysis has been emphasized.

Most of the recent experimental results have been obtained at a short wave-length (0·35 μm). They deal with the effect of non-uniform illumination, 2D hydrodynamics with either plane or spherical targets, and the study of thermal transport inhibition.
Laser-driven shock wave experiments at the University of British Columbia
Authors: Ng A. , Parfeniuk D. , Da Silva L. , Celliers P.
Published: March 2009

A review of recent laser-driven shock wave experiments at the University of British Columbia is presented. These include emissivity and reflectivity measurements on target rear surfaces when the shock wave emerges as well as measurements of the trajectories of shock propagation in initially transparent targets irradiated by temporally tailored laser pulses. The rear surface measurements allowed us to study the equation of state and electron conductivity of dense plasmas while coalescence of shock waves was evident in the trajectory of shock waves driven by a shaped pulse.
High speed proximity focused X-ray cameras
Authors: Kilkenny J. D.
Published: March 2009

Recent technological developments have resulted in sub 100 ps shutter times of X-ray cameras that are based on the gating of microchannel plates. Moreover, these cameras are reliable enough to be used on large experimental systems. A review is given of the development of gated proximity focused detectors and of the factors affecting their performance.
X-ray microscopy of laser-produced plasmas with the use of bent crystals
Authors: Förster E. , Gäbel K. , Uschmann I.
Published: March 2009

X-ray spectroscopical and microscopical methods are used for the determination of the spectral and spatial distribution of X-ray intensity of laser-produced plasmas. The use of Bragg reflections of two-dimensionally bent crystals enables the X-ray microscopical imaging in narrow spectral ranges (Δλ/λ = 10−4 to 10−2) with wavelengths 0.1 nm < λ > 2.6 nm. It is possible to adapt, in the X-ray microscope, the distances, magnification, position, and width of the spectral window to the special conditions of the laser facility. Manufacturing and testing of the two-dimensionally bent crystals requires a great deal of effort. It was demonstrated that a spatial resolution of about 5 μm was achieved, and that the experimentally determined reflectivity was found to be in close agreement with the dynamical theory of X-ray interferences. Due to high luminosity of the X-ray microscope, in experiments with laser-produced plasmas it was necessary to attenuate the radiation with aperture-limiting diaphragms or filters down to 0.01–1% of the original intensity in the case of a magnification of about one. Emission of the resonance line W 1–2, the intercombination line of helium-like ions, and Lyman alpha line were imaged simultaneously with a three-channel microscope. Such images form the foundation for establishing the Ne(r), Tz(r) maps.
On self-focusing of laser beams in plasma
Authors: Rubenchik A. M. , Turitsyn S. K.
Published: March 2009

Self-focusing of laser beams in plasma is studied analytically using the thermal (collision produced) and ponderomotive (nonlinear force produced) effects based on the model of Zakharov with solutions of the nonlinear Schrödinger equation. A basic difference appears if the electric field amplitude E is less than the threshold Eth (at which the electrodynamic energy density is equal to the gasdynamic pressure) from the contrary case, E > Eth.The length of the filamentation process is evaluated and results in large values for E below Eth.
The surface explosion of electron temperature due to microwave resonant plasma heating
Authors: Shvartsburg A. B.
Published: March 2009

The explosive growth of electron temperature, produced by microwave heating of a collisional magnetoplasma in the vicinity of Langmuir resonance, is illustrated. This explosion is localized near by the irradiated surface of plasma volume. Such effect is stipulated by an external magnetic field, herein this field may be weak enough.
On a theory of stimulated scattering in laser plasmas
Authors: Škorić Miloš M.
Published: March 2009

A linear parametric theory of laser light instabilities including decay, stimulated Raman and Brillouin scattering, etc. is currently well developed. However, attention is drawn to a novel laser light instability against parametric excitation of magneto-static fluctuations. In a collisionless plasma regime, magneto-static fields are driven by the ponderomotive electron magnetization current. Generally, two types of magneto-static instabilities exist: magneto-modulational instability and stimulated magneto-static scattering instability. Growth rates are calculated which indicate the possible importance for high laser intensity driven hot plasma regimes.
Ion mobility influence on stimulated Raman scattering in homogeneous laser-irradiated plasma
Authors: Bonnaud G.
Published: March 2009

1½ D computer simulations have been performed to illustrate the influence of ion dynamics on stimulated Raman scattering in laser irradiated plasmas. A flat density profile has been used. Backward and forward scatter and heated electron distribution have been studied as a function of ion mass and ion temperature. The results show clearly that the lighter the ions, the more inhibited the Raman scatter and associated fast electron production. Futhermore, when ions are cold enough to allow Brillouin scattering release, Raman scatter, as well as associated suprathermal electrons is even more reduced. These observations evidence the complex non-linear coupling of the electron plasma waves driven by the Raman instability and the ion fluctuations which can exist in the plasma.
Theoretical and experimental study of complete spectral series as a diagnostic tool for dense plasmas
Authors: d'Etat B. , Grumberg J. , Leboucher E. , Nguyen H. , Poquérusse A.
Published: March 2009

A theoretical and experimental study of line broadening and merging is presented and suggested for diagnosis of high density laser plasmas. For densities larger than 1022 cm−3 the hydrogenlike sequence is reduced to four lines for the emitter ion with ZE = 9. The perturbation effects on the latter come mainly from the interaction with plasma ions and electrons (Stark effect, multipolar interactions, ionization by tunnel effect, polarization line shift …).
Double Layers in Plasmas
Authors: Williams Alton C. , Hora Heinrich
Published: March 2009

The phenomenon of electric double layers in plasmas as a generalization of ambipolar effects and as an essential time dependent and oscillating phenomenon in the plasma interior, has emerged from studies in laser produced plasmas as well as from similar problems in space plasmas and their laboratory simulation experiments. While these results have been published occasionally in various places including the most prestigious journals and in small topical conferences, there was still a need to enter a more comprehensive presentation and overview into a referred journal.
Current driven weak double layers
Authors: Chanteur Gérard
Published: March 2009

Double layers in plasmas can be created by different means. For example, a potential difference forms between two plasmas with different temperatures (Hultqvist 1971; Ishiguro et al. 1985), in a plasma jet flowing along a converging magnetic field (Serizawa & Sato 1984), in a quiescent plasma submitted to an external difference of potential or in a turbulent plasma carrying an electric current. The first three cases can be current-free, but not necessarily, although the numerical simulations have been made under such conditions for the first two points (Ishiguro et al. 1985; Serizawa & Sato 1984). Apart from the third case, which is mainly of interest for laboratory experiments, these double layers are good candidates for accelerating the auroral electrons to the few keV observed.
Weak double layers in the auroral ionosphere
Authors: Hudson M. K. , Crystal T. L. , Lotko W. , Barnes C.
Published: March 2009

Previous work on the evolution of weak double layers in a hydrogen plasma has been extended to include H+ and O+ with relative drift. It has been shown (Bergmann & Lotko 1986) that the relative drift between hydrogen and oxygen ions due to a quasistatic parallel electric field gives rise to a strong linear fluid instability which dominates the ion acoustic mode at the bottom of the auroral acceleration region. This ion–ion instability can modify ion distributions at lower altitudes and the subsequent nonlinear evolution of weak double layers at higher altitudes in the ion acoustic regime. We have found that ion hole formation can occur for smaller relative electron-ion drifts than seen in previous simulations, due to the hydrogen-oxygen two-stream instability. This results in local modification of the ion distributions in phase space, and a partial filling of the valley between the hydrogen and oxygen peaks, which would be expected at higher altitudes on auroral field lines. It is shown that the observed velocity diffusion does not necessarily preclude ion hole and double layer formation in hydrogen in the ion acoustic regime. These simulation results are consistent with the experimentally measured persistence of separate hydrogen and oxygen peaks, and the observation of weak double layers above an altitude of 3000 km on auroral field lines.
Some aspects of double layer formation in a plasma constrained by a magnetic mirror
Authors: Lennartsson W.
Published: March 2009

The discussion of parallel electric fields in the earth's magnetosphere has undergone a notable shift of emphasis in recent years, away from wave-generated anomalous resistivity towards the more large-scale effects of magnetic confinement of current carrying plasmas. This shift has been inspired in large part by the more extensive data on auroral particle distribution functions that have been made available, data that may often seem consistent with a dissipation-free acceleration of auroral electrons over an extended altitude range.

Efforts to interpret these data have brought new vigor to the concept that a smooth and static electric field can be self-consistently generated by suitable pitch-angle anisotropies among the high-altitude particle populations, different for electrons and ions, and that such an electric field is both necessary and sufficient to maintain the plasma in a quasi-neutral steady state. This paper reviews and criticizes certain aspects of this concept, both from a general theoretical standpoint and from the standpoint of what we know about the magnetospheric environment. It is argued that this concept has flaws and that the actual physical problem is considerably more complicated, requiring a more complex electric field, possibly including double layer structures.
Some dynamical properties of very strong double layers in a triple plasma device
Authors: Carpenter T. , Torvén S.
Published: March 2009

We present experimental results on three dynamic properties of very strong double layers observed in a triple plasma device. First, it is observed that when an inductance of sufficient size is inserted in series with the external bias supply used to produce the double layer, disruptions in the plasma current occur accompanied by disruptions in the double layer potential. Second, it is observed that with all external reactances reduced as much as possible, a sort of jitter-motion occurs in the position of the double layer around its equilibrium position. Third, when the external bias supply is pulsed, the initial potential distribution is observed to have an essentially uniform slope, as in the case of a vacuum capacitor. The disruption phenomenon may be explained in terms of the behavior of the potential structure as a function of the bias voltage and this explanation is discussed along with the experimental evidence for its validity. A comparable understanding of the other two phenomena has not been achieved, but in both cases there are qualitative differences between the behavior reported here and what has been observed in Q-machines and these differences are discussed.
A laboratory investigation of potential double layers
Authors: Leung Philip
Published: March 2009

In a triple plasma device, the injection of electron current from the source chamber to the target chamber causes the formation of a potential double layer. At a low current density, the space charge of the injected current produces a virtual cathode-type potential double layer. This double layer is stable and various wave instabilities are observed to associate with this double layer. As the current density is increased, the double layer becomes unstable and a moving double layer results. As the current density is increased further, the enhanced ionization causes the neutralization of the space charge of the electron beam and the ‘beam plasma discharge’ is ignited.
Effect of double layers on magnetosphere–ionosphere coupling
Authors: Lysak Robert L. , Hudson Mary K.
Published: March 2009

The earth's auroral zone contains dynamic processes occurring on scales from the length of an auroral zone field line (about 10RE) which characterizes Alfven wave propagation to the scale of microscopic processes which occur over a few Debye lengths (less than 1 km). These processes interact in a time-dependent fashion since the current carried by the Alfven waves can excite microscopic turbulence which can in turn provide dissipation of the Alfven wave energy. This review will first describe the dynamic aspects of auroral current structures with emphasis on consequences for models of microscopic turbulence. In the second part of the paper a number of models of microscopic turbulence will be introduced into a large scale model of Alfven wave propagation to determine the effect of various models on the overall structure of auroral currents. In particular, we will compare the effect of a double layer electric field which scales with the plasma temperature and Debye length with the effect of anomalous resistivity due to electrostatic ion cyclotron turbulence in which the electric field scales with the magnetic field strength. It is found that the double layer model is less diffusive than the resistive model leading to the possibility of narrow, intense current structures.
Optical turbulence in multiple stimulated Brillouin backscattering
Authors: Montes Carlos , Coste Jean
Published: March 2009

Driven stimulated Brillouin rescattering, obtained by multiline laser light, each satellite line downshifted by twice the acoustic frequency ωs, is an efficient way to reduce stimulated Brillouin reflection (Colombant et al. 1983; Montes 1985). For long enough interaction lengths the nonlinear dynamics leads to optical turbulence. We consider a six wave coherent model whose wave frequencies are ω1 and ω3 = ω1 − 2ωs for the principal and auxiliary pump waves, ω2 = ω1 − ω2 and ω4 = ω1 − 3ωs for the backscattered waves, and ωs for the forward- and backward-traveling sound waves. The sound wave is weakly damped and its velocity is neglected (limit cs/c = 0). The space-time evolution is studied numerically. The model depends upon several parameters of nonlinearity. Increasing the interaction length L we observe: (1) a stationary regime for L smaller than a critical value Lcrit; then (2) an oscillatory behaviour appears through a Hopf bifurcation at L = Lcrit which becomes (3) more and more anharmonic and (4) finally chaotic for large L.
Preliminary design of a ≈10 MV ion accelerator for HIF research
Authors: Fessenden T. J. , Celata C. M. , Faltens A. , Henderson T. , Judd D. L. , Keefe D. , Laslett L. J. , Meneghetti J. , Pike C. , Vanecek D.
Published: March 2009

An experiment to study the physics of merging and of focusing ion beams is under development at the Lawrence Berkeley Laboratory. In this design, parallel beams of ions (C+, Al+, or Al++) are accelerated to several MV and merged transversely. The merged beams are then further accelerated and the growth in transverse and longitudinal emittance is determined for comparison with theory. The completed apparatus will be used to study problems associated with focusing ion beams to a small spot as required for heavy ion fusion. Details of the accelerator design and considerations of the physics of combining beams are presented.
Deflection of pulsed ion beams by toroidal magnetic fields
Authors: Kitamura Akira , Maebara Sunao , Yano Syukuro
Published: March 2009

The mechanism of deflection of pulsed annular ion beams by toroidal magnetic fields is investigated. It is found that the ions of the annular beam obey the single particle orbits in the toroidal field. The polarization electric field, which is measured with an electric double probe in the annular beam inside the toroidal field, is found to be smaller than 1/10 of the value necessary for the force cancelling. It is reasonably concluded that the short-circuiting occurs via the toroidal magnetic field lines of force that have some rotational transform resulting from the helical winding of the toroidal coil.
Power concentration of ion beam from high brightness part of PED
Authors: Matsukawa Y.
Published: March 2009

A conical-pinched electron-beam diode has been studied with the objective of increasing the brightness of this inherently high current ion beam. Experiments and calculations are described that suggest it may be possible to obtain powers as high as 1013W/cm2 at 4MV from a carefully designed insulated-anode-type pinched-electron beam diode.
Damage structures in Si3N4–Sic films and stainless steel irradiated by intense pulsed light-ion beam
Authors: Kamata Kiichiro , Yatsui Kiyoshi , Kanno Masayoshi , Aizawa Naoyoshi , Moriyamat Minoru
Published: March 2009

As the input power and energy content of Tokamaks are increased, the erosion rate of the first wall becomes larger, and a thick coating or cladding of low atomic number (Z) materials will be needed. Recently, the present authors prepared Si3N4–SiC films at alow temperature of 400°C by a plasma CVD method for the application to coating materials having high strength and wear resistance on metals and glasses. In this study, irradiation damage of the Si3N4–SiC films and 316 stainless steel (SUS-316) was investigated for the application to the first wall materials in a fusion reactor. The damage studies employed an intense pulsed light-ion beam (LIB) from the “ETIGO-I” device.
Directions for reactor target design based on the U.S. Heavy Ion Fusion Systems Assessment
Authors: Wilson D. C. , Dudziak D. , Magelssen G. , Zuckerman D. , Driemeyer D.
Published: March 2009

The Heavy-Ion Fusion Systems Assessment project is nearing completion of a two-year effort. The resulting system modelwill be used to set directions for future target design work.

Major uncertainties in target design were studied using thecost of electricity as a figure of merit. Net electric power was fixed at 1000 MW to eliminate large effects due to economies of scale. The system is relatively insensitive to target gain, factors of three changes in gain resulting in 8 to 12% changes in electricity cost. Possible increased peak power requirements pose only a small cost risk, but require many more beamlets for transport. A shortening ofthe required ion range causes both cost and beamlet difficulties. A factor of 4 decrease in the required range at a fixed driver energy increases electricity cost by 44% and raises the number of beamlets to 240. Finally, the heavy ion fusion system can accommodate large increases in target costs. Thus, to address the major uncertainties, target design should concentrate on requirements for ion range andpeak driver power.
Summary (I). Experiments
Authors: Vandevender J. Pace
Published: March 2009

The conference has shown some important advances toward the solution of problems required for inertial fusion. We can tentatively categorize as solved, or nearly solved, the following problems: Marx prefires, Marx jitter, gas-switch prefires, gas-switch jitter, power combination of multi-modules, high-current beam divergence (in barreltype, Applied-B/MID diodes), and preheat. In addition, there are a set of mature problems with promising solutions: pulsed power accelerator efficiency, ion sources, and the electron kinetics of an extractor ion diode. Newer problems that were addressed at the meeting but still require considerable work include: impedance control of efficient ion diodes, diagnostics for both beams and targets, the further development of target design tools and their experimental verification, targetfabrication processes to make the nearly perfect targets required for inertial fusion, channel formation and beam transport in those channels at the power levels required for fusion, and pulse-shaping.
Pseudospark ion diodes
Authors: Bauer W. , Brandelik A. , Citron A. , Ehrler H. , Halter E. , Melchior G. , Mittag K. , Rogner A. , Schultheiss C.
Published: March 2009

The Pseudospark is an axially symmetric, high-voltage gas discharge operating at pressures below 100 Pa. It is capable of producing pinched high current ion beams. Streak camera photographs of the operation of this discharge reveal that a pinch with a diameter of ∼1 mm occurs in the diode. The beam then expands to about 1 to 10 mm in a distance of 12 cm. The beam-target interaction shows a UV-emitting plasma corresponding to protons with a main energy of 100 keV and a current density of about 16 kA/cm2. Initial theoretical results for the pseudospark are given.
High-power microwave emission from a virtual cathode oscillator
Authors: Sze H. , Benford J. , Woo W.
Published: March 2009

Pinched electron beams emit high power microwaves by formation of a virtual cathode. Radiation occurs simultaneously with pinching or slightly thereafter. Observations of strong electrostatic fields and the partitioning of current into reflexing and transmitting populations at the same time that microwaves are emitted indicate virtual cathode formation. Microwaves originate mainly from the virtual cathode side of the anode. A two-dimensional model for the electron flow in the presence of a virtual cathode is presented. The model allows for electron reflexing and velocity distribution spread. Solutions with strong radial flow agree closely with microwave measurements, and result in the microwave frequency scaling linearly with diode current.
Production of pulsed sodium ion beams from anode plasma initiated by photon irradiation
Authors: Kitamura Akira , Mitsuhashi Ken'ichi , Yano Syukuro
Published: March 2009

Diode experiments that trigger the anode plasma formation by external radiation have been carried out with the goal of producing a pure beam of metallic ions. The anode of a race-track-type MID, which is coated with a sodium film in situ by vapor deposition, is synchronously irradiated by radiation emitted from a vacuum diode. Pure beams of Na+ are extracted only under operation with the radiation trigger. The current density reaches the Child–Langmuir limit.
Gas–puff Z pinches with strong axial magnetic fields
Authors: Felber F. S. , Wessel F. J. , Wild N. C. , Rahman H. U. , Fisher A. , Fowler C. M. , Liberman M. A. , Velikovich A. L.
Published: March 2009

Ultrahigh axial magnetic fields have been compressed and measured in a gas-puff Z pinch. A 0·5-MA, 2–cm-radius annular gas-puff Z pinch with a 3-minute repetition rate was imploded radially onto an axial seed field, causing the field to compress. Axial magnetic field compressions up to 180 and peak magnetic fields up to 1·6 MG were measured. Faraday rotation of an argon laser (515·4 nm) in a quartz fiber on axis was the principal magnetic field diagnostic. Other diagnostics included a nitrogen laser interferometer, x-ray diodes, and magnetic field probes.

The magnetic field compression results are consistent with simple snowplow and self-similar analytic models, which are presented. The axial magnetic fields strongly affect the Z pinch dynamics. Even small axial fields help stabilize the pinches, some of which exhibit several stable radial bounces during a current pulse.

The method of compressing axial fields in a gas-puff Z pinch is extrapolable to the order of 100 MG. Scaling laws are presented. Potential applications of ultrahigh axial fields in Z pinches are discussed for x-ray lasers, inertial confinement fusion, and collimated sources of gamma radiation.
High-density compression experiments at ILE, Osaka
Authors: Azechi H. , Jitsuno T. , Kanabe T. , Katayama M. , Mima K. , Miyanaga N. , Nakai M. , Nakai S. , Nakaishi H. , Nakatsuka M. , Nishiguchi A. , Norrays P. A. , Setsuhara Y. , Takagi M. , Yamanaka M. , Yamanaka C.
Published: March 2009

Direct-drive implosion experiments on the GEKKO XII laser (9 kJ, 0.5 μm, 2 ns) with deuterium and tritium (DT) exchanged plastic hollow shell targets demonstrated fuel areal densities (ρR) of ˜0.1 g/cm2 and fuel densities of ˜600 times liquid density at fuel temperatures of ˜0.3 keV. (The density and ρR values refer only to DT and do not include carbons in the plastic targets.) These values are to be compared with thermonuclear ignition conditions, i.e., fuel densities of 500–1000 times liquid density, fuel areal densities greater than 0.3 g/cm2, and fuel temperatures greater than 5 keV. The irradiation nonuniformity in these experiments was significantly reduced to a level of <5% in root mean square by introducing random-phase plates. The target irregularity was controlled to a 1% level. The fuel ρR was directly measured with the neutron activation of Si, which was originally compounded in the plastic targets. The fuel densities were estimated from the ρR values using the mass conservation relation, where the ablated mass was separately measured using the time-dependent X-ray emission from multilayer targets. Although the observed densities were in agreement with one-dimensional calculation results with convergence ratios of 25–30, the observed neutron yields were significantly lower than those of the calculations. This suggests the implosion uniformity is not sufficient to create a hot spark in which most neutrons should be generated.
Implosion symmetry and burn efficiency in ICF
Authors: Atzeni Stefano
Published: March 2009

The effect of long-wavelength irradiation nonuniformities on the performance of singleshell, reactor targets is investigated by means of 2-D numerical simulations. The stages of target collapse, hot-spot formation, ignition, and burn are illustrated. Evidence is shown for the occurrence of the Rayleigh–Taylor instability during target stagnation. It is then shown that the sensitivity of a given family of targets to the nonuniformities of the driving pressure critically depend on the 1–D ignition margin and on the spark convergence ratio of the target. The tolerable levels of nonuniformity as a function of the perturbation mode number are determined, for selected targets, by means of a parametric numerical study.
Investigations of pressure nonuniformity in laser-irradiated targets using incoherent optical smoothing
Authors: Williams I. R. G. , Rickard G. J. , Bell A. R.
Published: March 2009

From analytic models of the ablation process in laser-plasma experiments, as well as simulations with Fokker–Planck and Spitzer codes, we have identified a new effect, thermal inertia smoothing. This effect results in a smoother Fokker–Planck temporal and spatial variation of the ablation pressure than that for Spitzer, for the same applied timevarying laser intensity. It is therefore advantageous for incoherent optical smoothing schemes. This is especially true at early times in the laser pulse (≤100 ps).
Influence of ablation-to-critical surface distance upon Rayleigh–Taylor instability
Authors: Sanz J. , Estevez A.
Published: March 2009

The Rayleigh—Taylor instability is studied by means of a slab model and when slab thickness D is comparable to the ablation-to-critical surface distance. Under these conditions the perturbations originating at the ablation front reach the critical surface, and in order to determine the instability growth rate, we must impose boundary conditions at the corona. Stabilization occurs for perturbation wave numbers such that kD ˜ 10.
Laser interaction with a sharp-edged overdense plasma
Authors: Bonnaud Guy , Gibbon Paul , Kindel Joe , Williams Edward
Published: March 2009

Recent studies on short-pulse interaction with steep-density gradient plasmas (L/λ0) uncovered some new absorption mechanisms. One such process was proposed by Brunei (1987), in which a laser beam is obliquely incident on a perfectly conducting surface. During one half-cycle, electrons dragged from the surface into the vacuum region are returned to the plasma with velocities of the same order as that of the quiver electron velocity. We have reexamined this mechanism using a 1–D (Lagrangian) plasma model, but without Brunel's assumption that the electric field vanishes inside the plasma. Analytical and numerical calculations of electron trajectories and the self-consistent electric fields are presented and comparisons are made with 1–D particle-in-cell simulations.
Self-similar regimes of anisotropic collapses
Authors: Bergé L. , Pelletier G. , Pesme D.
Published: March 2009

The anisotropic wave collapses governed by the Zakharov equations or by the nonlinear Schrödinger equation are investigated by means of a transformation group exhibiting self-similar anisotropic solutions characterized by two contraction rates. We show the existence of two infinite sets of anisotropic self-similar collapses corresponding, respectively, to “pancake” (oblate) and “cigar” (oblong) shaped collapsing solutions. Both of these classes of anisotropic structures are furthermore shown to be bounded from below by two peculiar solutions whose validity extends from the subsonic to the supersonic regime (the so-called “trans-sonic” solutions) and from above by the standard isotropic solutions. Spatial profiles of trans-sonic anisotropic solutions are analytically derived.
Experimental simulation of hydrodynamic phenomena accompanying laser beam interactions in a gas
Authors: Barkhudarov E. M. , Midivishvili M. O. , Sokolov I. V. , Takatishvili M. I. , Terekhin V. E.
Published: March 2009

Cumulative effects in gases accompanying hydrodynamic motion due to powerful laser energy deposition deal with the problems of high-speed jet generation and plasma heating. In the present paper, on the basis of experimental simulation and theoretical analysis we investigate the behavior of a cumulative ring shock wave near the axis of symmetry. Such a shock wave arises after the energy deposition into the volume of a gas having the form of a thin torus.