bluuebunny/crossref_metadata_2025 huggingface dataset:
Gas, Dust and Plasma in Extragalactic Space
Authors: Arp Halton
Published: March 2009

On the average, intergalactic space contains a component of gas, dust, and plasma. The numerical density of this medium depends very strongly on what the actual distance is to objects of intermediate and high redshifts. The average density could be enormously higher than currently assumed. In addition, there is the problem of how the material outside the galaxies is distributed. X-ray emission observed in clouds exterior to galaxies as well as in diffuse backgrounds in clusters of galaxies also attest to the radiation of hot plasmas between galaxies. The sizes of these X-ray emitting regions scale with their distances.
The Hubble expansion as ascribed to mutual magnetic induction between neighboring galaxies
Authors: Bostick W. H.
Published: March 2009

A 32-year-old hypothesis of the formation of barred-spiral galaxies (Bostick 1957, 1958, 1986; Laurence, 1956) which become coherent-self-exciting homopolar generators has recently gained confirmative support from 3-D, particle-in-cell computer simulations (Nielsen et al. 1979; Buneman et al. 1980; Peratt et al. 1980, 1984, 1986). Such galaxies should be able to convert an appreciable fraction, f, of the energy from their gravitationally-collapsing plasmas to coherently-increasing magnetic energy via their coherent, self-exciting, homopolar-generator action. The following simple calculation shows that the resulting mutually-induced magnetic repulsions (Len's law) between neighboring galaxies is greater than the gravitational attractive forces between the galaxies. The observed expansion of the Universe can be thus simply accounted for without recourse to the ‘Big Bang’ hypothesis, with its unaccounted-for mysteries.
Laboratory and near-earth space plasma as a key to the plasma universe
Authors: Fälthammar Carl-Gunne
Published: March 2009

Experiments in the laboratory andin situmeasurements in space represent an essential, but often overlooked, key to reliable understanding of our plasma universe. This will be illustrated by discussing several fundamental aspects of matter in the plasma state. They include (1) conduction of electric current, (2) magnetic-field aligned electric fields, (3) acceleration of charged particles to high energy, (4) coupling between magnetic fields and the motion of matter, (5) rapid release of magnetically stored energy, (6) chemical separation, and (7) critical-velocity interaction between plasma and neutral gas.
A criticism of big bang cosmological models based on interpretation of the red shift
Authors: Kierein J. W.
Published: March 2009

The interaction of light with the intergalactic plasma produces the Hubble red shift versus distance relationship. This interaction also produces an isotopic long wavelength background radiation from the plasma. Intrinsic red shifts in quasars and other objects are similarly explained, showing why they are exceptions to Hubble's law. Because the red shift is not doppler-shifted, big bang cosmological models should be replaced with static models.
Plasma model of microwave background and primordial elements: an alternative to the big bang
Authors: Lerner Eric J.
Published: March 2009

A plasma model of the origin of the light elements and the microwave background is presented. In contrast to the conventional Big Bang hypothesis, the model assumes that helium, deuterium and the microwave background were all generated by massive stars in the early stages of galaxy formation. The microwave background is scattered and isotropized by multi-GeV electrons trapped in the jets emitted by active galactic nuclei. The model produces reasonable amounts of heavy elements, accurately predicts the gamma-ray background intensity and spectrum, and explains the statistics of quasars, compact and extended radio sources.
The stimulated emission of Bremsstrahlung in a fully ionized plasma
Authors: Thompson W. B.
Published: March 2009

The process of induced bremsstrahlung is studied and it is found that anisotropy in the electron distribution can lead to the amplification of radiation. The gain rate is ,Λ where ν is the electron-ion collision frequency, ωp and ω the plasma and radiation frequency, and Λ a numerical factor which is positive only for anisotropic distributions.
Quasi-static MHD processes in Earth's magnetosphere
Authors: Voigt Gerd-Hannes
Published: March 2009

The purpose of this paper is to demonstrate how the MHD equilibrium theory can be used to describe the global magnetic field configuration of Earth's magnetosphere and its time evolution under the influence of magnetospheric convection. The MHD equilibrium theory represents magneto-hydrodynamics in the slow-flow approximation. In this approximation time scales are long compared to typical Alfvén wave travel times, and plasma flow velocities are small compared to the Alfvén speed. Under those conditions, the inertial term ρ(dv/dt) in the MHD equation of motion is a small second order term which can be neglected. The MHD equilibrium theory is not a static theory, though, because time derivatives and flow velocities remain first order quantities in the continuity equation, in the thermodynamic equation of state, and in the induction equation. Therefore one can compute slowly time-dependent processes, such as magnetospheric convection, in terms of series of static equilibrium states. However, those series are not arbitrary; they are constrained by thermodynamic conditions according to which the magnetosphere evolves in time.

It is an interesting question, whether or not the magnetosphere, driven by slow, lossless, adiabatic, earthward convection of magnetotail flux tubes, can reach a steady state. There exist magnetospheric equilibria in which magnetotail flux tubes satisfy the steady-state condition d/dt (Pρ−γ) = 0. Those configurations exhibit a deep magnetic field minimum in the equatorial plane, near the inner edge of the tail plasma sheet. The magnetosphere becomes tearing-mode unstable in the neighborhood of such a minimum, thus leading to periodic onsets of substorms in the inner plasma sheet. This explains why distinct magnetic field minima have not been observed in this region. Magnetic substorms seem to be an inevitable element of the global convection cycle which inhibit the establishment of an ultimate steady state.

MHD equilibria discussed in this paper result from linear and non-linear solutions to the two-dimensional Grad-Shafranov equation for isotropic thermal plasma pressure.
X-ray spectrometer using a free-standing transmission grating and a microchannel plate as detector for laser plasma studies
Authors: Aleksandrov Yu. M. , Koshevoi M. O. , Murashova V. A. , Nikitina T. F. , Rupasov A. A. , Sklizkov G. V. , Shikanov A. S. , Yakimenko M. N. , Zakharenkov Yu. A. , Eidmann K. , Sigel R. , Tsakiris G. D.
Published: March 2009

We have developed a new soft x-ray spectrometer covering the photon energy range 50–500 eV. It employs a free-standing transmission grating coupled to a microchannelplate detector. The performance of the device was tested by using radiation from a synchrotron with a continuous spectrum. The detector shows a rather flat response over most of the useful spectral range, with an abrupt decrease in the sensitivity at the short-wavelength end. Its simplicity of operation makes the device attractive for such applications as the study of soft x-ray emission from laser-produced plasmas.
Dynamic process of the second harmonic emission in laser produced plasmas
Authors: Min Gu , Weihan Tan
Published: March 2009

In terms of energy conservation and vector matching relations, the dynamic process of the second harmonic emission from a laser plasma has been analyzed in this article for the first time. Then, considering the Langmuir wave spectrum which reflects the second harmonic spectrum, we derive the kinetic equation of the Langmuir wave. After a numerical Fourier analysis, the spectrum profiles are obtained, which coincide well with the experiments.
X-ray gain at 18·2 nm (CVI Balmer α) in laser-produced recombining carbon plasmas
Authors: Brunner W. , John R. , Schlegel Th.
Published: March 2009

Plasma heating by short laser pulses is investigated theoretically. Gain coefficients of 3… 4 cm−1 at the Balmer α transition in carbon could be obtained. The theoretical results agree with the corresponding experimental findings.
Dynamic superposition of laser fields for acceleration of ions and of electrons up to TeV/cm gain
Authors: Hora Heinrich
Published: March 2009

With the aim to provide more economic systems for acceleration of electrons, the possibilities of laser accelerators are discussed. The driving of electrons in laser wave fields in a longitudinal direction is based on nonlinear forces, which in simplified form cause the ponderomotion. Since the formulation of the Sessler theorem it is evident that optical signals moving with the speed of light in vacuum may not transfer energy to charged particles. A slowing down—even for a very minor difference only—does result in acceleration. Since the beat-wave accelerator using plasma led to numerous problems, a scheme is proposed that works without such dielectric effects by the superposition of laser wave fields in vacuum. Then the reduction of the signal velocity is performed by a controlled time dependence of the frequency with a phase or direction of at least one of the laser beams in interference.
Propagation of microsecond electron beams in gases and excimer laser-ionized channels in the ion-focused regime
Authors: Lucey R. F. , Gilgenbach R. M. , Tucker J. E. , Enloe C. L.
Published: March 2009

Experiments have been performed to investigate the transport and stability of microsecond-pulselength intense relativistic electron beams in the ‘ion-focused regime’ (IFR) in low-pressure neutral gas and laser-preionized channels. Beams have been generated by the Michigan Electron Long Beam Accelerator (MELBA) which operates with parameters: voltage = −0·7 to −1 MV electrically compensated for collapsing diode impedance over the first 1·5 μs, pulselength = 0·1 to 4μs limited by diode closure, and current = 0·2 to 30 kA.

Long pulse beam propagation experiments have demonstrated the following effects:

1) At pressures of 1–230 m Torr in air and helium with no laser-preionized channel:

a) the electron-beam transport efficiency peaks after times longer than the time calculated for beam-induced ionization to reach fe. = 1. Up to 100% efficient transport occurs during short spikes over a 1 m propagation distance.

b) Within 100 ns of efficient transport the propagated beam exhibits rapid beam cutoff in air and helium. This initial pulse of propagated current is followed by a series of 10 ns to 60 ns duration spikes for the remainder of the injected beam pulse. At higher gas pressures usually less current is propagated in the later peaks. At the lowest pressure for which significant current is propagated (7·6 m Torr air, 14 m Torr helium) the maximum transported current occurs in one of the later peaks.

2) In initial experiments with excimer-laser-ionized channels in diethylaniline at pressures of 3–8 × 10−4 Torr the electron-beam transport over 1·2 m is efficient (80% to 100%) for at least the first 0·5 μs and does not exhibit the erratic transport observed in the electron-beam induced channels. For fixed laser energy, a narrow pressure window exists for efficient and stable long pulse electron-beam transport. Pressures below optimal give inefficient transport while higher pressures cause ejection of the beam from the ionized channel at later times.
Filamentation instability of rotating light ion beam
Authors: Okada T. , Niu K.
Published: March 2009

Filamentation instability for a rotating light ion beam (LIB) fusion system is investigated. Stability conditions, including the effects of fractional current neutralization, rotation of LIB and beam temperature, are derived for propagation through a background plasma. The results are illustrated by plotting stability boundaries for a rotating proton beam propagating in a plasma.
Nonequilibrium emission from laser-generated target plasma
Authors: Bazylev B. N. , Borovik F. N. , Vergunova G. A. , Kaskova S. I. , Romanov G. S. , Rozanov V. B. , Stanchits L. K. , Stepanov K. L. , Teterev A. V.
Published: March 2009

Radiation characteristics of laser targets are studied in the soft X-ray region where photorecombination, bremsstrahlung and transitions in the discrete spectrum are the basic mechanisms of spectrum formation. The impact-radiational model is employed to describe the states of the laser target plasma. Characteristics obtained from the solution of the kinetic problem are used to compute absorption and emission coefficients. To set the time scale for a given field of gas-dynamic parameters, the transfer equation is solved and detailed information is obtained on the spectral composition of the outgoing radiation and its temporal evolution. Effective emission temperatures and radiation losses are determined. Integral radiation parameters are compared which have been derived from the solution of the transfer equation employing a volume luminescence approximation.
Numerical experiment for focus of rotating and propagating LIB in Plasma I—Quasi-neutral approximation
Authors: Aoki Takayuki , Niu Keishiro
Published: March 2009

Focusing processes of a rotating and propagating light ion beam in the drift region are studied numerically by using a 2-dimensional hybrid (particle–fluid) code. An intense ion beam with the current density of 8 kA/cm2 and the total current of 2·5 MA, which is extracted from the diode with the applied voltage of 5·6 MV, is injected into the drift region filled with a low-density plasma. When a radial magnetic field is applied to the neighborhood of entrance, the beam ions start to rotate in the azimuthal direction owing to the Lorentz force. When the pressure of the background plasma is chosen such as the density of the beam becomes comparable with that of the background plasma in the vicinity of the focal spot, the current-neutralization fraction decreases and large self-magnetic fields are induced. The beam is confined by the fields within a small radius, even after passing the focal spot. Because the angular momentum of the beam is conserved, the beam rotation velocity increases up to the same order of the propagation one at a few mm radius. This rotation motion induces the azimuthal magnetic field and stabilizes the beam propagation. In the case where the plasma pressure was 3·0 Torr and the 0·2-Tesla radial magnetic field was applied over the distance of 2·0 cm near the entrance, the maximum beam intensity of 108TW/cm2 in the axial direction was obtained and the half width at half maximum (HWHM) of the focused profile was 3·5 mm.
Rayleigh–Taylor instability in multi-structured inertial confinement fusion targets
Authors: Gupta N. K. , Lawande S. V.
Published: March 2009

A formalism for the analysis of the Rayleigh–Taylor instability in the multi-structured solid or shell targets is presented. The formulation covers both the plane and the curved geometry targets. A generalized eigenvalue equation for the exponential growth rate of the instability is derived along with the necessary boundary conditions. Analytical solutions for the growth rate are presented for some elementary density profiles and a comparative study is made between the plane, cylindrical and spherical targets. The solution for the step function density profile is generalized for any number Nof zones forming an arbitrary density profile. This general formulation is illustrated with the explicit calculations for N = 3 and 4. A qualitative treatment of the effects of the ablative flow is also presented. This study predicts a stabilizing effect of the ablative flow on the growth of the instability. Further, a dynamic analysis of the instability growth rate is presented for a representative inertial confinement fusion spherical solid target driven by the laser beams. This study demonstrates that an approximate analysis of the instability with the time independent initial density profile gives the conservative results for the instability growth rate.
Kinetic extraordinary-mode eigenvalue equation for relativistic nonneutral electron flow in planar geometry
Authors: Davidson Ronald C. , Uhm Han S.
Published: March 2009

Use is made of the Vlasov–Maxwell equations to derive an eigenvalue equation describing the extraordinary–mode stability properties of relativistic, non-neutral electron flow in high-voltage diodes. The analysis is based on well-established theoretical techniques developed in basic studies of the kinetic equilibrium and stability properties of nonneutral plasmas characterized by intense self fields. The formal eigenvalue equation is derived for extraordinary-mode flute perturbations in a planar diode. As a specific example, perturbations are considered about the choice of self-consistent Vlasov equilibrium , where . is the electron density at the cathode (x = 0), H is the energy, and Py is the canonical momentum in the Y-direction (the direction of the equilibrium electron flow). As a limiting case, the planar eigenvalue equation is further simplified for low-frequency long-wavelength perturbations with |ω − kvd, ≪ ωυ where and and ⋯c = eB0/mc, and B0ệz is the applied magnetic field in the vacuum region xb < x ≤ d. Here, the outer edge of the electron layer is located at x = xb; ω is complex oscillation frequency; k is the wavenumber in the y-direction; ωυ is the characteristic betatron frequency for oscillations in the x′-orbit about the equilibrium value x′ = x0 = xb/2; and Vd is the average electron flow velocity in the y-direction at x = x0. In simplifying the orbit integrals, a model is adopted in which the eigenfunction approximated by , where x′(t′) is the x′-orbit in the equilibrium field configuration. A detailed analysis of the resulting eigenvalue equation for , derived for low-frequency long-wavelength perturbations, is the subject of a companion paper.
Linear conversion theory on the second harmonic emission from a plasma filament
Authors: Weihan Tan , Min Gu
Published: March 2009

The linear conversion theory of laser produced plasma filaments is studied in this paper. By calculations for the energy flux of the second harmonic emission on the basis of the planar wave-plasma interaction model, it has been found that there exists no 2ω0 harmonic emission in the direction perpendicular to the incident laser, in contradiction with the experiments. Therefore, we have proposed a linear conversion theory on the second harmonic emission from a plasma filament and discovered the intense 2ω0 harmonic emission in the direction perpendicular to the incident laser, which is in agreement with the experiments.
Kinetic analysis of propagating ion beam with leading and trailing edges as ICF energy driver
Authors: Kaneda Takeshi , Niu Keishiro
Published: March 2009

Analysis is given for nonstationary propagation of rotating ion beam which has a finite length on the basis of Vlasov–Maxwell equations. The beam velocity distribution function is assumed to have a form of product of a modification function g which depends on time and axial coordinate multiplied by a steady solution fb0 which is a known function of particle velocity and radial coordinate. Unknown function g is solved as the solution of Vlasov equation through electromagnetic fields induced by leading and trailing edges. These electromagnetic fields can be solved from the Maxwell equations by using beam distribution function and motion of electrons in background plasma.
Coronal fluid-dynamics in laser fusion
Authors: Sanmartín Juan R.
Published: March 2009

The fluid-dynamics of the corona ejected by laser-fusion targets in the direct-drive approach (thermal radiation and atomic physics unimportant) is discussed. A two-fluid model involves inverse bremsstrahlung absorption, refraction, different ion and electron temperatures with energy exchange, different ion and electron velocities and magnetic field generation, and their effect on ion-electron friction and heat flux. Four dimensionless parameters determine coronal regimes for one-dimensional flows under uniform irradiation. One additional parameter is involved in two-dimensional problems, including the stability of one-dimensional flows, and the smoothing of non-uniform driving.
Hydrodynamics of layer-structured targets impinged by intense ion beams
Authors: Barrero A.
Published: March 2009

A model for the hydrodynamics of a layer-structured target impinged by an intense ion beam is presented. For some power law time pulses, the flow in the absorber region, which is entirely different from that in the tamper, becomes self-similar for planar geometries. Scaling laws for the ablation pressure and the implosion velocity have been obtained from the analysis.
Pusherless implosion, pulse tailoring and ignition scaling law for laser fusion
Authors: Mima K. , Takabe H. , Nakai S.
Published: March 2009

The conventional implosion scheme for high gain and high density compression depends upon the piston action of an accelerated heavy pusher. However, the contact surface between the pusher and the fuel layer is very unstable in the stagnation phase. In this paper, the laser pulse tailoring and the scaling laws for pellet gain, fuel ρR, etc. are discussed under the condition of very weak piston action of the pusher. The scaling laws indicate that the fuel will be ignited by 100 kJ, 0·35 μm wavelength laser irradiation.
Long Ion Mean-Free Path and Nonequilibrium Radiation Effects on High-Aspect-Ratio Laser-Driven Implosions
Authors: Yabe Takashi , Tanaka Kazuo A.
Published: March 2009

The implosion dynamics of experiments with high-aspect-ratio laser-driven targets are re-examined by taking account of long ion-mean-free paths. The mean-free path is found to be comparable to the fuel size and this can cause a significant departure from a fluid-like description. One of such effects stemming from the long ion-mean-free path; namely, real viscosity, seriously changes the results; the compression ratio becomes 5 times smaller with this real viscosity. In addition to this, inclusion of non-LTE (local thermodynamic equilibrium) atomic process is shown to critically determine the implosion dynamics because of bound-free opacity associated with a small fraction of hydrogen-like ions.
Time-resolved spectroscopic measurement of anode plasma in magnetically-insulated diode
Authors: Kawano Yasunori , Yumino Norihida , Masugata Katsumi , Yatsui Kiyoshi
Published: March 2009

A new diagnostic technique has been developed for the time-resolved spectroscopic measurement of anode plasma in a single-current-feed magnetically-insulated iondiode. From the measurement of Stark broadening of Hα line of hydrogen, we have estimated the electron density to be 4 ∼ 5 × 1016 cm−3 using the pulse-power generator, ‘ETIGO-I’, typically operated with diode voltage, 550 and 600 kV, diode current, 36 and 53 kA, and pulse width ∼ 90 ns (FWHM of diode current). Assuming local thermodynamic equilibrium, we have estimated the electron temperature to be l·9∼2·4eV from the measurement of light intensity ratio of successive ionization stages of carbon. The expansion velocity of the anode plasma has been found to be 4∼4·5cm/μS.
Two-dimensional focusing of self-magnetically insulated “Plasma Focus Diode”
Authors: Masugata Katsumi , Isobe Hironobu , Aga Keigo , Matsumoto Masami , Kawata Shigeo , Jiang Weihua , Yatsui Kiyoshi
Published: March 2009

A new and simple type of self-magnetically insulated, vacuum ion diode named “Plasma Focus Diode” has been successfully developed with a large solid angle of irradiation and low divergence angle. The diode has a pair of coaxial cylindrical electrodes similar to a Mather-type plasma focus device. Ion-current density of 1·9 kA/cm2 has been obtained on the anode surface under the experimental conditions of diode voltage ∼1·4 MV, diode current ∼180 kA, and pulse width ∼75 ns. The generated ion beam has been two-dimensionally focused (line focusing) with a focusing radius of ∼0·18 mm, giving a maximum ion current density and beam power density at the axis of ∼0·14 MA/cm2 and ∼0·18 TW/cm2, respectively. The motion of electrons in the gap has been numerically simulated by use of a newly developed particle-in-cell computer simulation code, and good agreement has been obtained between the simulation and the experiment.
Simulation code for ICF including radiative energy transfer
Authors: Velarde G. , Aragonés J. M. , Honrubia J. J. , Martínez-Val J. M. , Mínguez E. , Ocaña J. L. , Perlado J. M.
Published: March 2009

New improvements in the atomic physics models for numerically treating high density plasmas, typical of ICF, together with new algorithms for multigroup radiation transport are presented.

The performance of Large High Aspect Ratio Targets has been numerically determined by using those models implemented in a one-dimensional hydro code. Some differences from experiments are identified, and a comparative analysis with other numerical codes is given.
On electron acceleration by plane transverse electromagnetic pulses in vacuum
Authors: Scheid Werner , Hora Heinrich
Published: March 2009

The longitudinal acceleration of electrons by the transverse electromagnetic field of laser pulses of definite shapes is studied. It is shown that already a pulse of the length of a half wavelength from a CO2 laser is sufficient to accelerate an electron to energies up to the order of TeV if intensities of 1022 W/cm2 are applied. Various aspects of the electron acceleration by this method are discussed.
Pellet and implosion scaling
Authors: Nakai S.
Published: March 2009

Recent progress of pellet implosion research is remarkable in the obtainment of a high density (100 times solid density) and a high temperature plasma (which produces thermonuclear neutrons of 1013 per shot or a pellet gain of 0·2%) and in the corresponding understanding of the implosion physics. The data bases for laser fusion have been accumulated in preparation for a fusion ignition experiment and the achievement of break-even condition, which is estimated to be possible with 100 kJ blue laser.

The recent progress of driver technology, such as new types of solid state lasers, excimer laser, light ion beam (LIB), heavy ion beam (HIB) and free electron laser, now enabled us to design a high pellet gain experiment with a MJ driver.
A 5.107-A/kg dose rate compact X-ray generator
Authors: Filatov A. L. , Kotov Yu. A. , Mesyats G. A. , Sokovnin S. Yu.
Published: March 2009

A wide applicaton of high-power braking x-radiation and electron beams is obstructed at present by the absence of compact, screened, inexpensive and reliable generators capable of producing an electron energy of ∼1·5 MeV and a dose rate to objects a few centimeters in size of ∼107 A/kg. This paper presents results from experiments carried out on an X-ray generator with an accelerating voltage of up to 1·8 MV, which meets the above requirements in performance.
HgBr (B–X) formation due to collisions involving O+/ and HgBr2 at kinetic energies (lab.) above 100 eV
Authors: Mahmood Mohammad F.
Published: March 2009

The emission spectra of HgBr (B–X) band system and atomic mercury lines have been observed during collisions involving O+/ and HgBr2 in the kinetic energy (lab.) range of 100–1000 eV.
Experimental and theoretical works performed by the Institute of Physics and Power Engineering on the physics of nuclear-induced plasmas
Authors: Dyachenko P.P.
Published: March 2009

In review, general results obtained by Institute of Physics and Power Engineering (IPPE) during 1981–1992 are presented in the field of physics of nuclear-induced plasmas in the following directions: processes of primary ionization of different media by nuclear reaction products; function of electron distribution in nuclear-induced plasmas; processes of excitation and relaxation; track structure of nuclear-induced plasmas. Prospects of study progress are discussed with a view to improve the current concepts of physics of elementary processes occurring in nuclear-induced plasmas and obtain experimental and theoretical data on process constants needed to calculate the nuclear-pumped lasers.
Ultimate efficiency of nuclear-pumped gas lasers
Authors: Melnikov Sergei P. , Sinyanskii Anatolii A.
Published: March 2009

We suggest several cascade lasing schemes: (1) cascade of laser transitions between atom (ion) excited levels when the lower laser level of one laser transition is simultaneously the upper laser level of another transition located below; (2) successive lasing, first, on ion transitions, then after ion recombination on atom transitions; (3) while using multicomponent mixtures, successive lasing on atoms (ions) of separate components. These possibilities are discussed in terms of specific lasers, some of which have been studied experimentally.
Kinetics of the active media of nuclear-pumped lasers
Authors: Boichenko A.M. , Karelin A.V. , Sereda O.V. , Yakovlenko S.I.
Published: March 2009

Numerical simulation of active media nuclear-pumped lasers on noble gases and their mixtures with metal vapors are presented. Prospects of creation of high-power short-wavelength nuclear-pumped excimer lasers are discussed.
Plane electromagnetic waves in heterogeneous medium under approximation regarding relative rate of change of wave resistance
Authors: Tsapenko Nikolai E.
Published: March 2009

In this article, we derived new formulas for approximate representation of components of a plane electromagnetic wave in heterogeneous medium that has parameters changing along some fixed direction in an arbitrary manner. The formulas differ from ordinary WKB approximation by factors regarding relative rate of medium characteristics change and give solutions remaining continuous at turning points. Conditions of full opaque and of no reflectionbased on the solution are obtained.
Resonance line reabsorption in a laser-produced plasma showing specific deviations from axial symmetry
Authors: John R.W. , Brunner W.
Published: March 2009

To predict the gain in a lasing transition in ions of a laser-produced plasma, it is essential to calculate the amount of the reabsorption of radiation emitted in the transition from the lower laser level to the ground state. An important quantity influencing the reabsorption is the plasma geometry as resulting from the design of the laser and target system. Modeling a nonaxially symmetrical geometry of the plasma arising from a target irradiated by line-focused laser beams, we consider the plasma in the form of a longitudinally cut-out circular cylinder, with central angle ø, and the length of the plasma much larger than its transversal extension. Accounting for the effect of resonance line trapping via the escape probability approach, and taking the absorption profile in the line center approximation, an explicit formula for the photon escape probability depending on the radial and angular coordinates of an interior point in the plasma is derived. This function is averaged over the angular variable to obtain an only radially varying mean escape probability.
Application of high-power ion beams for technology
Authors: Remnev G.E. , Shulov V.A.
Published: March 2009

Industrial applications of high-power ion beams, basically in the field of material engineering, are presented. The results of experimental investigations of some kinds of applications, such as ion implantation, metal modification, and compounds production of thin films, are considered.
Sound waves and shock waves in high-density deuterium
Authors: Inoue Kazuko , Ariyasu Tomio
Published: March 2009

The possibility of compressing the cryogenic hollow pellet of inertial confinement nuclear fusion with multiple adiabatic shock waves is discussed, on the basis of the estimation of the properties of a high-density deuterium plasma (1024−1027 cm−3, 10−1−104 eV), such as the velocity and the attenuation constant of the adiabatic sound wave, the width of the shock wave, and the surface tension.

It is found that in the course of compression the wavelength of the adiabatic sound wave and the width of the weak shock wave sometimes become comparable to or exceed the fuel shell width of the pellet, and that the surface tension is negative. These results show that it is rather difficult to compress stably the hollow pellet with successive weak shock waves.
RFQ final-focusing lens at the GSI
Authors: Heimrich B. , Laue H. J. , Wollnik H.
Published: March 2009

For first investigations of hot dense matter produced by intense heavy-ion beams we built an electrostatic quadrupole doublet that focused Ar+and Kr+ ions of 45 keV/amu after acceleration through the radio frequency quadrupole (RFQ) accelerator at the GSI onto a small spot of approximate area 1 mm2. This beam then deposited a specific beam power of about 1.5 GW/g to targets.
Numerical method for finding uniform irradiation conditions of a fusion capsule driven by X-ray radiation
Authors: Nakamura M. , Kondo K. , Nishimura H. , Endo T. , Shiraga H. , Miyamoto S. , Kato Y. , Nakai S.
Published: March 2009

A three-dimensional model to calculate X-ray intensity distribution on an indirectly driven fusion target is presented. The model includes conversion of laser light into X rays, radiation reemission from X-ray-heated wall of a cavity, and influence of an inner pellet (i.e., a fuel capsule) on radiation redistribution. Intensity distribution of an X ray inside a cylindrical cavity heated by intense blue laser light (wavelength 351 nm, energy 5.2 kJ, duration 0.7 ns) was determined by measuring a burn-through signal from a diagnostic foil integrated onto the cavity. The experimental result is well replicated by the model calculation. By using this model, optimum conditions for uniform irradiation of afusion capsule by X-ray radiation are evaluated for use in Gekko XII laser fusion experiments.
Differential measurement of the absolute ion yield from laser-produced C plasmas
Authors: Mann K. , Rohr K.
Published: March 2009

The ion flux produced by an obliquely incident Nd Q-switch pulse on a graphite target has been analyzed with regard to its kinetic energy, charge, and angular distribution. The laser intensity has been varied in a range between 109–5·1010 W/cm2, appropriate for many low-irradiance applications. It is observed that for ions of charge state n the emission cone of the number of ions scales with cos2n+1. The angular emission probability of the kinetic energy of the individual ions is found to be independent of their charge and scales as a cosine function. Due to the asymmetrical heating of the expanding plasma by the obliquely incident laser pulse, the maximum of emission is rotated away from the target normal toward the incoming laser, depending upon the ion's charge and the laser energy. The measured kinetic energy spectra are determined by the recombination during the plasma expansion: There are no low-energetic highly charged ions and no high-energetic lowly chargedions. If the laser energy (intensity) is enhanced, it is observed that the additional heating essentially serves only to increase the velocity of the higher charged ions; the energy of the individual singly charged ions is not altered.
Fokker-Planck simulations of ultrashort-pulse laser-plasma interactions
Authors: Drska L. , Limpouch J. , Liska R.
Published: March 2009

The interaction of ultrashort laser pulses with a fully ionized plasma is investigated in the plane geometry by means of numerical simulation. The impact of the space oscillations in the amplitude of the laser electric field on the shape of the electron distribution function, on laser beam absorption, and on electron heat transport is demonstrated. Oscillations in the absorption rate of laser radiation with the minima coincident to the maxima of the laser electric field lead to a further decrease in the absorption of laser radiation. Heat flux in the direction of increasing temperature in the underdense region is caused by the modification of the electron distribution function and by the density gradient. A limitation of heat flux to the overdense plasma isobserved with the flux limiter in range 0.03–0.08, growing moderately with the intensity 1014–1016 W/cm2 of the incident 1.2-ps laser pulse.
Possibility of amplification of a femtosecond pulse up to he energy 1 kJ
Authors: Mikheev L. D.
Published: March 2009

Optically excited active medium at XeF(A)transition(λ = 481 nm) is considered from the viewpoint of its possible application in ultrashort (down to 10 fs) light pulses amplification due to the extremely wide amplification band of the transition. Photolytical pumping of XeF(C–A)by pulsed discharge or shock wave radiation allows one to amplify light beams with the cross-section at least upto ∼1 m2. Taking into account strong bulk and surface nonlinear effects at high-power density, it seemsfeasible to get the output energy up to ∼ 1 kJ and the power density in the focal spot up to 1023 W/cm2. Consideration of spatial-time distributionof the excited XeF(C) molecules, formed in the XeF;2 photodissociation wave under the action of powerful optical pumping, shows a possibility in principle to design multipass amplifiers with the inversion running wave, which are intended for the amplification of ultrashort pulsesup to the energies noted above.
Nonlinear theory of ion stopping in classical plasmas: Application to the Barkas effect
Authors: Sayasov Yu. S.
Published: March 2009

A nonlinear theory of ion stopping in classical ideal plasmas is formulated on the basis of formalism of higher-order dielectric functions accounting for nonlinear relationship between polarisation and electric fields generated in plasma by the projectile ion. Corrections to the linear theory corresponding to the Barkas effect are evaluated explicitly. The result differs (what concerns the numerical coefficient) from that following from the harmonic oscillator model.
Simulations of longitudinal instabilities in ion induction linear accelerators
Authors: Humphries Stanley
Published: March 2009

This article describes computer simulations of a longitudinal instability that affects induction linear accelerators for high-power ion beams. The instability is driven by axial bunching of ions when they interact with acceleration gaps connected to input transmission lines. The process is similar to the longitudinal resistive wall instability in continuous systems. Although bunching instabilities do not appear in existing induction linear accelerators for electrons, they may be important for proposed ion accelerators for heavy ion fusion. The simulation code is a particle-in-cell model that describes a drifting beam crossing discrete acceleration gaps with a self-consistent calculation of axial space charge forces. In present studies with periodic boundaries, the model predicts values for quantities such as the stabilizing axial velocity spread that are in good agreement with analytic theories. The simulations describe the nonlinear growth of the instability and its saturation with increased axial emittance. They show that an initially cold beam is subject to a severe disruption that drives the emittance well above the stabilized saturation levels. The simulation results confirm that axial space charge forces do not reduce axial beam bunching. In fact, space charge effects increase the axial velocity spread required for stability. With simple resistive driving circuits, the model predicts velocity spreads that are too high for heavy ion fusion applications. Several processes currently under study may mitigate this result, including advanced pulsed power switching methods, enhanced gap capacitance, and an energy spread impressed between individual beams of a multibeam transport system.
Bandwidth effects on laser–plasma interaction with a ¼-μm laser
Authors: Yoneda H. , Miura T. , Yokota Y. , Motoki Y. , Sasaki A. , Ueda K. , Takuma H.
Published: March 2009

Bandwidth effects on laser-plasma interaction were investigated with a ¼-μm laser. Planar targets were irradiated with a 1- to 40-cm–1 bandwidth laser at I = 1 × 1013–4 × 1015 W/cm2. Above 3 × 1013 W/cm2, stimulated Brillouin scattering (SBS) was observed with 1 cm–1 light. This process was strongly reduced with a 40-cm–1 light. Evolution of the convective SBS was studied with 1-D fluid simulation code. Bandwidth effect on the SBS growth was discussed to compare the theoretical prediction and experimental results. The scalelength dependence exists for the SBS reduction with a broadband laser.
Diamond photovoltaic cells as a first-wall material and energy conversion system for inertial confinement fusion
Authors: Prelas Mark A. , Charlson Earl J. , Charlson Elaine M. , Meese J.M. , Popovici Galina , Stacy Tina
Published: March 2009

Diamond film technology has advanced to the point where electronic devices are now becoming feasible. In addition, diamond has outstanding mechanical properties. The energy given off in fusion reactions may be converted to a narrow-band light spectrum that can be absorbed by wide-bandgap photovoltaic cells to directly produce electricity. The properties of possible wide-bandgap photovoltaic cells are examined for the purpose of fusion energy conversion.
Radiation-driven cannonball targets for high-convergence implosions
Authors: Nishimura H. , Shiraga H. , Endo T. , Takabe H. , Katayama M. , Oshikane Y. , Nakamura M. , Kato Y. , Nakai S.
Published: March 2009

In the last few years, systematic studies on radiation hydrodynamics in the X-ray confining cavity and a fuel capsule have attained remarkable progress. This makes it possible to analyze quantitatively the energy transfer processes from laser to the fusion capsule and find uniform irradiation conditions of the fusion capsule driven by thermal X rays. As a result, reproducible and stable implosions were achieved. Throughout implosion experiments with the Gekko XII blue laser system (351 nm, kJ, 0.8 ns), good agreement of implosion has been obtained between the experiment and numerical simulations, assuming perfectly spherical symmetry, up to a radial convergence ratio of 15. Described are particularly the issues of (1) energy transfer processes from laser to a fuel capsule and conditions for uniform irradiation, (2) properties of the X-ray propagation through aluminum heated by X-ray radiation, and (3) dependence of the convergence ratio ofRi/Rf(whereRiandRfare the initial and final radii) of the capsule on the initial fill pressure ofD–Tgas and its influence on the core parameters and fusion products to evaluate implosion sphericity.
Simplified model for designing large KrF amplifiers
Authors: Sullivan J. A.
Published: March 2009

A simplified model for determining the performance of large krypton-fluoride laser amplifiers is presented. The model includes a straightforward treatment of the controlling kinetics, an exact solution for energy extraction, and an approximation to amplified spontaneous emission losses; it can be easily programmed to run on personal computers. The inclusion of the controlling basic physics for KrF lasers makes the model ideally suited for the many calculations that are necessary to optimize the design of a specific amplifier. The basic parameters determined in the model are compared to experimental data wherever possible, and the large amplifier performance predictions are compared to the results from the most sophisticated kinetics and a 3-D extraction model that includes a full treatment of losses due to amplified spontaneous emission.
Electron beam control using experimentally measured transport matrices
Authors: McKee C.B. , Madey John M.J.
Published: March 2009

Free electron lasers (FELs) place very stringent requirements on the quality of electron beams. Present techniques for commissioning and operating electron accelerators may not be optimized to produce the high brightness beams needed. Therefore, it is proposed to minimize the beamline errors in electron accelerator transport systems by minimizing the deviations between the experimentally measured and design transport matrices of each beamline section. The transport matrix for each section is measured using evoked responses. In addition, the transverse phase space of the beam is reconstructed by measuring the spatial distribution of the electrons at a number of different betatron phases and applying tomographic techniques developed for medical imaging.
LISP: Laser impulse space propulsion
Authors: Phipps C.R. , Michaelis M.M.
Published: March 2009

It is not often that a new form of transportation suddenly appears and replaces what was hitherto regarded as mankind's only realistic option. In space and upper atmosphere transportation, chemical rockets have held center stage for over half a century. Tsiokolvsky's ideas led to Wernher von Braun's V2, which in turn led to the Soyuz, Apollo, and Ariane programs and the Space Shuttle. But recently theoretical and computational studies as well as a few initial experiments have pointed to a new option: laser impulse space propulsion (LISP). This may offer a more efficient and less ecologically damaging means of putting payloads into orbit. The world high-power laser community is well suited to following and aiding developments in LISP, though most practical research is still at an embryonic level. Obviously an effort of the size required to develop a laser-driven low-earth-orbit (LEO) launcher would require a multinational commitment. LISP could then be regarded as a parallel challenge to those of achieving ICF rriicrofusion yield and of improving X-ray lasers, especially in the “water window.” Any physicist or engineer involved with the latter projects would find many points in common with the former. It therefore seems appropriate to briefly review the progress made in LISP and also to communicate some recent results from high-power laser-matter experiments that have lead to conceptual designs.
Fokker–Planck simulations of interactions of femtosecond laser pulses with dense plasmas
Authors: Limpouch J. , Drska L. , Liska R.
Published: March 2009

The interaction of femtosecond laser pulses with solid-state density plasmas in regime of normal skin effect is investigated by means of numerical simulation. For short-wavelength lasers and laser pulses with length ≲ 120 fs full width at half maximum, the regime of normal skin effect is shown to hold for peak intensities up to 1017 W/cm2. The basic characteristics of the interaction are revealed and certain departures from simplistic models in electron distribution function, in plasma dielectric constant, and in laser absorption are pointed out. Comparison with the published experimental results is made.
The gamma-ray laser—status and issues in 1988
Authors: Collins C. B. , Anderson J. A. , Davanloo F. , Eberhard C. D. , Carroll J. J. , Coogan J. J. , Byrd M. J.
Published: March 2009

Efforts to demonstrate the feasibility of a gamma-ray laser scored major advances in 1987. Culminating with the successes in optically pumping the first of the 29 actual candidate isomers, priority issues were brought into better focus by the lessons learned from a wealth of new results. Perceptions were advanced so greatly that we must reassess the critical issues for 1988. Only the bottom line remains the same. A gamma-ray laser is feasible if the right combination of energy levels occurs in some real material. The likelihood of this favorable arrangement has been markedly increased by the experimental results to date.
Creation of X-ray laser media by high power laser heating of capillary discharge
Authors: Zigler A. , Lee R. W. , Mrowka S.
Published: March 2009

A large, high density, high temperature plasma has been produced by using a high power laser with a capillary electrical discharge. The laser beam is synchronized with the discharge to reach the plasma after it emerges several hundred microns from the capillary.