bluuebunny/crossref_metadata_2025 huggingface dataset:
Ponderomotive force effect on plasma density profile in the underdense region
Authors: Singh D. P. , Vaselli M. , Singh R.
Published: March 2009

The flux transport effect on the radiation-induced plasma density profile and ablative flow outside the resonance layer in steady state in one dimensional spherical geometry studied. The numerical predictions conclude the existence of plateau-like plasma density profile rather than overdense bump formation in the underdense plasma. The plasma density profile, though retaining its shape, becomes more pronounced as the heat flux is increased. However, the length of the plasma density plateau is found to be quite small when compared with the isothermal case.
The peculiarities of laser cryogenic target destruction and their injection into a powerful laser focus
Authors: Koresheva E. R. , Merculiev Yu. A. , Nikitenco A. I. , Osipov I. E. , Tolokonnikov S. M.
Published: March 2009

The formation conditions of a cryogenic target with a quality fusion cryolayer were found. The special device for the injection of the cryotarget into the ICF focus was devised.
Analysis of atomic models for the extinction coefficient calculation
Authors: Mínguez E. , Serrano J. F. , Gámez M. L.
Published: March 2009

The quantitative analysis of the collisional line broadening and the ionization state distributions for determining optical properties of aluminum plasmas are the main goal of this paper. In a preliminary analysis, results from an average atom model are compared with those from detailed configurations, assuming LTE conditions. The sensitivity to these physical aspects in the extinction coefficient and in the Rosseland and Planck mean opacities are carefully studied.
Gain and radiation trapping in laser-produced plasmas
Authors: Brunner W. , Schlegel Th.
Published: March 2009

The spatial and temporal behaviour of the X-ray gain in laser-produced plasmas is investigated theoretically. Hydrodynamical 1–D simulations of plasma heating and expansion for different laser parameters are combined with calculations of the corresponding density distributions for the ionic states in the plasma. The interesting energy level populations in hydrogen-like ions are found with radiation reabsorption taken into account. Results will be presented for cylindrical C and Al targets for the 3→2 (C) and 4→3 (C, Al) transitions. It is shown that the reabsorption of the Lα-line reduces the value of the gain for the 3→2 transition and modifies its spatial and temporal distribution.
Raman and Brillouin scattering in the filaments in laser-irradiated plasma
Authors: Tan Weihan , Liu C. S.
Published: March 2009

In this paper we generalize the filament study to include the Raman side scattering by solving the coupling equations of an electron plasma wave and a side-scattering electromagnetic wave. We also give an explanation of the physical phenomenon observed in the Raman-scattering experiments.
Scaling laws for pressure, temperature, and ionization with two-temperature equation-of-state effects in laser-produced plasmas
Authors: Szichman H. , Eliezer S.
Published: March 2009

A two-temperature equation of state (EOS) for a plasma medium was developed. The cold-electron temperature is taken from semiempirical calculations, while the thermal contribution of the electrons is calculated from the Thomas–Fermi–Dirac model. The ion EOS is obtained by the Gruneisen–Debye solid–gas interpolation method. These EOS are well behaved and are smoothed over the whole temperature and density regions, so that the thermodynamical derivatives are also well behaved. Moreover, these EOS were used to calculate the average ionization 〈Z〉 and 〈Z2〉 of the plasma medium. Furthermore, the thermal conductivities have been calculated with the use of an extrapolation between the conductivities in the solid and plasma (Spitzer) states. The two-temperature EOS, the average ionization 〈Z〉 and 〈Z2〉, and the thermal conductivities for electrons and ions were introduced into a two-fluid hydrodynamic code to calculate the laser-plasma interaction in carbon, aluminum, copper, and gold slab targets. It was found that the two EOS are important mainly from the ablation surface outward (toward the laser). In particular, the creation of cavitons in the distribution of the electrons is predicted here, especially for light materials such as aluminum. These studies enable us also to establish that the commonly used exponential scaling laws of the type Pa = A[I/(1014 W/cm2)]α for the ablation pressure and similar laws for the temperature are valid only for absorbed laser intensities in the range 3 × 1012-3 × 1014 W/cm2, while the degree of ionization (at the corona) follows a quite different scaling law. We also found that the parameters A and α. in the above expression are dependent on material, laser wavelength, and pulse shape. Thus we determined for the ablation pressure, using a trapezoidal Nd laser pulse, that α varies between 0.78 and 0.84 and that A varies between 14 and 8 Mbar for 6 ≤ Z ≤ 79. Beyond the range of validity the scaling laws may give values at least twice as large as those obtained by the simulation.
Simultaneous stimulated Raman forward and backward scattering in hot, well-underdense plasmas
Authors: Karttunen S. J. , Salomaa R. R. E.
Published: March 2009

The competition of stimulated Raman forward scattering and backscattering in a hightemperature, underdense, nearly homogeneous plasma slab is investigated. In such plasmas Landau damping limits the growth of the Raman backscattering, and the weaker forward process may reach comparable levels. A modest seeding of one of the scattered electromagnetic waves influences the competition to a large extent. The conversion of the pump wave to scattered waves is calculated. The simultaneous operation of the two processes can lead to considerable modifications in the electron distribution; e.g., two hot tail components are formed because the plasma waves involved have different phase velocities. The generation regions of the scattering processes are spatially separated. Consequently, a large number of thermal electrons can be accelerated to very high energies in two stages. The backward plasmons preaccelerate the electrons and the faster plasmons, excited in the forward scattering, operate as a booster.
Scaling model for high-aspect-ratio microballoon direct-drive implosions at short laser wavelengths
Authors: Schirmann Daniel , Juraszek Denis , Lane Stephen M. , Campbell E. Michael
Published: March 2009

A scaling model for hot spherical ablative implosions in direct-drive mode is presented. The model results have been compared with experiments from LLE, ILE, and LLNL. Reduction of the neutron yield due to illumination nonuniformities is taken into account by the assumption that the neutron emission is cut off when the gas shock wave reflected off the center meets the incoming pusher, i.e., at a time when the probability of shell breakup is greatly enhanced. The main advantage of this semiempirical scaling model is that it elucidates the principal features of these simple implosions and permits one to estimate very quickly the performance of a high-aspect-ratio direct-drive target illuminated by short-wavelength laser light.
Semiclassical study of the muon transfer process between hydrogen isotopes in strong electromagnetic fields
Authors: Henis Z. , Eliezer S.
Published: March 2009

The possibility of enhancement of the muon transfer process between hydrogen isotopes in the field of an intense electromagnetic wave is discussed. The muon transfer cross section between the ground states of deuterium and tritium under laser irradiation is calculated from a semiclassical model. It is shown in this case that the muon transfer cross section is hardly affected, even at the very large laser intensities of the order of 1016 W/cm2.
Volume ignition of inertial confinement fusion of deuterium-helium(3) and hydrogen-boron(ll) clean fusion fuel
Authors: Pieruschka P. , Cicchitelli L. , Khoda-Bakhsh R. , Kuhn E. , Miley G. H. , Hora H.
Published: March 2009

Since DT laser fusion with 10-MJ laser pulses for 1000-MJ output now offers the physics solution for an economical fusion energy reactor, the conditions are evaluated assuming that controlled ICF reactions will become possible in the future using clean nuclear fusion fuel such as deuterium-helium(3) or hydrogen-boron(11). Using the transparent physics mechanisms of volume ignition of the fuel capsules, we show that the volume ignition for strong reduction of the optimum initial temperature can be reached for both types of fuels if a compression about 100 times higher than those in present-day laser compression experiments is attained in the future. Helium(3) laser-pulse energies are then in the same range as for DT, but ten times higher energies will be required for hydrogenboron(11).
Preheating of heavy-ion-beam targets by secondary particles
Authors: Basko M. M.
Published: March 2009

The contribution of different sorts of secondary particles to the preheating of thermonuclear targets driven by heavy-ion beams is analyzed. Two types of illumination geometry are considered: side-on and face-on locations of the fuel with respect to the ion beam. It is shown that a substantial preheating can be expected from (1) nuclear fission fragments for the face-on fuel position and (2) δ-electrons and low-Z nuclear fragments for the side-on fuel location. All the X-ray and gamma photons of various origin are shown to produce a negligible fuel heating.
Multimode flux-limited diffusion theory
Authors: Pomraning G. C.
Published: March 2009

We present a diffusion approximation describing the flow of thermal radiation that preserves several important features of the underlying equation of radiative transfer. Specifically, this diffusion description: (1) is flux limited; (2) reduces to the correct transport weak gradient limit; (3) allows correct and simultaneous exponential growth and Decay for a certain class of problems; (4) gives correct transport results for certain contiguous half-space problems; and (5) allows the radiative flux and the gradient of the radiation energy density to point in independent directions. This treatment extends and generalizes earlier flux-limited diffusion approximations that are widely used in radiation–hydrodynamics calculations.
Development of dye lasers with bleaching wave
Authors: Stoilov Yu. Yu. , Logunov O. A. , Nikolaenko D. A. , Startsev A. V.
Published: March 2009

Dye lasers with bleaching wave (LBW) are the first condensed state lasers where the restriction on energy and duration of optical exciting pulses are practically removed. This gives an opportunity to create tunable lasers in the visible range with average powers significantly higher than that of any available laser of this type. Physical principles and current experimental results along with prospects of future LBW development are presented.
Radiochemistry measurements on the Phebus laser
Authors: Schirmann D. , Bayer C. , Garçonnet J. P. , Juraszek D. , Bertin A. , Grenier G.
Published: March 2009

We are developing neutron diagnostics to characterize the implosions performed with the Phebus laser, operating at 5 kJ blue light delivered in 1·3 ns. For measuring the glass pusher areal density, (ρΔR), of the target, a silicon radiochemistry diagnostic has been implemented and is currently being used. We describe the diagnostic and its performance. Pusher areal density measurements, (ρΔR) and calculated values of fuel density are given. Deuterium (D)-tritium (T) final densities as high as 100 × D-T liquid density (20 g/cm3) have been achieved.
Forward second harmonic emission from laser plasma filaments
Authors: Deha I. , Biancalana V. , Bianconi F. , Borghesi M. , Chessa P. , Giulietti A. , Giulietti D. , Gizzi L. A. , Nocera L. , Schifano E.
Published: March 2009

Experimental observations are reported on the interaction of 1-μm laser light with underdense plasmas (n ≤ 0·25 nc) from thin foil plastic targets. Nominal laser intensity on target was up to 3 × 1013 W/cm2 in a 3-ns pulse, but much higher intensity was reached due to spiky laser pulses. We studied forward-emitted second harmonic light as a diagnostic of the interaction and in particular of the occurrence of filamentation. Measurements included: energy monitoring of 2ω forward emission vs. target position and laser energy; time resolved (120-ps gate) imaging of the interaction region cross section. The second harmonic energy level was found to be sensitive to target position. In addition, the images obtained with the target in position of maximum second harmonic generation showed unstable structures whose scale length is comparable with the expected one for maximum filamentation growth. These results are shortly discussed in the framework of stationary filamentation theory and second harmonic generation in inhomogeneous media.
Analysis of atomic physics models for gold plasmas in local thermodynamic equilibrium
Authors: Mínguez E. , Falquina R.
Published: March 2009

In previous works, we developed several atomic physics models for calculating opacities for low-Z materials. In this work, we used those models for obtaining opacities for Au plasmas in local thermodynamic equilibrium. In this particular case, a great number of configurations must be considered for a full treatment of atoms at plasma conditions. Thus, we included several changes in the aforementioned models, which are extensively reported here.
Comparative electron density measurements for the refractive fringe diagnostic and Nomarski interferometry
Authors: Buccellato R. , Cunningham P. F. , Michaelis M. M. , Prause A.
Published: March 2009

Massive carbon targets were irradiated with a pulsed ruby laser and the laser-produced plasma electron densities were simultaneously evaluated using Nomarski interferometry and the refractive fringe diagnostic. An agreement of half an order of magnitude between the two diagnostics was obtained.
Radiation imprisonment in laser blow-off plasma
Authors: Bakos J. S. , Földes I. B. , Ignácz P. N. , Kedves M. Á. , Szigeti J.
Published: March 2009

Sodium laser blow-off plasma of low temperature (in the 1-eV range) is generated by laser intensities of 108–5.109 W cm−2. Imprisonment of resonant laser light has been observed. These experiments show that basic processes of interaction of radiation with level populations can be studied in the visible range, where the atomic levels have longer lifetimes than the ionic ones in hot plasmas, corresponding to X-ray generation. The imprisonment and resonant effects with various experimental parameters were investigated together with the nonresonant scattering on fragments.
Optimization of X-ray emission from a laser-produced plasma in a narrow wavelength band
Authors: Van Dorssen G. E. , Louis E. , Bijkerk F.
Published: March 2009

The X-ray emission from laser-produced plasmas at an X-ray wavelength of approximately 10.4 nm was measured for Al and Gd target materials. The laser power density on the target surface was varied between 1.5 × 1010 and 3 × 1012 W/cm2 to obtain different electron temperatures. The output from the plasma was measured using an X-ray reflecting Pd-C multilayer coating as a wavelength-selective element and a diamond photoconductive detector. The emission at 10.4 nm is strongest at the low end of the power density range investigated. A strong increase is found for Al targets due to a contribution of line radiation, which is not present in the Gd plasmas. The measured conversion efficiency for Al plasmas was (4.5 ± 1)% in a 3% bandwidth at an X-ray wavelength of 10.4 nm.
Linear laser plasma toward large-sized uniform soft X-ray source
Authors: Wang Xiaofang , Xu Zhizhan , Chen Shisheng , Qian Aidi , Li Yueling , Fan Pinzhong , Lin Lihuang
Published: March 2009

The effect of laser intensity distribution along the line focus on the uniformity of the line-shaped plasmas produced is investigated with time-integrated and time-resolved soft X-ray and optical diagnostics. Evident plasma condition nonuniformities along the line focus resulting from nonuniform laser intensity distributions have been observed with a conventional simple line-focusing technique. With a new line-focusing technique producing a uniform laser illumination, a uniform, line-shaped plasma can be obtained. It is also found that nonuniformities under uniform laser illumination occur mostly during laser heating. The line-shaped uniform laser plasma can be used as a large, uniform X-ray source besides its importance in X-ray laser demonstration and amplification. As an application of such line-shaped plasmas as X-ray sources, the no-overcoat 5F X-ray film is calibrated for the first time by a new method in the soft X-ray range from 10–80 A.
Population inversion in H- and He-like Al using laser-produced counterstreaming plasmas
Authors: Glas P. , Schnürer M.
Published: March 2009

The possibility of the occurrence of a population inversion between n = 3, 2 levels in H-like Al, as well as between levels of the n = 4, 3 manifold in He-like Al, has been inferred from time integrated K-line intensity ratios. Opacity-corrected inversion factors (1 − Ni/Nj) of about 0.6 for both He- and H-like Al have been obtained in counterstreaming Al-Au plasmas from which gain values of about 0.5 cm−1 have been estimated.
A pulsed iodine photodissociation laser with slow pumping
Authors: Beránek J. , Chvojka M. , Hermoch V. , Králiková B. , Krása J. , Láska L. , Mašek K. , Musil J. , Rohlena K. , Rus B. , Schmiedberger J. , Skála J. , Štirand O. , Trenda P. , Basov N. G. , Divilkovskiy I. M. , Zuev V. C. , Kanaev A. V. , Katulin V. A. , Korolkov K. S. , Mikheev L. D. , Orlov E. P. , Petrov A. L. , Yalovoy V. I.
Published: March 2009

A construction and exploitation of a comparatively large I photodissociation laser system (Perun) is reported. This system was constructed in cooperation between the Institute of Physics of Czechoslovak Academy of Science in Prague and the Lebedev Institute of Physics of Soviet Academy of Science in Moscow. The laser produces subnanosecond pulses of maximum 50 J and 0·5 ns in duration. Although the pumping time by Xe flashlamps is long enough for an acoustic disturbance released in the active medium to introduce an optical inhomogeneity across the whole cross section of the laser tube, the radiation can be focused in a focal spot of a power density exceeding 1014 W/cm2, enough for meaningful laser target experiments both for a laser plasma production or a modification of solid surfaces. The repetition time of the shots is about 10 min.
Nova Upgrade Program: Ignition and beyond
Authors: Storm E. , Campbell E.M. , Hogan W.J. , Lindl J.D.
Published: March 2009

The Lawrence Livermore National Laboratory (LLNL) Inertial Confinement Fusion (ICF) Program is addressing the critical physics and technology issues directed toward demonstrating and exploiting ignition and propagating burn to high gain with ICF targets for both defense and civilian applications. Nova is the primary U.S. facility employed in the study of the X-ray-driven (indirect drive) approach to ICF. Nova's principal objective is to demonstrate that laser-driven hohlraums can achieve the conditions of driver-target coupling efficiency, driver irradiation symmetry, driver pulseshaping, target preheat, and hydrodynamic stability required by hot-spot ignition and fuel compression to realize a fusion gain.

The LLNL ICF Program believes that the next major step in the national ICF Program is the demonstration of ignition and moderate gain (G ≤ 10). Recent theoretical and experimental results show that the ignition drive energy threshold can be reduced significantly by operating indirectly driven targets at radiation temperatures ∼ 1.3–1.6 times higher (thereby achieving higher implosion velocity) than originally proposed for the Laboratory Microfusion Facility (LMF). (Temperatures of ∼ 1.3 times higher have already been demonstrated on Nova.) Specifically, it should be possible to demonstrate ignition and propagating with burn about 1–2 MJ of laser energy as against the 5–10 MJ necessary for the high-yield LMF. LLNL proposes to upgrade the existing Nova facility to 1–2 MJ (2- to 4-ns pulses) and demonstrate ignition and propagating burn to moderate gain with appropriately scaled hydrodynamic equivalents of high-yield targets.

Once moderate gain has been demonstrated at 1–2.0 MJ on the Nova Upgrade, investigations into improving, by about 50%, the coupling efficiency between the driver and the capsule could provide gains >20 at about 1 MJ or less. A database for gain below 1-MJ driver energies could lead to a low-capital-cost Engineering Test Facility (ETF) for a first inertial fusion energy engineering reactor. Because the capital cost for both the target chamber and the driver scale with size, there is the opportunity to realize large savings by lowering the required driver energy necessary to demonstrate the technology for a first demonstration power plant. A target gain, G ∼ 25, at a driver energy, ED ∼ 0.75 MJ, would be self-sustaining for a driver efficiency of ∼10% and a thermal-to-electric conversion efficiency of ∼33% and at 12 Hz would generate ∼10 MW of gross electric power. Although the cost of electricity would be high, the combination of low capital cost and early demonstration of reactor technology would be an attractive step in the development of inertial fusion energy.
The Nova Upgrade Facility
Authors: Lowdermilk W.H. , Campbell E.M. , Campbell J.H. , Hunt J.T. , Murray J.R. , Powell H.T. , Smith R.L. , Storm E. , Tobin M.T. , Trenholme J.B.
Published: March 2009

The Nova Upgrade Facility is being designed to achieve inertial confinement fusion (ICF) ignition and gain. A baseline design of the laser and experimental facilities has been completed, and a development plan, which includes a fully integrated laser demonstration, has been formulated. With adequate funding, the activities in this plan could be completed by late 1993. Construction of the Nova Upgrade beginning at that time would make possible the achievement of ICF ignition before the end of the decade.
OMEGA Upgrade laser for direct-drive target experiments
Authors: Soures J.M. , McCrory R.L. , Boehly T.R. , Craxton R.S. , Jacobs S.D. , Kelly J.H. , Kessler T.J. , Knauer J.P. , Kremens R.L. , Kumpan S.A. , Letzring S.A. , Seka W.D. , Short R.W. , Skeldon M.D. , Skupsky S. , Verdon C.P.
Published: March 2009

Validation of the direct-drive approach to inertial confinement fusion requires the development of a 351-nm wavelength, 30-kJ, 50-TW laser system with flexible pulse shaping and irradiation uniformity approaching 1%. An upgrade of the existing OMEGA direct-drive facility at Rochester is planned to meet these objectives. In this article, we review the design rationale and specifications of the OMEGA Upgrade laser with particular emphasis on techniques planned to achieve the required degree of beam smoothing, temporal pulse shape, and beam-to-beam power balance.
KrF amplifier design issues and application to inertial confinement fusion system design
Authors: Sullivan J.A. , Allen G.R. , Berggren R.R. , Czuchlewski S.J. , Harris D.B. , Jones M.E. , Krohn B.J. , Kurnit N.A. , Leland W.T. , Mansfield C. , McLeod J. , McCown A.W. , Pendergrass J.H. , Rose E.A. , Rosocha L.A. , Thomas V.A.
Published: March 2009

Los Alamos National Laboratory has assembled an array of experimental and theoretical tools to optimize amplifier design for future single-pulse KrF lasers. The next opportunity to exercise these tools is with the design of the second-generation NIKE system under construction at the Naval Research Laboratory with the collaboration of Los Alamos National Laboratory. Major issues include laser physics (energy extraction in large modules with amplified spontaneous emission) and diode performance and efficiency. Low cost is increasingly important for larger future KrF single-pulse systems (low cost and high efficiency is important for larger repetitively pulsed applications such as electric power production). In this article, we present our approach to amplifier scaling and discuss the more important design considerations for large single-pulse KrF amplifiers. We point out where improvements in the fundamental database for KrF amplifiers could lead to increased confidence in performance predictions for large amplifiers and address the currently unresolved issues of anomalous absorption near line center and the possibility of diode instabilities for lowimpedance designs. Los Alamos has applied these amplifier design tools to the conceptual design of a 100-kJ Laser Target Test Facility and a 3-MJ Laboratory Microfusion Facility.
Heavy-ion accelerators for inertial confinement fusion
Authors: Rubbia Carlo
Published: March 2009

Two concepts have been applied to the classical problem of accelerators for the ignition of indirectly driven inertial fusion. The first is the use of non-Liouvillian stacking based on photoionisation of a singly charged ion beam. A special FEL appears the most suited device to generate the appropriate light beam intensity at the required wavelength. The second is based on the use of a large number of (>1000) beamlets–or “beam straws”–all focussed by an appropriate magnetic structure and concentrated on the same spot on the pellet. The use of a large number of beams–each with a relatively low-current density–elegantly circumvents the problems of space charge, making use of the non-Liouvillian nature of the stopping power of the material of the pellet. The present conceptual design is based on a low-current (〈i〉 ≈ 50 mA) heavy-ion beam accelerated with a standard LINAC structure and accumulated in a stack of rings with the help of photoionisation. Beams are then extracted simultaneously from all the rings and further subdivided with the help of a switchyard of alternate paths separating and synchronising the many bunches from each ring before they hit the pellet. Single beam straws carry a reasonable number of ions: Beams and technology are directly relatable to the ones presently employed, for instance, at the CERN-PS. Space-charge-dominated conditions arise only during the last few turns before extraction and in the beam transport channel to the reaction chamber. In a practical example, we aim at a peak power of 500 TW delivered to the pellet for a duration of 10–15 ns. High-energy (10 GeV) beam straws of Ba doubly ionised ions are concentrated on several (four) focal spots of a radius of about 1 mm. The power density deposited on these tiny cylindrical absorbers inside a hermetic “hohlraum” is about 2.5 × 1016 w/g. These conditions are believed to be optimal for X-ray conversion, i.e., with an estimated conversion efficiency of about 90%.
Inertial confinement fusion with magnetically compressed ion rings
Authors: Sudan R.N.
Published: March 2009

Ballistic propagation and focusing of intense light-ion beams requires (1) close limits on allowable beam divergence (∼5 mrad) and (2) gas-filled magnetic lenses that must function effectively even if deleterious self-fields are generated during the passage of the beam through the lens. An alternative to ballistic focusing was suggested some years ago in which magnetically compressed light-ion rings capable of delivering 3–4 MJ in a pulse of ∼1 ns are transported to the target in a tube. This concept is reexamined in light of recent work on the creation of ion rings and magnetic compression of stabilized liners. The physics issues of (1) magnetic compression, (2) transport of ion rings in a tube, and (3) the interaction of the ring with the target will be explored to evaluate the feasibility of this scheme.
Transformer-type accelerator for inertial confinement fusion
Authors: Irisawa Juichi , Takano Saburo
Published: March 2009

In pulse-power technology, a transformer-type accelerator is a good candidate for a highvoltage pulse generator suitable for repetitive operations. In this article, a reverse-conducting thyristor has been used as a switching element in a primary circuit and good operations have been obtained. A dual-resonant mode and the mode proposed by Reed, preferable to the former in the sense of voltage gain, have been investigated experimentally. A voltage gain of 25% increase compared to that of the dual-resonant mode operation has been obtained. Two different types of transformers, a spiral and a Tesla type with various turn ratios, were constructed and the characteristics of each type when applied to the same circuit have also been investigated in detail. As a result, it has been made clear that the stray capacitance of the secondary winding restricts the upper limit of the turn ratio to get the large voltage multiplication.
Analysis of experimental and theoretical research of nuclear-pumped lasers at the Institute of Technical Physics
Authors: Magda Edward P.
Published: March 2009

The nuclear-pumped laser program at the Institute for Technical Physics at Chelyabinsk- 70 is described. Work has primarily concentrated on rare gas and metal vapor lasers.
Nuclear-powered laser beam profile control method
Authors: Petra M. , Miley G.H.
Published: March 2009

The control of the extracted beam quality of a nuclear-pumped laser is a major issue. One possible control method involves changing the spatial power deposition profile, which is a function of the gas pressure and the pumping mechanism. Thus, we proposed a combined He-3 and wall coating (e.g., B-10 or U-235) technique. Then, the pump power deposition profile can be adjusted by varying the He-3 partial pressure. To examine this technique, measurements are being performed with an in-core cell by imaging the radiation-induced fluorescence onto a linear diode array located some distance from the cell. Results from these measurements are presented and other related issues such as gas dynamics, index of refraction effects, and efficient beam extraction from a large-volume cavity are discussed.
Experiments with a wire array Z pinch on the inductive storage generator
Authors: Baksht R.B. , Bugaev S.P. , Datsko I.M. , Kim A.A. , Koval'chuk B.M. , Kokshenev V.A. , Russkich A.G. , Mesyats G.A.
Published: March 2009

We report experiments that were carried out at the inductive storage machine GIT-4 with wire arrays. The tungsten wire array parameters were the following: the mass per centimeter was equal to 370 μg/cm, the length was 4 cm, and the initial radius was 0.2 cm. When the wire array current was 1.5 MA, the rise time was 100 ns and the total radiation energy was 50 kJ at the 80–100–kJ energy transferred to the wire array.
Cosmology in the Plasma Universe
Authors: Alfvén Hannes
Published: March 2009

Space observations have opened the spectral regions of X-rays and γ-rays, which are produced by plasma processes. ThePlasma Universederived from observations in these regions is drastically different from the now generally accepted ‘Visual Light Universe’ based on visual light observations alone. Historically this transition can be compared only to the transition from the the geocentric to the heliocentric cosmology.

The purpose of this paper is to discuss what criteria a cosmological theory must satisfy in order to be acceptable in the Plasma Universe.
Acceleration in the plasma focus and in astrophysics
Authors: Browne P. F.
Published: March 2009

Both, in the laboratory (specifically the plasma focus) and in astrophysics, charges are accelerated in magnetically pinched current channels. The current channels are annular cylinders, defined by an electric double layer of thickness δrE and radius R due to radial polarization of the plasma. The electric field Er in the double layer and the azimuthal magnetic field Bϕ ensure drifts of charges in the axial direction, but ions do not take up the full drift velocity because their Larmor radius exceeds δrE. Magnetic pinching of the channel reduces the cross sectional area S, and an instability of drift velocity may denude a region of current channel. The inductively maintained current J then cannot be carried by free charges, even with relativistic drift velocity. A displacement current (S/4π) δEz/δt arises, Ez growing until all energy in Bϕ is transferred into Ez. During this transfer Bϕ decreases, so the pinch weakens, permitting discharge of accumulated space charge via a conduction current without reversal of J. Thereafter the cycle repeats quasi-periodically.

In astrophysics acceleration occurs in a pinched magnetic vortex tube (MVT). The difference is that now Bϕ(r, +z) = −Bϕ(r, −z) due to winding of loops of field lines. Hence J reverses across mid-pinch, which implies accumulation of space charge of one sign at mid-pinch and of opposite sign at the ends of the pinch. Now there is reversal of J when the space charge relaxes.
The influence of a thermal plasma on synchrotron radiation
Authors: Crusius A.
Published: March 2009

The synchrotron emission from relativistic electrons in a thermal plasma with large-scale random magnetic fields is considered. In this case, the spectral synchrotron power of a single electron can be given in closed form allowing exact analytical expressions for the synchrotron emissivity, absorption coefficient, intensity and total energy loss of particles to be derived. The influence of various physical parameters such as gas density, magnetic field strength, particle's Lorentz factor on the resulting emissivities, intensities and energy loss is discussed in detail. Below the Razin– Tsytovich frequency vR = 20 Hz (ne/l cm−3) (B/l Gauss)−1, the spectral appearance of synchrotron radiation both in the optically thin and thick case is quite different than the vacuum behaviour. Since in the quasar broad line regions, vR is of the order 1011 Hz the suppression of synchrotron radiation may explain why most quasars are radio quiet. Likewise, the necessary physical conditions for the occurrence of synchrotron masering in the optically thick case are given. We obtain optical depth |τ|>1 for compact nonthermal sources. The total energy loss of a single particle is shown to be exponentially reduced at Lorentz factors less than γR = 2·1. 10−3 (ne/1 cm−3)½ (B/1 Gauss)−1.
The role of particle beams and electrical currents in the plasma universe
Authors: Peratt Anthony L.
Published: March 2009

Cosmic plasma physics and our concept of the universe is in a state of rapid revision. This change started with in-situ measurements of plasmas in Earth's ionosphere, cometary atmospheres, and planetary magnetospheres; the transition of knowledge from laboratory experiments to astrophysical phenomena; discoveries of helical and filamentary plasma structures in the Galaxy and double radio sources; and the particle simulation of plasmas not accessible to in-situ measurement. Because of these, Birkeland (field-aligned) currents, double layers, and magnetic-field aligned electric fields are now known to be far more important to the evolution of space plasma, including the acceleration of charged particles to high energies, than previously thought. This paper reviews the observational evidence for a plasma universe threaded by Birkeland currents and particle beams.
Containment forces in stable plasma configurations
Authors: Wells D. R.
Published: March 2009

It is demonstrated that finite pressure gradients can be maintained in the lowest free energy state (‘relaxed state’) of a plasma configuration. The pressure forces are supported by the Magnus Force in a compressible adiabatic plasma if mass motions are considered. It has been demonstrated elsewhere that these forces can be of the same order of magnitude as the Lorentz forces in some laboratory plasmas.
Focusing of intense light-ion beam by self magnetic field
Authors: Matsumoto M. , Kawata S. , Masubuchi Y. , Masugata K. , Murayama M. , Ito M. , Yatsui K.
Published: March 2009

This paper presents an analysis for focusing of an intense proton beam by a self-magnetic field. In this analysis, the self-magnetic field is used in a positive sense for beam focusing. The computation employs an equation for the beam trajectory in which the effect of the self-magnetic field is included. The results show that it is possible to use the self-magnetic field for the good beam focusing.
Numerical simulation of high current relativistic electron flow
Authors: Astrelint V. T. , Vrba P. , Ullschmied J. , Člupek M.
Published: March 2009

We studied the electron beam generation in high-current diode with various cathode shapes and the beam propagation through vacuum or plasma delivered to metallic drift tube. The combined effect of external longitudinal and self-consistent azimuthal magnetic fields with the accelerating electric field is discussed. We are interested in obtaining the diode efficiency and beam characteristic in stationary state.
Investigation of the ω0 harmonic generation in plasma on the ‘Delfin-1’ installation
Authors: Bychenkov V. Yu. , Koshevoi M. O. , Osipov M. V. , Rupasov A. A. , Shanditsev D. V. , Shikanov A. S. , Silin V. P. , Sklizkov G. V. , Tikhonchuk V. T. , Zozulya A. A.
Published: March 2009

Scattered emission from the laser plasma created in shell target heating experiments using the Delfin-1 laser has been studied. It is shown that the ω0 spherical harmonics can be used to determine both the plasma temperature in the nc/4 region and also the plasma flow through this region.
A reflexing electron microwave amplifier for rf particle accelerator applications
Authors: Fazio M. V. , Hoeberling R. F.
Published: March 2009

The evolution of rf-accelerator technology toward high-power, high-current, lowemittance beams produces an ever-increasing demand for efficient, very high power microwave power sources. The present klystron technology has performed very well but is not expected to produce reliable gigawatt peak-power units in the 1- to 10-GHz regime. Further major advancements must involve other types of sources. The reflexing-electron class of sources can produce microwave powers at the gigawatt level and has demonstrated operation from 800-MHz to 40-GHz. The pulse length appears to be limited by diode closure, and reflexing-electron devices have been operated in a repetitively pulsed mode. A design is presented for a reflexing electron microwave amplifier that is frequency and phase locked. In this design, the generated microwave power can be efficiently coupled to one or several accelerator loads. Frequency and phase-locking capability may permit parallel-source operation for higher power. The low-frequency (500-MHz to 10-GHz) operation at very high power required by present and proposed microwave particle accelerators makes an amplifier, based on reflexing electron phenomena, a candidate for the development of new accelerator power sources.
Analysis of magnetron instability for relativistic nonneutral electron flow in cylindrical high-voltage diodes
Authors: Davidson Ronald C. , Tsang Kang T.
Published: March 2009

Use is made of the extraordinary-mode eigenvalue equation to investigate detailed properties of the magneteron instability for relativistic nonneutral electron flow in a cylindrical high-voltage diode with cathode located at r = a and the anode located at r = b. The model is based on the cold-fluid-Maxwell equations including the full influence of self-field and cylindrical effects. The equilibrium radial electric field Er (r)êr and axial magnetic field Bz (r)êz induce an azimuthal flow of electrons with angular velocity ωb(r) = Vθb (r)/r. The stability analysis assumes flute perturbations with extraordinary-mode polarization. The equilibrium radial electric field is specified by Er (r) = const, sinh k (r − a) within the electron layer (a ≤ r ≤ rb), and emphasis is placed on calculating equilibrium and stability behavior in a parameter regime characteristic of the PBFA-II diode experiments. In particular, voltages in the range 10 MV to 14·75 MV are considered, assuming a = 12 cm, b = 15 cm, and normalized layer thickness Δb = (rb − a)/(b − a) ranging from Δb = 0·3 to Δb = 0·6. At the high voltages characteristic of PBFA-II operation, a moderately strong applied magnetic field B0 is required to assure magnetic insulation of the layer electrons from the anode. Here, B0 is the magnetic field in the vacuum region rb < r ≤ b. Correspondingly, the value of normalized density is typically small. Here, ωc0 = eB0/mc, and ωp0 is the plasma frequency at the cathode. As a general remark, for fixed values of the geometric factors Δb, b − a, etc., it is found that there is a sensitive dependence of the magnetron instability growth rate on the relativistic flow velocity as measured by , with higher values of γ(rb) favoring stronger growth. Typical maximum growth rates are in the range of a few to several percent of ωc0.
Line radiation transfer in non-equilibrium laser plasma
Authors: Kaśkova S. I. , Romanov G. S. , Stepanov K. L.
Published: March 2009

The self-radiation characteristics of plasma created under the effect of a powerful laser radiation on a target are considered. The radiation in the spectral range from 1 to 1300 Å is calculated in coherent assumption for given gas-dynamic fields corresponding to various phases of laser target explosion. The source function was determined in accordance with a plasma radiation-collision model with the assumption of its transparency. Calculations show that the contribution of line radiation to the total flux may be from 20 to 60%. Mainly, this paper considers radiation transfer. The effect of self-radiation on level populations and frequency redistribution at resonance scattering is taken into account. The resonance scattering is predominant in the coronal plasma. Exit of photons from deeper layers of the target in comparison with the coherent case increases. Macroscopic plasma motion leading to spectral line shift is taken into consideration in the calculations. Output radiation spectral intensity distribution in oxygen and silicon H-like ions resonance lines has been determined. Spectral line profiles calculated with account of basic broadening mechanisms were used.
Radiation reabsorption in a laser-produced plasma
Authors: Brunner W. , John R. W. , Paul H. , Steudel H.
Published: March 2009

Taking into account the emission and absorption of resonance radiation in a recombining laser-produced plasma of intermediate density, the system of rate equations for the population densities coupled with the radiative transfer equation is approximately treated. In the case of spatially varying absorption we derive an approximate form of the rate equation determining the population density of the upper resonance level. By applying this relation to an axially symmetric plasma a simple formula that describes the effect of radiation reabsorption on the spatial behaviour of the population density is obtained.
Kinetic stability properties of relativistic nonneutral electron flow for low-frequency extraordinary-mode perturbations
Authors: Davidson Ronald C. , Uhm Han S.
Published: March 2009

The kinetic stability properties of relativistic nonneutral electron flow in planar diode geometry are examined for extraordinary-mode perturbations about the self-consistent Vlasov equilibrium . Here, the cathode is located at x = 0; the anode is located at x = d the outer edge of the electron layer is located at is the equilibrium flow velocity in the x-direction; n^b is the electron density at the cathode (x = 0); and is the axial magnetic field, with const. in the vacuum region (xb < x ≤ d). The extraordinary-mode eigenvalue equation, derived in a companion paper for low-frequency, long-wavelength perturbations, is solved exactly. This leads to a formal dispersion relation, which can be used to determine the complex eigenfrequency ω over a wide range of system parameters and wavenumber k in the y-direction. The formal dispersion relation is further simplified for and , assuming low-frequency perturbations about a tenuous electron layer with and . Here, , and , where denotes the average equilibrium orbit, and [γ(x) − 1]mc2 is the average kinematic energy of an electron fluid element. The resulting approximate dispersion relation is solved numerically over a wide range of system parameters to determine the detailed dependence of stability properties on electromagnetic effects, layer thickness, and electron energy, as measured by , and γb − 1, respectively. Here, γb = γ(xb) denotes the electron energy at the outer edge of the electron layer. As a general remark, it is found that increasing the electron energy (γb − 1), increasing the strength of electromagnetic effects , and/or decreasing the layer thickness (xb/d) all have a stabilizing influence.
Effect of thermal flux inhibition on the coupling of core with hot corona in a laser irradiated plasma pellet
Authors: Singh D. P. , Herrera J. J. E. , Vaselli M.
Published: March 2009

The effect of thermal flux transport inhibition on the coupling of the spherical dense pellet core with the hot electron halo produced at the plasma resonance layer has been investigated. The analytic expressions for the core-corona coupling and the optimum temperature of the overlapping region (at which this coupling is maximum) have been derived as a function of ‘flux limit’ parameter and the laser wavelength. Relevant calculations indicate that the core-corona coupling is sensitive to the mean electron temperature and the scaling of its maximum value with the laser wavelength remains absolutely unaffected by plasma ablation. The subsequent results on laser wavelength scaling are compared and contrasted with the predictions of other investigations. The heat transfer from the hot electron cloud to the dense core can be increased by an order of magnitude in case of the uninhibited flux.
Field distributions and resonance absorption in a laser plasma filament
Authors: Min Gu , Weihan Tan
Published: March 2009

In this paper we have theoretically studied the field distributions and resonance absorption in a laser-produced plasma filament. Under the condition of the cold plasma we derive the field equations, as well as their analytical solutions, to the radial and axial components of the electric field. Then, by the numerical calculations, we find that there exists a tunnel effect along the radial direction of the filament, i.e., the electric field reaches a maximum near the radial resonance point r0. Thus, the curves of variance of the radial and axial field components are obtained.
Microsecond REB generation in a planar diode at the U-2 device
Authors: Arzhannikov A. V. , Avrorov A. P. , Lyamzin M. P. , Sinitsky S. L. , Yushkov M. V.
Published: March 2009

Experimental studies on high power ∼ 10 μs electron beam generation have been carried out. High efficiency (about 75%) of energy transfer from a capacitor storage to the electron beam with total energy about 150 kJ has been attained.
A shock tube study of high temperature reaction of CO–N2O–H2 mixtures and its application to CO2 gasdynamic laser
Authors: Miyama H. , Fujii N. , Takeishi N. , Tokuda T. , Sakatsume N.
Published: March 2009

In order to investigate the gasdynamic laser (GDL) a conventional pressure driven shock tube equipped with the nozzle apparatus was used. Kinetic study of CO2 formation in CO–N2O–H2 system behind a reflected shock wave was carried out by measuring 4·25 μm emission of CO2. Then, population inversions of the vibrational level of CO2 in an expanding flow of mixtures containing CO2 produced by high temperature reaction of CO–N2O–H2 system behind reflected shock wave were observed by measuring 10.6 μm small signal gains. The experimental data are compared with those obtained by computer simulation assuming quasi-one dimensional steady flow and three vibrational energy modes model. The optimum conditions for CO2 gasdynamic laser by using the shock heated CO–N2O–H2 system are discussed.
Convenient computational forms for the frequency and damping of electrostatic waves in an unmagnetized plasma
Authors: Casanova M.
Published: March 2009

Empirical expressions are proposed for the frequency and damping rate of electron plasma waves and ion acoustic waves in an unmagnetized, partly collisional plasma.